U.S. Department of the Interior

U.S. Geological Survey

Methods of Analysis by the U.S. Geological Survey National Water 

Quality Laboratory—Determination of Organochlorine Pesticides 

and Polychlorinated Biphenyls in Bottom and Suspended Sediment 

by Gas Chromatography with Electron-Capture Detection

Water-Resources Investigations Report 03–4293
Methods of Analysis by the U.S. Geological Survey 

National Water Quality Laboratory—Determination of 

Organochlorine Pesticides and Polychlorinated 

Biphenyls in Bottom and Suspended Sediment by Gas 

Chromatography with Electron-Capture Detection

By Mary C. Noriega, Duane S. Wydoski, and William T. Foreman

U.S. Department of the Interior

U.S. Geological Survey

Water-Resources Investigations Report 03-4293
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Denver, Colorado: 2004

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 iii

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Safety considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Analytical method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

1. Scope and application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

2. Summary of method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

3. Interferences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

4. Apparatus and equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

5. Reagents and consumable materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

6. Collection, shipment, and storage of sediment samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7. Sample preparation procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8. Gas chromatography/electron-capture detection analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

9. Gas chromatography/electron-capture detection compound calibration. . . . . . . . . . . . . . . . 27

10. Calculation of results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

11. Gas chromatography/electron-capture detection performance. . . . . . . . . . . . . . . . . . . . . . . . . 32

12. Reporting of results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

13. Laboratory quality assurance/quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

14. Method performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Summary and conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

References cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Figures

1. Flowchart showing the analytical method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2. Gel permeation chromatogram of the fraction test solution at attenuation 8 

showing the analyst-determined collection start and end times for the 

organochlorine pesticide fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

3-8. Gas chromatograms showing:

3. Electron-capture detection of a fraction-1 extract from a laboratory reagent spike 

fortified with 50 nanograms of individual organochlorine pesticides and 250 

nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-5 column . . . . . . . . . . . . . .20

4. Electron-capture detection of a fraction-1 extract from a laboratory reagent spike 

fortified with 50 nanograms of individual organochlorine pesticides and 250 

nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-1701 column. . . . . . . . . . .21

5. Electron-capture detection of a fraction-2 extract from a laboratory reagent spike 

fortified with 50 nanograms of individual organochlorine pesticides and 250 

nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-5 column . . . . . . . . . . . . . .22

6. Electron-capture detection of a fraction-2 extract from a laboratory reagent spike 

fortified with 50 nanograms of individual organochlorine pesticides and 250 

nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-1701 column. . . . . . . . . . .23
iv 

7. Electron-capture detection of a 1,000-picorgrams-per-microliter toxaphene 

calibration standard solution prepared from an NSI Solutions, Inc. stock solution 

on a Restek Rtx-5 column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

8. Electron-capture detection of a 1,000-picorgrams-per-microliter toxaphene 

calibration standard solution prepared from an NSI Solutions, Inc. stock solution 

on a Restek Rtx-1701 column. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Tables

1. Laboratory codes, parameter codes, and Chemical Abstracts Service registry 

numbers for method compounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Suggested gel permeation chromatography autosequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

3. Alumina/silica fractionation and mean percent recovery of method compounds 

from the analyses of three to seven set spikes processed through the entire 

analytical procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4. Retention times of individual organochlorine method compounds, selected 

peaks for PCB Aroclor 1016/1242, 1254, 1260, and toxaphene on the Rtx-5 and 

Rtx-1701 columns from figures 3 through 8 example gas chromatograms. . . . . . . . . . . . . . . . .26

5. Compound coelutions commonly observed on the gas chromatography 

capillary columns used in this analytical method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

6. Suggested gas chromatography/electron-capture detection autosequence . . . . . . . . . . . . .28

7. Surrogate observations that indicate alumina/silica adsorption chromatography 

errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

8. Estimated method detection limits for method compounds from eight sodium 

sulfate reagent organochlorine-fortified replicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

9. Interim reporting levels for dry-weighted sediment samples, in micrograms 

per kilogram, assuming a 25-gram sample size, and for suspended-sediment 

samples collected on filters, in micrograms per liter, assuming 63 liters filtered. . . . . . . . . . . .40

10. Bias and precision data for method compounds in sodium sulfate reagent, 

Evergreen Lake sediment, and Clear Creek sediment from sets of eight replicates, 

each spiked at 1, 2, and 10 micrograms per kilogram (μg/kg) for individual 

organochlorine compounds; and 20, 40, and 5 μg/kg for each PCB Aroclor 1242, 

1254, and 1260; toxaphene spiked separately . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
 v

Conversion Factors

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 x °C) + 32

ABBREVIATED WATER-QUALITY UNITS ABBREVIATIONS AND ACRONYMS

μg/kg microgram per kilogram CAS Chemical Abstracts Service

μg/L microgram per liter CCV continuing calibration verification 

°C/min degree Celsius per minute ECD(s) electron-capture detector(s)

cm/s centimeter per second F1(s) fraction 1(s)

mL/min milliliter per minute F2(s) fraction 2(s)

ng/g nanogram per gram FEP tetrafluoroethylene-hexafluoropropylene copolymer

ng/μL nanogram per microliter GC gas chromatography 

(or gas chromatograph)

ng/mL nanogram per milliliter

pg/μL picogram per microliter

Multiply By To obtain

Length

centimeter (cm) 3.94 x 10-1 inch

micrometer (μm) 3.94 x 10-5 inch

millimeter (mm) 3.94 x 10-2 inch

meter (m) 3.28 x 100 foot

nanometer (nm) 3.94 x 10-8 inch

Mass

gram (g) 3.53 x 10-2 ounce, avoirdupois

kilogram (kg) 3.53 x 101 ounce, avoirdupois

microgram (μg) 3.53 x 10-8 ounce, avoirdupois

nanogram (ng) 3.53 x 10-11 ounce, avoirdupois

picogram (pg) 3.53 x 10-14 ounce, avoirdupois

Volume

liter (L) 2.64 x 10-1 gallon

liter (L) 3.38 x 10-1 ounce, fluid 

microliter (μL) 2.64 x 10-7 gallon

milliliter (mL) 2.64 x 10-4 gallon

Pressure

kilopascal (kPa) 1.45 x 10-1 pounds per square inch
vi 

GC/ECD gas chromatography/electron-capture detection

GC/MS gas chromatography/mass spectrometry

GPC gel permeation chromatography

HCB hexachlorobenzene

HPLC high-performance liquid chromatography

ID inside diameter

IRL(s) interim reporting level(s)

K-D Kuderna-Danish

LRB laboratory reagent blank

LRS(s) laboratory reagent spike(s)

MDL(s) method detection limit(s)

NAWQA National Water-Quality Assessment Program

NWQL National Water Quality Laboratory

N-EVAPTM nitrogen gas evaporator 

OC(s) organochlorine(s)

OCIIS organochlorine internal-injection standard

PAH(s) polycyclic aromatic hydrocarbon(s)

PCB(s) polychlorinated biphenyl(s)

PEM performance evaluation mix

PTFE polytetrafluoroethylene 

QA quality assurance

QC quality control

rpm revolutions per minute

RPD(s) relative percent difference(s)

SRM(s) standard reference material(s)

S-EVAPTM steam evaporator

TPC(s) third-party check(s)

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

± plus or minus

> greater than or equal to

< less than or equal to
Methods of Analysis by the U.S. Geological Survey National 

Water Quality Laboratory–Determination of Organochlorine 

Pesticides and Polychlorinated Biphenyls in Bottom and 

Suspended Sediment by Gas Chromatography with 

Electron-Capture Detection

Abstract

A method applicable for the determination of 19 

organochlorine (OC) pesticides, including total toxaphene 

as a complex mixture, and 3 polychlorinated biphenyl 

(PCB) mixtures as Aroclor® equivalents—Aroclor 

1016/1242, 1254, and 1260—in soil, aquatic bottom 

sediment, and suspended sediment is described. Method 

performance data are presented. The solvent system is 

designed to extract simultaneously selected OC pesticides 

and PCBs from the same sample matrix. The compounds 

are extracted by conventional Soxhlet extraction with 

dichloromethane, followed by partial isolation using gel 

permeation chromatography (GPC) to remove inorganic 

sulfur and large naturally present molecules from the 

sediment extract. The aliquot of extract collected from the 

GPC for OCs (OC pesticides and PCBs) is split into two 

sample fractions by alumina/silica combined-column 

chromatography, followed by Florisil adsorption 

chromatography to remove interfering compounds in the 

second fraction. The OC fractions are analyzed by dual 

capillary-column gas chromatography with 

electron-capture detection (GC/ECD). This report is 

limited to the determination of selected OC pesticides and 

PCBs by GC/ECD using this method. Interim reporting 

levels (IRLs) have been set at 0.400 to 3.12 micrograms 

per kilogram (μg/kg) for 18 individual OC pesticides, 200 

μg/kg for toxaphene, and 4.04 to 4.68 μg/kg for the PCBs, 

based on a sample size of 25-gram equivalent dry weight. 

These reporting levels may change following additional 

determinations of method detection limits.

Introduction

Most organochlorine (OC) pesticides and 

polychlorinated biphenyls (PCBs) have low water 

solubilities; thus, these organic contaminants typically are 

associated with soil, bottom sediment, and suspended 

sediment in hydrologic environments that possess a 

measurable total of organic carbon. The method described 

in this report was designed to extract OC pesticides and 

PCBs from a sediment or soil matrix and to isolate the 

contaminants from co-extracted natural organic matter by 

gel permeation and adsorption chromatography prior to 

instrumental analysis by dual capillary-column gas 

chromatography (GC) with electron-capture detection 

(ECD).

The determination of selected OC pesticides and 

PCBs as Aroclor equivalents was implemented as a 

custom method at the National Water Quality Laboratory 

(NWQL) in July 1996 at the request of the Reconstructed 

Trends Program for a study as part of the National 

Water-Quality Assessment (NAWQA) Program (Van 

Metre and others, 1997, 2000). The custom method 

developed into the present (2004) new method described 

in this report. The new method is based largely on USGS 

method O-5129-95 (Foreman and others, 1995, p. 4–49) 

originally developed for the NAWQA Program. The new 

method includes a Florisil clean-up step for fraction-2 

extracts to minimize interferences that would compromise 

the performance of the GC columns used for quantifying 

the selected OCs determined by this method. The 

extensive preparation protocol provides cleaner extracts, 

thus increasing signal-to-noise ratios and improving 

method detection limits compared to the method by 

Foreman and others (1995). The new method also 

determines fewer compounds in a shorter gas 

chromatographic analysis time compared to the method 

by Foreman and others (1995). The selected OCs in the 

new method are determined by using a GC oven 

temperature program that is 42 minutes shorter per sample 

fraction than the gas chromatographic program described 

by Foreman and others (1995, p. 30), which was 

By Mary C. Noriega, Duane S. Wydoski, and William T. Foreman
2 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

lengthened to enhance PCB congener and OC pesticide 

separations and to determine the permethrin isomers. 

Furthermore, the new method specifically reports PCBs 

as Aroclor equivalent concentrations at the request of the 

Reconstructed Trends Program.

Before 2004, the NWQL reported PCBs eluting in the 

Aroclor 1242 region of the gas chromatogram as Aroclor 

1242 only. However, Aroclor 1242 and Aroclor 1016 

have nearly identical PCB congener composition, and, 

thus, practically indistinguishable gas chromatographic 

profiles. Therefore, in the new method, PCBs eluting in 

this region will be classified and the concentration will be 

reported as Aroclor 1016/1242 (U.S. Geological Survey 

National Water Quality Laboratory Technical 

Memorandum No. 99.10, 1999) to minimize 

misclassification of these two Aroclors in environmental 

and quality-assurance samples. In the methodperformance evaluation, PCB Aroclor 1242 (and not 

Aroclor 1016) was determined; however, the results for 

Aroclor 1242 are reported as Aroclor 1016/1242 (see 

section 14). The new method was approved October 2003. 

The method was implemented at NWQL in March 2004.

Purpose and Scope

The purpose of this report is to describe an analytical 

method for the determination of 19 OC pesticides and 3 

PCB mixtures in soil, aquatic bottom sediment, and 

suspended sediment. An aliquot of the concentrated, 

filtered extract is injected quantitatively onto two 

polystyrene-divinylbenzene gel permeation 

chromatography (GPC) columns connected in series. The 

compounds are eluted with dichloromethane. A specific 

range of time is set on the GPC for the collection of the 

OC aliquot containing the OC pesticides and PCBs. An 

adsorption chromatography step using an alumina/silica 

combined column separates the OCs into two sample 

fractions; the second fraction undergoes an additional 

adsorption chromatography step using a Florisil column 

for cleanup. These two adsorption chromatography steps 

reduce interferences that might produce a response in the 

electron-capture detector, or contribute to degradation of 

analytes in the injection port of the gas chromatograph. 

Each fraction then is analyzed by dual capillary-column 

GC/ECD.

This method combines elements of U.S. Geological 

Survey (USGS) methods outlined in OC pesticides and 

PCBs in bottom sediment (Foreman and others, 1995). In 

addition, this method adapts components of U.S. 

Environmental Protection Agency (USEPA) method 

3620C (Florisil cleanup) (U.S. Environmental Protection 

Agency, 2000). 

A description of the method from sampling protocol 

through calculation and reporting of results for OC 

pesticides and PCBs, estimated method detection limits, 

laboratory quality assurance and quality control, and bias 

and precision data from a method-performance evaluation 

are presented.

Acknowledgments

The authors note the substantial contributions made 

by Dan Bottinelli, Troy Engstrom, and Deborah Vaught 

of the NWQL's Analytical Services Section for much of 

the sample preparation for the data presented in this 

report. The authors also wish to acknowledge the 

following NWQL staff members for their assistance and 

contributions leading to the design, development, testing, 

and implementation of this method: Edward T. Furlong of 

the Methods Research and Development Program, and 

Sonja Abney, Dawn Fulton, Jana L. Iverson, Virendra 

Jha, Leslie (Merten) Kanagy, Dennis Markovchick, Mary 

C. Olson, and Michael Schroeder, Analytical Services. 

Additional thanks to Barbara Kemp for assistance with 

manuscript preparation and to Jon Raese for report 

editing.

Safety Considerations

This method involves the handling of known, 

suspected, and possibly unknown hazardous chemicals 

and reagents. The method uses substantial volumes of 

dichloromethane, a suspected carcinogen, during sample 

extraction and some extract clean-up steps. Wear 

SilverShield® (also known as Norfoil®) gloves for the 

most resistance to dichloromethane; most other gloves 

(including nitrile gloves) do not provide adequate 

protection when handling the solvent. Carefully follow all 

standard safety practices regarding the use of solvents, 

compressed gases, OC pesticides, PCBs, polycyclic 

aromatic hydrocarbons, and other method-related 

chemicals. Consult material safety data sheets and 

chemical labels for proper storage, handling, and 

additional safety information. The USEPA has special 

regulations covering the handling and disposal of PCBs. 

Always wear appropriate protective clothing, gloves, and 

eye wear, and use adequate ventilation when preparing 

samples or standard solutions. Electron-capture detectors 

contain radioactive 63nickel and are cleaned by trained 

personnel only.
Analytical Method 3

Analytical Method

Organic Compounds and Parameter Codes: 

Organochlorine pesticides, polychlorinated biphenyls, 

soil, bottom and suspended sediment by mass per mass, 

high-performance gel permeation chromatography, dual 

capillary-column gas chromatography, electron-capture 

detection, O-5504-03; and suspended sediment by mass 

per volume, O-7504-03 (see table 1)

1. Scope and Application

This method is suitable for the determination of 19 

individual OC pesticides, including total toxaphene as a 

complex OC pesticide mixture, and 3 PCB mixtures as 

Aroclor equivalents—Aroclor1016/1242, 1254, and 

1260—in soil, bed sediment, suspended sediment, and dry 

sludge. This method is applicable to samples with OC 

compounds that are (1) efficiently extracted from the solid 

matrix by methanol or dichloromethane, (2) adequately 

separated from natural co-extracted compounds by gel 

permeation chromatography (GPC), (3) efficiently 

recovered from the alumina-over-silica adsorption 

chromatography clean-up/fractionation step and the 

Florisil adsorption chromatography clean-up step, (4) 

sufficiently volatile and thermally stable for gas 

chromatographic analysis, and (5) responsive to 

electron-capture detection. This method is applicable to a 

25-g equivalent dry-weight sample size for extraction. A 

minimum of 0.1-g dry-weight sample size can be used, 

with reporting levels raised accordingly. This method also 

is applicable to suspended-sediment samples collected on 

glass-fiber filters, with concentrations reported in 

micrograms per liter for known sample-volume filtered 

(Mahler and others, 2001).

2. Summary of Method

A flowchart for the method is shown in figure 1. In 

brief, a bottom-sediment sample is centrifuged to remove 

excess water. A sample size of 25-g equivalent dry weight 

is extracted overnight with dichloromethane (93 percent) 

and methanol (7 percent). The sample extract is 

concentrated and first filtered through a 1.0-μm 

polytetrafluoroethylene syringe filter, then through a 

0.2-μm polytetrafluoroethylene syringe filter connected 

in series. For the determination of OC pesticides and 

PCBs, a 1,100-μL aliquot of the sample extract is injected 

quantitatively onto two serial polystyrene-divinylbenzene 

GPC columns. Compounds are eluted with 

dichloromethane at a flow rate of 1 mL/min and are 

collected in a distinct fraction time window. Interferences 

elute first from the GPC columns and are not collected. 

The method compounds then are collected in a GPC 

fraction for about 8.9 minutes. Sulfur elutes immediately 

after this GPC fraction and is not collected. The collected 

GPC fraction of OCs is concentrated and solvent 

exchanged, then undergoes cleanup using alumina/silica 

combined column adsorption chromatography and further 

split into two OC fractions. The second OC fraction 

undergoes additional cleanup using a Florisil column. 

Both OC fractions are analyzed by dual capillary-column 

gas chromatography with electron-capture detection 

(GC/ECD). The GC/ECD is calibrated for both capillary 

columns by the external standard method using multipoint 

calibration standards. The OCs subsequently are 

quantitated against the calibration curve processed for 

each column.

3. Interferences

This method is designed to minimize false positives 

through dual-column confirmation. However, nonmethod 

organohalogen, oxygenated, and other ECD-sensitive 

compounds that are co-extracted, collected in the GPC 

fraction and the adsorption chromatography fractions, and 

have GC retention times identical to those of the selected 

OCs of interest potentially can interfere with the 

analytical method. Hydrocarbon contamination from oils 

on the analytical instrument or in sediments, 

polychlorinated napthalenes, phthalates, and inorganic 

sulfur that is incompletely removed during the GPC step 

can interfere with qualification and quantification of 

method compounds. Follow-up analysis by mass-spectral 

confirmation also may be used to confirm identification, 

if uncertain. For some samples, reliable detection might 

not be possible because of the levels of interferences in the 

matrix, and interim reporting levels might have to be 

raised. Furthermore, the shorter GC oven temperature 

program in contrast with that described by Foreman and 

others (1995, p. 30) causes some recognizable coelutions, 

for example, dieldrin and p,p'-DDE on the Rtx® –5 primary 

column (5.10.1.1), and p,p'-DDE and a PCB congener on 

the Rtx® –1701 secondary column (5.10.1.2). 

Consequently, high PCB concentrations might interfere 

with p,p'-DDE determination.

4. Apparatus and Equipment

The apparatus and equipment required for this 

method, listed as follows, are grouped by the specific 

preparation step or analysis but are not repeated if used in 
4 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

Table 1. Laboratory codes, parameter codes, and Chemical Abstracts Service registry numbers for method compounds. 

[NWQL, National Water Quality Laboratory; P-code, parameter code; CAS, Chemical Abstracts Service; 

--, not assigned] 

Method 

O-5504-03 

Dry-weighted 

sediment 

 Method 

O-7504-03 

Wet-weighted 

sediment 

Compound name Abbreviation 

NWQL

result

code 

P-code 

 NWQL

result

code 

P-code 

CAS 

number 

Aldrin -- 4450 39333B 4550 39332B 309-00-2 

cis-Chlordane (alpha-Chlordane) -- 4451 62802A 4551 62956A 5103-71-9 

trans-Chlordane (beta-Chlordane) -- 4452 62803A 4552 62957A 5103-74-2 

4,4'-Dichlorodiphenyldichloro-ethane p,p'-DDD 4453 39363B 4553 39362B 72-54-8 

4,4'-Dichlorodiphenyldichloro-ethene p,p'-DDE 4454 39368B 4554 39367B 72-55-9 

4,4'-Dichlorodiphenyltrichloro-ethane p,p'-DDT 4455 39373B 4555 39372B 50-29-3 

Dieldrin -- 4456 39383B 4556 39382B 60-57-1 

Endosulfan I -- 4457 39389B 4557 34363B 959-98-8 

Endrin -- 4458 39393B 4558 39392B 72-20-8 

Heptachlor -- 4459 39413B 4559 39412B 76-44-8 

Heptachlor epoxide (Isomer B) -- 4460 39423B 4560 39422B 1024-57-3 

Hexachlorobenzene HCB 4547 39701B 4561 34402A 118-74-1 

alpha-Hexachlorocyclohexane α-HCH 4461 39076B 4562 34254A 319-84-6 

beta-Hexachlorocyclohexane β-HCH 4462 34257B 4563 34256A 319-85-7 

gamma-Hexachlorocyclohexane 

(Lindane) 

γ-HCH 4463 39343B 4564 39342B 58-89-9 

p,p'-Methoxychlor -- 4464 39481B 4565 82351B 72-43-5 

Mirex -- 4465 39758B 4566 39757B 2385-85-5 

trans-Nonachlor -- 4466 62804A 4567 62958A 39765-80-5 

Polychlorinated biphenyl 

Aroclor 1016/1242 

PCB Aroclor 

1016/1242 

4548 46343A 4568 62959A -- 

Polychlorinated biphenyl 

Aroclor 1016 

PCB Aroclor 1016 -- -- -- -- 12674-11-2 

Polychlorinated biphenyl 

Aroclor 1242 

PCB Aroclor 1242 -- -- -- -- 53469-21-9 

Polychlorinated biphenyl 

Aroclor 1254 

PCB Aroclor 1254 4468 39507A 4569 39506A 11097-69-1 

Polychlorinated biphenyl 

Aroclor 1260 

PCB Aroclor 1260 4469 39511A 4570 39510A 11096-82-5 

Toxaphene (technical) -- 4471 39403B 4572 39402B 8001-35-2 

Surrogates 

alpha-Hexachlorocyclohexane-d6 α-HCH-d6 4472 62837A 4573 99990A -- 

Isodrin -- 4473 62836A 4574 99991A 465-73-6 

2,2',3,3',4,4',5,6,6'- 

Nonachlorobiphenyl 

PCB-207 4474 62838A 4575 99992A 53742-07-7 
Analytical Method 5

Homogenize wet sediment; 

or cut suspended-sediment sample adhered to 

glass-microfiber filters into strips 

using cutting tools rinsed with dichloromethane

↓

Centrifuge a portion to remove excess water; 

determine percent moisture 

(not applicable for suspended-sediment sample adhered to filters) 

↓

Weigh centrifuged sediment into a beaker 

(25-gram equivalent dry weight); 

or put all strips of the suspended-sediment sample adhered to 

filters into a beaker 

↓

Mix with sodium sulfate to form loose mixture 

to absorb residual moisture 

↓

Transfer mixture to glass extraction thimble; 

add method surrogates; include preparation of 

quality-assurance/quality-control (QA/QC) samples; 

add method spike solutions to the set spike (QC) sample 

↓

Wash mixture with 25 milliliters (mL) methanol 

to remove water not bound by sodium sulfate; 

wait 30 minutes; extract sample plus wash for 12 hours 

with 350 mL dichloromethane at 70°C in Soxhlet apparatus; 

cool; dry extract with sodium sulfate 

↓

Reduce extract volume to 1.0 mL using Kuderna-Danish (K-D) apparatus 

and N2 gas evaporator (N-Evap); centrifuge and filter sample extract; 

increase volume to 4.0 mL with dichloromethane 

↓

Gel permeation chromatography (GPC) on a 1,100 aliquot of sample extract; 

elute with dichloromethane and collect GPC fraction of organochlorine (OC) compounds 

[OC pesticides and polychlorinated biphenyls (PCBs)] 

in a distinct time window 

↓

Concentrate GPC fraction using micro-K-D apparatus and N-Evap; 

solvent exchange to hexane; reduce volume to 1.0 mL 

↓

Alumina/silica combined column adsorption chromatography; 

collect 30 mL of hexane (fraction 1: OC pesticides and PCBs) and 

35 mL of 5-percent acetone in hexane (fraction 2: OC pesticides) 

↓

Reduce fraction 2 to 1.0 mL; Florisil column cleanup of fraction 2; 

collect 20 mL of 1-percent acetone in hexane 

↓

Reduce fractions to 0.5 mL final volume using micro-K-D apparatus and N-Evap; 

add OC internal-injection (retention time marker) standards 

↓

Dual capillary-column gas chromatography with electron-capture detection 

 Figure 1. Flowchart showing the analytical method. Details are in the text of this report.
6 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

more than one part of the method. Specific models and 

sources that were used to develop or implement this 

method also are listed, as appropriate.

 Prior to use, wash all glassware (except class–A 

volumetric glassware) with phosphate-free detergent, 

rinse sequentially with tap and distilled water, and heat to 

450°C for a minimum of 2 hours. With the exception of 

vials, micropipet bores, and Pasteur pipets, prerinse all 

glassware with the solvent used in the procedure requiring 

the glassware. Clean class–A volumetric glassware by 

rinsing with acetone followed by triple rinsing with 

pesticide-grade dichloromethane. Solvent-rinsing steps 

may be substituted for the final heating step for other 

glassware.

Unless otherwise indicated, prerinse all nonglass 

items that will be in contact with the sample or sample 

extract with the solvent used in the procedural step or with 

pesticide-residue grade acetone.

4.1 Sample storage, dewatering, and percent 

moisture determination

4.1.1 Freezer—upright, capable of storing 100 

or more 1,000-mL wide-mouth jars at –15°C for up to 1 

year.

4.1.2 Centrifuge—with four-place swinging 

bucket rotor and buckets capable of centrifuging 250-mL 

centrifuge bottles at up to 5,000 revolutions per minute; 

International Equipment Co. Model EXD or comparable.

4.1.3 Centrifuge bottles—250-mL capacity 

made of a tetrafluoroethylene-hexafluoropropylene 

copolymer (FEP), with sealing cap assemblies and 

centrifuge bottle adapter.

4.1.4 Analytical balance—top-loading, 

capable of weighing 250 ± 0.1 g.

4.1.5 Drying (or moisture determination) 

balance—capable of moisture determination on a 1.8- to 

2.2-g aliquot of sediment sample to ±0.1 percent moisture; 

Sartorius Corp. Thermo Control Balance Model YTC 

O1L or comparable. 

4.1.6 Glass beakers—borosilicate, 50- and 

400-mL volumes.

4.2 Sediment extraction

4.2.1 Soxhlet apparatus—85-mL extractor 

capacity, with 45/50 standard taper-top joint and 24/40 

standard taper-bottom joint; fitted with a 500-mL roundor flat-bottom flask with a 24/40 standard taper joint and 

water-cooled extractor condenser with 45/50 bottom joint.

4.2.2 Soxhlet extraction sample thimble—

borosilicate glass, 35 x 90 mm, extra-coarse glass frit; 

Kontes, Inc. Model K-586500-0022EC or comparable.

4.2.3 Soxhlet extraction combined steam 

bath/condenser unit—Organomation Associates, Inc. 

Model 13055 ROT-X-TRACT or comparable.

4.2.4 Fixed volume micropipet—10- and 

100-μL; Drummond micropipetor-microdispenser or 

comparable.

4.3 Sediment extract concentration

4.3.1 Kuderna-Danish (K-D) evaporative 

concentrator—500-mL flask, three-ball Snyder column, 

and a custom-designed 10-mL centrifuge receiver tube 

(see 4.3.2), all with 19/22 standard taper joints.

4.3.2 Centrifuge receiver tube—custom made 

by fusing the top of a 10-mL K-D receiver tube to an 8-cm 

long by 1.6-cm outer diameter centrifuge tube, volume 

graduated at 2, 3 and 5 mL, with 19/22 standard female 

taper joint; Allen Scientific Glassblowers, Inc. 

ASG-215-01 or comparable. 

4.3.3 Kuderna-Danish combined steam 

bath/condenser unit—Organomation Associates, Inc. 

Model 120 S-EVAPTM or comparable.

4.3.4 Nitrogen manifold sample 

concentrator—Organomation Associates, Inc. Model 124 

N-EVAPΤΜ or comparable.

4.4 Sediment extract filtration

4.4.1 Centrifuge—International Equipment 

Co. Model HN-SII or comparable.

4.4.2 Syringe—5- or 10-mL gas-tight or 

ground-glass syringe equipped with Luer-Lok® fitting.

4.5 Gel permeation chromatography

4.5.1 Gel permeation chromatography 

system—an automated GPC system consisting of the 

following components from Waters Corp. or comparable:

4.5.1.1 High-performance liquid 

chromatography (HPLC) pump—Model 501.

4.5.1.2 Autosampler—Model 717 with 

2-mL injection loop capacity with tray storage region 

maintained at 20°C.

4.5.1.3 Absorbance detector—Model 

441, with excitation wavelength set at 254 nm. 

4.5.1.4 Data module and integrator—

Model 746.

4.5.1.5 Fraction collector—no model 

number, fitted with in-house built tube holder capable of 

holding thirty-six, 25-mL K-D receiver tubes.

4.5.1.6 HPLC in-line, precolumn filter 

unit—Model WATO84560, with replaceable 0.2-μm 

filters.

4.5.2 Column heater—set at 27.0°C; Jones 

Chromatography Ltd. or comparable.

4.5.3 Nitrogen pressurization system—

consisting of a regulated grade 5 nitrogen source, 

polytetrafluoroethylene (PTFE) tubing, a 23-gage needle, 

and associated metal fittings and Vespel® ferrule for 

connecting the needle to the nitrogen source by the tubing.
Analytical Method 7

4.5.4 Helium sparging system—used for 

deoxygenating the dichloromethane solvent prior to GPC.

4.5.5 HPLC pump priming syringe—25-mL; 

Hamilton Gas-Tight 1,000 Series, Model 82520 or 

comparable.

4.5.6 Balance—capable of weighing to 200 

±0.0001 g; Mettler-Toledo Model AT 200 or comparable.

4.5.7 K-D receiver tube, 25-mL—graduated to 

25 mL, with 19/22 ground-glass stopper. 

4.6 GPC OC fraction solvent exchange and 

reduction

4.6.1 Water bath—Precision Scientific Co. 

Model 82 or equivalent, fitted with a rack capable of 

holding at least eighteen 25-mL receiver tubes.

4.6.2 Micro-Snyder column—three-ball.

4.7 Adsorption chromatography and cleanup

 4.7.1 Nitrogen head-pressure system—an 

eight-column, in-house built system designed to deliver 

nitrogen gas head pressure from 0 to 70 kilopascals (kPa) 

gage pressure and to allow precise and accurate control of 

solvent flow at 1 mL/min through each column at less than 

70 kPa delivery pressure. The system uses eight Norgen 

Model 11-018-146 relieving regulators or comparable, 

fitted with pressure gages, along with associated hardware 

to connect the regulators to the columns, including 

3.2-mm inside diameter (ID) PTFE tubing, shut-off 

valves, tubing fittings, ferrules, and pinch clamps. The 

system also includes a molecular sieve/activated-charcoal 

filter that is used to purify the nitrogen gas, and an 

in-house built eight-position rack for holding the 40-mL 

K-D receiver tubes (see 4.7.3).

4.7.2 Glass alumina/silica adsorption 

chromatography clean-up column—30-cm long by 

10-mm ID fitted with coarse glass frit, PTFE stockcock, 

solvent reservoir top capable of holding at least 60 mL of 

solvent, and fitted with a 28/15 female ball joint for 

connection to the nitrogen head pressure system (4.7.1) by 

a 28/15 male ball joint; Allen Scientific Glassblowers, 

Inc., items ASG-201-01 and ASG-202-01 or comparable.

4.7.3 K-D receiver tube, 40-mL—custommade using a 25-mL K-D receiver tube modified with a 

top reservoir capable of containing 40 mL of solvent, 

graduated at 25, 30, 35, and 40 mL, and has a 19/22 joint; 

Allen Scientific Glassblowers, Inc., item ASG-210-01 or 

comparable.

4.7.4 Bottle-top solvent dispenser—5- or 

10-mL; Brinkmann Dispensette or comparable.

4.7.5 Glass Florisil column—11-cm long by 

5-mm ID with top reservoir capable of containing 15 mL 

of solvent; Allen Scientific Glassblowers, Inc., item 

ASG-MC01 or comparable.

4.8 Fraction concentration

4.8.1 Micropipet—10-μL fixed-volume, 

calibrated; Hamilton Co. Model 80366 or comparable; for 

addition of internal-injection standard solution.

4.9 Gas chromatography/electron-capture 

detection analysis

4.9.1 Gas chromatograph/electron-capture 

detector—Hewlett-Packard 5890 or Perkin-Elmer 

Autosystem, equipped with two electron-capture 

detectors, an autosampler, a split/splitless injector, and a 

computer controller (Perkin-Elmer's Turbochrom®

Client/Server instrument control software and Thru-Put 

System's Target® data review software) or comparable. 

The GC system needs to be suitable for use with single 

injection, dual capillary-column GC analysis.

4.9.2 Syringe—10-μL volume; Hamilton Co. 

Model 80377 for GC autosampler or comparable.

4.10 Instrument calibration and spike standards 

solution preparation

4.10.1 Volumetric flasks—class A, varied 

volumes from 25- to 100-mL.

4.10.2 Micropipets—10- to 250-μL fixed- and 

variable-volume, calibrated.

4.10.3 Syringes—variable volumes from 10- to 

500-μL, calibrated.

4.10.4 Pipets—class A, varied volumes from 

1- to 5-mL.

4.10.5 Disposable pipets—Pyrex®, sterile, pack 

plugged, 1-mL volume, graduated in 1/100.

5. Reagents and Consumable Materials

The reagents and consumable materials required for 

this method, listed as follows, are grouped by the specific 

preparation step or analysis but are not repeated if used in 

more than one part of the method. Specific models and 

sources that were used for the development or 

implementation of this method also are listed, as 

appropriate. 

5.1 Sample storage, dewatering, and percent 

moisture determination

5.1.1 Sample containers—wide-mouth, 1,000 

mL, with PTFE-lined lids.

5.1.2 Weighing boats—disposable, aluminum, 

5.1-cm diameter.

5.1.3 Sodium sulfate—anhydrous, granular, 

reagent grade, bake at 450°C for 8 hours and store at 

150°C in a stoppered, prebaked Erlenmeyer flask until 

used.
8 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

5.2 Sediment extraction

5.2.1 Solvents—dichloromethane and 

methanol, pesticide grade, or higher purity.

5.2.2 Boiling chips—bake at 450°C for 8 

hours. Store in sealed, prebaked glass jar until used.

 5.2.3 Disposable glass capillaries—for the 

10-, 25-, 50-, 100-, 200-, and 250-μL fixed- and 

variable-volume micropipets described in sections 4.2.4 

and 4.10.2. 

5.2.4 OC surrogate solution—contains isodrin, 

nonachlorobiphenyl (PCB-207), and deuterium-labeled 

alpha-hexachlorocyclohexane (alpha-HCH-d6), 

commercially obtained as concentrated solutions in 

hexane; Protocol Analytical Supplies, Inc. or comparable, 

except isodrin, which is commercially obtained as a 

concentrated solution in methanol; Absolute Standards, 

Inc. or comparable. Dilute an aliquot of each solution to a 

final single solution concentration (Ca) of 0.5 ng/μL of 

each OC surrogate in methanol. Other appropriate 

surrogate compounds may be added or substituted into 

this method after demonstrating acceptable method 

performance.

Note: Surrogate and other standard solutions (spike, 

OC internal-injection, calibration, and quality-control 

solutions) typically are prepared in advance but can 

become concentrated. Therefore, prepare all standard 

solutions every 6 months, or sooner if any one of the 

solutions becomes concentrated. Store all standard 

solutions at –15°C in a freezer specified for OC standards 

and free from samples.

5.2.5 Individual OC-pesticide spike 

solution—contains the individual OC pesticides listed in 

table 1, commercially obtained as concentrated solutions 

in hexane or other solvent; Absolute Standards, Inc. or 

comparable. Dilute in hexane an aliquot of each solution 

to an intermediate single solution concentration of 10 

ng/μL of each component. Dilute the intermediate 

solution further to a final solution concentration (Cb) of 

0.5 ng/μL of each individual OC pesticide in methanol. 

Note: Currently (2004), OC surrogate (section 5.2.4) 

and individual OC-pesticide spike solutions (section 

5.2.5) also are used in water extraction methods at the 

NWQL. Consequently, the latter solution contains 

additional (water-method or commercially present) 

compounds (endosulfan II, endosulfan sulfate, endrin 

aldehyde, endrin ketone, delta-HCH, and perthane) that 

are not suitable for this sediment method (Foreman and 

others, 1995, p. 53). The polarity of the methanol solvent 

renders the solutions applicable to the water methods. 

Ideally, n-hexane is the suggested solvent for preparing all 

surrogate and spike (and calibration) solutions to help 

ensure proper compound dissolution, especially of the 

higher molecular-weight OC compounds [see PCB (5.2.6) 

and toxaphene (5.2.7) spike solutions]. Use of some 

higher boiling intermediate polarity solvents (for 

example, toluene or ethyl acetate) in the spike solutions is 

not suggested because of potential fraction 

irreproducibilities during adsorption chromatography.

5.2.6 PCB spike solution—contains PCB 

Aroclor 1242, 1254, and 1260, each commercially 

obtained as concentrated solutions in isooctane; NSI 

Solutions, Inc. or comparable. Dilute an aliquot of each 

solution to a single final solution concentration (Cb) of 25 

ng/μL of each Aroclor in hexane.

5.2.7 Toxaphene spike solution—contains 

toxaphene at a final solution concentration (Cb) of 250 

ng/μL in hexane, prepared by diluting an aliquot of a 

commercially obtained concentrated solution of 

toxaphene in methanol; NSI Solutions, Inc. or 

comparable.

5.2.8 Standard reference materials (SRMs) or 

other quality-assurance (QA) reference materials—any 

SRM consisting of naturally present organochlorine 

compounds, interlaboratory comparison sample, or other 

(spiked) sediment or soil reference material available to 

test the method for recovery of some or all of the method 

compounds may be an appropriate QA material. Spiked 

soil from Environmental Resource Associates—

PriorityPollutnT® Certified Reference Material (CRM), 

catalog number 720—predominately was used in this 

method. An example of a natural material is 

SRM 1941b from The National Institute of Standards 

and Technology.

5.3 Sediment extract concentration

5.3.1 Nitrogen gas—for solvent evaporation, 

grade 5 or equivalent.

5.4 Sample extract filtration

5.4.1 Filters—0.2- and 1.0-μm pore sizes, 

25-mm diameter disposable PTFE membrane syringe 

filters, Gelman Sciences’ Acrodiscä CR or comparable.

5.4.2 Pasteur pipets—14.6- and 22.9-cm-long 

disposable pipets with rubber bulbs. Clean by baking at 

450°C for 8 hours, no solvent rinse.

5.4.3 GPC vials—4-mL, amber glass, with 

open-top screw cap and PTFE-faced silicone rubber 

septum. Clean by baking at 450°C for 8 hours, no solvent 

rinse.

5.5 Gel permeation chromatography

5.5.1 Helium gas—grade 5 or equivalent.

5.5.2 Gel permeation chromatography 

columns—two 30-cm-long by 7.5-mm ID columns 

packed with 5-μm diameter styrene-divinylbenzene resin 
Analytical Method 9

particles having 50-angstrom pore size; Polymer 

Laboratories, Ltd. PL GelTM or comparable. Connect the 

columns in series with a low dead-volume union.

5.5.3 GPC–OC fraction test solution—

contains trans-permethrin, hexachlorobenzene, and 

elemental sulfur each at about a concentration of 20 ng/μL 

in dichloromethane. The components in the GC–OC 

fraction test solution are the same as those used by 

Foreman and others (1995, p. 13). 

Note: Compound trans-permethrin has not been 

tested as a method compound in this method; however, 

trans-permethrin is a method compound in the analytical 

method O-5129-95 (Foreman and others, 1995, p. 5). The 

GPC–OC fraction test solution is shared between these 

two methods.

5.6 GPC fraction concentration and solvent 

exchange

5.6.1 Hexane—pesticide-residue grade or 

higher purity.

5.7 Alumina/silica adsorption chromatography 

cleanup and fractionation

5.7.1 Alumina—Woelm Alumina N Activity I, 

50 to 200 mesh, finer particle size preferred; Scientific 

Adsorbents, Inc., catalog number 02087 or comparable, 

lot number E1002-2 tested (see note in section 7.7). 

5.7.2 Silica gel—Woelm Active, 100 to 200 

mesh, finer particle size preferred; Scientific Adsorbents, 

Inc., catalog number 02747 or comparable, lot number 

K18P3 tested (see note in section 7.7). 

5.7.3 Acetone—pesticide-residue grade or 

higher purity.

5.7.4 Water—ASTM Type I reagent water 

(American Society for Testing and Materials, 2001, p. 

107–109).

5.7.5 Fraction-2 elution solvent for 

alumina/silica cleanup—Prepare a 5-percent acetone and 

95-percent hexane solution by combining 30 mL of 

acetone with 570 mL of hexane.

Note: Carefully prepare the 5-percent acetone and 

95-percent hexane solution. Slight variations from the 

specified mixture composition might result in 

fractionation differences in the alumina/silica 

fractionation process.

5.8 Florisil adsorption chromatography cleanup

5.8.1 Florisil® —adsorbent for gas 

chromatography, 60 to 100 mesh; EM Science, catalog 

number FX0284-1 or comparable, lot number 37300940 

tested. 

5.8.2 Fraction-2 elution solvent for Florisil 

cleanup—Prepare a 1-percent acetone and 99-percent 

hexane solution by combining 10 mL of acetone with 990 

mL of hexane. 

Note: Carefully prepare the 1-percent acetone and 

99-percent hexane solution. Slight variations from the 

specified mixture might result in unwanted interferences 

in the fraction-2 extract.

5.8.3 Glass wool—plug, deactivated 

borosilicate.

5.9 Fraction concentration

5.9.1 Vial—1.8- or 2-mL, amber glass, screw 

top, with hole-top screw caps that have PTFE-faced 

silicone septa, 0.5-mL marked calibration preferred. 

Clean by baking at 450°C for 8 hours, no solvent rinse.

5.9.2 OC internal-injection standard (OCIIS) 

solution—contains tetrachloro-m-xylene and 

decachlorobiphenyl, commercially obtained as a 

concentrated solution of tetrachloro-m-xylene and 

decachlorobiphenyl in acetone; Supelco, Inc. or 

comparable. Dilute the concentrated solution to a final 

concentration of 10,000 pg/μL in hexane. 

5.10 Gas chromatography/electron-capture 

detection analysis

5.10.1 Capillary GC columns:

5.10.1.1 Primary column—fused-silica, 

30-m by 0.25-mm ID, internally coated with a 5-percent 

diphenyl- and 95-percent dimethyl-polysiloxane 

stationary phase having a 0.25-μm film thickness; Restek 

Corp.'s Rtx®-5 or comparable.

5.10.1.2 Secondary column— fusedsilica, 30-m by 0.25-mm ID, internally coated with a 

14-percent cyanopropylphenyl- and 86-percent 

dimethyl-polysiloxane stationary phase having a 0.25-μm 

film thickness; Restek Corp.'s Rtx®-1701 or comparable.

Note: Other column types can be used after 

demonstration of acceptable separation and quantitation 

performance.

5.10.2 Column connector—glass Y-type; 

Restek Corp. catalog number 20405 or comparable.

5.10.3 GC guard column—deactivated, 

uncoated fused-silica tubing, 5-m by 0.32-mm ID; Restek 

Corp. catalog number 10044 or comparable.

5.10.4 GC injection-port liners—glass. Use any 

instrument-specific splitless or direct injection-port liner 

that provides minimal breakdown of endrin, p,p'-DDT, 

and p,p'-methoxychlor following deactivation with a 

silanization reagent, and that provides acceptable peak 

shape and detector response.

5.10.5 Silanizing reagent—for deactivating GC 

injection-port liners; Supelco, Inc. Sylon-CT® solution 

(5-percent dimethyldichlorosilane in toluene) or 

comparable.
10 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

5.11 GC/ECD calibration and quality-control 

solutions

Note: Prior to analysis, add 10 μL of the OCIIS 

solution (5.9.2) to each of the GC/ECD calibration 

standard (5.11.1) and quality-control (5.11.2) solutions 

listed below. The OCIIS solution is added to a known 

volume (for example, 0.5 mL) of solution in a 1.8-mL 

amber vial to allow for compound dilution correction and 

for use of internal-injection standard quantitation (see 

option in section 9.1). Use the same lot number or NWQL 

standard solution number of the OCIIS solution that will 

be added to the sample extracts under section 7.9.5.

5.11.1 GC/ECD calibration standard solutions:

5.11.1.1 Individual OC pesticide 

calibration standard solutions—Prepare working 

calibration standard solutions containing the individual 

OC pesticides listed in table 1 and the surrogates at 1, 2, 

5, 10, 20, 50, 100, and 200 pg/μL in hexane, using 

commercially prepared higher concentration, single- or 

mixed-compound stock solutions; Absolute Standards, 

Inc. or comparable.

5.11.1.2 PCB calibration standard 

solutions—Prepare separate working calibration standard 

solutions for Aroclor 1242, Aroclor 1254, and Aroclor 

1260 at 100 pg/μL in hexane, using commercially 

prepared higher concentration stock solutions; NSI 

Solutions, Inc. or comparable. Aroclor 1016 typically is 

not used as a calibration standard solution because its 

peak pattern of polychlorinated biphenyl congeners is 

nearly identical to Aroclor 1242 (U.S. Geological Survey 

National Water Quality Laboratory Technical 

Memorandum No. 99.10, 1999). See section 9.2 for PCB 

calibration and section 9.2.1 for guidance on PCB peak 

selection.

5.11.1.3 Toxaphene calibration standard 

solution—Prepare a working calibration standard solution 

of toxaphene at 1,000 pg/μL in hexane, using a 

commercially prepared higher concentration stock 

solution; NSI Solutions, Inc. or comparable. See section 

9.2 for toxaphene calibration and section 9.2.2 for 

guidance on toxaphene peak selection.

5.11.2 GC/ECD quality-control (QC) solutions: 

5.11.2.1 Performance evaluation mix 

(PEM)—used to monitor the degradation of problem 

compounds in the GC injection port. The PEM typically 

contains p,p'-DDT (100 pg/μL), endrin (50 pg/μL), and 

p,p'-methoxychlor (250 pg/μL) at a minimum; Supelco, 

Inc. pesticide PEM catalog number 48397 or comparable.

5.11.2.2 Continuing calibration 

verification (CCV) standard solution—used to monitor 

calibration stability. The CCV contains the entire suite of 

individual OC pesticides listed in table 1, typically 

prepared at 20 pg/μL in hexane. The individual OC 

pesticide calibration standard solution at 20 pg/μL 

(5.11.1.1) typically is used for the CCV.

5.11.2.3 Third-party check (TPC) 

solution—an independent, commercially available 

standard solution that is used to verify the accuracy of the 

concentrations of the calibration standard components. 

The TPC contains selected OC pesticides of interest, 

typically with its component concentrations equivalent to 

the CCV. Prepare the TPC solution to a final working 

concentration of 20 pg/μL in hexane, using a 

commercially prepared higher concentration 

multicomponent stock solution; Supelco, Inc. or 

comparable.

5.11.2.4 600-each Aroclor solution—

used to monitor the PCB calibration linearity. Prepare a 

1:1:1 mixture of Aroclor 1242, 1254, and 1260 at 600 

pg/μL for each Aroclor in hexane, using the commercially 

prepared higher concentration stock solutions that were 

used to make the PCB calibration standard solutions 

(5.11.1.2). Additional 1:1:1 mixtures at higher 

concentrations may be used to monitor the PCB 

calibration linearity.

6. Collection, Shipment, and Storage of Sediment 

Samples

6.1 Sampling methods and sample-collection 

equipment—Use sampling methods that will collect 

bottom-sediment and suspended-sediment samples that 

accurately represent organic contaminant compositions 

and concentrations at a given location and time. Use 

sample collection equipment that is free of plastic tubing, 

gaskets, and other parts that might leach interferences, 

sorb contaminants, or abrade and thus contaminate 

sediment samples. Detailed descriptions of samplers used 

to collect representative bottom-sediment samples as well 

as procedures for sampling and postcollection processing 

are contained in the USGS National Field Manual 

(Radtke, 1998), and specifically for the USGS National 

Water-Quality Assessment Program, in Shelton and Capel 

(1994). A method for the collection of a 

suspended-sediment sample on glass-fiber filters, where 

the volume of water pumped is recorded, is described by 

Mahler and others (2001). 

6.2 Cleaning procedures—Wash all samplecollection equipment with phosphate-free detergent, rinse 

with distilled or tap water to remove all traces of 

detergent, and finally rinse with methanol (reagent grade 

or better, ultrapure preferred; contain methanol in a PTFE 
Analytical Method 11

squeeze-bottle). Clean all sample-collection equipment 

before each sample is collected to prevent 

cross-contamination of the samples.

6.3 Sample shipment—Ship samples, contained in 

either 500- or 1,000-mL wide-mouth glass jars 

(precleaned by baking at 450°C for at least 2 hours) with 

PTFE-lined lids or other NWQL-approved containers, on 

ice by overnight carrier to the NWQL as soon as possible 

following collection. Decant excess water to allow space 

in the jars for expansion from freezing.

6.4 Sample storage—Following login at the 

NWQL, samples are stored at –15°C in freezers dedicated 

to OC sediment samples until time of analysis. Sample 

holding times for this method have not been established 

but are expected to be in excess of 6 months (Mudroch 

and MacKnight, 1991, p. 164). Foil may be wrapped 

around the glass jars to prevent breakage and possible 

contamination. After analysis, the remaining sample 

materials are stored at –15°C for a minimum of 3 years; 

however, the sample extracts are stored indefinitely at 

–15°C.

7. Sample Preparation Procedure

Samples are grouped into sets of 16 total samples, 

including QA/QC samples, because two extraction units 

accommodate up to 16 samples. Typically, 13 field 

samples are included in a set, depending on the number of 

laboratory QC samples.

7.1 Sample dewatering and percent dry-weight 

determination

7.1.1 Retrieve samples from the freezer and 

allow to thaw. 

7.1.2 Thoroughly homogenize each sample 

with spatula or scoopula.

7.1.3 Remove about a 20-g wet-weight aliquot 

to an appropriate container for separate determination of 

total carbon and total inorganic carbon (Wershaw and 

others, 1987). Total organic carbon is obtained by 

difference.

7.1.4 Weigh about 150 g of homogenized 

sample into a 250-mL PTFE centrifuge bottle and record 

sediment weight (Wa). Repeat with a second sample, 

identically weighing to ±0.1 g of the first sample for 

balanced centrifuge operation. Repeat for two more 

samples and centrifuge (4.1.2) the two pairs of four 

individual samples for 20 minutes at 2,000 revolutions per 

minute (rpm). CAUTION: Make sure the centrifuge is 

balanced properly prior to operation. Carefully decant the 

clear supernatant water; pipet the supernatant using a 

Pasteur pipet if the sediment pellet is too soft. If the 

supernatant is not clear, repeat centrifugation before 

decanting. Record weight of sediment after decanting 

water (Wb). 

Note: If there is an unpaired sample in the centrifuge, 

add a centrifuge bottle of water of equal weight to 

counterbalance. 

7.1.5 Thoroughly rehomogenize the sediment 

sample in the centrifuge bottle. Using the drying balance 

(4.1.5), determine the percent moisture content to ±0.1 

percent on a 1.8- to 2.2-g aliquot of the centrifuged 

sediment. The wet-weight fraction (fw) is calculated by 

dividing the percent moisture content by 100. Calculate 

the dry-weight fraction of sediment (fd):

 fd = 1 – fw (1)

Option: Set the drying balance (4.1.5) to display 

percent dry weight (Pd) (for example, on the Model YTC 

O1L drying balance, select the setting "100 – 0%" to 

display "Pd" on the balance screen). Record the percent 

dry weight to ±0.1 percent on a 1.8- to 2.2-g aliquot of the 

centrifuged sediment. Calculate the dry-weight fraction of 

sediment (fd) by dividing Pd by 100.

7.1.6 Weigh a maximum of 30 g of wet, 

centrifuged sediment sample into a tared 400-mL beaker. 

Record the weight as actual sample (wet) weight (Ww).

7.1.7 Add 130 g of anhydrous sodium sulfate to 

the beaker. Mix thoroughly, and, if necessary, add 

additional sodium sulfate to ensure that the mixture is dry 

and loose.

7.1.8 For suspended sediment collected in the 

field on burned, glass-microfiber filters, sample 

dewatering and percent dry-weight determinations do not 

apply. On a clean watch glass, cut the filters to 

quarter-inch-wide strips with razor blades rinsed with 

dichloromethane. Transfer the strips to a beaker and tare 

to zero on the top-loading analytical balance (4.1.4). Add 

70 g of anhydrous sodium sulfate to the beaker. Mix 

thoroughly, and, if necessary, add additional sodium 

sulfate to ensure that the mixture is dry and loose, so that 

the strips are not clinging to each other.

7.2 Sediment extraction

7.2.1 Add all of the sediment-sodium sulfate 

mixture (7.1.7 or 7.1.8) to a Soxhlet extraction sample 

thimble (4.2.2). Repeat for all field-sediment samples.

7.2.2 Prepare the following QA/QC samples as 

required, depending on types of analyses to be performed:

7.2.2.1 Reagent blank sample 

(laboratory reagent blank or set blank)—Place 125 g of 

sodium sulfate into an extraction thimble.

7.2.2.2 Reagent OC spike sample 

(laboratory reagent spike or set spike)—Place 125 g of 
12 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

sodium sulfate into an extraction thimble, and spike the 

sodium sulfate with 100 μL (Vb) of individual 

OC-pesticide spike solution (5.2.5), using a calibrated 

micropipet or syringe. The expected final spiked 

concentration for the individual OC pesticides is 

2 μg/kg, assuming a 25-g equivalent dry weight (see 

following second note). Additional set spike solutions: In 

addition to the individual OC-pesticide spike solution, 

spike either 10 μL (Vb) of the PCB spike solution (5.2.6), 

or spike 100 μL (Vb) of the toxaphene spike solution 

(5.2.7) as desired into the set spike. The expected final 

spiked concentration is 10 μg/kg for each PCB Aroclor, or 

1,000 μg/kg for toxaphene, assuming a 25-g equivalent 

dry weight. Preparation of a set spike sample containing 

both the PCB and toxaphene spike solutions generally is 

not used because of the complexity of the PCB and 

toxaphene mixtures.

Note: When possible, implement all new spiking 

standard solutions in one sample set and keep in 

synchrony with new calibration standard solutions to 

avoid undesirable data shifts.

Note: This same laboratory reagent spike (LRS) 

typically is fortified with spiking solutions used for other 

sediment methods, for example, organophosphate 

analysis (Jha and Wydoski, 2003) and polycyclic 

aromatic hydrocarbon (PAH) analysis (Olson and others, 

in press). Compound HCB is currently (2004) a 

component in a PAH spike solution at a final solution 

concentration of 6 ng/μL in dichloromethane. If the LRS 

is fortified with 100 μL of this PAH spike solution in 

addition to the individual OC-pesticide spike solution, 

then the expected final spiked concentration for HCB in 

the LRS is 26 μg/kg—2 μg/kg from the individual 

OC-pesticide spike solution and 24 μg/kg from the PAH 

spike solution, assuming a 25-g equivalent dry weight.

7.2.2.3 Standard reference material 

(SRM) sample—Place 1 to 25 g of appropriate SRM 

(5.2.8) into an extraction thimble; the amount extracted 

will depend on SRM availability, compound 

concentrations relative to the reporting level, and cost. 

Mix in 123 g of anhydrous sodium sulfate for 2 g of SRM 

1941b, for example, to simulate step 7.1.7. (SRMs usually 

do not contain much water so a separate dry-weight 

determination is unnecessary.)

7.2.3 Extract and process the QA/QC samples 

through the remainder of the method exactly as for the 

field-sediment samples.

7.2.4 Place the extraction thimble into a 

Soxhlet apparatus connected to a 500-mL flask containing 

350 mL dichloromethane and 5 to 10 boiling chips.

7.2.5 Add 100 μL (Va) of OC surrogate 

solution (5.2.4) on top of each sample contained in a 

thimble, using a calibrated micropipet or syringe.

7.2.6 Carefully add 25 mL methanol to the top 

of the sample and allow 20 minutes for the solvent to 

percolate through the sample to the thimble frit. This step 

helps to remove any residual moisture not bound by the 

sodium sulfate.

Note: Do not use more than 25 mL of methanol during 

this step. The amount of methanol added must not exceed 

7 percent of the total volume of dichloromethane plus 

methanol used during the extraction (see note in section 

7.3.2).

7.2.7 Attach the Soxhlet apparatus to the 

condenser, adjust coolant flow to 1,500 cubic centimeters 

per minute, and extract the sample at 70°C on the steam 

bath (4.2.3) for at least 12 hours.

7.2.8 Following extraction, cool the extract to 

room temperature, then add about 20 g of anhydrous 

sodium sulfate to the flask and swirl to remove residual 

water. Add additional sodium sulfate as needed to ensure 

water removal. Excessive amounts of water might require 

separation using a 1-L separatory funnel. Seal the flask 

with a ground-glass stopper and store sodium 

sulfate-containing extract in a refrigerator for at least 2 

hours.

7.3 Sediment extract concentration

7.3.1 Transfer the extract (but not the sodium 

sulfate) from the flask to a K-D evaporative concentrator 

(4.3.1) fitted with a 10-mL centrifuge receiver tube (4.3.2) 

containing boiling chips. Rinse the flask three times using 

5- to 10-mL aliquots of dichloromethane and transfer 

these rinses to the K-D concentrator. 

7.3.2 Concentrate the extract to about 4 to 6 mL 

at 70°C using the K-D combined steam bath/condenser 

unit (4.3.3), then remove the extract from the unit and 

allow to cool.

Note: Remove all methanol during this K-D 

concentration step, otherwise the solvent will cause 

problems during the GPC cleanup (7.5). Methanol is 

removed completely only by the formation of an 

azeotrope having a 92.7-percent dichloromethane and 

7.3-percent methanol composition that boils at 37.8°C (at 

101.3 kPa). Therefore, the amount of methanol must not 

exceed 7 percent of the total extract volume of 

dichloromethane plus methanol in the Soxhlet extract 

(7.3.1); otherwise, the desired azeotrope composition will 

not occur during the K-D concentration (see 7.2.6 note).

7.3.3 Further reduce the extract in the receiver 

tube to 1.0 mL using a gentle stream of nitrogen gas 

(4.3.4). Cap tube and store the extract at 4°C until step 7.4.
Analytical Method 13

7.4 Sediment extract filtration

7.4.1 Centrifuge (4.4.1) paired sets of extracts, 

contained in uncapped centrifuge receiver tubes, at 2,150 

rpm for 10 minutes. Centrifugation improves the filtration 

process described in 7.4.2 to 7.4.6.

7.4.2 Weigh a labeled, 4-mL GPC vial with cap 

and septum attached (5.4.3) to ±0.0001 g and record the 

vial weight (Wv).

7.4.3 Attach a 1.0-μm PTFE filter (5.4.1) to a 

5-mL Luer-Lok syringe (4.4.2). Attach a 0.2-μm PTFE 

filter (5.4.1) to the 1.0-μm PTFE filter. Remove the 

syringe plunger and place a tared GPC vial under the 

filter-tip outlet.

7.4.4 Transfer the centrifuged extract to the 

syringe barrel using a Pasteur pipet, taking care not to 

dislodge the centrifuged solids.

7.4.5 Carefully insert the plunger into the 

syringe and pass the extract through the filter into the GPC 

vial. After expelling sample, push air through the filter to 

remove residual extract from the filter.

7.4.6 Rinse the centrifuge receiver tube with 

500 μL dichloromethane, washing down the tube walls 

using the Pasteur pipet. Transfer the rinse (including 

disrupted centrifuged solids) to the syringe barrel using 

the Pasteur pipet. Filter this rinse into the GPC vial as in 

7.4.5.

7.4.7 Repeat step 7.4.6.

7.4.8 The extract volume should be at 2 mL 

with the above additions (steps 7.4.6 and 7.4.7). Using 

dichloromethane, bring extract volume up to 4 mL. Cap 

the GPC vial.

7.4.9 Weigh the extract contained in the capped 

GPC vial to ±0.0001 g and record vial-plus-extract weight 

(WG). Calculate the weight of extract before GPC (W1):

 W1 = WG – Wv (2)

where

WG = weight of GPC vial with cap, septum, and 

extract, in grams; and 

 Wv = weight of empty GPC vial with cap and septum, in grams (7.4.2).

7.4.10 Store the extract at 4°C until step 7.5.

7.5 Gel permeation chromatography

Complete details of GPC operation are beyond 

the scope of this report. Instead, the following procedure 

outlines the steps necessary for GPC instrument 

configuration for elution fractions and subsequent 

cleanup of sample extracts. Consult the appropriate 

instrument manuals for additional details regarding 

general GPC system operation and NWQL standard 

operating procedure MS0024.0 (or subsequent revisions; 

available upon request) for detailed, method-specific GPC 

procedures. The chromatographic conditions are the same 

as those used for similar USGS method O-5129-95 

(Foreman and others, 1995, p. 20–23).

7.5.1 The GPC data system remains turned on 

continuously. Other system components (4.5.1), including 

the pump, autosampler, detector, fraction collector, and 

column heater (4.5.2), are turned on at least 2 hours in 

advance of fraction calibration.

7.5.2 Degas the dichloromethane mobile phase 

with helium for 30 minutes prior to use.

7.5.3 Pump degassed dichloromethane through 

the GPC columns at the mobile phase flow rate of 1 

mL/min for at least 2 hours prior to establishing start and 

end fraction collection times (7.5.7).

Note: Slowly ramp up the flow rate from 0.1 to 1 

mL/min at 0.1-mL/min intervals over a 5-minute period to 

minimize pressure shock to the GPC columns.

7.5.4 Bring the GPC vial containing the extract 

(7.4.10) to room temperature.

7.5.5 The GPC vial headspace of all sample 

extracts and GPC test solutions contained in 4-mL GPC 

vials is pressurized with nitrogen gas prior to beginning a 

GPC autosequence. This pressurization assists the syringe 

in withdrawing the correct aliquots of extract and test 

solutions for injection into the GPC. Pierce the vial 

septum with the pressurization needle (4.5.3), and 

pressurize with 200 kPa nitrogen for 1 minute. 

CAUTION: Do not place the needle into the liquid. Rinse 

the needle with dichloromethane between vial 

pressurizations. 

7.5.6 For OCs, establish GPC system 

cleanliness and baseline stability by injecting a 1,100-μL 

aliquot of fresh pesticide-grade dichloromethane (system 

blank) and monitoring detector response at low 

attenuation (usually at attenuation 8). Fractions typically 

are not collected for GPC system blank analyses. 

7.5.7 Perform GPC fraction calibration. 

Elution times might vary between analyses of a sample set 

because of GPC column aging, the presence of residual 

methanol from sample extraction, and other factors. 

Therefore, prior to beginning a GPC autosequence, 

establish start and end fraction collection times for the 

OCs to allow final configuration of the fraction collector. 

7.5.7.1 Establish OC fraction collection 

times by injecting 1,100 μL of the GPC–OC fraction test 

solution (5.5.3) and monitoring the elution times of the 

peaks at low attenuation. Repeat injections of the 

GPC–OC fraction test solution as necessary to ensure 

chromatographic reproducibility. Fractions typically are 
14 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

not collected for the GPC–OC fraction calibration test 

analyses. An example gel permeation chromatogram 

resulting from the analysis of the GPC–OC fraction test 

solution is shown in figure 2 (from Foreman and 

others,1995, p. 22).

7.5.7.1.1 Set the "start time" on the 

fraction collector for the GPC–OC fraction at least 10 

seconds earlier from the beginning of the transpermethrin peak (the first OC compound that elutes from 

the GPC; see fig. 2).

Note: Large natural substances that are being 

removed from the extract during the GPC step mostly 

elute prior to the method compounds. Therefore, do not 

set the collection "start time" much earlier than about 10 

seconds before the beginning of the trans-permethrin 

peak; otherwise, the natural material may not be 

successfully eliminated from the collected fraction.

7.5.7.1.2 Set the "end time" on the 

fraction collector for the GPC–OC fraction at least 10 

seconds later from the end of the hexachlorobenzene 

(HCB) peak (the last OC compound that elutes from the 

GPC before the sulfur peak; see fig. 2). The HCB peak is 

expected to be at least baseline separated from the sulfur 

peak, otherwise there might be some sulfur detected 

during GC/ECD analysis. Typically, small amounts of 

sulfur carry over into the collected GPC–OC fraction, 

DETECTOR RESPONSE, IN MILLIVOLTS

TIME, IN MINUTES Fraction start at 16.06 minutes trans-Permethrin

Hexachlorobenzene

Fraction end at 25.00 minutes

Sulfur

0 5 10 15 20 25 30

Figure 2. Gel permeation chromatogram of the fraction test solution at attenuation 8 showing the analystdetermined collection start and end times for the organochlorine pesticide fraction (from Foreman and others, 

1995). Chromatographic conditions are listed in the text.

. 
Analytical Method 15

which result in a small sulfur peak in the GC/ECD that 

does not interfere with the determination of any 

compounds (except for selected individual PCB 

congeners). Carryover of larger amounts of sulfur might 

result in a large, broad peak or a severe baseline rise in the 

GC/ECD chromatogram, which might interfere with 

compound determinations. Thus, it is important to 

establish GPC conditions and set up OC fraction 

collection times so that sulfur is eliminated (or at least 

greatly minimized) in the collected GPC–OC fraction.

7.5.8 Perform a GPC automated separation to 

collect the OC fraction. Inject 1,100 μL of the sample 

extract and collect the GPC–OC fraction in a 25-mL K-D 

receiver tube (4.5.7). Use a 30-minute total separation 

time per sample. A suggested GPC autosequence, 

assuming one reagent blank sample, a reagent OC spike 

sample, an SRM sample, 12 field samples, and one field 

sample duplicate or additional field sample, is listed in 

table 2. Repeated injections of the GPC–OC fraction test 

solution and the system blank help to ensure continued 

fraction calibration and system cleanliness.

7.5.9 Reweigh the GPC sample vial with 

original cap and septum to ±0.0001 g as soon as possible 

after injection of the sample or following completion of an 

overnight automated analysis, and record this weight as 

the weight of vial plus extract after GPC injection (WH). 

Calculate the weight of OC extract processed through the 

GPC (W2):

W2 = WG – WH (3)

where

WG = weight of GPC vial with cap, septum, and 

extract before GPC, in grams (7.4.9); and

WH = weight of GPC vial with cap, septum, and 

extract after GPC, in grams.

7.5.10 Cap K-D receiver tube containing the 

GPC–OC fraction and refrigerate until the solvent 

exchange step (7.6).

7.5.11 Replace the septum on the GPC sample 

vial and store the remaining portion of the extract not 

processed through the GPC in a freezer for possible 

reanalysis of an OC fraction, if necessary.

7.6 GPC–OC fraction solvent exchange and 

reduction 

7.6.1 Add 4 mL hexane and two to three small 

boiling chips to the GPC extract (7.5.10), and attach a 

3-ball micro-Snyder column to the top of the 25-mL K-D 

receiver tube.

7.6.2 Slowly introduce the 25-mL K-D receiver 

tube to a water bath (4.6.1) maintained at 70°C, and 

reduce the solvent volume to about 4 mL, or until solvent 

evaporation dramatically decreases. Remove the tube 

from the bath and cool.

7.6.3 Raise bath temperature to 85 to 87°C. 

Add two to three fresh boiling chips and 1 mL hexane to 

the 25-mL K-D receiver tube, vortex, and place into the 

water bath. Reduce solvent volume to 4 mL.

7.6.4 Remove the 25-mL K-D receiver tube 

from water bath and reduce the extract to 1 mL using a 

gentle stream of nitrogen (4.3.4). Cap and store the OC 

sample extract at 4°C until step 7.7.

7.7 Alumina/silica adsorption chromatography 

cleanup and fractionation for OCs

This procedure removes additional unwanted 

interferences and separates method compounds into the 

alumina/silica fractions 1 and 2. The alumina/silica 

fractionation of method compounds in the analyses of a 

limited number of set spikes processed through the 

sample preparation procedure described in this section is 

listed in table 3. 

Table 2. Suggested gel permeation chromatography autosequence.

[OC, organochlorine; GPC, gel permeation chromatography; SRM, Standard 

Reference Material]

Sequence Sample type

 1 System blank (7.5.6) 1

 2 Reagent blank (7.2.2.1)

 3 Reagent OC spike (7.2.2.2)

 4 Sample 1

 5 Sample 2

 6 Sample 3

 7 GPC–OC fraction test solution (5.5.3) 1

 8 System blank 1

 9 Sample 4

10 Sample 5

11 Sample 6

12 Sample 7

13 Sample 8

14 GPC–OC fraction test solution 1

15 System blank 1

16 Sample 9

17 Sample 10

18 Sample 11

19 Sample 12

20 Sample duplicate or additional sample

21 SRM (7.2.2.3)

22 GPC–OC fraction test solution1

23 System blank 1

1Fractions typically not collected for the GPC test solution and system 

blank injections.
16 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

Note: The adsorption chromatography procedure 

used the specific lots of alumina and silica listed in section 

5.7 at the specified levels of sorbent (heat) activation and 

sorbent (water) deactivation (7.7.1 and 7.7.2) for the 

fractionation listed in table 3. Use of different sources of 

sorbents or even different lots from the same source can 

alter the fractionation of method compounds. Ensure that 

sorbent materials are composed primarily of the finer 

particle sizes for acceptable fractionations. Verification of 

fraction recoveries is required prior to routine use of 

sorbent materials for samples and can be conducted using 

column-spike experiments of the method compounds 

solvent exchanged in hexane (Foreman and others, 1995, 

p. 24–26).

 7.7.1 Sorbent (heat) activation

7.7.1.1 Weigh out into a 500-mL 

Erlenmeyer flask two times the total amount of alumina 

(5.7.1) and silica gel (5.7.2) required to process one set of 

samples. 

Suggested amount of alumina = 

2 x (3 g x number of samples)

Suggested amount of silica = 

2 x (5 g x number of samples)

7.7.1.2 Activate the sorbents for at least 

12 hours in an oven at 150°C. Store sorbents in the 150°C 

oven until ready to begin deactivation.

7.7.2 Sorbent (water) deactivation

Table 3. Alumina/silica fractionation and mean percent recovery of method compounds from the 

analyses of three to seven set spikes processed through the entire analytical procedure. 

[±, plus or minus; --, not detected] 

Mean recovery ± standard deviation 

Compound1

Fraction 12

(percent) 

Fraction 23

(percent) 

Aldrin 62 ± 10 -- 

cis-Chlordane -- 63 ± 5 

trans-Chlordane -- 63 ± 6 

p,p'-DDD -- 61 ± 8 

p,p'-DDE 75 ± 11 8 ± 6 

p,p'-DDT -- 61 ± 8 

Dieldrin -- 64 ± 6 

Endosulfan I -- 53 ± 7 

Endrin -- 71 ± 10 

Heptachlor 54 ± 13 -- 

Heptachlor epoxide -- 62 ± 6 

Hexachlorobenzene 51 ± 8 -- 

alpha-Hexachlorocyclohexane -- 52 ± 8 

beta-Hexachlorocyclohexane -- 68 ± 8 

gamma-Hexachlorocyclohexane -- 57 ± 7 

p,p'-Methoxychlor -- 78 ± 13 

Mirex 67 ± 11 -- 

trans-Nonachlor -- 66 ± 6 

PCB Aroclor 1016/1242 75 ± 12 -- 

PCB Aroclor 1254 94 ± 20 -- 

PCB Aroclor 1260 94 ± 15 -- 

Toxaphene (technical) -- 70 ± 5 

Surrogates 

alpha-HCH-d6

 -- 76 ± 5 

Isodrin 67 ± 10 -- 

PCB-207 87 ± 24 3 ± 1 

1

Individual pesticides were spiked at 50 nanograms per column, PCB Aroclors at 250 nanograms per column, and 

toxaphene at 5 micrograms per column. 2

Fraction 1 is 30 milliliters (mL) of hexane. The number of observations (n) for the fraction-1 compounds was 7, except for 

hexachlorobenzene (n=5). 3

Fraction 2 is 35 mL of 5-percent acetone and 95-percent hexane. The number of observations (n) for the fraction-2 

compounds was 7, except for p,p'-DDE (n=3), and PCB-207 (n=5).
Analytical Method 17

7.7.2.1 Following activation, place the 

unstoppered flasks in a desiccator and allow the sorbents 

to cool to room temperature.

7.7.2.2 Sorbents are deactivated on a 

weight-to-weight basis using ultrapure water. Alumina is 

8.5-percent deactivated, and silica gel is 2-percent 

deactivated. For example, if 100 g of 8.5-percent 

deactivated alumina is desired, weigh 91.5 g of alumina 

into a 500-mL Erlenmeyer flask on the analytical balance 

(4.1.4) and add 8.5 g water using a Pasteur pipet. 

Immediately cap the flask with ground-glass stopper and 

vigorously shake by hand for 10 minutes. 

Note: Minimize contact of the sorbent to ambient air 

because the sorbents rapidly adsorb air moisture that can 

affect the level of deactivation. 

Note: Unused deactivated sorbents may be reused at 

a later time; simply reactivate the unused portion at 150°C 

(7.7.1).

7.7.2.3. Place flasks on a mechanical 

shaker for 2 hours to equilibrate. Secure the stopper of 

each flask with a rubber band wrapped around the stopper 

and the shaker clamp.

Note: Fractionation could be affected if a flask is 

fractured while on the mechanical shaker. If breakage 

occurs, repeat steps 7.7.1 and 7.7.2 for the sorbent. 

7.7.2.4. Store the flasks in a desiccator 

until ready to use.

7.7.3 Dry pack the chromatography columns in 

the following order: 

Note: Open the stopcock prior to packing the 

column, especially before adding solvent (7.7.4). This 

procedure minimizes back-pressure problems that disrupt 

the packing during solvent addition.

7.7.3.1 Add about 1 cm of sodium sulfate 

(5.1.3) to the chromatography column (4.7.2). (The 

sodium sulfate helps prevent clogging of the column frit 

by silica fines.)

7.7.3.2 Add 3.0 g of 2-percent 

deactivated silica gel. Assist the packing step by gently 

tapping the column above the sorbent layer.

7.7.3.3 Overlay with 5.0 g of 8.5-percent 

deactivated alumina. Gently tap the column above the 

sorbent layer to facilitate packing.

7.7.3.4 Add about 1 cm of sodium sulfate 

to the top of the packing.

7.7.4 Using the solvent dispenser, immediately 

add 40 mL hexane to the column. Collect the hexane 

prerinse in a 50-mL beaker. 

Note: Carefully add all solvents down the side of the 

column wall so as not to disturb the packing.

7.7.5 Attach a ball joint to the column and 

apply sufficient nitrogen gas pressure to pass the hexane 

rinse though the column in about 5 minutes. This helps 

drive out air and pack the sorbent. Take the solvent layer 

just into the top sodium sulfate layer; close stopcock.

CAUTION: At no time after wetting the column 

packing is the solvent level to fall below the top sodium 

sulfate layer and into the sorbents. If it does so prior to the 

addition of the sample extract (7.7.9), discard the column 

packing and repack with new deactivated sorbent.

7.7.6 Add another 10 mL hexane. Option: If 

30 mL of hexane is added instead of 10 mL here, the 

packed columns can sit unused, with stopcock closed and 

ball joint attached, for as many as 4 hours.

7.7.7 Pass the final hexane prerinse through at 

a flow rate of 2 to 5 mL/min based on packing, prerinsing, 

and running of simultaneous columns. When about 2 to 3 

mL of hexane prerinse remain, stop nitrogen pressure, and 

maintain solvent flow comparable to gravity flow (1 

mL/min) until the hexane goes just into the top sodium 

sulfate layer; close stopcock. 

7.7.8 Discard the prerinse and position a clean, 

hexane-rinsed 40-mL K-D receiver tube (4.7.3) labeled 

"fraction 1" (F1) at the column outlet.

7.7.9 Vortex the sample extract in the 25-mL 

K-D receiver tube (7.6.4), then carefully add the sample 

extract to the column head using a 22.9-cm Pasteur pipet. 

Position the pipet just above the top of the sodium sulfate 

layer and introduce the extract onto the sodium sulfate. Do 

not disturb the packing. 

Note: At the time of sample addition, the sample 

must be in a completely nonpolar solvent (for example, 

hexane) and at a volume ranging from 0.5 (minimum) to 

1.5 mL (maximum). The presence of residual 

dichloromethane or other "polar" solvent will produce 

undesirable and irreproducible compound separations. 

Consequently, dichloromethane or other "polar" solvent 

must be completely removed from the extract prior to 

adsorption chromatography.

7.7.10 Open stopcock and allow the sample to 

drop just into the top sodium sulfate layer; close stopcock.

Note: With GPC cleanup, the extracts generally are 

clean enough that application of nitrogen pressure during 

this and subsequent steps is not necessary. However, 

some sediment extracts might require application of slight 

nitrogen pressure to maintain adequate solvent flow; only 

use sufficient pressure to achieve previously unobstructed 

gravity-like flow rates (1 mL/min for hexane).

7.7.11 Rinse the 25-mL K-D receiver tube with 

1 mL hexane, then carefully pipet the solvent onto the 
18 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

column. Open stopcock and allow the rinse to drop just 

into the top sodium sulfate layer; close stopcock.

7.7.12 Repeat step 7.7.11. (The extract and two 

1-mL rinses of the 25-mL K-D receiver tube are now 

loaded onto the column.)

7.7.13 Carefully add 27 mL of hexane down the 

inside wall of the column (do not disturb the packing), cap 

the ball joint, open the stopcock, and collect solvent into 

the F1 receiver tube until the hexane just reaches the top 

sodium sulfate layer; close stopcock. The total volume of 

F1 is 30 mL.

7.7.14 Replace the F1 receiver tube with 

another clean, hexane-rinsed 40-mL K-D receiver tube 

labeled "fraction 2" (F2) at the column outlet.

7.7.15 Carefully add 35 mL (5 mL seven times) 

of the 5-percent acetone and 95-percent hexane mixture 

(see 5.7.5 note) down the inside wall of the column, cap 

the ball joint, open the stopcock, and collect the solvent 

into the F2 receiver tube until the solvent just reaches the 

top of the sodium sulfate layer; close stopcock. The total 

volume of F2 is 35 mL. 

7.7.16 Cap and store the F1 and F2 extracts at 

4°C until step 7.9 and step 7.8, respectively.

7.7.17 Remove remaining solvent from used 

columns using 35-kPa nitrogen pressure; the dried 

packing is easily discharged from the column and 

discarded.

7.8 Fraction-2 solvent reduction and Florisil 

adsorption chromatography cleanup for OCs

7.8.1 Fraction-2 reduction

7.8.1.1 Attach a 3-ball micro-Snyder 

column to the top of the 40-mL K-D receiver tube 

containing the F2 extract (7.7.15) and several small 

boiling chips.

7.8.1.2 Place the F2 receiver tube into a 

water bath (4.6.1) maintained at 85 to 87°C, and reduce 

the solvent volume to 4 mL.

7.8.1.3 Remove the F2 receiver tube 

from the water bath and reduce the F2 extract to 1 mL 

using a gentle stream of nitrogen (4.3.4). Cap and store the 

F2 extract at 4°C until step 7.8.2.

7.8.2 Florisil adsorption chromatography 

cleanup

7.8.2.1 Sorbent (heat) activation

7.8.2.1.1 Weigh into separate 

500-mL Erlenmeyer flasks two times the total amount of 

Florisil required to process one set of samples. 

Suggested amount of Florisil = 

2 x (0.5 g x number of samples)

7.8.2.1.2 Activate the sorbent for 

at least 24 hours in an oven at 150°C. Store the Florisil 

sorbent at 150°C until ready to use.

7.8.2.2 Dry pack the Florisil columns in 

the following order:

7.8.2.2.1 Insert a small plug of 

glass wool into the narrow end of the glass Florisil column 

(4.7.5).

7.8.2.2.2 Add about 0.5 g of 

activated Florisil cooled to room temperature in a 

desiccator. 

7.8.2.2.3 Overlay 1 cm of 

anhydrous sodium sulfate to the top of the packing. 

7.8.2.3 Prerinse the column by adding 

5 mL of hexane. Collect the hexane prerinse in a 50-mL 

beaker. 

CAUTION: At no time after wetting the column 

packing is the solvent level to fall below the top sodium 

sulfate layer and into the sorbent.

7.8.2.4 Discard the prerinse and position 

a clean, hexane-rinsed 40-mL K-D receiver tube (4.7.3) 

labeled "fraction 2" (F2) at the column outlet.

7.8.2.5 Vortex the F2 extract in the F2 

receiver tube (7.8.1.3), then carefully add the F2 extract to 

the column head, using a Pasteur pipet. Do not disturb the 

packing.

7.8.2.6 Allow the extract to drop just into 

the top sodium sulfate layer.

 7.8.2.7 Rinse the F2 receiver tube 

(7.8.2.5) with 1 mL of 1-percent acetone and 99-percent 

hexane solution (5.8.2) and carefully pipet the rinse onto 

the column. Allow the solution to drop just below the top 

sodium sulfate layer. 

7.8.2.8 Repeat step 7.8.2.7. (The extract 

and two 1-mL rinses of the F2 receiver tube are now 

loaded onto the column.)

7.8.2.9 Add 17 mL of the 1-percent 

acetone and 99-percent hexane solution down the inside 

wall of the column, and collect the solvent into the 40-mL 

K-D receiver tube labeled "fraction 2" positioned at the 

column outlet (7.8.2.4). The total volume of F2 is now 

20 mL.

7.8.2.10 Cap and store the F2 extract at 

4°C until step 7.9.

7.9 Fraction concentration for OCs

7.9.1 Add two small boiling chips to the F2 

extract (7.8.2.9), attach a 3-ball micro-Snyder column to 

the top of the K-D receiver tube, place the tube in a 80°C 

water bath, and reduce the solvent volume to 4 mL. 

Remove the tube from the bath and cool.
Analytical Method 19

7.9.2 Raise water bath to 85 to 87°C. Add one 

small boiling chip to the K-D receiver tube, vortex, and 

place into the water bath. Reduce the solvent volume to no 

less than 1 mL, or until solvent evaporation dramatically 

decreases. Remove the tube from the bath and cool.

7.9.3 Further reduce the fraction to 0.5 mL 

using a gentle stream of nitrogen (4.3.4). Record the final 

extract volume (VE) of the fraction.

7.9.4 Carefully transfer the fraction to a 1.8-mL 

amber vial (5.9.1), using a Pasteur pipet. 

7.9.5 Add 10 μL of OCIIS (5.9.2) to the 

fraction in the vial, using a micropipet (4.8.1). Cap the vial 

and vortex. Mark on the vial the level of the extract and 

store at 4°C until GC/ECD analysis (see section 8).

Note: Exactly match the lot number or NWQL 

standard solution number of the OCIIS solution to that 

added in the calibration and quality-control solutions in 

section 5.11.

7.9.6 Repeat steps 7.9.2 through 7.9.5 for the 

F1 extract (7.7.13), which requires the higher water bath 

temperature.

8. Gas Chromatography/Electron-Capture 

Detection Analysis 

8.1 Setup—Analyze the sample extracts by gas 

chromatography with electron-capture detection 

(GC/ECD) using a dual capillary-column system (4.9.1) 

equipped with an autosampler, one split/splitless injection 

port (operated in the splitless mode), a 5-m section of 

deactivated, uncoated guard column (5.10.3), a Y-type 

column connector (5.10.2) to connect the guard column to 

the primary (5.10.1.1) and secondary (5.10.1.2) capillary 

columns, and two electron-capture detectors. Use a 

computer system to control the autosampler, GC 

operational conditions, and to acquire and process 

responses from the dual detectors. Complete details of 

GC/ECD operation are beyond the scope of this report. 

The following procedure outlines the suggested GC 

conditions and autosequence used in this method. Consult 

the appropriate instrument manuals for additional details 

regarding general GC/ECD system operation.

8.2 Suggested GC operational conditions—Use 

any operational conditions that provide acceptable levels 

of compound separation, identification, quantitation, bias, 

and precision.

8.2.1 Injection port temperature: 220°C.

8.2.2 Splitless injection split time: 60 seconds. 

Split flow rate: about 50 mL/min. Septum purge flow rate: 

about 3 mL/min.

8.2.3 Sample injection volume: 2 μL.

8.2.4 Oven temperature program: initial 

temperature 60°C (hold for 1 minute).

Ramp 1—30°C/min to 180°C

Ramp 2—1°C/min to 210°C

Ramp 3—4°C/min to 280°C, hold for 10 to 30 

minutes to allow for sufficient column bake-out.

Note: The GC temperature program is 42 minutes 

shorter than that used in USGS method O-5129-95 

(Foreman and others, 1995), which, for that method, was 

lengthened to allow for improved separation of PCB 

congeners and the additional analytes.

8.2.5 Electron-capture detector temperature: 

350°C (Hewlett-Packard); 380°C (Perkin-Elmer).

8.2.6 Carrier gas: helium at about 131 kPa 

pressure at the head of the column for a linear velocity of 

about 24 cm/s at 280°C.

8.2.7 Makeup gas: nitrogen at about 40 

mL/min flow rate.

8.3 Determine compound identifications—

Typical peak separations for the individual OC pesticides 

and the PCB Aroclors in analyzing fraction 1 of a 

laboratory reagent spike (LRS) using the GC operating 

conditions in section 8.2 are shown in figures 3 and 4 on 

the Rtx-5 and Rtx-1701 columns, respectively. Peak 

separations on the Rtx-5 and Rtx-1701 columns for 

fraction 2 of the same LRS are shown in figures 5 and 6, 

respectively. Toxaphene patterns obtained on the Rtx-5 

and Rtx-1701 columns from the analysis of the calibration 

standard solution, made using a stock standard solution 

from NSI Solution, Inc., are shown in figures 7and 8, 

respectively. Peak identifications and retention times for 

the method compounds are listed in table 4.

Note: Because of differences in GC columns, even 

from the same manufacturer, and chromatographic 

conditions between instruments, the elution profiles of the 

method compounds will vary. Therefore, it is critical to 

verify instrument-specific compound retention times. Use 

single-component standards to verify retention times of 

closely, or coeluting, compounds. Verify retention times 

following any GC maintenance procedures applied to the 

guard or capillary columns to improve chromatography.

8.4 Coelution problems—Coelutions among 

compounds in the individual OC pesticide calibration 

solutions (5.11.1.1) were observed on the GC/ECD 

instrument using the chromatographic conditions 

described in 8.2. Those compound coelutions that were 

commonly observed are listed in table 5. Coelution 

conditions require special identification (8.5.2) and 

calibration (9.1) considerations.
Figure 3. Gas chromatogram showing electron-capture detection of a fraction-1 extract from a laboratory reagent spike fortified with 50 nanogra

organochlorine pesticides and 250 nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-5 column. Compound identifications and retelisted in table 4. Chromatographic conditions are given in the text.

Tetrachlorom-xylene

Aroclor 1242 peak 1

Aroclor 1242 peak 2

Aroclor 1254 peak 1

Aroclor 1254 peak 2

Aroclor 1254 peak 3

Aroclor 1254 peak 4

Aroclor 1254 peak 5

Aroclor 1260 peak 1

Aroclor 1260 peak 2

Aroclor 1260 peak 3

Aroclor 1260 peak 4

Aroclor 1260 peak 5

Aroclor 1242 peak 3

Aroclor 1242 peak 4

Aroclor 1242 peak 5

Heptachlor

Aldrin

Isodrin

Dieldrin/p,p'-DDE

Mirex

HCB

Nonachlorobiphenyl

10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 

1.62.02.42.83.23.64.04.44.85.25.66.06.46.87.27.6

RESPONSE IN MICROVOLTS, Y (x10

5

)

RETENTION TIME, IN MINUTES
Figure 4. Gas chromatogram showing electron-capture detection of a fraction-1 extract from a laboratory reagent spike fortified with 50 nanog

organochlorine pesticides and 250 nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-1701 column. Compound identifications anlisted in table 4. Chromatographic conditions are given in the text.

Tetrachlorom-xylene

HCB Aroclor 1242 peak 1

Aroclor 1242 peak 2

Aroclor 1254 peak 1

Aroclor 1254 peak 2

Aroclor 1254 peak 3

Aroclor 1254 peak 4

Aroclor 1254 peak 5

Aroclor 1260 peak 1

Aroclor 1260 peak 2

Aroclor 1260 peak 3

Aroclor 1260 peak 4

Aroclor 1260 peak 5

Aroclor 1242 peak 3

Aroclor 1242 peak 4

Aroclor 1242 peak 5

Heptachlor

Aldrin

Isodrin

p,p'-DDE

Mirex

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 

0.180.240.300.360.420.480.540.600.660.720.780.840.900.961.021.08

RESPONSE IN MICROVOLTS, Y (x10

6

)

RETENTION TIME, IN MINUTES
Figure 5. Gas chromatogram showing electron-capture detection of a fraction-2 extract from a laboratory reagent spike fortified with 50 nanog

organochlorine pesticides and 250 nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-5 column. Compound identifications and relisted in table 4. Chromatographic conditions are given in the text. 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

RESPONSE IN MICROVOLTS, Y (x10

6

)

RETENTION TIME, IN MINUTES

Tetrachlorom-xylene

alpha-HCHd6 alpha-HCH

beta-HCH

gamma-HCH (Lindane)

Heptachlor epoxide

trans-Chlordane

trans-Nonachlor

cis-Chlordane

Endosulfan I

Dieldrin/p,p'-DDE

p,p'-DDD

p,p'-DDT

p,p'-Methoxychlor

Endrin

Nonachlorobiphenyl
Figure 6. Gas chromatogram showing electron-capture detection of a fraction-2 extract from a laboratory reagent spike fortified with 50 nanog

organochlorine pesticides and 250 nanograms of PCB Aroclors 1242, 1254, and 1260 on a Restek Rtx-1701 column. Compound identifications anlisted in table 4. Chromatographic conditions are given in the text.

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

RESPONSE IN MICROVOLTS, Y (x10

6

)

RETENTION TIME, IN MINUTES

10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 4

8

Tetrachlorom-xylene

alpha-HCHd6 alpha-HCH

beta-HCH

gamma-HCH (Lindane)

Heptachlor epoxide

trans-Chlordane

trans-Nonachlor

cis-Chlordane

Endosulfan I

Dieldrin

p,p'-DDD

p,p'-DDT

p,p'

Endrin

-Methoxychlor
Figure 7. Gas chromatogram showing electron-capture detection a 1,000-picograms-per-microliter toxaphene calibration standard solution pre

Solutions, Inc. stock solution on a Restek Rtx-5 column. Retention times of 10 selected peaks are listed in table 4. Chromatographic conditions 

10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 

2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 5.2 5.6 6.0 6.4 6.8 7.2 7.6 8.0

RESPONSE IN MICROVOLTS, Y (x10

5

)

RETENTION TIME, IN MINUTES

Tetrachlorom-xylene

Toxaphene peak 1

Toxaphene peak 2

Toxaphene peak 3

Toxaphene peak 4

Toxaphene peak 5

Toxaphene peak 6

Toxaphene peak 7

Toxaphene peak 8

Toxaphene peak 9

Toxaphene peak 10
Figure 8. Gas chromatogram showing electron-capture detection of a 1,000-picograms-per-microliter toxaphene calibration standard solution 

Solutions, Inc. stock solution on a Restek Rtx-1701 column. Retention times of 10 selected peaks are listed in table 4. Chromatographic conditio.

10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 

0.240.300.360.420.480.540.600.660.720.780.840.900.961.021.081.141.20

RESPONSE IN MICROVOLTS, Y (x10

6

)

RETENTION TIME, IN MINUTES

Tetrachlorom-xylene

Toxaphene peak 1

Toxaphene peak 2

Toxaphene peak 3

Toxaphene peak 4

Toxaphene peak 5

Toxaphene peak 6

Toxaphene peak 7

Toxaphene peak 8

Toxaphene peak 9

Toxaphene peak 10
26 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

Table 4. Retention times of individual organochlorine method compounds, selected peaks for PCB Aroclor 1016/1242, 1254, 1260, and toxaphene on the 

Rtx-5 and Rtx 1701 columns from figures 3 through 8 example gas chromatograms (listed in Rtx-5 retention-time order).

[±, plus or minus]

Compound

Retention time (minutes) Suggested width of retention time 

window (minute) Rtx-5 Rtx-1701

Tetrachloro-m-xylene1 10.65 9.77 ± 0.05

alpha-HCH-d6 

2 11.98 13.42 ± .05

PCB Aroclor 1016/1242 peak 1 12.05 11.93 ± .07

alpha-HCH 12.14 13.60 ± .05

Hexachlorobenzene (HCB) 12.49 11.57 ± .05

beta-HCH 13.32 3,4 22.28 ± .05

gamma-HCH (Lindane) 13.60 15.96 ± .05

PCB Aroclor 1016/1242 peak 2 14.97 13.90 ± .07

PCB Aroclor 1016/1242 peak 3 16.48 15.02 ± .07

PCB Aroclor 1016/1242 peak 4 16.57 15.34 ± .07

PCB Aroclor 1016/1242 peak 5 17.21 16.66 ± .07

Heptachlor 17.57 17.24 ± .07

Aldrin 20.04 19.12 ± .07

Isodrin2 22.41 3,4 22.41 ± .07

Heptachlor epoxide 23.41 25.34 ± .07

trans-Chlordane 25.62 28.92 ± .07

Endosulfan I 26.82 27.97 ± .07

PCB Aroclor 1254 peak 1 27.05 27.22 ± .07

cis-Chlordane 27.14 29.62 ± .07

trans-Nonachlor 27.61 30.00 ± .07

PCB Aroclor 1254 peak 2 28.78 29.76 ± .07

Dieldrin 3,4 29.62 32.05 ± .07

p,p'-DDE 3,4 29.62 31.06 ± .07

PCB Aroclor 1254 peak 3 30.46 30.65 ± .07

Toxaphene peak 1 31.42 35.42 ± .07

Endrin 32.00 34.43 ± .07

PCB Aroclor 1254 peak 4 33.49 34.97 ± .07

p,p'-DDD 34.62 40.12 ± .07

Toxaphene peak 2 36.25 37.60 ± .07

PCB Aroclor 1254 peak 5 36.65 38.86 ± .07

p,p'-DDT 38.73 41.40 ± .07

Toxaphene peak 3 39.09 38.09 ± .07

Toxaphene peak 4 40.80 38.46 ± .07

Toxaphene peak 5 41.42 40.60 ± .07

Toxaphene peak 6 42.60 41.93 ± .07

PCB Aroclor 1260 peak 1 42.62 40.69 ± .07

Toxaphene peak 7 42.81 42.14 ± .07

PCB Aroclor 1260 peak 2 43.05 43.12 ± .07

p,p'-Methoxychlor 43.98 46.37 ± .07

Toxaphene peak 8 44.42 44.73 ± .07

PCB Aroclor 1260 peak 3 44.76 43.52 ± .07

Toxaphene peak 9 45.46 45.29 ± .07

Mirex 46.25 44.05 ± .07

Toxaphene peak 10 46.78 47.00 ± .07

PCB Aroclor 1260 peak 4 47.36 45.24 ± .07

PCB Aroclor 1260 peak 5 47.70 47.34 ± .07

PCB-207 2 49.94 49.06 ± .1

Decachlorobiphenyl1 54.57 53.48 ± .1

1

Organochlorine internal-injection standard compound.

2

Surrogate compound.

3Compound largely or completely coelutes with another individual organochlorine compound on this column.

4

Compound is separated (baseline resolved) in similar U.S. Geological Survey method O-5129-95 (Foreman and others, 1995) using the gas chromatograph temperature program described.
Analytical Method 27

Note: Improved separations of some compounds 

may be achieved with temperature program 

modifications, but usually at the expense of other method 

compound separations (Foreman and others, 1995, p. 30). 

8.5 Positive identification of a compound—A 

compound is positively identified if it is found within the 

expected retention time window (see 8.5.1) on both 

columns and in similar amounts (see 8.5.2).

8.5.1 Retention time window—The size of the 

retention time window is compound dependent. For 

single-component compounds and selected congener 

peaks from the multicomponent compounds (PCBs and 

toxaphene, see sections 9.2.1 and 9.2.2), set the center of 

the retention time window using the average of at least 

three retention time determinations from the initial 

calibration of a GC/ECD autosequence (see table 6). 

Suggested widths of the retention time windows are listed 

in table 4. A ±0.1-minute width is suggested for the 

selected congener peaks used to quantitate PCBs and 

toxaphene. Alternatively, window widths can be set at 

plus or minus three times the standard deviation of the 

average retention time computed from injections of the 

calibration standard solutions.

8.5.2 Detection of a compound in similar 

amounts—Amounts typically within 30-percent relative 

percent difference (RPD) on both columns help to 

confirm compound identification. The RPD is calculated 

as follows:

where

 C1 and C2 are the compound concentrations from each 

column, or, in the case of duplicate samples (see 

13.5), the compound concentrations in the duplicate 

and original analyses.

Compound coelutions, and, especially, sedimentmatrix-specific GC interference problems, are commonly 

observed in this method, often resulting in RPDs greater 

than 30 percent. Under these conditions, an analyst's 

judgment is required for compound identification, and the 

data are qualified appropriately (raising the reporting 

level or labeling the concentration as estimated with an 

"E" code, for example). When applicable, consider the 

presence of other "family" compounds in the sample to 

assist in compound identification. (For example, if 

considering trans-chlordane, expect the detection of 

cis-chlordane in the sample; if considering p,p'-DDT, 

expect the detection of p,p'-DDD and p,p'-DDE in the 

sample.) Compounds that show coelution with another 

method compound (or interference from an unknown 

compound) on one column are quantified on the other 

column where no coelution (or interference) problem 

occurs. Typically, the compound concentration is 

reported from the column with the lower calibrated 

response (see 12.1). The compound still must be found 

within the expected retention time window on both 

columns for positive identification.

8.6 GC/ECD autosequence—A suggested 

sequence for an automated analysis of OC fractions F1 

and F2 in one analysis for 16 samples is listed in table 6. 

Note: Synchronize new calibration standard and 

quality-control solutions with new spiking standard 

solutions in a sample set to avoid undesirable data shifts.

9. Gas Chromatography/Electron-Capture Detection 

Compound Calibration

9.1 Multipoint external standard calibration for 

single-component compounds—For calibrating 

individual OC pesticides, multipoint curves are produced 

by analyzing the 1- to 200-pg/μL calibration standard 

solutions (5.11.1.1). Plot the GC/ECD peak area for the 

compound (Ac) in relation to the mass (in picograms) of 

the compound in each of the 1- to 200-pg/μL calibration 

standards injected. Calculate a calibration curve for this 

plot using a simple linear regression model {of the form Y

= m x X + b; where X = (Cc x V1)}

where

Ac = GC/ECD peak area of the compound in the 

calibration standard solution;

m = compound-specific slope, in area per picogram;

Cc = concentration of the compound in the calibration standard solution, in picograms per 

microliter (5.11.1.1); 

Table 5. Compound coelutions commonly observed on the gas 

chromatography capillary columns used in this analytical method.

Column Rtx-5 Column Rtx-1701

Dieldrin and p,p'-DDE beta-HCH and isodrin1

1Isodrin is a surrogate compound. 

RPD C1 C2 –

C1 + C2 ( ) ⁄ 2 = ------------------------------ × 100

Ac m Cc × V1 = × ( ) + b

(4)

(5)
28 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

V1 = volume of calibration standard solution 

injected into the GC/ECD, in microliters 

(8.2.3); and

b = compound-specific y-intercept, in area.

Note: Other regression models may be used as 

appropriate.

If compounds coelute on both analytical columns, 

calibrate as described by using one or more separate 

standard solutions that contain only one of the coeluting 

compounds. Identification and quantification of 

compounds that coelute both columns require careful 

consideration by the analyst. In most cases, the compound 

that coelutes on both columns will need to be reported as 

either an upper-limit value, as a raised reporting-limit 

value, or not reported because of coeluting interference 

(Foreman and others, 1995, p. 37).

Note: None of the compounds tested by this method 

coeluted on both analytical columns. The corrective 

action described in 9.1 is presented in case the 

complication occurs, for example, in replacing of a 

consumable material or in evaluating additional 

compounds by this method.

Option: The internal-injection standard method of 

calibration and compound quantitation may be used by 

selecting either one of the OCIIS compounds, tetrachlorom-xylene or decachlorobiphenyl, provided that there are 

no chromatographic interferences with these compounds 

in the standard solutions and samples. Details regarding 

internal-injection standard quantitation are not presented 

here but are provided in USEPA method 8000B (U.S. 

Environmental Protection Agency, 1996). (In the external 

standard calibration method, the OCIIS compounds are 

used as retention time markers to assist in compound 

identification.)

9.2 External standard calibration for PCBs and 

toxaphene—One-point calibrations are produced for PCB 

Aroclor 1016/1242, 1254, 1260, and toxaphene. Compute 

the response factor (RF) by summing the GC/ECD peak 

areas of five representative peaks for the Aroclor, or 10 

representative peaks for toxaphene, and dividing by the 

concentration of the PCB or toxaphene calibration 

standard solution. Representative peaks are selected on 

the basis of adequate peak intensity and separation from 

other congener, method compound, and interfering peaks 

(see sections 9.2.1 and 9.2.2). Calculate the response 

factor using

 Sum of selected peak areas in the PCB or

toxaphene calibration standard solutions

RF = __________________________________________ 

where 

RF = Aroclor-specific or toxaphene response factor, 

in area per picogram;

Cc = concentration of the PCB calibration standard 

solution (5.11.1.2) or toxaphene calibration 

standard solution (5.11.1.3), in picograms 

per microliter; and

V1 = volume of the calibration standard solution 

injected into the GC/ECD, in microliters 

(8.2.3).

Table 6. Suggested gas chromatography/electron-capture

detection autosequence. 

[pg/μgL, picrogram per microliter, F1, fraction1; F2, fraction 2]

Standard or sample type

Hexane gas chromatograph injection blank

Performance evaluation mix (PEM) (5.11.2.1)

Organochlorine pesticide calibration standard solutions at 1, 2, 

5, 10, 20, 50, 100, and 200 pg/μL or other appropriate concentration (5.11.1.1)

Third-party check solution (5.11.2.3)

Multicomponent polychlorinated biphenyl (PCB) Aroclor 1242 

calibration standard solution (F1) at 100 pg/μL or other 

appropriate concentration (5.11.1.2)

Multicomponent PCB Aroclor 1254 calibration standard solution (F1) at 100 pg/μL or other appropriate concentration 

(5.11.1.2)

Multicomponent PCB Aroclor 1260 calibration standard solution (F1) at 100 pg/μL or other appropriate concentration 

(5.11.1.2)

Polychlorinated biphenyl 600 solution (F1) at 1,800 pg/μL total 

PCBs (5.11.2.4) 

Multicomponent toxaphene calibration standard solution (F2) at 

1,000 pg/μL (5.11.1.3) 

Reagent blank sample (7.2.2.1)

Reagent organochlorine spike sample (7.2.2.2)

Standard reference material sample (7.2.2.3)

Continuing calibration verification (CCV) standard solution 

(5.11.2.2)

PEM

Six field samples (F1s)

CCV

PEM

Seven field samples (F1s)

CCV

PEM

Six field samples (F2s)

CCV

PEM

Cc × V

1

(6)
Analytical Method 29

9.2.1 PCB peak selection—Carefully compare 

the PCB gas chromatographic profiles of each Aroclor 

with the profiles of the individual OC pesticide calibration 

standard solutions and field samples. Select PCB peaks 

that show minimal interference problems in the standard 

and samples. This comparison may result in the selection 

of different PCB peaks for different field samples, 

depending on matrix-specific interference or other 

chromatographic separation problems. The peaks selected 

for calculating the response factor for each Aroclor 

(equation 6) must be the same peaks that are selected in 

calculating the peak-area response amount on the 

analytical instrument (equation 9, section 10) for final 

quantitation of PCBs in a given field sample (equation 10, 

section 10).

9.2.1.1 Selection of PCB peaks on the 

Rtx-5 column—Figure 3 shows an example gas 

chromatogram on the Rtx-5 column for a fraction-1 

extract of a laboratory reagent spike fortified with 

individual OC-pesticide spike solution (5.2.5) and PCB 

spike solution (5.2.6) containing a 1:1:1 mix of PCB 

Aroclor 1242, 1254, and 1260. Suggested selection of 

peaks from a mixed PCB standard solution on the Rtx-5 

column and tentative identification of congeners present 

in the suggested peaks from the stationary phase are 

described in USGS method O-5129-95 (Foreman and 

others, 1995, p. 41), referencing publications by Mullin 

and others (1984), Eganhouse and others (1989), and 

Schulz and others (1989). More recently, Frame (1997a, 

1997b) has reported coelution profiles on the Rtx-5 

stationary phase (and other phases) for all 209 PCB 

congeners and 6 Aroclors. Typically PCB peaks in the 

method described in this report are selected from the 

individual gas chromatogram of the PCB calibration 

standard solution for each Aroclor (5.11.1.2) on the 

column to facilitate the identification of Aroclors. Peaks 

selected from the Rtx-5 column for the Aroclor 

determinations presented in this report are listed in table 4.

9.2.1.2 Selection of PCB peaks on the 

Rtx-1701 column—Figure 4 shows an example gas 

chromatogram on the Rtx-1701 column for a fraction-1 

extract of a laboratory reagent spike fortified with 

individual OC pesticide spike solution (5.2.5) and PCB 

spike solution (5.2.6) containing a 1:1:1 mix of PCB 

Aroclor 1242, 1254, and 1260. Typically PCB peaks in 

the method described in this report are selected from the 

individual gas chromatogram of the PCB calibration 

standard solution for each Aroclor (5.11.1.2) on the 

column to facilitate the identification of Aroclors. Peaks 

selected from the Rtx-1701 column for the Aroclor 

determinations presented in this report are listed in table 4.

9.2.2 Toxaphene peak selection—Select 10 

peaks for toxaphene using the approach described for 

PCBs (9.2.1). Toxaphene peak selection is left to an 

analyst's discretion after careful comparison of sample 

and toxaphene standard gas chromatographic patterns.

Note: GC/ECD analysis of toxaphene in 

bed-sediment samples typically is much more 

complicated than the analysis of PCBs. Toxaphene 

reportedly contains hundreds of compounds (Jansson and 

Wideqvist, 1983; Saleh, 1991; Vetter and Luckas, 1995), 

and, unlike PCBs, has not been well characterized 

(Swackhamer and others, 1987; Bidleman and others, 

1993). Avoid selecting toxaphene peaks that might 

coelute with other commonly observed method 

compounds (especially p,p'-DDT, p,p'-DDD, dieldrin, 

cis- and trans-chlordane, and trans-nonachlor). 

Toxaphene also undergoes considerable environmental 

weathering, primarily because of differential 

environmental partitioning as a result of the widely 

varying physicochemical properties of its components. 

Additionally, many toxaphene components are 

susceptible to reductive dechlorination reactions in anoxic 

bed sediments. These environmental weathering 

processes (especially the dechlorination process) often 

produce an enrichment in earlier eluting components, 

resulting in chromatographic patterns that are not 

characteristic of the chromatogram obtained with the 

technical toxaphene calibration standard solution 

(Williams and Bidleman, 1978; Harder and others, 1983). 

In this method, determination of toxaphene relies on 

visual pattern recognition of toxaphene in a sample 

chromatogram relative to the toxaphene standard solution. 

Therefore, an analyst may not readily recognize heavily 

altered toxaphene in a field sample by GC/ECD. The 

presence of toxaphene can be confirmed using GC with 

electron-capture negative ionization mass spectrometry or 

electron-impact ionization combined with high-resolution 

mass spectrometry (for example, see Swackhamer and 

others, 1987; Patton and others, 1989; Lau and others, 

1996; Glassmeyer and others, 1999). Because of its 

complexity in pattern recognition, toxaphene 

concentration is qualified as estimated with an "E" code in 

this method.

10. Calculation of Results

10.1 Calculate the dry weight of sediment extracted 

(Ws), in grams:

Ws Ww f = × d (7)
30 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

where

Ww = wet weight of sediment, in grams (7.1.6); and

fd = dry-weight fraction of sediment (calculated 

from equation 1).

10.2 Calculate the peak-area response amounts in the 

sample extract and concentrations of compounds in the 

sample.

10.2.1 Calculation of peak-area response 

amount 

10.2.1.1 For individual OC compounds, 

use the compound-specific regression parameters m and b 

(equation 5) from the calibration curve to calculate the 

peak-area response amount (RA) of identified compound 

in the analyzed sample extract:

where 

RA = peak-area response amount (or on-column 

amount) of identified compound in the sample extract, in picograms per microliter; 

As = GC/ECD peak area of the identified compound in the sample extract; and

V2 = volume of the sample extract injected into the 

GC/ECD, in microliters (8.2.3).

10.2.1.2 For PCBs and toxaphene, sum 

the GC/ECD peak areas of the selected peaks eluting in 

the range of the particular Aroclor or toxaphene in the 

sample that match the retention times of those peaks 

selected from the chromatogram of the PCB or toxaphene 

calibration standard solution (see sections 9.2.1 and 9.2.2 

for PCB and toxaphene peak selections, respectively). 

Calculate the peak-area response amount (RA) of the 

Aroclor or toxaphene analyzed in the sample extract by 

using

 Sum of selected peak areas for the 

Aroclor or toxaphene in the sample extract RA = ___________________________________________ 

where

RA = peak-area response amount (or on-column 

amount) of the Aroclor or toxaphene in the 

sample extract, in picograms per microliter;

 RF = Aroclor-specific or toxaphene response factor, 

in area per picogram (calculated from equation 6); and

V2 = volume of the sample extract injected into the 

GC/ECD, in microliters (8.2.3).

10.2.2 Calculate the concentration (Cs) of the 

identified compound in the sample by using 

where

Cs = determined concentration of compound in the 

sample, in micrograms per kilogram (equivalent 

to nanograms per gram); or, for suspended sediment of known sample volume filtered, in micrograms per liter (equivalent to nanograms per 

milliliter);

RA = peak-area response amount of compound in the sample extract, in nanograms per milliliter (equivalent 

to picograms per microliter) (calculated from 

equation 8 or 9, as appropriate);

VE = final volume of sample extract prior to GC/ECD 

analysis, in milliliters (7.9.3);

W1 = weight of extract before GPC, in grams (calculated 

from equation 2); 

W2 = weight of OC extract processed through the GPC, 

in grams (calculated from equation 3); and

Ws = dry weight of sample extracted, in grams (calculated 

from equation 7). 

Note: For the reagent blank and reagent OC spike 

samples, assume a dry weight (Ws) of 25 g in equation 10. 

Note: For suspended-sediment samples submitted on 

filters, substitute the volume of sample filtered in the field 

(Vf

), in milliliters, for Ws in equation 10.

 10.3 Calculate the percent recovery of the 

surrogate compounds in each sample by using

where

Ra = recovery of surrogate in sample, in percent;

Cs = determined concentration of surrogate in sample, in nanograms per gram (equivalent to 

micrograms per kilogram) or, for suspended 

sediment, in nanograms per milliliter (equivalent to micrograms per liter) (calculated from 

equation 10);

RA

As ( –b )

m V × 2

= ----------------- (8)

RF V × 2

Cs

RA VE W1 W2 × × ( ⁄ )

Ws

= ----------------------------------------------------

Ra

Cs

(Ca × Va ) Ws ⁄ = ------------------------------------- 100 ×

 (9)

 

(11)

(10)
Analytical Method 31

Ca = concentration of compound in the OC surrogate solution added to the sample, in nanograms per microliter (5.2.4);

Va = volume of OC surrogate solution added to the 

sample, in microliters (7.2.5); and

Ws = dry weight of sample extracted, in grams 

(calculated from equation 7).

Note: For the reagent blank and reagent OC spike 

samples, assume a dry weight (Ws) of 25 g in equation 10. 

Note: For suspended-sediment samples submitted on 

filters, substitute the volume of sample filtered in the field 

(Vf

), in milliliters, for Ws in equation 10.

10.4 Calculate the percent recovery of compounds in 

reagent OC spike sample by using 

where 

Rb = recovery of spiked compound in the reagent 

OC spike sample, in percent;

Cs = determined concentration of compound in 

reagent OC spike sample, in nanograms per 

gram (calculated from equation 10);

Cb = concentration of individual compound in the 

OC-pesticide spike solution added to sample, in nanograms per microliter (5.2.5); 

concentration of Aroclor in the PCB spike 

solution added to sample, in nanograms per 

microliter (5.2.6); or concentration of toxaphene spike solution added to sample, in 

nanograms per microliter (5.2.7);

Vb = volume of individual OC-pesticide, PCB, or 

toxaphene spike solution added to the sample, in microliters (7.2.2.2); and

Ws = specified method dry weight, 25 g. 

Note: The assumed sample weight (Ws) of the matrix 

used for preparing the reagent spike sample is equivalent 

in equations 10 and 12.

10.5 Calculate the percent degradation of p,p'-DDT 

and endrin on the GC/ECD from injections of the PEM 

(5.11.2.1) by using the following equations:

Percent p,p'–DDT loss =

and

Percent endrin loss =

where

Acompound = peak area of given compound in the 

PEM chromatogram.

10.6 Compute the CCV percent difference.

10.6.1 Calculate the peak-area response amount 

for each compound in the CCV standard solution (RAccv) 

by using equation 8.

10.6.2 Calculate the percent difference between 

the determined and expected CCV concentrations by 

using

where 

RAccv = calculated peak-area response amount of 

compound in the CCV standard solution, in picograms per microliter (from 

10.6.1); and

Ce = expected concentration of compound in 

the CCV standard solution, in picograms per microliter (5.11.2.2).

10.7 Calculate the percent moisture of the 

uncentrifuged sediment (7.1.4) by using

Percent moisture in uncentrifuged sediment =

where

Wa = weight of sample-water mixture prior to 

 centrifugation, in grams (from 7.1.4); 

Wb = weight of centrifuged sample-water mixture 

after decanting water, in grams (from 7.1.4); 

and

fw = wet-weight fraction of centrifuged and 

decanted sediment (calculated in 7.1.5).

Note: The percent moisture of the uncentrifuged 

sediment is not required for calculation of the compound 

concentrations in micrograms per kilogram dry-weight 

sediment. Users can calculate the percent moisture value 

of the compound concentrations in micrograms per 

kilogram wet-weight sediment for comparison with 

historical data that are normalized to wet-weight of 

Rb

Cs

Cb ( × ) Vb Ws ⁄ = ------------------------------------ 100 ×

Ap p, ′– DDD + Ap p, ′– DDE

Ap p, ′– DDT + + Ap p, ′– DDD Ap p, ′– DDE

------------------------------------------------------------------------------------------ 100 × (13)

Aendrin aldehyde + Aendrin ketone

Aendrin + + Aendrin aldehyde Aendrin ketone

---------------------------------------------------------------------------------------------- 100 ×

RAccv Ce –

Ce

CCV percent difference = ------------------------- 100 ×

Wa Wb – ) Wb ( fw ( + × )

Wa

-------------------------------------------------------- 100 × (l6)

(12)

(15)

(14)
32 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

sediment. The percent moisture of the uncentrifuged 

sediment calculated in equation 16 does not include the 

amount of water decanted from the sediment sample prior 

to sample freezing for storage (6.4). Concentrations 

normalized to dry weight are more accurate than those 

normalized to wet weight because of the highly variable 

amounts of water used to process the sediment samples on 

site. 

10.8 Compute the revised reporting levels for a 

suspended-sediment sample submitted on filters if known 

sample volume filtered is less than 63 L.

10.8.1 Calculate the lowest 

suspended-sediment revised reporting level for the 

compound of lowest reporting level (for example, 

gamma-HCH in table 9, section 14) based on a 2-pg/μL 

calibration by using

where

SSRLlowest = lowest suspended-sediment revised 

reporting level, in micrograms per 

liter (equivalent to picograms per 

microliter) for compound of lowest 

reporting level (see table 9, section 

14);

 2 = lowest calibrator for determining concentration of compounds in a suspended-sediment sample of known 

sample volume filtered, in picograms 

per microliter;

VE = final volume of sample extract just prior 

to GC/ECD, in milliliters (7.9.3);

W1 = weight of extract before GPC, in grams 

(calculated from equation 2); 

W2 = weight of OC extract processed through 

the GC, in grams (calculated from 

equation 3); and

Vf = volume of sample filtered in the field, in 

milliliters. 

 

10.8.2 Calculate the suspended-sediment 

revised reporting levels for all other compounds by using

 where

SSRLother = compound-specific suspended-sediment revised reporting level, in 

micrograms per liter, for compound 

of other-than-lowest reporting level 

(see table 9, section 14);

SSRLlowest = lowest suspended-sediment revised 

reporting level, in micrograms per 

liter (calculated from equation 17); 

IRLother = compound-specific interim reporting 

level (IRL), in micrograms per kilogram, for compound of other-thanlowest IRL (see table 9, section 14); 

and

IRLlowest = lowest interim reporting level, in 

micrograms per kilogram (see table 

9, section 14).

Note: A laboratory reporting level (Childress and 

others, 1999) may be substituted for the IRL when 

established.

11. Gas Chromatography/Electron-Capture Detection 

Performance

11.1 GC/ECD instrument system—For GC/ECD 

instrumental analysis, performance of the gas 

chromatograph is indicated by peak shape, the efficiency 

of separation for closely eluting compound pairs, and by 

the variation in detector response over time for 

compounds from calibration and CCV standard solutions. 

Daily assessments of these characteristics are made 

relative to the performance obtained with new capillary 

columns and GC inlet liner, and by using freshly prepared 

standard calibration solutions. When peak shape, 

separation efficiency, or response fail to meet 

performance criteria, instrument maintenance is required. 

Routine maintenance includes replacement of the 

injection port liner (5.10.4) and septum. If this does not 

result in acceptable performance, short lengths (0.3 m) of 

the guard column (5.10.3) are removed first to try to 

restore the chromatographic performance. Continued 

poor chromatographic performance might require 

replacement of the entire guard column and Y-connector 

(5.10.2), and removal of short lengths (0.3 to 1 m) of the 

capillary columns (5.10.1), or complete replacement of 

the capillary columns. Continued decrease or instability in 

response factor also can be caused by instability in 

electron-capture detector performance. Refer to the 

appropriate instrument manual for operating the detector 

system and controlling signal output. If the 

aforementioned steps do not improve response factors, 

then electron-capture detector maintenance might be 

required.

11.2 GC/ECD performance criteria

11.2.1 Calibration standards—Calibration 

standards containing the individual component 

SSRLlowest

2 VE W1 W2 × × ( ⁄ )

Vf

= ------------------------------------------------

SSRLother

SSRLlowest × IRLother

IRLlowest

= ----------------------------------------------------

(17)

(18)
Analytical Method 33

compounds should bracket the compound concentrations 

expected in the sample extracts. Stock solutions used in 

preparing the individual OC pesticide calibration standard 

solutions (5.11.1.1) were obtained from Absolute 

Standards, Inc. Prepare calibration standards at eight 

different concentrations (1, 2, 5, 10, 20, 50, 100, and 200 

pg/μL) containing the individual OC pesticide and 

surrogate compounds by adding known volumes of stock 

standard solutions to a volumetric flask. Dilute to volume 

with hexane. Typically multicomponent compounds—the 

PCB Aroclors and toxaphene—each have one calibration 

standard solution. Stock solutions used in preparing the 

PCB and toxaphene calibration standard solutions 

(5.11.1.2, and 5.11.1.3, respectively) were obtained from 

NSI Solutions, Inc. Prepare the PCB calibration standard 

solutions at 100 pg/μL for each Aroclor and the toxaphene 

calibration standard solution at 1,000 pg/μL by adding a 

known volume of stock standard solution to the respective 

volumetric flask of each multicomponent compound. 

Dilute to volume with hexane.

11.2.2 Calibration curve—Starting with the 

lowest concentration, each calibration standard solution 

(5.11.1) is analyzed in the sample set prior to analyzing 

the samples (table 6), and the response (peak area) is 

tabulated in relation to the concentration in the standard. 

This method is an external standard quantitation method 

and uses multipoint external standard calibration for 

individual component compounds. PCB Aroclors and 

toxaphene are one-point, external standard calibrations. 

External standard calibrations for all the OC compounds 

are described in section 9. The multipoint calibration 

curve contains a minimum of four to eight concentrations. 

For multipoint calibrations, use the results to prepare a 

calibration curve by a linear regression model (equation 

5) for each compound. If a linear calibration relation 

cannot be achieved, especially at low concentrations, then 

a quadratic calibration may be used. The calibration curve 

should have a correlation coefficient (r2) equal to or 

greater than 0.995. The determined concentration for each 

individual OC pesticide and surrogate is expected to be 

within ±20 percent of the known concentration for each 

compound on at least one column, especially at the 

2-pg/μL calibration level, before proceeding with sample 

quantitation. If the instrument does not meet these 

calibration criteria, correct the problem by maintaining 

the GC or by preparing new calibration standards and 

reanalyzing the new standards. 

11.2.3 Third-party check (TPC)—One TPC 

solution (5.11.2.3) is analyzed in each GC/ECD 

autosequence after the calibration standards to verify the 

calibration curve. The original sources for the compounds 

in the TPC solution are independent of those used in 

creating the calibration curve. The determined 

concentration for all compounds in the TPC solution is 

expected to be within ±30 percent of the known 

concentration. If the determined concentrations fall 

outside of the acceptance criteria, reanalysis of the 

samples might be required. The source of the problem 

needs to be identified and resolved before continuing 

analyses. Maintain the instrument as necessary, or prepare 

a new TPC solution or new calibration standard solutions 

if one or the other is suspect. Report SRM and field 

sample data as suspect with an estimated (E-code) 

qualifier for the compounds that fail recovery in the TPC.

11.2.4 Performance evaluation mix (PEM)—

The PEM (5.11.2.1) is injected at the beginning of a 

GC/ECD autosequence and is injected after each 

continuing calibration verification in the autosequence 

(table 6) to monitor the degradation of labile compounds 

(especially p,p'-DDT and endrin) in the GC injection 

system. The calculated percent loss of p,p'-DDT (equation 

13) or endrin (equation 14) is not to exceed 20 percent on 

more than one column. If losses exceed 20 percent, 

replace the injection port liner with a clean, deactivated 

liner (5.10.4), followed by other GC maintenance (11.1) 

as required to reduce the losses to acceptable levels. 

Note: Foreman and Gates (1997) reported that 

substantial sample-matrix specific degradation (or signal 

enhancement) beyond that indicated by the PEM can 

occur for p,p'-DDT (and presumably other thermolabile 

compounds), even though the PEM is within acceptance 

criteria.

11.2.5 Continuing calibration verification 

(CCV)—CCV standard solutions (5.11.2.2) are injected 

typically every six to seven samples throughout the 

GC/ECD autosequence (table 6) to monitor the calibration 

of the GC/ECD for bias and precision. The calculated 

CCV percent difference (equation 15) is expected to be 

within ±30 percent for each compound on at least one 

column. If CCV percent differences are outside of the 

acceptance criteria, reanalysis of the affected field 

samples might be required, especially if there is a loss of 

detection capability. Maintain the GC/ECD as needed to 

return to acceptable CCV performance. If CCV recoveries 

continue to fall outside of the acceptance criteria, then 

qualify the sample data as suspect with an estimated 

(E-code) qualifier for compounds affected by the CCV 

recoveries for the samples bracketed by the CCV (M.R. 

Burkhardt and T.J. Maloney, U.S. Geological Survey, 

written commun., 1998).

Note: There are no CCVs for the multicomponent 

compounds—PCBs and toxaphene. PCBs use the 
34 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

600-each Aroclor solution (5.11.2.4) to check linearity 

(11.2.6) beyond the calibration at 100 pg/μL (5.11.1.2). 

Toxaphene, on the other hand, is a permanently E-coded 

compound in this method, with its estimated final 

concentration in the sample quantitated from the 

one-point calibration at 1,000 pg/μL (5.11.1.3).

11.2.6 PCB calibration linearity check—The 

600-each Aroclor solution (5.11.2.4) is injected after the 

PCB calibration standard solutions in the GC/ECD 

autosequence (table 6). The recovered concentration for 

each Aroclor is expected to be within ±20 percent of the 

concentration in the solution on at least one column for 

linearity. If the acceptance criteria are not met, reanalysis 

of the affected field samples might be required. If the 

recovered concentration for the Aroclor continues to fall 

outside of the acceptance criteria, then qualify the sample 

data as suspect with an estimated (E-code) qualifier for 

the Aroclor affected by the recovery in the solution.

11.3 Other GC/ECD requirements—Quantitate 

sample concentrations within the range of calibration 

standard concentrations. Sample concentrations that 

exceed the high concentration calibration standard are 

diluted in hexane to within the calibration range.

12. Reporting of Results

12.1 Column-dependent quantitation—The 

quantitative value reported is column dependent. Report 

the lower concentration produced by the two GC columns 

unless it has been demonstrated by the calibration, CCV, 

TPC, or PEM standards that one of the columns is causing 

a method compound to degrade or otherwise produce 

errant results. Column-specific quantitation also will be 

necessary for those compounds that exhibit coelution or 

other apparent interference on one GC column (see 8.5.2). 

If a compound is split between fractions, add the lower 

concentration or the preferential column concentration of 

fractions 1 and 2 and report the sum.

12.2 Reporting units—Compound concentrations in 

field samples and in the SRM sample are reported in 

micrograms per kilogram for dry-weighted sediment 

(equation 10). Compound concentrations for 

suspended-sediment samples collected on filters are 

reported in micrograms per liter for known volume 

filtered (equation 10). Compounds quantified in the 

reagent blank sample (laboratory reagent blank, or LRB) 

are reported in micrograms per kilogram, assuming a 25-g 

sample dry weight (equation 10). Surrogate data for all 

sample types are reported in percent recovered (equation 

11). Data for the reagent OC spike sample (laboratory 

reagent spike, or LRS) are reported in percent recovered, 

assuming a 25-g sample dry weight (equation 12). 

12.3 Reporting levels—Estimates of method 

detection limits (MDLs) using the procedures outlined by 

the U.S. Environmental Protection Agency (1997) have 

been calculated for this method and are discussed further 

in sections 14.8 and 14.9 and are listed in table 8 (see 

section 14). Interim reporting levels (IRLs) for this 

method are listed in table 9 (see section 14) for sediment 

samples on a dry-weight basis and for 

suspended-sediment samples collected on filters. The 

IRLs in micrograms per kilogram are set at 2 times the 

estimated MDL for all compounds except toxaphene. The 

IRL for toxaphene is arbitrarily set in this method at 200 

micrograms per kilogram to minimize false positive 

detections through dual GC column confirmation. For 

samples with dry weights <12.5 g, raise the reporting 

levels by a factor of (25/Ws) above the IRLs based on a 

25-g equivalent dry weight of the sample, where Ws is the 

dry weight of the sample extract, in grams (calculated 

from equation 7). For suspended-sediment samples of 

known sample volume filtered, revise the IRLs 

accordingly (10.8). IRLs may be replaced by laboratory 

reporting levels based on long-term method detection 

levels described by Childress and others (1999).

12.4 Reporting data results—Report surrogate and 

LRS recoveries to three significant figures. Compounds 

not detected are reported as less than the IRL or as a raised 

reporting level (12.3). Report concentrations in the SRM, 

LRB, and field samples to three significant figures. If the 

peak-area response amount (equation 8 or 9, as 

appropriate) in the sample extract is greater than the 

highest calibration standard, or in the case of PCBs, is 

greater than the 1:1:1 Aroclor mixture (5.11.2.4) used in 

checking PCB calibration linearity, dilute the sample 

extract to bring the peak-area response amount within 

calibration range, and report the final concentration. If the 

peak-area response amount for a positively identified 

Aroclor in the extract is less than the one-point calibration 

at 100 μg/kg, report the final concentration of the Aroclor 

in the sample with the estimated (E-code) qualifier for the 

final concentration at or greater than the estimated MDL. 

Reporting less than the estimated MDL in this method is 

not appropriate because the method is not 

"information-rich" (Childress and others, 1999). Use the 

E-code qualifier for a data result if the recovery in the 

TPC or LRS is outside the acceptance criteria (sections 

11.2.3 and 13.3, respectively). The E-code qualifier also is 

used when the CCV is outside of expected limits and the 

set is not reanalyzed, or any time the analyst suspects that 

the quantitation might not be accurate. The method 
Analytical Method 35

compound p,p'-DDE in the presence of PCB Aroclor 1254 

or Aroclor 1260 interference (see 14.10) is reported with 

the E-code qualifier in the LRB, LRS, SRM (if PCBs are 

a component), and in the field samples if resolution on the 

GC/ECD instrument cannot be resolved with the GC 

conditions described in section 8.2. Likewise, PCB 

Aroclor 1254 and Aroclor 1260 may be reported with the 

E-code qualifier in the presence of p,p'-DDE interference. 

Method compounds p,p'-methoxychlor and toxaphene are 

reported permanently with the E-code qualifier in this 

method.

13. Laboratory Quality Assurance/Quality Control

Laboratory extraction samples are prepared in 

sample sets, each consisting of a laboratory reagent blank 

(LRB), a laboratory reagent spike (LRS), a standard 

reference material (SRM), and 13 field samples, which 

may include a laboratory duplicate. The aspects of the 

analytical process that the QA/QC samples monitor are 

described in this section.

Note: See Pirkey and Glodt (1998) for additional 

QA/QC practices that can be used with this method.

13.1 Surrogates—Three surrogate compounds are 

added at the time of extraction to all sample types to 

monitor recoveries from the sample preparation process. 

Surrogate recoveries are used to measure gross 

sample-processing problems and matrix effects. The 

surrogate recoveries are not used to correct concentrations 

of other method compounds because the surrogates do not 

mimic chemically all of the method compounds. The 

surrogates were selected to indicate problems with the 

alumina/silica adsorption chromatography part of the 

method. The fraction-1 surrogates are isodrin and 

PCB-207; the fraction-2 surrogate is alpha-HCH-d6

(table 3). The surrogates selected are not expected to be 

present in the environment. Surrogate observations that 

indicate errors in the alumina/silica adsorption 

chromatography procedure are listed in table 7. There 

have been no known F2 surrogate observations indicative 

of Florisil adsorption chromatography errors. As 

previously noted (section 7.7), changes in the source or lot 

of sorbent used can result in fractionation differences. 

Severe matrix effects can result in erroneous 

fractionations. In any case, report the sum of the recovery 

in fractions 1 and 2 for the surrogate compound. Statistical 

process control techniques (preferrably nonparametric 

statistics) are used to establish control limits for surrogate 

recoveries (M.R. Burkhardt and T.J. Maloney, U.S. 

Geological Survey, written commun., 1998). When 

surrogate recovery for a sample is greater than the upper 

control limits or less than the lower control limits and 

fractionation is accounted for, check the following: (1) 

calculations, to locate possible mathematical errors; (2) 

spike, calibration, and surrogate solutions for degradation 

and concentration, and notes pertaining to the solution 

preparation; (3) contamination, which usually produces 

positive bias; and (4) instrument performance (section 

11.1). If those steps do not reveal the cause of the 

problem, reanalyze the extract. If the problem can be 

identified as a correctable laboratory failure, take 

corrective action for surrogate recovery (M.R. Burkhardt 

and T.J. Maloney, U.S. Geological Survey, written 

Table 7. Surrogate observations that indicate alumina/silica adsorption chromatography errors.

[F1, fraction 1; F2, fraction 2]

Surrogate observation Possible reason for error

alpha-HCH-d6 in F1 Not all dichloromethane removed from extract before adsorption chromatography step.

Collected more than 30 milliliters of hexane for F1.

Used 5-percent acetone in hexane instead of hexane for F1.

Incorrect sorbent activation or deactivation.

Isodrin and PCB-207 in F2 Collected less than 30 milliliters of hexane for F1. 

Incorrect sorbent activation or deactivation.

No alpha-HCH-d6 in F1 or F2 Collected less than 35 milliliters of 5-percent acetone/hexane for F2.

Used hexane instead of 5-percent acetone in hexane for F2.

F2 elution solvent contains less than 5-percent acetone.

Incorrect sorbent activation or deactivation.

No surrogates in F1 or F2 Forgot to add surrogates to sample.

Incorrect sorbent activation or deactivation.
36 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

commun., 1998) before continuing analysis. If the sample 

extract reanalysis meets the surrogate recovery 

acceptance criteria, then report the sample results 

appropriately using the reanalyzed extract data. If sample 

extract continues to fail the recovery acceptance criteria, 

report, if necessary, the sample data as suspect with an 

estimated (E-code) qualifier for only those analytes 

affected by the surrogate recovery, or do not report the 

data if the unacceptable surrogate recovery might indicate 

that the sample results are unsalvageable (M.R. Burkhardt 

and T.J. Maloney, U.S. Geological Survey, written 

commun., 1998).

13.2 Laboratory reagent blank (LRB)—The LRB is 

a sodium sulfate sample of 25-g equivalent dry weight 

fortified with method surrogates only. One LRB is 

included with each sample set and is carried through the 

entire sample preparation and analytical procedure. The 

LRB is used to monitor for impurities and contamination 

from reagents and glassware. Concentration of each 

analyte (a nonsurrogate method compound) is expected to 

be undetected, or less than the IRL. If the LRB contains 

interfering peaks that would prevent the determination of 

one or more compounds, then determine the source of the 

contamination and eliminate the interferences before 

continuing sample processing and analysis. If the 

interferences cannot be eliminated, then qualify the 

sample data as suspect with an estimated (E-code) 

qualifier for only those analytes affected by the blank 

contribution (M.R. Burkhardt and T.J. Maloney, U.S. 

Geological Survey, written commun., 1998).

13.3 Laboratory reagent spike (LRS)—The LRS 

(7.2.2.2) is a sodium sulfate sample of 25-g equivalent dry 

weight fortified with individual OC-pesticide spike 

solution (5.2.5). The LRS also can be fortified with PCB 

spike solution (5.2.6) or toxaphene spike solution (5.2.7). 

(Other spike solutions might be added; see second note in 

section 7.2.2.2.) The expected spiked concentration for 

each PCB Aroclor 1242, 1254, and 1260 is 10 μg/kg; 

1,000 μg/kg for toxaphene, if added; and 2 μg/kg for the 

individual OC pesticides (see second note in section 

7.2.2.2 for method compound HCB). One LRS is included 

with each sample set and is carried through the entire 

sample preparation and analytical procedure. The 

concentration of each compound in the LRS needs to be 

within the range of the calibration standards. The LRS 

recoveries reflect method performance in the absence of 

any environmental sample matrix. These results are used 

to determine if overall set recoveries are acceptable, or if 

there are gross changes in method performance in the set. 

Acceptability is defined from analysis of a series of LRS 

samples, typically 30 or more, processed by multiple 

operators using different GC/ECD instruments. Statistical 

process control techniques (preferrably nonparametric 

statistics) are used to establish control limits for LRS 

recoveries (M.R. Burkhardt and T.J. Maloney, U.S. 

Geological Survey, written commun., 1998). Control 

limits for this method are updated annually. Failure of 

LRS recoveries needs to be evaluated. If the recovery of 

any compound does not fall within the control-limit 

criteria, the compound is judged out of control. 

Reanalysis of sample extract or sample repreparation 

might be required. The source of the problem needs to be 

identified and resolved before continuing the analyses. 

Report SRM and field sample data as suspect with an 

estimated (E-code) qualifier for the compounds that fail 

recovery in the LRS, or do not report the sample result if 

an unacceptable LRS recovery might indicate that the 

sample result is completely uninterpretable (M.R. 

Burkhardt and T.J. Maloney, U.S. Geological Survey, 

written commun., 1998).

13.4 Standard reference material (SRM)—An 

SRM containing many compounds of interest is used to 

monitor performance through the sample preparation and 

analytical procedure in the presence of matrix 

interferences. One SRM is included with each sample set. 

The SRM results are compared to certified 

concentrations.

13.5 Laboratory duplicate—One laboratory 

duplicate sample may be processed with each set of 

samples and selected at random from one of the field 

samples within the set. The duplicate analysis provides an 

indication of method precision within that particular 

matrix by the relative percent difference computation 

(equation 4). The NWQL has not established corrective 

action for laboratory duplicates. For the purpose of 

production efficiency, the laboratory duplicate may be 

replaced in this method with an additional field sample for 

the sample set.

13.6 Verification of standard solution 

concentrations—This is a critical quality-assurance 

requirement. Verify compound concentrations in all 

prepared calibration and spiking standard solutions prior 

to use to avoid possible significant changes in determined 

recoveries. Determined concentrations are expected to be 

within ±20 percent of the known concentrations in the 

solutions. Third-party check standards (for example, 

standard reference solutions from the National Institute of 

Standards and Technology) can be used to assist in this 

verification process, provided that the original sources of 

the OC pesticides used to prepare the TPCs are not the 

same sources used to prepare the solutions being verified 

(11.2.3). 
Analytical Method 37

14. Method Performance

Method performance is tested by establishing the 

recoveries of the method compounds spiked at a 

minimum of two concentrations in at least three different 

matrices. A minimum of seven replicates is determined at 

each test condition. For this method, three concentrations 

were tested in three matrices, with as many as eight 

replicates for each test condition. Unfortunately, as few as 

three replicates were used for one of the method 

performance determinations.

14.1 The matrices used to test method performance 

included a reagent (sodium sulfate); a sediment sample 

collected from Evergreen Lake, Evergreen, Colorado; and 

a sediment sample collected from Clear Creek near 

Central City, Colorado.

14.2 The Evergreen Lake sediment was dredged as 

part of routine dam maintenance; the sample was 

collected from a mound that had been dredged several 

weeks prior to collection. The Evergreen Lake sediment 

sample was coarse with substantial sand component.

14.3 The Clear Creek sediment sample was bottom 

sediment that had been size-separated after collection. 

Particles less than 63 mm in diameter were used in this 

evaluation for the Clear Creek sediment sample. This 

sediment was light brown and was received as a dry 

sample from the donor, unlike the Evergreen Lake 

sample, which was damp.

14.4 Each of the three sample matrices was 

homogenized and split into twenty-four 25-g 

dry-weighted samples. All samples were fortified with 

OC surrogates at 2 μg/kg. One set of eight samples 

(replicates) was fortified with selected OC pesticides at 1 

μg/kg (50 μL of an individual OC-pesticide spike solution 

at 0.5 ng/μL in methanol) and with PCB Aroclor 1242, 

1254, and 1260 at 20 μg/kg each Aroclor (10 μL of a PCB 

spike solution at 50 ng/μL in hexane). A second set was 

fortified with the OC pesticides at 2 μg/kg (100 μL of an 

individual OC-pesticide spike solution at 0.5 ng/μL in 

methanol) and with each Aroclor at 40 μg/kg (20 μL of a 

PCB spike solution at 50 ng/μL in hexane). A third set 

was fortified with the OC pesticides at 10 μg/kg (100 μL 

of an individual OC-pesticide spike solution at 2.5 ng/μL 

in methanol) and with each Aroclor at 5 μg/kg (5 μL of a 

PCB spike solution at 25 ng/μL in hexane). Excess PCBs 

were added in the first two sets as an estimated guess in 

determining the Aroclor method detection limits (MDLs) 

based on the total PCB minimum reporting level at 50 

μg/kg in similar USGS method O-5129-95 (Foreman and 

others, 1995, p. 49). After determining the estimated 

MDL results from the first two sets (extracted and 

analyzed during spring 2000), the decision was made to 

spike excess individual OC pesticides for a third level and 

to spike lower for the PCBs (extracted and analyzed 

during fall 2001) to obtain the estimated MDLs listed in 

table 8 for the Aroclors. Aroclor 1016 intentionally was 

not spiked.

14.5 Replicates for toxaphene were prepared 

separately and fortified with OC surrogates. Toxaphene 

was spiked at only one concentration into eight replicates 

of each of the three sample matrixes. One-milliliter 

aliquots of a 5,028-ng/μL toxaphene stock standard 

solution from NSI Solutions, Inc. were spiked into the 

replicates. The replicates were diluted 1:1,000 to obtain 

an expected final concentration of 201 μg/kg, assuming a 

25-g equivalent dry-weight sample size. Toxaphene 

replicates were extracted and analyzed during winter 

2003.

14.6 Replicates in a given sample set were extracted 

on the same day. Extracts were analyzed on one GC/ECD 

instrument under one operator, but different 

concentrations and matrices were analyzed at different 

times. Bias and precision data are listed in table 10 at the 

end of this section.

14.7 Additional 25-g dry-weighted samples (matrix 

blanks) for each of the three sample matrices were 

fortified with surrogates only, extracted with replicates, 

and analyzed to determine background concentrations of 

method compounds. Method compounds p,p'-DDT and 

PCB Aroclor 1254 were detected in the Evergreen Lake 

matrix blank at 1.24 μg/kg and 6.29 μg/kg, respectively, 

for the replicates spiked at 1 and 2 μg/kg for individual 

OC pesticides and at 20 and 40 μg/kg for each PCB 

Aroclor 1242, 1254, and 1260, all extracted on the same 

day. The background concentrations were subtracted from 

concentrations determined in the replicates to give the 

corrected results in table 10.

14.8 Estimated MDLs, determined by fortifying 

eight sodium sulfate reagent replicates with method 

compounds, and the corresponding spiked concentrations 

are listed in table 8. The estimated MDLs in table 8 reflect 

variation with replicate preparations and GC/ECD 

calibrations. The lot numbers of the method compounds in 

the spiking solutions used to prepare the replicates were 

the same lot numbers for the compounds in the calibration 

standard solutions used to make the calibration curves. 

Estimated MDLs were calculated by using the following 

equation outlined by the U.S. Environmental Protection 

Agency (1997): 

MDL S t = × ( ) n – 1 1, – α = 0.99 (19)
38 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

Table 8. Estimated method detection limits for method compounds from eight sodium sulfate reagent organochlorine-fortified replicates.

Compound

Spiked 

conc.1

(μg/kg)

Mean

conc.

(μg/kg)

Standard

deviation

(μg/kg)

Relative 

standard 

deviation

(percent)

Mean 

recovery

(percent)

Number 

of 

observations2

Estimated 

method 

detection 

limit3

(μg/kg)

Aldrin 2 1.48 0.27 18.43 74.0 7 0.859

cis-Chlordane 2 1.25 .13 10.51 62.5 8 .415

trans-Chlordane 1 .701 .06 9.42 70.1 7 .207

p,p'-DDD 2 1.64 .32 19.95 82.0 7 1.03

p,p'-DDE 1 1.36 .22 16.86 136.0 8 .688

p,p'-DDT 1 .711 .14 19.78 71.1 7 .442

Dieldrin 1 .905 .06 7.55 90.5 7 .215

Endosulfan I 2 .952 .07 7.81 47.6 7 .234

Endrin 1 1.14 .10 9.32 114.7 7 .336

HCB4 13 8.06 .47 5.92 62.0 8 1.43

alpha-HCH 2 1.16 .17 15.08 58.0 8 .550

beta-HCH 1 .727 .07 9.68 72.7 7 .221

gamma-HCH 1 .548 .06 11.60 54.8 7 .200

Heptachlor 1 .662 .10 15.54 66.2 8 .309

Heptachlor epoxide 2 1.53 .19 12.44 76.5 8 .601

p,p'-Methoxychlor5 1 6.08 .49 8.19 6 607.8 7 1.56

Mirex 2 1.47 .18 12.75 73.5 7 .589

trans-Nonachlor 1 .569 .12 21.58 56.9 7 .385

PCB Aroclor 1016/1242 5 4.35 .64 14.82 87.0 7 2.02

PCB Aroclor 1254 5 9.02 .66 7.38 180.4 7 2.09

PCB Aroclor 1260 5 6.93 .74 10.77 138.6 7 2.34

Toxaphene (technical)7 201 134 19.09 14.25 66.6 8 57.3

[conc., concentration; μg/kg, micrograms per kilogram; mL, milliliter; ng/μL, nanograms per microliter]

1

The spiked concentrations assume a 25-gram sample size. 

2

Number of observations less than eight resulted from loss of sample in the preparation procedure. 

3

Estimated method detection limits (MDLs) were determined from these reagent organochlorine-fortified replicate results and calculated by the U.S. 

Environmental Protection Agency (1997) procedure using Student's t-values for the 99-percent confidence interval. More than one significant figure was 

included for the standard deviations used to calculate the estimated MDLs. 4

Hexachlorobenzene (HCB) is a component in the individual organochlorine (OC)-pesticide spike solution and in a polycyclic aromatic hydrocarbon 

(PAH) spike solution, which also was spiked into the sodium sulfate reagent replicates for other performance method evaluations not shown in this report. 

The data represent a 1-μg/kg spiked concentration of HCB from the individual OC-pesticide spike solution and a 12-μg/kg spiked concentration from the 

PAH spike solution. 5Interference from a nonmethod compound suspected in calculating the mean recovery.

6

The mean recovery from 18 laboratory reagent spikes in calendar year 2002 was 77.9 percent with a standard deviation of 17 percent for

p,p'-methoxychlor spiked at 2 μg/kg.

7Toxaphene replicates were diluted 1:1,000 to obtain a final expected concentration of 201 μg/kg for 1-mL aliquots of a 5,028-ng/μL toxaphene 

solution spiked per replicate.
Analytical Method 39

where

 S = standard deviation of replicate 

analyses, in micrograms per 

kilogram;

t(n-1, 1- α = 0.99) = Student's t-value for the 99-percent 

confidence level (two-tail test) 

with n-1 degrees of freedom; and

 n = number of replicate analyses.

Note: More than one significant figure was included 

for the standard deviations used to calculate the estimated 

MDL.

14.9 According to the U.S. Environmental 

Protection Agency (1997) procedure, the fortified 

concentration for a compound is expected to be no more 

than five times the estimated MDL; otherwise, an optional 

iterative procedure is followed to verify the 

reasonableness of the MDL estimate. Because the spiked 

concentrations are nearly two to five times the estimated 

MDLs for most of the compounds in table 8, these 

estimated MDLs appear to be appropriate. In the 

method-performance evaluation, estimated MDLs lower 

than those listed in table 8 of about 0.1 μg/kg were 

obtained for the compounds aldrin, cis-chlordane, 

p,p'-DDD, endosulfan I, and mirex from a fortified 

concentration at 1μg/kg; however, that concentration did 

not meet U.S. Environmental Protection Agency (1997) 

criteria. For endosulfan I, even a fortified concentration at 

2 μg/kg, being greater than five times its estimated MDL 

listed in table 8, does not satisfy the criteria. In the 

method-performance evaluation, a fortified concentration 

at 10 μg/kg yielded an estimated MDL of 3.21 μg/kg for 

endosulfan I, but that MDL was calculated from only four 

replicate results. 

14.10 The mean recovery data for the concentrations 

spiked for the estimated MDL determinations also are 

listed in table 8. The mean recovery for p,p'-DDE reflects 

possible interferences from PCB Aroclor 1254 and 1260, 

which is a potential problem to p,p'-DDE quantitation if 

PCBs are present at high concentration. For example, at 

the spiked concentration of 1 μg/kg for p,p'-DDE in the 

sodium sulfate reagent OC-fortified replicates, PCBs also 

were spiked in the same replicates at 20 μg/kg, assuming 

a 25-g sample size. Conversely, the mean recoveries for 

PCB Aroclor 1254 and 1260 reflect possible interferences 

from p,p'-DDE, especially at the spiked concentration of 

5 μg/kg for the Aroclors because individual OC pesticides 

were spiked also in the same replicates at 10 μg/kg, 

assuming a 25-g sample size, and from a more 

concentrated solution, 2.5 ng/μL in methanol in relation to 

0.5 ng/μL (5.2.5). For comparison, a reagent OC spike 

sample (or LRS) typically is spiked at 10 μg/kg for PCB 

Aroclors and 2 μg/kg for most individual OC pesticides, 

assuming a 25-g sample size (7.2.2.2). In the analysis of 

18 typical LRSs in calendar year 2002, p,p'-DDE mean 

recovery was 85.3 percent with 14.54-percent relative 

standard deviation, Aroclor 1254 mean recovery was 92.9 

percent with 18.22-percent relative standard deviation, 

and Aroclor 1260 mean recovery was 91.7 percent with 

13.14-percent relative standard deviation. 

Through the years as a custom method, seven LRSs 

were not fortified with PCBs. In the absence of PCB 

interference in those LRSs, p,p'-DDE mean recovery was 

69.1 percent with 20.73-percent relative standard 

deviation. Unfortunately, bias and precision data are not 

available for LRSs fortified with the PCB Aroclors in the 

absence of OC pesticide interference.

14.11 The abnormally high mean recovery of 608 

percent for p,p'-methoxychlor from the reagent replicates 

spiked at 1 μg/kg most likely was caused by interference 

from a nonmethod compound in preparing the replicates. 

The relative standard deviation was about 8 percent in the 

determination of the estimated MDL listed in table 8. For 

the reagent replicates spiked at 2 μg/kg, the mean 

recovery for p,p'-methoxychlor was 507 percent with a 

much higher relative standard deviation of about 58 

percent. For comparison, in the analysis of 18 typical 

LRSs in calendar year 2002, p,p'-methoxychlor mean 

recovery was 77.9 percent with a relative standard 

deviation of about 22 percent for the compound spiked at 

2 μg/kg. 

14.12 The interim reporting levels (IRLs) for this 

method are listed in table 9 for sediment samples on a 

dry-weight basis, assuming a 25-g sample size, and for 

suspended-sediment samples collected on filters based on 

a total of 63 L of water filtered (Mahler and others, 2001). 

The IRLs in micrograms per kilogram were set at 2 times 

the estimated MDL for all compounds except toxaphene. 

Considering toxaphene detectability relative to typical 

matrix-derived instrumental noise levels encountered in 

most sediment samples processed to date with this 

method, the IRL for toxaphene was arbitrarily set at 200 

μg/kg to minimize false positive detections through dual 

GC column confirmation.

14.13 Bias (percent mean recovery) and precision 

(percent relative standard deviation) are shown for all 

matrices in table 10. The data presented in table 10 

represent results from eight or fewer replicates. One 

replicate sample was rejected in the reagent sample set 

spiked at 2 μg/kg because the surrogate recoveries (< 35 

percent in both fractions) were outside of the statistical 

control limits established, indicating errors in the sample 

preparation. One replicate sample was entirely ruined in 
40 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

preparation in the reagent and Clear Creek sample sets 

spiked at 10 μg/kg. The second fraction (F2) for one 

replicate sample was ruined in preparation in the reagent 

sample set spiked at 1 μg/kg. Results for PCB Aroclor 

1016/1242, 1254, and 1260 from one replicate sample in 

the reagent sample set spiked at 20 μg/kg for each Aroclor 

(except Aroclor 1016) were rejected because the 

recoveries appeared to be doubled. The rejection or ruin of 

the entire sample, an extracted fraction, or method 

compounds in these sample sets left only seven replicates 

to evaluate method performance. With the exception of 

p,p'-DDT, two replicate results were rejected for all F2 

compounds in the Evergreen Lake sample set spiked at 1 

μg/kg because of low (14 percent) recoveries for the F2 

surrogate alpha-HCH-d6. Correcting the p,p'-DDT results 

for the large matrix blank contribution (1.24 μg/kg) in this 

sample set resulted in rejecting five replicate results for 

p,p'-DDT because of low (< 26 percent) recoveries being 

outside of the statistical control limits used during spring 

2000 (35–114 percent for p,p'-DDT) when the sample set 

was extracted and analyzed. One to three replicate results 

were rejected for several F2 method compounds in the 

reagent and Clear Creek sample sets spiked at 10 μg/kg 

because of low (< 26 percent) recoveries owing to 

problems with the GPC instrument.

14.14 In the overall method-performance evaluation, 

relative standard deviations for method compounds were 

equal to or less than 25 percent for all but two compounds 

(endrin and p,p'-methoxychlor) in the sodium sulfate 

reagent matrix, for all but nine compounds (cis- and 

Compound Interim reporting level1

(μg/kg)

Interim reporting level2

(μg/L)

Aldrin

cis-Chlordane

trans-Chlordane

p,p'-DDD

p,p'-DDE

p,p'-DDT

Dieldrin

Endosulfan I

Endrin

HCB

alpha-HCH

beta-HCH

gamma-HCH

Heptachlor

Heptachlor epoxide

p,p'-Methoxychlor

Mirex

trans-Nonachlor

PCB Aroclor 1016/1242

PCB Aroclor 1254

PCB Aroclor 1260

Toxaphene (technical)

1.72

0.830

0.414

2.06

1.38

0.884

0.430

0.468

0.672

2.86

1.10

0.442

0.400

0.618

1.20

3.12

1.18

0.770

4.04

4.18

4.68

200

0.000273

.000132

.0000656

.000327

.000219

.000140

.0000681

.0000741

.000107

.000453

.000174

.0000700

.0000634

.0000979

.000190

.000495

.000187

.000122

.000640

.000662

.000742

.03

1The interim reporting level (IRL) for dry-weighted sediment samples was set at 2 times the estimated method detection limit (see 

table 8), except for toxaphene, which was arbitrarily set at about 3.5 times the estimated method detection limit to minimize false positive 

detection on the gas chromatography/electron capture detection instrument. 

2The IRL for suspended-sediment samples collected on filters was determined from equations 17 and 18 given in the text, assuming a 

typical weight of extract before gel permeation chromatography (GPC) (W1) of 6 g, assuming a typical weight of organochlorine extract 

processed through the GPC (W2) of 1.5 g, and assuming a composite of 63 liters of water filtered based on a case study by Mahler and 

others (2001).

Table 9. Interim reporting levels for dry-weighted sediment samples, in micrograms per kilogram, assuming a 25-gram sample size, and for 

suspended-sediment samples collected on filters, in micrograms per liter, assuming 63 liters filtered.

[μg/kg, micrograms per kilogram; μg/L, micrograms per liter; mL, milliliter; ng/μL, nanograms per microliter]
Analytical Method 41

Table 10. Bias and precision data for method compounds in sodium sulfate reagent, Evergreen Lake sediment, and Clear Creek 

sediment from sets of eight replicates, each spiked at 1, 2, and 10 micrograms per kilogram (μg/kg) for individual organochlorine 

compounds; and 20, 40, and 5 μg/kg for each PCB Aroclor 1242, 1254, and 1260; toxaphene spiked separately.

[conc., concentration; μg/kg, micrograms per kilogram; g, gram; mL, milliliter; μL, microliter; ng/μL, nanogram per microliter; RSD, relative standard 

deviation; OC, organochlorine; PCB, polychlorinated biphenyl]

Compound

Sodium sulfate Evergreen Lake Clear Creek

Spiked 

conc.1

(μg/kg)

Mean 

recovery 

(percent)

RSD

(percent)

Mean

recovery

(percent)

RSD

(percent)

Mean

recovery

(percent)

RSD

(percent)

Aldrin 1 57.4 8.09 64.7 6.89 70.4 11.86

2 2 74.0 18.43 68.0 8.71 71.3 12.16

10 2 64.8 5.80 64.3 15.98 2 69.4 4.44

cis-Chlordane 1 2 63.9 7.57 3 41.4 27.07 72.9 3.16

2 2 62.5 10.51 29.6 43.94 60.9 9.02

10 2 66.0 3.46 59.9 12.22 2 63.0 8.32

trans-Chlordane 1 2 70.1 9.42 3 47.9 24.44 71.8 4.50

2 2 70.1 11.29 35.7 41.78 65.0 8.84

10 2 65.1 7.51 65.4 13.82 2 69.5 9.51

p,p'-DDD 1 2 88.8 3.99 3 70.6 27.07 85.6 7.07

2 2 82.0 19.95 66.7 44.34 82.3 9.54

10 3 77.3 13.67 59.0 15.51 2 82.7 20.10

p,p'-DDE7 1 136.0 16.86 125.8 11.32 134.8 10.22

2 2 136.7 12.37 137.2 7.79 129.1 11.45

10 2 83.1 4.22 71.4 12.99 2 83.1 3.07

p,p'-DDT 1 2 71.1 19.78 5,6 48.7 14.48 91.6 13.57

2 2 78.9 12.88 6 58.1 16.81 84.3 14.04

10 2 87.4 4.72 64.1 15.51 2 98.5 7.60

Dieldrin 1 2 90.5 7.55 3 60.0 13.69 74.2 14.89

2 2 88.7 11.47 71.5 27.43 74.7 16.14

10 4 43.8 15.16 69.3 13.81 4 49.2 34.08

Endosulfan I 1 2 49.3 5.26 3 42.1 9.91 42.4 5.35

2 2 47.6 78.81 45.1 23.36 44.9 7.58

10 4 49.3 14.35 62.4 13.53 4 57.6 31.26

Endrin 1 2 114.7 9.32 3 109.8 9.03 126.1 8.54

2 2 122.0 21.25 134.3 28.49 117.3 10.07

10 4 65.1 26.15 75.0 14.09 4 96.8 33.57

HCB8 13 62.0 5.92 91.8 10.85 74.2 6.47

26 2 62.0 10.93 103.9 11.12 62.3 8.12

14.8 2 59.8 6.80 49.1 13.54 2 63.0 4.44

alpha-HCH 1 2 43.6 14.11 3 50.2 10.44 38.5 18.76

2 2 58.0 15.08 61.3 34.56 45.1 9.45

10 2 69.6 4.53 54.8 15.04 2 80.8 8.38

beta-HCH 1 2 72.7 9.68 3 61.9 7.89 72.5 5.03

2 2 81.1 11.60 72.7 25.35 70.4 7.88

10 3 72.5 16.84 60.6 14.56 2 75.0 26.33
42 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

Table 10. Bias and precision data for method compounds in sodium sulfate reagent, Evergreen Lake sediment, and Clear Creek 

sediment from sets of eight replicates, each spiked at 1, 2, and 10 micrograms per kilogram (μg/kg) for individual organochlorine 

compounds; and 20, 40, and 5 mg/kg for each PCB Aroclor 1242, 1254, and 1260; toxaphene spiked separately.—Continued

[conc., concentration; μg/kg, micrograms per kilogram; g, gram; mL, milliliter; μL, microliter; ng/μL, nanogram per microliter; RSD, relative standard 

deviation; OC, organochlorine; PCB, polychlorinated biphenyl]

Compound

Sodium sulfate Evergreen Lake Clear Creek

Spiked 

conc.1

(μg/kg)

Mean 

recovery 

(percent)

RSD

(percent)

Mean

recovery

(percent)

RSD

(percent)

Mean

recovery

(percent)

RSD

(percent)

gamma-HCH 1 2 54.8 11.60 3 57.7 8.78 65.5 6.09

2 2 68.6 15.95 70.3 28.6 63.9 7.62

10 2 63.2 19.37 57.7 14.81 2 74.2 13.25

Heptachlor 1 66.2 15.54 87.3 10.51 79.8 10.48

2 2 88.8 16.27 91.0 9.23 71.7 12.80

10 2 69.3 5.80 58.6 15.42 2 72.9 3.76

Heptachlor epoxide 1 2 74.8 7.17 3 58.7 8.91 73.1 9.79

2 2 76.5 12.44 67.4 27.02 72.1 8.91

10 4 54.8 12.32 64.5 13.26 4 59.0 29.79

p,p'-Methoxychlor* 1 2,13 607.8 8.19 3 108.3 12.26 545.1 6.38

2 2,13 506.6 57.69 538.2 24.94 451.0 6.61

10 4 24.9 33.18 62.6 14.91 4 40.8 23.99

Mirex 1 70.6 6.32 64.4 11.59 72.9 9.65

2 2 73.5 12.75 65.4 8.64 68.1 10.68

10 2 62.8 4.27 49.5 12.08 3 59.1 3.14

trans-Nonachlor 1 2 56.9 21.58 3 70.9 10.01 75.6 14.72

2 2 63.3 13.90 75.1 8.50 71.8 5.69

10 2 71.1 1.73 64.1 14.74 2 75.1 7.56

PCB Aroclor 1016/12429 20 2 75.9 10.32 112.1 12.80 83.4 8.07

40 2 76.3 12.39 101.4 7.12 80.1 11.90

5 2 87.0 14.82 65.6 21.33 2 103.6 9.24

PCB Aroclor 125410 20 2 179.1 17.39 6 171.6 12.57 194.0 8.23

40 2 198.6 12.26 6 172.6 7.24 201.9 14.73

5 2 180.4 7.38 119.9 17.19 2 213.4 4.20

PCB Aroclor 126010 20 2 120.5 10.32 146.4 9.95 125.8 8.66

40 2 131.6 13.70 147.7 8.31 139.9 16.15

5 2 138.6 10.77 82.5 18.74 2 157.4 4.17

Toxaphene (technical)11* 201 66.6 14.25 49.3 9.52 46.2 5.20
Analytical Method 43

Table 10. Bias and precision data for method compounds in sodium sulfate reagent, Evergreen Lake sediment, and Clear Creek 

sediment from sets of eight replicates, each spiked at 1, 2, and 10 micrograms per kilogram (μg/kg) for individual organochlorine 

compounds; and 20, 40, and 5 mg/kg for each PCB Aroclor 1242, 1254, and 1260; toxaphene spiked separately.—Continued

[conc., concentration; μg/kg, micrograms per kilogram; g, gram; mL, milliliter; μL, microliter; ng/μL, nanogram per microliter; RSD, relative standard 

deviation; OC, organochlorine; PCB, polychlorinated biphenyl]

1

One sample set for each sample matrix contained two subsets of replicates: one subset spiked at 1 μg/kg for individual OC pesticides and 20 

μg/kg for each PCB Aroclor 1242, 1254, and 1260, and 2 μg/kg for surrogates, assuming a 25-g sample size; the other subset spiked at 

2 μg/kg for individual OC pesticides and 40 μg/kg for each PCB Aroclor 1242, 1254, and 1260, and 2 μg/kg for surrogates, assuming a 25-g 

sample size. A second sample set for each sample matrix contained replicates spiked at 10 μg/kg for individual OC pesticides, and 5 μg/kg for 

each PCB Aroclor 1242, 1254, and 1260, and 2 μg/kg for surrogates, assuming a 25-g sample size. PCB Aroclor 1016 intentionally was not spiked 

in any of the replicates. A third sample set for each sample matrix contained replicates fortified with surrogates at 2 μg/kg, assuming a 25-g sample 

size, and 1-mL aliquots of a 5,028-ng/μL toxaphene solution, then diluted 1:1,000 to obtain a final expected concentration of 201 μg/kg for 

toxaphene.

2

Number of observations was 7.

3

Number of observations was 6.

4

Number of observations was 4.

5Number of observations was 3.

6

Recovery corrected for matrix blank contribution detected at or greater than the interim reporting level for the compound.

7Possible interference from PCB Aroclor 1254 or 1260.

8Hexachlorobenzene (HCB) is also a component of a polycyclic aromatic hydrocarbon (PAH) spike solution at 6 ng/μL

that additionally was spiked into the replicates for the performance evaluation of PAHs in a separate sediment method not presented in this report. 

For the replicates spiked at the 1-μg/kg level of the individual OC-pesticide spike solution, HCB was spiked also at 12 μg/kg from the addition 

of PAH spike solution (50 μL), totaling 13 μg/kg HCB. For the replicates spiked at the 2-μg/kg level of the individual OC-pesticide spike solution, 

HCB also was spiked at 24 μg/kg from the addition of the PAH spike solution (100 μL), totaling 26 μg/kg HCB. For the replicates spiked at the 

10-μL/kg level of the individual OC-pesticide spike solution, HCB also was spiked at 4.8 μg/kg from the addition of the PAH spike solution (20 

μL), totaling 14.8 μg/kg HCB.

9

PCB Aroclor 1242 is reported by the National Water Quality Laboratory as the combined Aroclor 1016/1242 (U.S. Geological Survey

National Water Quality Laboratory Technical Memorandum No. 99.10, 1999). PCB Aroclor 1016 was not spiked in this method-performance 

evaluation.

10Possible interference from p,p'-DDE.

11Replicates were neither fortified with individual OC pesticides nor PCBs.

12Spiked into the toxaphene replicates; only the fraction-2 surrogate was analyzed.

13The mean recovery from 18 laboratory reagent spikes in calendar year 2002 was 77.9 percent with a relative standard deviation of about 22 

percent for p,p'-methoxychlor spiked at 2 μg/kg. *

Compound is permanently "E" coded (estimated) in this method.

Compound

Sodium sulfate Evergreen Lake Clear Creek

Spiked 

conc.1

(μg/kg)

Mean 

recovery 

(percent)

RSD

(percent)

Mean

recovery

(percent)

RSD

(percent)

Mean

recovery

(percent)

RSD

(percent)

Surrogates

alpha-HCH-d6 2 2 85.9 11.10 3 102.4 9.09 82.4 6.50

2 2 89.9 15.77 110.1 30.17 99.2 6.62

2 2 75.1 5.72 64.6 16.27 2 88.0 9.56

12 2 97.7 8.59 91.0 6.70 89.2 7.10

Isodrin 2 69.0 7.77 69.4 7.11 66.6 9.39

2 2 99.6 16.29 71.4 7.43 72.9 11.51

2 2 76.2 9.14 66.9 16.60 2 88.8 5.01

PCB-207 2 117.7 6.32 78.0 7.82 105.5 15.68

2 2 118.0 12.89 75.3 7.94 77.5 10.00

2 2 88.0 4.18 71.2 14.41 2 92.7 3.49
44 Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Bottom and Suspended Sediment

trans-chlordane, p,p'-DDD, dieldrin, endrin, alpha- and 

gamma-HCH, heptachor epoxide, and alpha-HCH-d6) in 

the Evergreen Lake matrix, and for all but five compounds 

(dieldrin, endosulfan I, endrin, beta-HCH, and heptachlor 

epoxide) in the Clear Creek matrix. 

14.15 Compound p,p'-methoxychlor had high mean 

recoveries (451 to 608 percent) in all three matrices but 

not at all spiked concentrations. Interference from a 

nonmethod compound introduced upon fortifying the 

replicates is suspected for the high mean recoveries for 

p,p'-methoxychlor. Despite the high variable 

p,p'-methoxychlor recoveries, the compound is retained 

in this method because of customer request; however, data 

results for p,p'-methoxychlor will be reported 

permanently with the estimated (E-code) qualifier in 

samples. 

14.16 Toxaphene also is retained in this method 

because of customer request. Though mean recoveries for 

toxaphene were 49 and 46 percent in the Evergreen Lake 

and Clear Creek sediments, respectively, mean recovery 

was 67 percent in the sodium sulfate reagent, and relative 

standard deviations were less than 15 percent in all three 

matrices. Because of pattern recognition problems (9.2.2), 

data results for toxaphene will be reported permanently 

with the estimated (E-code) qualifying in samples. 

14.17 The mean recoveries listed in table 10 for 

p,p'-DDE reflect possible interferences from one or more 

coeluting congeners present in PCB Aroclor 1254 and 

1260. Likewise, the mean recoveries listed in table 10 for 

PCB Aroclor 1254 and 1260 reflect possible interferences 

from p,p'-DDE. Qualifying the data results of these 

compounds in the presence of interference is discussed in 

section 12.4. 

14.18 Hexachlorobenzene (HCB) is a component of 

a polycyclic aromatic hydrocarbon (PAH) spike solution 

that was spiked in addition to the individual OC-pesticide 

spike solution in the replicates for the purpose of 

evaluating PAH performance in a separate sediment 

method. Performance data for the PAHs are not presented 

in this report. The total amount of HCB in each set of 

replicates, however, is taken into account in table 10. See 

the footnote for HCB in table 10 for details.

14.19 Before 2004, the complex mixture technical 

chlordane was analyzed and identified by the detection of 

a few of its component compounds, namely, 

cis-chlordane, trans-chlordane, and trans-nonachlor as a 

trio. In the absence of performance data, technical 

chlordane has been dropped from the new method. 

Instead, performance data for the two octachlor and the 

nonachlor compounds characteristic of technical 

chlordane are presented in table 10, and the compounds 

will be reported individually in the new method.

Summary and Conclusions

A new method was developed to determine 19 

organochlorine (OC) pesticides, including total 

toxaphene, and polychlorinated biphenyls quantified as 

Aroclor 1016/1242, 1254, and 1260 equivalents. The new 

method determines individual OC pesticide 

concentrations as low as 0.400 microgram per kilogram 

(μg/kg) and PCB Aroclors as low as 4.04 μg/kg in 

dry-weighted bed and suspended-sediment samples. The 

interim reporting level (IRL) for toxaphene is set at 200 

μg/kg in this method. For wet-weighted 

suspended-sediment samples adhered to filters, the IRLs 

as determined by the new method are reported in 

micograms per liter. Reporting levels are subject to 

change following additional method-detection-limit 

determinations. The method provides effective 

preparatory separation of OCs using gel permeation 

chromatography, combined-column alumina/silica 

adsorption chromatography, and Florisil adsorption 

chromatography. The method also provides effective 

instrumental separation of selected OCs, using dual 

capillary-column gas chromatography with a 

time-efficient temperature ramp program, although 

superior PCB congener separations were obtained with 

the longer gas-chromatograph temperature ramp program 

in the U.S. Geological Survey (USGS) method 

O-5129-95. The new method modifies the earlier USGS 

method O-5129-95 (Foreman and others, 1995). Though 

the new method has fewer compounds than USGS method 

O-5129-95, there are fewer compound coelutions. 

Moreover, the additional Florisil adsorption 

chromatography step provides cleaner extracts which 

increases signal-to-noise ratios and improves method 

detection limits compared to the method by Foreman and 

others (1995).

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