415.3 - 1

METHOD 415.3 DETERMINATION OF TOTAL ORGANIC CARBON AND

SPECIFIC UV ABSORBANCE AT 254 nm IN SOURCE WATER

AND DRINKING WATER

 Revision 1.2 

September, 2009 

B. B. Potter, USEPA, Office of Research and Development, National Exposure Research Laboratory

J. C. Wimsatt, The National Council On The Aging, Senior Environmental Employment Program 

NATIONAL EXPOSURE RESEARCH LABORATORY

OFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCY

CINCINNATI, OHIO 45268

EPA Document #: EPA/600/R-09/122
415.3 - 2

METHOD 415.3

 DETERMINATION OF TOTAL ORGANIC CARBON AND SPECIFIC UV ABSORBANCE

AT 254 nm IN SOURCE WATER AND DRINKING WATER

1.0 SCOPE AND APPLICATION

1.1 This method provides procedures for the determination of total organic carbon (TOC),

dissolved organic carbon (DOC), and UV absorption at 254 nm (UVA) in source

waters and drinking waters. The DOC and UVA determinations are used in the

calculation of the Specific UV Absorbance (SUVA). For TOC and DOC analysis, the

sample is acidified and the inorganic carbon (IC) is removed prior to analysis for

organic carbon (OC) content using a TOC instrument system. The measurements of

TOC and DOC are based on calibration with potassium hydrogen phthalate (KHP)

standards. This method is not intended for use in the analysis of treated or untreated

industrial wastewater discharges as those wastewater samples may damage or

contaminate the instrument system(s).

1.2 The three (3) day, pooled organic carbon detection limit (OCDL) is based on the

detection limit (DL) calculation.1

 It is a statistical determination of precision, and

may be below the level of quantitation. The determination of OCDL is dependent on

the analytical instrument system’s precision, the purity of laboratory reagent water

(LRW), and the skill of the analyst. Different TOC instrument systems have

produced significantly different OCDLs that range between 0.02 and 0.12 mg/L OC

for both TOC and DOC measurements. Examples of these data can be seen in

Section 17, Table 17.1. It should be noted that background levels of OC

contamination are problematic. The minimum reporting level (MRL) for TOC and 

DOC will depend on the laboratory’s ability to control background levels (Sect. 4).

2.0 SUMMARY OF METHOD

2.1 In both TOC and DOC determinations, organic carbon in the water sample is oxidized

to produce carbon dioxide (CO2

), which is then measured by a detection system. 

There are two different approaches for the oxidation of organic carbon in water

samples to carbon dioxide gas: (a) combustion in an oxidizing gas and (b) UV

promoted or heat catalyzed chemical oxidation with a persulfate solution. Carbon

dioxide, which is released from the oxidized sample, is detected by a conductivity

detector or by a nondispersive infrared (NDIR) detector. Instruments using any

combination of the above technologies may be used in this method.

2.2 Settleable solids and floating matter may cause plugging of valves, tubing, and the 

injection needle and/or injection port. The TOC procedure allows the removal of

settleable solids and floating matter. The suspended matter is considered part of the
415.3 - 3

sample. The resulting water sample is then considered a close approximation of the

original whole water sample for the purpose of TOC measurement.

2.3 The DOC procedure requires that the sample be passed through a 0.45-μm filter prior

to analysis to remove particulate OC from the sample.

2.4 The TOC and DOC procedures require that all IC be removed from the sample before

the sample is analyzed for organic carbon content. If the IC is not completely

removed, significant error will occur. The sample, which is then free from IC

interference, is injected into a TOC instrument system. The organic carbon is

oxidized to CO2, which is released from the sample, detected, and reported as mg/L or

ppm TOC or DOC.

2.5 The UVA procedure requires that the sample be passed through a 0.45-μm filter and 

transferred to a quartz cell. It is then placed in a spectrophotometer to measure the

UV absorbance at 254 nm and reported in cm-1.

2.6 The SUVA calculation requires both the DOC and UVA measurement. The SUVA is

calculated by dividing the UV absorbance of the sample (in cm-1) by the DOC of the

sample (in mg/L) and then multiplying by 100 cm/M. SUVA is reported in units of

L/mg-M. The formula for the SUVA may be found in Section 12.2.

3.0 DEFINITIONS AND TERMS

NOTE: To assist the reader, a table of acronyms can be found in Section 3.20.

3.1 ANALYSIS BATCH - A set of samples prepared and analyzed on the same

instrument during a 24-hour period. For a TOC/DOC analysis batch, the set may

contain: calibration standards, laboratory reagent blank and/or filter blanks, field

blank, field samples, laboratory fortified matrix sample, field duplicate sample, and

continuing calibration check standards. For a UVA analysis batch, the set may

contain: filter blanks, field samples, field blank, field duplicate sample, and

spectrophotometer check solutions with associated blank. An analysis batch is

limited to 20 field samples. QC samples are not counted towards the 20 sample limit. 

QC requirements are summarized in Table 17.6.

3.2 BLANKS - Prepared from a volume of LRW (Sect. 3.9) and used as needed to fulfill

quality assurance requirements and to monitor the analytical system.

3.2.1 CALIBRATION BLANK (CB) - The calibration blank is a volume of LRW

that is treated with the same reagents used in the preparation of the calibration

standards. The CB is a “zero standard” and is used to calibrate the TOC

instrument. The CB is made at the same time as the calibration standards and

stored along with and under the same conditions as the calibration standards.

The CB is also used to monitor increases in organic background found in the
415.3 - 4

calibration standards over time by analyzing it as a sample and comparing the

results with initial analysis of the CB. 

3.2.2 FIELD REAGENT BLANK (FRB) - A volume, equivalent to that which is

collected at a sample site, of LRW is placed in a sample bottle or vial. A

second empty sample bottle or vial accompanies the LRW sample container to

the sample site. At the sample site, the LRW is transferred into the empty

bottle or vial which then becomes the FRB. The FRB is treated as a sample in

all respects including shipment from the sampling site, exposure to the

sampling site conditions, storage, preservation, and all analytical procedures. 

The purpose of the FRB is to determine if the TOC, DOC, and UVA

measurements of the samples collected in the field are free from interferences

or contamination as a result of the sample collection procedure and/or

transport of the sample(s) to the laboratory. The FRB is optional and is

usually used when the laboratory suspects a problem in sample collection and

handling.

3.2.3 FILTER BLANK (FB) - The FB is an aliquot of LRW that is filtered and

analyzed using the same procedures as field samples undergoing DOC and

UVA determinations. For DOC and UVA analyses, the FB serves as the LRB. 

The FB will give an indication of overall contribution of organic carbon

contamination from laboratory sources such as the LRW itself, labware

cleaning procedures, reagents, the filter apparatus, filter, and instrument

system(s).

3.2.4 LABORATORY REAGENT BLANK (LRB) - A volume of LRW that is

prepared with each sample set and is treated exactly as a TOC sample

including exposure to all glassware, plasticware, equipment, and reagents that

are used with other samples. The LRB is used to determine if organic

contamination or other interferences are present in the laboratory environment,

reagents, apparatus, or procedures. The LRB must be acidified and sparged

following the same procedure as is used to prepare the TOC sample(s). 

3.3 CALIBRATION SOLUTIONS - Calibration should be performed according to the

manufacturer’s operation manual. The following solutions are used to calibrate the

TOC instrument system for TOC or DOC determinations (calibration solutions are

not used for UVA determination): 

3.3.1 ORGANIC CARBON PRIMARY DILUTION STANDARD (OC-PDS) - A

concentrated solution containing potassium hydrogen phthalate (KHP) in

LRW water that is prepared in the laboratory or is an assayed KHP standard

solution purchased from a commercial source. The OC-PDS is used for the

preparation of organic carbon calibration standards (OC-CAL), continuing
415.3 - 5

calibration check standards (CCC), and laboratory fortified matrix samples

(LFM). 

3.3.2 ORGANIC CARBON CALIBRATION STANDARD (OC-CAL) - A solution

prepared from the OC-PDS and diluted with LRW to various concentrations. 

The OC-CAL solutions are used to calibrate the instrument response with

respect to organic carbon concentration.

3.3.3 CONTINUING CALIBRATION CHECK (CCC) - An OC-CAL solution

which is analyzed periodically to verify the accuracy of the existing calibration

of the instrument (Sect. 10.3).

3.4 DISSOLVED ORGANIC CARBON (DOC) - Organic matter, contained in a water

sample that is soluble and/or colloidal, that can pass through a 0.45-μm filter.

3.5 FIELD DUPLICATES (FD1 and FD2) - Two separate samples collected at the same

time and place under identical circumstances, and treated exactly the same throughout

field and laboratory procedures. Analyses of FD1 and FD2 give a measure of the

precision associated with sample collection, preservation, and storage, as well as

laboratory procedures.

3.6 INORGANIC CARBON (IC) - Carbon in water samples from non organic sources,

composed mainly from dissolved mineral carbonates and carbon dioxide. IC can

interfere with the determination of TOC and DOC if it is not removed.

3.7 LABORATORY FORTIFIED BLANK (LFB) – An aliquot of LRW or other blank

matrix to which a known quantity of KHP is added in the laboratory. The LFB is

subjected to the same preparation and analysis as a sample. The purpose of the LFB

is to determine whether the methodology is in control, and whether the laboratory is

capable of making accurate and precise measurements. For this method, a TOC LFB

is the same as a CCC (Sect. 10.3) and no additional LFB is required. One LFB is

required with each DOC analysis batch. No LFB is required for UVA analysis. 

3.8 LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An aliquot of a field 

sample to which a known quantity of KHP is added in the laboratory. The LFM is

subjected to the same preparation and analysis as a sample, and its purpose is to

determine whether the sample matrix affects the accuracy of the TOC or DOC

analytical results. The background concentration of organic carbon in the sample

matrix must be determined in a separate aliquot and the measured value in the LFM

corrected for background concentration.

3.9 LABORATORY REAGENT WATER (LRW) - The LRW may be distilled and/or

deionized (DI) water, or high pressure liquid chromatography (HPLC) reagent grade
415.3 - 6

or equivalent water which is low in TOC concentration, meeting the requirements as

stated in Section 7.2.

3.10 MATERIAL SAFETY DATA SHEET (MSDS) - Written information provided by a

vendor describing a chemical’s toxicity, health hazards, physical and chemical

properties (flammability, reactivity, etc.), storage, handling, and spill precautions.

3.11 MINIMUM REPORTING LEVEL (MRL) - The minimum concentration of organic

carbon that can be reported as a quantified value in a sample following analysis. This

concentration is determined by the background level of the analyte in the LRBs and

the sensitivity of the method to organic carbon. See Section 9.10 for guidelines in the

establishment of the MRL. 

3.12 ORGANIC CARBON DETECTION LIMIT (OCDL) - The calculated minimum

concentration of a known amount of organic carbon (OC) added to the LRW that can

be identified, measured as either TOC or DOC, and reported with 99% confidence

that the OC concentration is greater than zero as per the procedure in Section 9.2.7.

3.13 ORGANIC CARBON (OC) - In this method, when a concentration or instrument

reading applies to either a TOC or DOC determination, the term “OC” may be used. 

For example, the LRB must not exceed 0.35 mg/L OC. 

3.14 ORGANIC MATTER - A mixture of organic compounds (carbon-carbon, carbonhydrogen bonded compounds) naturally occurring and/or man-made that are found in

source water used by drinking water utilities. The quantity and quality of the OM in

source water is measured by TOC/DOC instrument systems or is measured by UVA.

3.15 QUALITY CONTROL SAMPLE (QCS) - A solution containing a known

concentration of an organic carbon compound(s) which is analyzed exactly like a

sample. The QCS is obtained from a source external to the laboratory and is different

from the source used for preparing the calibration standards. It is used to check

laboratory and instrument performance.

3.16 SOURCE WATER - Surface water or ground water that is used by a drinking water

utility to produce potable water for public consumption.

3.17 SPECIFIC UV ABSORBANCE AT 254 nm (SUVA) - A measure of DOC aromatic

content that is calculated by measuring the DOC and the UV absorbance at 254 nm of

a 0.45-μm filtered water sample. SUVA is calculated according to the equation given

in Section 12.2.

3.18 TOTAL CARBON (TC) - A measure of the OC and IC contained in a water sample. 

In this method, IC is removed from the sample. Therefore, the TC reported by a TOC

instrument system will be equal to the TOC or DOC measurement.
415.3 - 7

3.19 TOTAL ORGANIC CARBON (TOC) - The gross amount of organic matter (carbon

not removed by the IC removal step) found in natural water. Suspended particulate,

colloidal, and dissolved organic matter are a part of the TOC measurement. For this

method, the TOC definition excludes the contribution of floating vegetative or animal

matter, and volatile organic matter found in source water. Settleable solids consisting

of inorganic sediments and some organic particulate are not transferred from the

sample by the laboratory analyst and are not a part of the TOC measurement.

3.20 TABLE OF ACRONYMS

Acronym Term

CB calibration blank

CCC continuing calibration check

COMM-BKS commercial spectrophotometer background

solution

COMM-SCS commercial spectrophotometer check

solution

DOC dissolved organic carbon

FB filter blank

FD field duplicate

FRB field reagent blank

IC inorganic carbon

IDC initial demonstration of capability

KHP potassium hydrogen phthalate

LFB laboratory fortified blank

LFM laboratory fortified matrix

LRB laboratory reagent blank

LRW laboratory reagent water

MRL minimum reporting level

MSDS material safety data sheet

OC-CAL organic carbon calibration standard
Acronym Term

415.3 - 8

OC-PDS organic carbon primary dilution standard

OCDL organic carbon detection limit

QCS quality control sample

SCS spectrophotometer check solution

SDWA Safe Drinking Water Act

SOP standard operating procedure

SUVA specific UV absorbance

TC total carbon

TOC total organic carbon

UVA UV absorbance

4.0 CONTAMINATION AND INTERFERENCES

4.1 SPECIAL CONSIDERATIONS FOR ONSITE UTILITY LABORATORIES -

Aerosols (foam and mist) from the operation of a water treatment plant contain 

organic carbon and will contaminate glassware, reagents, sample collection

equipment, and onsite laboratory equipment if they are exposed to air at the water

utility. For an onsite laboratory, it is recommended that air be filtered and isolated

from organic fumes generated by petroleum products and combustion gases which

come from the operation of some water utility equipment. Work traffic in the onsite

laboratory should be minimized as it may produce dust containing organic matter that

will result in the contamination of unprotected samples and laboratory equipment.

4.2 All glassware must be meticulously cleaned. Wash glassware with detergent and tap

water, rinse with tap water followed by reagent water. Non-volumetric glassware may

then be heated in a muffle furnace at 425 oC for 2 hours to eliminate interferences. 

Volumetric glassware should not be heated above 120 oC. Alternate cleaning

procedures, such as acid rinsing and heating at lower temperatures, may be employed,

providing that these procedures are documented in a laboratory SOP and LRBs are

monitored as per Section 9.9.

4.3 Laboratory water systems have been known to contaminate samples due to bacterial

breakthrough from resin beds, activated carbon, and filters. Laboratory water systems

should be maintained and monitored frequently for carbon background and bacterial

growth. It is recommended that the LRW be filtered through a 0.22-μm filter

membrane to prevent bacterial contamination of TOC instrument systems, reagents,
415.3 - 9

and samples. The LRW, sample transfer (pipet), glassware, and sample bottles are the

principle source for organic background in the analytical system. However, it is not

possible to control all sources of organic carbon contamination. Therefore, this

method allows for instrument background correction or adjusting the zero reference

point of the instrument for organic carbon background that is found in the analytical

system. 2

 There are many ways to correct for organic carbon background. Consult the

instrument manufacturer’s operation manual for the instrument background correction

procedure. Subtraction of LRB or FB measurements from TOC, DOC, or UVA

sample results is not allowed.

4.4 High concentrations of OC, both man-made and naturally occurring, can cause gross

contamination of the instrument system, changes in calibration, and damage to valves,

pumps, tubing, and other components. It is recommended that analysis of a sample

known to have a concentration of OC > 10 mg/L OC be followed by the analysis of an

LRB. It is highly recommended that known samples containing OC concentrations 

> 50 mg/L OC be diluted or not run on instruments used to analyze low-level drinking

water samples. 

4.5 Source waters containing ionic iron, nitrates, nitrites, and bromide have been reported

to interfere with measurements of UVA absorbance at 254 nm. 3 The concentration of

the interferences and their effect on the UVA cannot be determined as each unique

sample matrix may produce a different UVA response for the same concentration of

interference or combination of interferences. This method does not treat or remove

these interferences. Therefore, suspected or known interferences may affect results

and must be flagged in the SUVA result as “suspected UVA interferences.”

4.6 Chloride exceeding 250 mg/L may interfere with persulfate oxidation methods.4, 5 

Some instrument systems may require increased persulfate concentration and

extended oxidation times. Consult with your instrument manufacturer’s

representative or instrument operation manual for instrument settings and reagent

strengths when analyzing samples containing high levels of chloride.

4.7 Inorganic carbon (IC) interferes with TOC and DOC measurements. TOC instrument

bias due to incomplete IC removal has been reported.6, 7 If inorganic carbon is not

completely removed from the water sample, it will result in a positive or negative bias

depending on the way the instrument system calculates TOC (e.g., TOC =TC - IC, 

TC = TOC + IC, or TOC = TC). When inorganic carbon (IC) is removed from the

sample prior to the TOC assay, as required in this method, TOC = TC and the method

bias is minimized.

5.0 SAFETY

5.1 Fast-moving source water, steep inclines, water conduits, and electrical hazards may

present special safety considerations for the sample collector. The sample collector
415.3 - 10

should be aware of any potential safety hazards and take necessary precautions while

collecting samples. 

5.2 Each chemical reagent used in this method should be regarded as a potential health

hazard. Exposure to these compounds should be minimized and/or avoided by active

participation in safety planning and good laboratory practices.8

 Each laboratory is

responsible for maintaining a current awareness file of OSHA regulations9

 regarding

the safe handling of the chemicals specified in this method. Material Safety Data

Sheets (MSDS) containing information on chemical and physical hazards associated

with each chemical should be made available to all personnel involved in the

chemical analysis.

5.3 Potassium persulfate is a strong oxidizing and corrosive reagent. The analyst should

avoid eye and skin contact by wearing eye/face protection, powderless gloves and

laboratory clothing. If body tissue comes in contact with this reagent, apply large

quantities of water for at least 15 minutes (see MSDS) while removing contaminated

clothing. This reagent may cause delayed burns. Seek immediate medical attention if

the area becomes irritated or burned. This reagent can also cause a fire or explosion if

it is allowed to come in contact with combustible materials. 

5.4 Protect your hands by wearing laboratory disposable gloves during the preparation

and disposal of corrosive (acids and oxidants) laboratory reagents. Do not reuse

laboratory gloves that have been discarded or are suspected of being contaminated.

6.0 EQUIPMENT AND SUPPLIES 

NOTE: Brand names, and/or catalog numbers are included for illustrative purposes

only. No endorsement is implied. Equivalent performance may be achieved using

apparatus, instrument systems, and reagents other than those that are illustrated

below. The laboratory is responsible for the assurance that alternate products,

apparatus, instrument systems, and reagents demonstrate equivalent performance as

specified in this method.

6.1 FILTER APPARATUS - Nalgene® or Corning® 250 mL Filter System, 0.45-μm

Nylon (NYL) or Polyethersulfone (PES) Low Extractable Membrane/Polystyrene

Body with optional glass fiber prefilters (nominal 1 to 7 um). Packaging and filter

apparatus are recyclable (NALGE-NUNC International: Nalgene Labware CAT.

numbers NYL: 153-0045, PES: 168-0045). It is recommended that filter membranes

be hydrophilic 0.45-μm filter material. 

NOTE: Alternate filter membranes (e.g., polypropylene, silver or Teflon®), apparatus

technologies such as cartridges, reusable filter bodies, syringe filters, and their

associated syringes, peristaltic pumps or vacuum pumps may be selected. The

complexity of an alternative filter apparatus is left to the analyst’s ingenuity

providing that the apparatus meets quality control and initial demonstration of
415.3 - 11

capability requirements as stated in Section 9.3.2, and that FB requirements are met

(Sect. 9.9). It is recommended that the analyst review the AWWA journal article

“Selecting filter membranes for measuring DOC and UV254”, Karanfil, et. al.10, prior

to the selection of an alternative filter membrane, apparatus, and wash procedure. 

Karanfil tested 11 filter membranes (0.45-μm pore size and 47-mm disc size)

representing four different manufacturers and seven different types of filter materials

for both desorption and adsorption. Hydrophilic polyethersulfone (PES) filters

available from two manufacturers (Osmonics Micro-PES and Gelman Supor 450,

both 0.45 micron absolute pore size and 47-mm disc size) and a hydrophilic

polypropylene filter (Gelman GH Polypro, 0.45 micron absolute pore size and 47-mm

disc size) were found to be the best options among those tested in the study. 

6.2 INJECTION VIALS - Specially cleaned 40-mL glass vials, with caps and

polytetrafluoroethylene (PTFE)/silicone septa. Eagle-Picher TOC Certified, Cat. No.

40C-TOC/LL, Eagle-Picher Technologies®. These vials are specially cleaned by the

manufacturing process and certified to contain < 10 μg TOC. Vials may be reused if

cleaned as per Section 4.2. The PTFE/silicone septa once pierced by the sample

injector must be discarded. 

6.3 INSTRUMENT SYSTEMS - The TOC and UVA procedures allow for the use of

several different types or combinations of TOC instrumental system technologies.

Examples of typical TOC instrument systems, as well as a UV spectrophotometer, are

described below. Data from these instruments may be found in Section 17. Only one

TOC instrument is required to perform this method.

6.3.1 TOC INSTRUMENT 1: UV/Persulfate/Wet Oxidation with

Permeation/Conductivity Detection. The Ionics-Sievers® 800 TOC analyzer

is based on UV catalyzed persulfate digestion to produce CO2

, which is

detected by a membrane permeation/conductivity detector.

6.3.2 TOC INSTRUMENT 2: Elevated Temperature/Catalyzed/Persulfate/Wet

Oxidation/Nondispersive Infrared Detection (NDIR). The O.I. Analytical®

TOC Model 1010 is based on elevated temperature (95-100°C) catalyzed

persulfate digestion to produce CO2

, which is then detected by an NDIR

detector.

6.3.3 TOC INSTRUMENT 3: UV/Low Temperature/Persulfate/Wet

Oxidation/NDIR. The Tekmar-Dohrmann® Phoenix 8000 TOC analyzer is

based on UV catalyzed persulfate digestion to produce CO2

, which is then

detected by an NDIR detector.

6.3.4 TOC INSTRUMENT 4: Catalyzed/Combustion Oxidation(680 °C)/NDIR. 

The Shimadzu® model TOC-5000A analyzer is based on a catalyzed
415.3 - 12

combustion in air or oxygen reagent gas to produce CO2, which is then

detected by an NDIR detector.

6.3.5 TOC INSTRUMENT 5: High Temperature Combustion Oxidation/NDIR. 

The Thermo Environmental® ThermoGlasTM 1200 TOC is based on a dual

zone furnace with individually adjustable ovens from 700 to 1250 °C for final

high temperature combustion of the sample with air or oxygen reagent gas to

produce CO2, which is then detected by an NDIR detector.

6.3.6 UV SPECTROPHOTOMETER: The spectrophotometer is used for the UVA

determination only. The spectrophotometer must be able to measure UVA

(254 nm), with an absorbance from 0.0045 to at least 1.0 cm-1 UVA, and

accommodates a sample cell with a path length of 1, 5, or 10 cm.

6.4 LABORATORY REAGENT WATER TREATMENT SYSTEM - The LRW used for

the development of this method was generated using a Millipore®, Milli-Q Plus

Ultra-Pure Water Treatment System with a 0.22-μm sterile pack filter capable of

producing organic carbon free (< 0.010 mg/L OC), ultrapure deionized water.11 The

maximum amount of OC allowed in the LRW for this method is 0.35 mg/L. When

purchasing a treatment system for general laboratory use, it is recommended that a

system be purchased capable of producing LRW of the above stated quality in order

to be of use in other laboratory analyses. 

6.5 MUFFLE FURNACE - A muffle furnace capable of heating up to 425 °C. 

6.6 FIELD SAMPLE pH TEST - Sample pH indicator test strips, non-bleeding

(colorpHast® Indicator Strips 0 - 2.5, cat. 9580), EM Science, 480 Democrat Road,

Gibbstown, N.J. 08027. Pocket pH test kits, pocket pH meters, or laboratory pH

meters are acceptable for field sample pH measurements. 

6.7 PIPET, DISPOSABLE TRANSFER - Large volume bulb (15mL), non-sterile, with

flexible long stem polyethylene transfer pipet. “Sedi-Pet TM”, Fisher Scientific® Cat. 

13-711-36. Pipets are used for sample transfer from the middle of a sample bottle

containing floating material (scum).

6.8 SAMPLE COLLECTION REAGENT BOTTLES - Specially cleaned, 1-L Boston

round glass bottles with cap. Eagle-Picher TOC Certified, Cat. No. 112-01A/C TOC,

Eagle-Picher Technologies, LLC. These bottles are specially cleaned by the

manufacturing process and certified to meet EPA OSWER Directive # 9240.0-05A

“Specifications And Guidance For Contaminant-Free Sample Containers 12/92.” 

Amber bottles are preferred, but clear glass bottles may be used if care is taken to

protect samples from light. The laboratory may select glass bottles of any volume that

meet the utility and laboratory sample processing and quality control sampling needs. 
415.3 - 13

Glass bottles may be reused after cleaning (see Sect. 4.2 for glassware cleaning

instructions) or discarded. 

6.9 SPARGE APPARATUS - N-EVAPTM, Nitrogen Evaporator System Model 111,

Organomation Associates Inc. This apparatus is not used for its originally designed

purpose of evaporating sample extracts. In this method, the apparatus is used as a

sparging device. The stainless steel needles of the apparatus are lowered into the 40-

mL sample vials containing the TOC or DOC samples to remove inorganic carbon by

sparging with nitrogen gas. 

Alternately, some TOC auto-samplers provide a pre-sparging or membrane IC

removal option prior to injection of the sample into the TOC instrument system. The

analyst is encouraged to utilize these instrument options, if available. Another

alternative is for the laboratory analyst to fabricate a sparging apparatus. For

example, an apparatus may consist of copper tubing from a regulated gas source,

connected to a needle valve used for gas flow control, a length of silicone tubing with

a glass Pasteur pipet inserted into the tubing and a ring stand with clamp for

positioning the pipet. The Pasteur pipet is inserted into the sample bottle or vial to

remove inorganic carbon by sparging with nitrogen gas (Sect. 11.5). The complexity

of the alternative sparging apparatus is left to the analyst’s ingenuity providing that

the apparatus meets quality control and initial demonstration of capability (IC

removal test) requirements as stated in Section 9.2.4. 

6.10 VACUUM SOURCE - Aspirator, air flow or water flow, hand-operated or low

pressure electric vacuum pump, providing a vacuum of 15 inches of mercury (Hg) or

better. If an alternative choice is made, see note in Section 6.1.

6.11 VARIABLE PIPETTES - Programable automated pipettes. Rainin Instrument®

EDP-Plus Pipette 10ml, Cat. No. EP-10 mL; EDP-Plus Pipette 1000 μL, Cat. No. EP1000; EDP-Plus Pipette 100 μL, Cat. No. EP-100, or manual variable pipets with

disposable tips having a calibrated range of 0 to 100-μL, 0 to 1000-μL, and 0 to 10

mL.

6.12 VOLUMETRIC FLASK AND PIPETS - All volumetric glassware used in this

method are required to be “Class A”.

6.13 WAVELENGTH VERIFICATION FILTER SET- Wavelength verification may be

provided by the instrument manufacturer, a scientific instrument service company, or

if this not practical, wavelength verification may be made by the laboratory using

certified spectrophotometric filter sets with values traceable to NIST. Fisher

Scientific Cat. No. 14-385-335, Spectronic No. 333150.
415.3 - 14

7.0 REAGENTS AND STANDARDS

NOTE: The chemicals required for this method must be at least reagent grade. 

Unless otherwise indicated, it is intended that all reagents shall conform to the

specifications of the Committee on Analytical Reagents of the American Chemical

Society (ACS) and/or ACS certified, when available. Some instrument manufacturers

provide reagents specifically prepared for the optimum performance of their TOC

instruments and provide calibration services and/or calibration standards. The

analyst is allowed to use these services or prepare reagents and/or standards

according to the instrument manufacturer’s operation manual.

7.1 COMPRESSED GASES – Carbon dioxide free Ultra High Purity (UHP) grade

nitrogen gas or an optional Ultra-low level TOC gas delivery system. For combustion

based TOC systems, zero grade air and UHP grade oxygen may be needed. The use

of lesser grades of compressed gases will result in high background noise in the TOC

instrument systems. The TOC Instrument 1 described in Section 6.3.1. does not

require compressed gasses for operation.

7.2 LABORATORY REAGENT WATER (LRW) - Water that has a TOC reading of 

< 0.35 mg/L and < 0.01 cm-1 UVA. Although the LRW TOC and UVA limits in this

method are 0.35 mg/L and 0.01 cm-1, respectively, the system specified in Section 6.4

is capable of producing better quality organic carbon free, ultrapure deionized water. 

For optimum performance, it is recommended that LRW with < 0.05 mg/L TOC and 

< 0.0045 cm-1 UVA be used for this method. Alternatively, LRW may be purchased

(ACS HPLC grade or equivalent).

7.3 DISODIUM HYDROGEN PHOSPHATE, [Na2HPO4, CAS# 7558-79-4] -

Anhydrous, ACS grade or better.

7.4 O-PHOSPHORIC ACID (85%), [H3PO4, CAS# 7664-38-2] - ACS grade or better.

7.5 POTASSIUM DIHYDROGEN PHOSPHATE, [KH2PO4, CAS# 7778-77-0]-

Anhydrous, ACS grade or better.

7.6 POTASSIUM HYDROGEN PHTHALATE (KHP), [C8H5O4K, CAS# 877-24-7] -

Anhydrous, ACS grade or better.

7.7 REAGENT SOLUTIONS FOR WET CHEMICAL OXIDATION - It is assumed that

each instrument manufacturer has optimized reagent solutions for their respective

instruments and has provided the instructions for the preparation of reagents in the

instrument’s operation manual. NOTE: TOC Instrument 1 does not require gas

sparge of reagents as the manufacture provides reagent packs for the operation of the

instrument.
415.3 - 15

7.7.1 PERSULFATE REAGENT - Prepare this solution according to the instrument

manufacturer’s instructions or purchase the solution from the instrument

manufacturer. If the laboratory prepares the solution, transfer the solution to

the instrument reagent bottle and cap. It is recommended that this solution be

sparged gently with carbon dioxide free UHP grade nitrogen gas for

approximately 1 hour. If the instrument system provides continuous sparge, it

is recommended that the reagent bottles be allowed to sparge for 10 minutes to

1 hour before operating the instrument. Self contained reagent packs or other

types of reagent systems may not require reagent sparging. Discard the

solution as per expiration time/date listed in the manufacturer’s operation

manual. 

7.7.2 PHOSPHORIC ACID SOLUTION - Prepare this solution according to the

instrument manufacturer’s instructions or purchase the solution from the

instrument manufacturer. If the laboratory prepares the solution, transfer the

solution to the instrument reagent bottle and cap. It is recommended that this

solution be sparged gently with carbon dioxide free UHP grade nitrogen gas

for approximately 1 hour. If the instrument system provides continuous

sparge, it is recommended that the reagent bottles be allowed to sparge for 10

minutes to 1 hour before operating the instrument. Self contained reagent

packs or other types of reagent systems may not require reagent sparging. 

Discard the solution as per expiration time/date listed in the manufacturer’s

operation manual.

7.8 STANDARD SOLUTIONS

NOTE: Consult with the instrument manufacturer or operation manual for the

recommended concentrated acid used for preservation of standard solutions. The

concentrated acid used to preserve the standards is usually HCl, H2SO4

, or H3PO4

depending upon the instrument operation manual recommendation. The acid used for

the standards must be the same as the one used for the samples. Standard solutions

may be alternatively prepared in larger or smaller volumes and concentrations as

needed for the calibration of instruments. Standard solutions may be prepared by

gravimetric or volumetric techniques. This section provides guidance for the

preparation of calibration solutions. 

7.8.1 INORGANIC CARBON PRIMARY TEST SOLUTION (IC-TEST)

REAGENTS

7.8.1.1 AMMONIUM CHLORIDE, [NH4Cl, CAS# 12125-02-9] - ACS grade

or better.

7.8.1.2 CALCIUM CHLORIDE DIHYDRATE, [CaCl2 C 2H2O, CAS# 10035-

04-8] - ACS grade or better.
415.3 - 16

7.8.1.3 CALCIUM NITRATE TETRAHYDRATE, [Ca(NO3)2 C 4H2O, CAS#

13477-34-4] - ACS grade or better.

7.8.1.4 MAGNESIUM SULFATE HEPTAHYDRATE, [MgSO4 C 7H2O,

CAS# 10034-99-8] - ACS grade or better.

7.8.1.5 POTASSIUM CHLORIDE, [KCl, CAS# 7447-40-7] - ACS grade or

better.

7.8.1.6 SODIUM BICARBONATE, [NaHCO3

, CAS# 144-55-8] - ACS grade

or better.

7.8.1.7 SODIUM CHLORIDE, [NaCl, CAS# 7647-14-5] - ACS grade or

better.

7.8.1.8 SODIUM-META SILICATE NONAHYDRATE, [Na2SiO3C 9H2O,

CAS# 13517-24-3] 

7.8.1.9 SODIUM PHOSPHATE DIBASIC HEPTAHYDRATE, [Na2HPO4

C

7H2O, CAS# 7782-85-6] - ACS grade or better.

7.8.2 PREPARATION OF THE IC-TEST SOLUTION, 100 MG/L IC - This

solution is used in the performance of the IC removal sparging efficiency test

(Sect. 9.2.4 ). The ionic content of the IC-TEST mixture solution was chosen

from a previous investigation in which the authors wanted to simulate waters

likely to be found in waste treatment plants.12 Because the inorganic salts are

not soluble in a single concentrated solution, prepare four separate stock

solutions by diluting each of the following to one liter with LRW: 
415.3 - 17

FLASK

(1 L)

SALT WEIGHT

(g)

A magnesium sulfate heptahydrate, MgSO4 C 7H2O 2.565

B ammonium chloride, NH4Cl 0.594

calcium chloride dihydrate, CaCl2 C 2H2O 2.050

calcium nitrate tetrahydrate, Ca(NO3)2 C 4H2O 0.248

potassium chloride, KCl 0.283

sodium chloride, NaCl 0.281

C sodium bicarbonate, NaHCO3 2.806

sodium phosphate dibasic heptahydrate, Na2HPO4C 7H2O 0.705

D sodium-meta silicate nonahydrate, Na2SiO3

C 9H2O 1.862

Prepare a 102.5 mg/L IC-TEST mixture, based on bicarbonate calculations

and impurities, by adding a 10-mL aliquot of each of the above solutions to a

40-mL vial. Add 40 μL of H3PO4, HCl, or H2SO4, depending upon instrument

requirements (see note, Sect. 7.8), to the 40-mL injection vial. An IC-TEST

mixture of approximately 100 mg/L was chosen to represent the extreme

inorganic carbon concentration the analyst may encounter. Although the

mixture is turbid after preparation, clarification occurs after acidification.

7.8.3 ORGANIC CARBON PRIMARY DILUTION STANDARD (OC-PDS), 500

mg/L (1 mL = 0.5 mg OC) - Prepare an acid preserved (pH #2) OC-PDS by

pouring approximately 500 mL of LRW into a 1-liter volumetric flask, adding

1 mL of concentrated acid for preservation (see note, Sect. 7.8), carefully

transferring 1.063 g KHP into the LRW, stirring until it is dissolved, and then

diluting to the mark with LRW (1.0 mg KHP = 0.471 mg Organic Carbon). 

Transfer this solution to a marked amber glass reagent bottle and cap for

storage. This solution does not require refrigeration for storage and is stable

for an indefinite period of time (6 months to a year). Replace the OC-PDS if

the instrument system fails to pass the QCS requirements (Sect. 9.11).

7.8.4 ORGANIC CARBON CALIBRATION (OC-CAL) - At least 4 calibration

concentrations and the CB (i.e., a minimum of 5 total calibration points) are

required to prepare the initial calibration curve. Prepare the calibration

standards over the concentration range of interest from dilutions of the OCPDS. The calibration standards for the development of this method were

prepared as specified in the table below. Calibration standards must be
415.3 - 18

prepared using LRW preserved to pH # 2 with concentrated acid (see note,

Sect. 7.8). Filtration of the CAL standards for DOC analysis is unnecessary,

since interferences from the filtration unit are monitored via the FB. 

Therefore, the OC-CAL may be applied to TOC or DOC determinations. The

OC-CAL standards must be sparged, or otherwise treated for IC removal, like

a sample following the procedure in Section 11.5. 

PREPARATION OF CALIBRATION (OC-CAL) CURVE STANDARDS

CAL

 Level

Initial Conc. of

OC-PDS

(mg/L)

Vol. of 

OC-PDS

(mL)

Final Vol. of

 OC-CAL Std.

(mL)

Final Conc. of

OC- CAL Std.

(mg/L)

CB – 0 1000 – 

1 500 1.0 1000 0.5

2 500 2.0 1000 1.0

3 500 4.0 1000 2.0

4 500 10.0 1000 5.0

5 500 20.0 1000 10.0

6 * 500 5.0 100 25.0

7 * 500 10.0 100 50.0

* Note: OC-CAL 6 - 7 are optional calibration standards for use when

operating the instrument in a higher concentration range.

The calibration blank (CB) is a “0.0 mg/L OC ” standard which approximates

zero mg/L OC concentration plus the background carbon contributed from the

LRW. The CB is stored and treated the same as all other calibration

standards. When analyzed, the CB must not exceed 0.35 mg/L TOC.

7.8.5 Calibration standards may be stored at room temperature in amber glass

bottles (Sect. 6.8) and/or in a dark cabinet (if clear glass used) for a period of

30 days. If stored OC-CALs are used to recalibrate the instrument during this

30 day period, the CB which has been stored with the OC-CALs must be

analyzed as a sample prior to recalibration. The CB must not exceed 0.35

mg/L OC. If the CB does not meet this criteria, the CB and OC-CALs may

have absorbed OC from the laboratory atmosphere and must be discarded. 

7.9 COMMERCIAL SPECTROPHOTOMETER CHECK SOLUTION (COMM-SCS) -

The laboratory may use a commercially prepared COMM-SCS for the purpose of

checking the performance of the spectrophotometer. The analyst should purchase the

COMM-SCS in the absorbance range that is commonly observed for the samples
415.3 - 19

analyzed. The IN-SPECTM optical standard and background solution for a 254 nm

spectrophotometric check is NIST traceable, and is available from GFS Chemicals,

PO Box 245, Powell, Ohio 43065.

7.9.1 COMMERCIAL SPECTROPHOTOMETER BACKGROUND SOLUTION

(COMM-BKS) - A background solution provided by the COMM-SCS

provider that is used to correct for stabilizing agents present in the COMMSCS.

7.10 LABORATORY PREPARED KHP-SPECTROPHOTOMETER CHECK

SOLUTIONS (KHP-SCS) - The laboratory may elect to prepare a KHP based

spectrophotometer check solution (KHP-SCS) for the purpose of checking the

performance of the spectrophotometer at the absorbance of the average UVA sample. 

This requires the preparation of a buffered KHP solution having a known

concentration and a known absorbance at 254 nm. The analyst should prepare the

KHP-SCS that will provide an absorbance similar to the absorbance in the range (low,

mid, high) of the sample analyzed. NOTE: If the phosphate buffer reagents used

below have been exposed to laboratory humidity, it is recommended that potassium

dihydrogen phosphate (KH2PO4

) and disodium hydrogen phosphate (Na2HPO4

) be

dried for 1 hour at 105°C.

7.10.1 KHP-SCS-BLANK - Prepare a 1-L volumetric flask containing approximately

500 mL of LRW. Transfer and dissolve 4.08 g anhydrous KH2PO4 and 2.84 g

anhydrous Na2HPO4 in 500 mL. Dilute to the mark with LRW and transfer to a

1-L amber glass bottle.

7.10.2 KHP-SCS - Prepare the KHP-SCS that will provide an absorbance similar to

the absorbance of the samples analyzed. Prepare a 1-L volumetric flask

containing approximately 500 mL of LRW. Transfer and dissolve 4.08 g

anhydrous KH2PO4 and 2.84 g anhydrous Na2 HPO4 into the 500 mL of LRW. 

From the example calculation, or table located below (Sect. 7.10.2.1), transfer

the amount of OC-PDS (in mL) needed to produce the representative

absorbance of the sample into the buffered KHP-SCS and dilute with LRW to

the 1 L mark.

7.10.2.1 KHP-SCS, CONCENTRATION CALCULATION - Standard

Method 5910 B provides for a spectrophotometer check using a

correlation equation which was based on the analyses of 40-samples

of KHP solution. 3 The correlation formula is as follows: UV254 =

0.0144 KHP + 0.0018. This formula may be algebraically solved for

the concentration of KHP, expressed as mg/L OC, needed to

produce a KHP-SCS for the observed sample absorbance as

follows:
415.3 - 20

KHP-OC conc. = (UV254 !0.0018) ' 0.0144

Using the calculated KHP-OC concentration, determine the amount

of OC-PDS (Sect. 7.8.3, 1 mL = 0.5 mg OC) needed to produce a

known absorbance for the KHP-SCS. For example, if you typically

run samples that have an average UVA equal to 0.08 cm-1, you can

calculate the KHP in the following manner:

 5.431 KHP mg/L as OC = (0.08 cm-1 UVA254 !0.0018) ' 0.0144

The 5.431 mg/L is the same as 5.431 mg/L KHP. It follows that to

produce a 1-L KHP-SCS solution having a UVA absorbance of 0.08

cm-1, you will need 10.9 mL of OC-PDS as calculated below:

(5.431 KHP-SCS mg/L)(1000mL/L) / 500 OC-PDS mg/L = 10.9 mL of OC-PDS

In summary, 10.9 mL OC-PDS is needed to make a 1-L KHP-SCS

solution that will have a UVA absorbance of 0.08 cm-1

.

Alternately, the following table, which is based on the above

calculation, can be used. From this table, cross reference the

amount of the OC- PDS (in mLs) needed to produce the desired

UVA for the KHP-SCS. Transfer the required amount of OC-PDS

into a 1-L flask and dilute to the mark with LRW.

KHP-SCS Preparation

UVA@254nm

(cm -1)

ORGANIC

CARBON (mg/L)

OC-PDS (mL

added per liter of

LRW)

0.0738 5 10

 0.1458 10 20

 0.2898 20 40

 0.4338 30 60

7.10.3 Verify that the KHP-SCS-BLANK and the KHP-SCS buffered solutions are at 

pH 7. Check the pH by placing a drop from the SCS bottle onto pH test paper. 

Do not put the pH paper into the SCS bottle. Placing the pH paper in the 

bottle will contaminate the sample with organic carbon. If this happens, the

spectrophotometer check solution must be discarded and a new solution

prepared in a clean bottle. If the buffered KHP-SCSs are not at a pH of 7, the
415.3 - 21

solution must be discarded and a new solution made. Store these solutions at

approximately < 6 °C. These solutions are not preserved. In a sterile

environment these solutions may be stable for a month. However, the shelf life

of these solutions may be shortened as a result of microbial growth. Therefore,

it is recommended that the above solutions be made fresh weekly and/or be

replaced if any significant change in absorbance is noted. 

8.0 SAMPLE COLLECTION, FILTRATION, AND HOLDING TIMES

NOTE: Consult with the instrument manufacturer or operation manual for the

recommended type of concentrated acid used for preservation of TOC or DOC

samples. The concentrated acid used to preserve the sample is usually HCl, H2SO4, or

H3PO4 depending upon the instrument operation manual recommendation. The acid

used for the standards must be the same as the one used for the samples. Samples for

DOC and UVA analyses may be filtered in the field using alternate apparatus

technologies such as cartridges, reusable filter bodies, syringe filters, and their

associated syringes, peristaltic pumps or vacuum pumps providing that the filter blank

requirements are met (Sect. 9.9). 

8.1 SUVA SAMPLE COLLECTION - SUVA is determined by the analysis of a DOC

sample and a UVA sample, together called the SUVA sample set. A single sample

may be collected and split for the DOC and UVA analyses or two individual samples

may be collected at the same time. For example: if the sample is to be determined by

two separate laboratories (i.e., one lab determines UVA and a second lab determines

the DOC), the sample collector may collect two representative samples for shipment. 

A 1-L volume is recommended for the collection of DOC and UVA samples, but other

volumes may be collected depending on the sample volume needed for the filtration

apparatus used by the analyzing laboratory. The SUVA sample set is collected in clean

glass bottles by filling the bottle almost to the top. The sample set is NOT preserved

with acid at the time of collection. The sample set is delivered as soon as possible to

the laboratory and should arrive packed in ice or frozen gel packs. The sample set is

processed by the laboratory and stored at < 6 °C, until analysis. If there is no visible

ice or the gel packs are completely thawed, the laboratory should report these

conditions to the data user. Samples shipped that are improperly preserved, and/or do

not arrive at the laboratory within 48 hrs, cannot be used to meet compliance

monitoring requirements under the Safe Drinking Water Act (SDWA). 

8.1.1 The DOC sample must be filtered in the field or in the laboratory within 48

hours of sample collection according to the procedure detailed in Section 11.4

prior to acidification and analysis. After filtration, the DOC sample is acidified

with 1 mL of concentrated acid per 1 L of sample or the sample is preserved by

drop wise adjustment to a pH < 2 (Sect. 8.3). The DOC bottle is capped and

inverted several times to mix the acid and is stored at < 6 °C. The sample must

be analyzed within 28 days from time of collection.
415.3 - 22

8.1.2 The UVA sample must be filtered in the field or in the laboratory according to

the procedure detailed in Section 11.4. The sample used for the UVA

determination is not acidified. The UVA bottle is capped and stored at < 6 °C

for up to 48 hours from the time of collection. The UVA sample must be

analyzed within 48 hours from the time of collection.

8.2 TOC SAMPLE COLLECTION - The typical sample volume collected may vary from

40 mL to 1 L of sample. It is recommended that the sample collector coordinate the

size of collection volume with the needs of the analytical laboratory. If the TOC

sample is collected in a 40-mL injection vial, it is acidified to pH < 2 by adding 2

drops of concentrated acid. If the TOC sample is collected in a 1-L bottle, 1 mL of

concentrated acid is added or the sample is drop wise adjusted to a pH < 2 (Sect. 8.3). 

TOC samples must be acidified at the time of collection. Cap the bottle or injection

vial and invert several times to mix the acid. The sample is delivered as soon as

possible to the laboratory and should arrive packed in ice or frozen gel packs. If there

is no visible ice or the gel packs are completely thawed, the laboratory should report

the conditions to the data user. Samples that are improperly preserved or shipped,

cannot be used for compliance monitoring under the SDWA. The sample is stored at

< 6 °C, until analysis. Stored and preserved samples must be analyzed within 28 days 

from time of collection. 

8.3 SAMPLE pH CHECK - The pH of the preserved sample (DOC, TOC only) or filtrate

should be checked to ensure adequate acidification for the preservation. This should

only be performed by an adequately trained sample collector. Check the pH by placing

a drop from the sample onto pH test paper. Do not put the pH paper into the sample

bottle. Placing the pH paper in the sample bottle will contaminate the sample with

organic carbon. If this happens, the sample or filtrate must be discarded and a new

sample collected. 

9.0 QUALITY CONTROL

9.1 Each laboratory using this method is required to operate a formal quality control (QC)

program. QC requirements for TOC include: the initial demonstration of laboratory

capability (IDC) followed by regular analyses of continuing calibration checks (CCC),

independent quality control samples (QCS), laboratory reagent blanks (LRB), field

duplicates (FD), and laboratory fortified matrix samples (LFM). For this method, a

TOC laboratory fortified blank (LFB) is the same as a CCC (Sect. 10.3) and no LFB is

required. QC requirements for DOC include: the IDC followed by regular analyses of

CCCs, QCSs, filter blanks (FB), LFB, FDs, and LFMs.

For laboratories analyzing both TOC and DOC samples, only the DOC IDC

determination is required, as it is similar to, yet more rigorous than, the TOC IDC. 

The IDC must be performed the first time a new instrument is used and/or when a new

analyst is trained. 
415.3 - 23

QC requirements for UVA analysis include: the performance of the IDC followed by

the regular analysis of spectrophotometer check solutions (SCS), FBs, and FDs. For

UVA analysis, no LFB or DL determination is required.

The control of instrument background is crucial prior to the performance of the IDC. 

It is required that a critical evaluation be made of the instrument background 2

associated with an instrument system before proceeding with the IDC. Once an

acceptable instrument background is established, it is safe to proceed with the IDC. 

In summary, this section describes the minimum acceptable QC program, and

laboratories are encouraged to institute additional QC practices to meet their specific

needs. The laboratory must maintain records to document the quality of the data

generated. All users of this method are encouraged to write their own SOPs stating

exactly how their lab executes the method. A summary of QC requirements can be

found in Tables 17.5 and 17.6.

9.2 INITIAL DEMONSTRATION OF CAPABILITY FOR TOC DETERMINATION

9.2.1 INITIAL DEMONSTRATION OF LOW SYSTEM BACKGROUND - Before

any samples are analyzed, and any time a new set of reagents is used, prepare a

laboratory reagent blank (LRB) and demonstrate that it meets the criteria in

Section 9.9. 

9.2.2 INITIAL INSTRUMENT CALIBRATION VERIFICATION - Prior to the

analysis of the IDC samples, calibrate the TOC instrument as per Section 10.2. 

Verify calibration accuracy with the preparation and analysis of a QCS as

defined in Section 9.11.

9.2.3 INITIAL ORGANIC CARBON FLOW INJECTION MEMORY CHECK -

Inject the highest OC-CAL used, followed by two injections of the LRB. If the

first LRB is > 0.35 mg/L OC and the second LRB is in QC compliance (i.e., 

< 0.35 mg/L OC), a memory problem is indicated. Therefore, an LRB may

need to be placed after every sample. If the instrument system provides a rinse

or system flush with LRB between injections, activate the event control settings

and repeat this section. If the memory problem persists, then an LRB must be

placed after every sample.

9.2.4 INORGANIC CARBON REMOVAL SPARGING EFFICIENCY TESTVarious sample sparge times (3-10 minutes) and sparging flow rates have been

reported for the removal of IC. 13 A multi-laboratory study reported large

variations and positive bias in analyses of solutions of standards containing

even small amounts of IC, demonstrating the importance of IC removal.14

Since IC must be removed in order to reduce interferences with the TOC and
415.3 - 24

DOC quantitation, an IDC of the IC removal is performed. Please note: any

manipulation of the sample may inadvertently introduce organic carbon from

the apparatus.

Prepare an inorganic carbon mixture, IC-TEST solution, as specified in Section

7.8.2. Using the procedure outlined in Section 11.5, sparge at least three

portions of the acidified IC-TEST solution in the same manner, and of the same

volume, as field samples will be sparged. After the IC-TEST solution is treated

by the IC removal apparatus, analyze the solution as an LRB for OC. The IC

removal apparatus must produce an acceptable IC-TEST by meeting the LRB

requirements as stated in Section 9.9. These IC removal parameters are then

used for all subsequent samples. 

The sparging time recommended in Section 11.5.2 is based on a sparging study

with an N2 flow rate of approximately 200 mL/min and a pH of 2.0. The

following inorganic carbon concentration reduction was observed after the

external sparging of a 40-mL IC-TEST solution:

IC REMOVAL SPARGE EFFICIENCY STUDY

sparging time (minutes) 0 5 10 15 20

concentration IC

(mg/L), measured as

OC interference

102.5 6.11 0.611 0.049 0.044

The LRB during the above study was < 0.05 mg/L, thus a 20-minute sparge

time ensured that no measurable organic carbon remained in the sample. 

The above sparge efficiency table should be used only as a guide. The analyst

may find that a higher flow rate may reduce the time necessary to remove the

inorganic carbon to a level at or near the TOC measurements found in the LRB. 

The IC-TEST solution is also used to test alternate IC removal apparatus that

remove IC by internal chemical treatment, alternate sparging procedures,

and/or membrane IC removal. Any alternative procedure or IC removal

apparatus must be tested using the IC-TEST solution and meet the LRB

requirements as stated in Section 9.9.

9.2.5 INITIAL DEMONSTRATION OF ACCURACY - The initial demonstration of

accuracy consists of the analysis of five (5) LFBs analyzed as samples at a

concentration between 2 to 5 mg/L OC. If DOC analysis is being performed,

the LFB must be filtered according to the procedure in Section 11.4. The

average recovery between 2 to 5 mg/L OC must be within ±20% of the true
415.3 - 25

value. If ±20% of the true value is exceeded, identify and correct the problem

and repeat Sections 9.2.5 and 9.2.6.

9.2.6 INITIAL DEMONSTRATION OF PRECISION - Calculate the average

precision of the replicates in the Initial Demonstration of Accuracy (Sect.

9.2.5). The RSD% must be no greater than 20%. If the RSD% exceeds 20%,

identify and correct the problem and repeat Sections 9.2.5 and 9.2.6.

9.2.7 ORGANIC CARBON DETECTION LIMIT (OCDL) DETERMINATION -

The OCDL determination must be conducted over at least three (3) days with a

minimum of seven (n=7) replicate LFB analyses. Before conducting the initial

OCDL, the OC-CAL-1 standard is used to estimate the starting concentration

for the OCDL study. If DOC analyses are being performed, the low-level LFBs

must be filtered according to procedure in Section 11.4 prior to analysis for the

OCDL. If the instrument can easily detect the OC-CAL-1 standard, the analyst

should lower the concentration to a level so that the LFB produces a signal 2 to

5 times the background noise level of the instrument. It is recommended that

the LFB be fortified somewhere between 0.1 to 0.5 mg/L OC. All available

instrument digits are carried for the OCDL calculation. After completion of the

OCDL, the calculation is rounded up or down according to Standard Method

1050 B.15 The final result is reported in units used for the TOC or DOC

procedure and recorded to two significant figures in the instrument log book. 

Calculate the OCDL using the equation:

Organic Carbon Detection Limit = St( n - 1, 1 - alpha = 0.99)

where:

t

(n-1,1-alpha = 0.99) = Student's t value for the 99% confidence level with n-1 degrees

of freedom (t = 3.14 for 7 replicates)

n = number of replicates, and

S = standard deviation of replicate analyses.

If the initial OCDL exceeds 0.35 mg/L or the mean recovery of the LFB used in

the OCDL determination exceeds + 50% of the true value, then the OCDL

determination must be repeated. 

9.3 INITIAL DEMONSTRATION OF CAPABILITY FOR DOC DETERMINATION

9.3.1 Perform Sections 9.2.1 through 9.2.4 as prescribed for TOC. 

9.3.2 INITIAL DEMONSTRATION OF FILTER MEMBRANE SUITABILITY -

Filter membranes are capable of affecting DOC and UVA analyses either by

desorption (leaching) of DOC and UV-absorbing materials from the filters to
415.3 - 26

the samples, or by adsorption (uptake) of DOC and UV-absorbing materials

from the samples onto the filters. Filter membranes selected for DOC and

UVA measurements must not desorb nor adsorb significant DOC and UVabsorbing materials. Desorption is minimized by pre-washing selected filters

as described in Section 9.3.2.2. Adsorption is minimized by filtering a portion

of the sample to waste before sample collection as described in Section 9.3.2.3. 

Because the filtration of relatively turbid samples may cause filters to clog, prefiltration may be necessary and pre-filter preparation is described in Section

9.3.2.1. Due to the possibility of lot-to-lot variations in the levels of

contamination or adsorption, it is recommended that for each filter lot, the user

determine the amount of LRW needed to wash the filters and the amount of

sample that needs to be filtered and discarded prior to collection of filtrate

(filter-to-waste volume). A minimum of three filters (from each new lot)

should be cleaned and checked for desorption/adsorption prior to using the

filters for actual samples. This evaluation must be repeated when filters are

purchased from another manufacturer or when the type of filter being used is

changed.

9.3.2.1 PRE-FILTER PREPARATION - If the analyst anticipates that the UVA

and DOC sample will clog the 0.45-μm pore size filter membrane

before enough filtrate can be collected, glass fiber pre-filters without

organic binders may be used. Karanfil et al 10 suggested cleaning the

pre-filter by heating to 550 °C for one hour, cooling to room

temperature, then washing it with 500 mL of LRW. A 25-mL filter-towaste volume (Sect. 9.3.2.3) was also recommended. The pre-filters

must be demonstrated as acceptable using the procedures described

below in Sections 9.3.2.2 and 9.3.2.3. Depending on the design of the

filter apparatus, the analyst may be able to insert a pre-filter into the

filter apparatus. The pre-filter and filter apparatus could then be

washed as a unit, following the procedure in Section 9.3.2.2. Prefilter

adsorption and desorption may also be tested separately from the filter

membrane.

9.3.2.2 FILTER CLEANING - UV-absorbing materials and DOC are removed

from the filter and filter apparatus by passing LRW through the filter. 

The volume of LRW required depends on the type and disc size of the

filter. For the filter apparatus used to generate the data in this method,

three successive rinses of 250 mL each (for a total of 750 mL) removed

UV-absorbing materials and DOC that could leach from the filter and

apparatus. (The Karanfil 10 study found that a 500 mL wash was

sufficient to prepare the 47-mm disk filters recommended in their study

for DOC samples and a wash of 100 mL was sufficient for filters used

solely to prepare UVA samples.) Acceptable cleaning is demonstrated

by analyzing filter blanks (Sects. 11.4.3, 11.6) and meeting the criteria
415.3 - 27

in Section 9.9. The volume of LRW required to obtain acceptable filter

blanks is then used to clean filters for analyses of all samples (Sect.

11.4). Filters that cannot be cleaned to meet the referenced criteria

must not be used in the preparation of DOC and UVA samples.

9.3.2.3 FILTER-TO-WASTE VOLUME DETERMINATION - In order to

minimize the loss of sample onto the filter by adsorption, a portion of

the sample must be used to saturate the adsorption sites on the filter

after it is cleaned according to Section 9.3.2.2. The amount of sample

filtrate that must be discarded prior to collecting filtrate for DOC and/or

UVA analyses will vary depending upon the type and size of filter and

the volume should be minimized in order to prevent filter clogging. A

25-mL filter-to-waste volume was recommended when using the

hydrophilic polyethersulfone and hydrophilic polypropylene filters of

47-mm disc size studied by Karanfil et al 10 based on evaluations using

low-turbidity model waters prepared from preconcentrated humic and

fulvic materials. 

In this method, a low-turbidity (i.e., TOC = DOC) finished water

sample can be used in the filter-to-waste determination. For

laboratories that are analyzing samples from a variety of sources, the

selected water should have a TOC concentration in the range of 1 to 3

mg/L. For laboratories that only analyze samples from one source, the

selected water should be a finished water with the lowest TOC that is

generally observed (NOTE: Depending on the quality of the source

water, this could be water with a TOC concentration much higher than

the 1 to 3 mg/L recommended for laboratories that are analyzing

samples from a variety of sources.)

A series of at least three filtrates are collected in separate containers for

the filter-to-waste volume determination. The volume of each filtrate is

determined based on the minimum volume required to make an

analytical determination. For example, if the DOC analysis requires 30

mL, then a series of at least three successive 30-mL filtrates should be

collected. For UVA, three successive 10-mL filtrates can be collected. 

If DOC and UVA analyses are to be performed on the same filtrate,

then the volume of each filtrate should be adjusted to provide the

minimum volume necessary to accommodate both analyses (in the

above example, three successive 40-mL washes).

Each filtrate is analyzed according to the procedure in Section 11 and

the concentration is compared to the concentration of the unfiltered

sample. When the concentration of the filtrate is within ± 15% of the

concentration measured in the unfiltered sample, then the recommended
415.3 - 28

filter-to-waste volume is the sum of the volumes of that filtrate and any

previous filtrates in the series. For example, if the unfiltered sample

has a TOC concentration of 3.5 mg/L and the filtrate series (each filtrate

= 30 mL) have concentrations of 2.3, 3.2, and 3.4 mg/L, then a

minimum of 60 mL of sample should be filtered-to-waste prior to

collecting filtrate for DOC analyses. It is recommended that the filterto-waste volume be determined by performing this test on at least three

filters from each lot and averaging the results. Filters that require

large volumes of filter-to-waste should be avoided, because they will

be more subject to clogging prior to the collection of the necessary

volume of filtrate for analysis. The filter-to-waste volume that is

determined in this section must be used in the filtration procedure

described in Section 11.4.4.

9.3.3 Perform Sections 9.2.5 through 9.2.7 using filtered LFBs. The LFBs must be

prepared using the same procedure used to prepare samples (Sect. 11.4).

9.4 INITIAL DEMONSTRATION OF CAPABILITY FOR UVA DETERMINATION

9.4.1 INITIAL CHECK OF SPECTROPHOTOMETER PERFORMANCE - The UV

Spectrophotometer must be checked annually for 0 % transmittance,

wavelength accuracy, stray radiant energy, accuracy and linearity, and optical

alignment. It is recommended that the instrument performance be verified

through the manufacturer or a scientific instrument service company. If

independent verification of performance is not feasible, the laboratory may

acquire a certified spectrophotometric filter set and conduct the evaluation. 

Wavelength verification is made using certified spectrophotometric filter sets

with values traceable to NIST. Using the filter set, test two wavelengths

between 220 and 340 nm. The instrument performance should be recorded in

the instrument log and be used to monitor the spectrophotometer performance

over time. Follow the instrument manufacturer’s operation manual when

measuring the acceptable wavelength transmittance limits.

9.4.2 Verify the spectrophotometer performance according to the procedure as

outlined in Section 10.4.

9.4.3 Conduct the filter membrane suitability study described in Section 9.3.2 for

UVA.

9.5 CONTINUING CALIBRATION CHECK (CCC) - With each analysis batch, analyze a

Low-CCC at or below the MRL (Sect. 9.10) prior to TOC or DOC sample analysis. 

Subsequent CCCs are analyzed after every ten samples and after the last sample. The

concentrations should be rotated to cover the instrument calibration range. A MidCCC is required during every analysis batch. Acceptance criteria are as follows: Low-
415.3 - 29

CCC, + 50% of true value; Mid-CCC, + 20% of true value; High-CCC, + 15% of true

value, see Section 10.3 for concentrations.

9.6 FIELD DUPLICATE (FD) - Within each analysis batch, a minimum of one set of field

duplicates must be analyzed (FD1 and FD2). Sample homogeneity and the chemical

nature of the sample matrix can affect analyte recovery and the quality of the data. 

Duplicate sample analyses serve as a check on sampling and laboratory precision. 

Two samples are collected at the field site and are treated exactly alike. 

9.6.1 Calculate the relative percent difference (RPD) for duplicate measurements

(FD1 and FD2) using the equation:

9.6.2 Relative percent difference for field duplicates having an average concentration

of > 2 mg/L OC should fall in the range of < 20% RPD. If field duplicates in

this concentration range exhibit an RPD greater than 20%, results should be

flagged and the cause for the greater difference (e.g. incomplete IC removal or

matrix interference), investigated. UVA readings should be < 10% RPD. 

NOTE: Greater variability may be observed for samples with OC approaching

the OCDL. 

9.7 LABORATORY FORTIFIED BLANK (LFB) - Within each DOC analysis batch,

analyze an aliquot of reagent water or other blank matrix which has been fortified with

KHP at a concentration of 1-5 mg/L OC. Recovery for the LFB must be within ±20%

of the true value. One LFB is required with each DOC analysis batch. For the DOC

analysis, an LFB is subjected to the same preparation and analysis as a sample,

including filtration (Sect. 11.4). The LFB is not determined for the TOC or UVA

measurements.

9.8 LABORATORY FORTIFIED MATRIX (LFM) - Within each TOC or DOC analysis

batch, an aliquot of one field sample is fortified with an aliquot of the OC-PDS (Sect.

7.8.3). The spike concentration used should result in an increase in the LFM

concentration of 50 to 200% of its measured or expected concentration. Over time,

samples from all routine sample sources should be fortified. For DOC analysis, the

LFM is filtered prior to acidification and analysis.

9.8.1 Calculate the percent spike recovery (%REC) using the equation:
415.3 - 30

where

A = measured concentration in the fortified sample

B = measured concentration in the unfortified sample,

and

C = fortification concentration.

9.8.2 Recoveries may exhibit a matrix dependence. If the LFM recovery falls outside

of 70 to 130% for any fortified concentration, the analyst should suspect that

inorganic carbon was not properly removed (Sect. 11.5) from the sample or that

contamination or matrix interference exists (Sect. 4) and can not be removed. 

If the source of the poor recovery can not be identified, the analyst should label

the sample report “suspect/contamination or matrix interference” to inform the

data user that the sample data quality is questionable but should not be rejected. 

Failure to meet the recovery criteria after repeated sampling may suggest that

the sample matrix may need further study.

9.9 LABORATORY REAGENT BLANK (LRB) AND FILTER BLANK (FB) - Within

each analysis batch, a minimum of one LRB must be analyzed. For DOC and UVA

analysis, the FB serves as the LRB. If more than one lot of filters is used in a DOC or

UVA analytical batch, a FB must be analyzed for each lot. The analyst should be

aware that additional filter blanks, up to one for each sample, are required by some

regulations (e.g., 40 CFR 141.131(d)(4)(i)). 

The LRB or FB is used to assess contamination from the laboratory environment and

background contamination from the reagents used in sample processing and is treated

exactly the same as a sample. The volume of the FB must be the same as the sample

volume. If UVA is to be determined, the FB (UVA-FB) must have an absorbance of 

< 0.01 cm-1 UVA. The LRB and/or the FB (DOC-FB) must be < 0.35 mg/L OC. If

0.35 mg/L OC or 0.01 cm-1 UVA is exceeded, background carbon or reagent

contamination should be suspected. The cause for significant changes in the LRB or

FB value must be identified and any determined source of contamination must be

eliminated. For the FB, this may mean redetermination of filter membrane suitability

(Sect. 9.3.2). The cause of the contamination and the corrective action used to remedy

the problem is then recorded in the instrument log for future reference.

9.10 MINIMUM REPORTING LEVEL (MRL) - The OCDL should not be used as the

MRL. For TOC analysis, it is recommended that an MRL be established no lower than

the mean LRB measurement plus 3F, or two times the mean LRB measurement,

whichever is greater. For DOC analysis, the FB is substituted for the LRB. This value

should be calculated over a period of time, to reflect variability in the blank

measurements. Although the lowest calibration standard for OC may be below

the MRL, the MRL for OC must never be established at a concentration lower

than the lowest OC calibration standard.
415.3 - 31

9.11 QUALITY CONTROL SAMPLE (QCS) - During the analysis of the IDC (Sects. 9.2,

9.3), each time new OC-PDS solutions are prepared (Sect. 7.8.3), or at least quarterly,

analyze a QCS from a source different from the source of the calibration standards. 

The QCS is used to provide an independent verification of the method and the TOC

instrument system. To verify the stock or calibration solutions by comparison with the

QCS, dilute the calibration solution and QCS to a concentration in the mid range of the

calibration curve (approx. 1 - 5 mg/L TOC) in the same manner that the OC-CAL

standards are made (Sect. 7.8.4). Acceptable verification of the calibration is made

when the means of 3 analyses for both the calibration solution and QCS, having a

concentration range between 1 to 5 mg/L OC, agree to within ±20% of the true value. 

If the measured QCS concentration is not within ±20% of the true value, the

calibration solution must be remade and/or the source of the problem must be

determined and corrected. Analysis of the QCS only applies to TOC and DOC

determination.

9.12 SPECTROPHOTOMETER CHECK REQUIREMENT - The performance of the

spectrophotometer is initially demonstrated using the procedure in Section 9.4.1. The

day-to-day performance of the spectrophotometer is checked using KHP-SCS (Sect.

7.10) or a commercially available SCS (COMM-SCS, Sect. 7.9) according to the

procedure in Section 10.4. 

10.0 CALIBRATION AND STANDARDIZATION

10.1 INSTRUMENT SET UP AND OPTIMIZATION - Prior to calibrating the TOC

instrument, clean the instrument system with carbon dioxide free water and sparge

reagents with ultra high purity reagent gas as specified by the instrument manufacturer

to remove background carbon dioxide. NOTE: TOC Instrument 1 does not require

reagent gas for operation. Monitor the instrument background carbon dioxide levels

for at least 30 minutes or until the background signal reaches the manufacturer’s

recommended level. The instrument should have a stable background and be free from

drift caused by CO2

 contaminated gas or leaks in the system. Adjust instrument

temperature, reagent gas and reagent pump flow settings according to the

manufacturer’s operation manual. Some instruments may require reagent priming runs

to clean the flow injection system and reduce carbon background. After the instrument

is judged to be stable, load the auto-injector or prepare to manually inject four LRB

samples and start the analysis. The data collected from the first injection of LRB is

discarded and is considered a system cleanup blank. The next three LRB injections

should produce consecutive readings that fall within 20% of their mean. If these

conditions are met, the instrument is ready for calibration. If not, use the OC-CAL-1

standard and repeat this section. If the three injections of OC-CAL-1 do not produce

consecutive readings that fall within 20% of their mean, the instrument is not ready to

operate and maintenance must be performed according to the instrument operation

manual before proceeding. 
415.3 - 32

10.2 CALIBRATION CURVE - A new calibration curve is generated when fresh standards

are made (Sect. 7.8.4) or when CCCs fall out of QC limits (Sect. 10.3). Use a CB and

at least four OC-CAL standards that span the concentration range of the samples to be

analyzed. For example, if the samples to be analyzed are low in concentration (a range

falling between 0.5 to 5 mg/L OC), prepare a calibration blank and a minimum of four

TOC calibration standards (CB, OC-CAL 1 - 4, see Sect. 7.8.4). The lowest

concentration calibration standard must be at or below the MRL, which may depend on

system sensitivity. Add an additional 40 μL of H3PO4, HCl, or H2SO4, depending upon

instrument requirements (Sect. 8.0), to the 40-mL injection vial(s). Sparge the

calibration standards using the IC removal procedure in Section 11.5 prior to

calibrating the instrument. Inject the standards from low to high concentration and

calibrate the instrument. Be careful not to extend the calibration range over too wide

of a concentration range as flow injection memory may cause analytical error (Sect.

9.2.3). The optional OC-CAL 6 - 7 may be used when operating the instrument in a

higher concentration range. 

NOTE: For instruments that have an internal calibration setting, the calibration is

checked by comparing the five point calibration curve with the internal calibration

point. If the five point calibration curve does not agree with the internal calibration

using the CCC criteria in Section 10.3, the internal calibration of TOC instrument

must be reset by the manufacturer or adjusted by the analyst, following the

manufacturer’s operation manual. 

10.2.1 With the instrument in the ready mode, initiate the automated instrument

calibration routine as per the instrument manufacturer’s operation manual. 

The computer generated calibration curve must have r2 $ 0.993 before

proceeding with analyses. Ideally the instrument calibration should be 

r

2 $ 0.9995 for best results. After the instrument system has been calibrated,

verify the calibration using the Continuing Calibration Check (CCC, Sect.10.3)

and QCS (Sect. 9.11).

10.2.2 Save the data from the initial calibration curve and record it in the laboratory

notebook or instrument log. The initial calibration curve serves as a historical

reference so that future calibrations curves can be compared to determine if the

slope or sensitivity of calibration has changed. If the slope or sensitivity of the

instrument changes such that QC requirements cannot be met, consult the

instrument manual or lab SOP for corrective action, which may include

instrument maintenance and recalibration. 

10.3 CONTINUING CALIBRATION CHECK (CCC) - Demonstration and documentation

of continuing calibration is required and must meet the requirements listed below. The

CCC solutions are made up weekly or just prior to a sample run and are prepared in the

same manner as the OC-CALs (Sect. 7.8.4). An analysis batch begins with the

analysis of a Low-CCC. CCCs are analyzed every 10 samples and must also include a
415.3 - 33

Mid-CCC. Subsequent CCCs should alternate between low, medium, and high

concentrations, and must end the analysis batch. In summary, at least one Low-CCC

and one Mid-CCC is analyzed with each analysis batch in order to verify the

calibration curve. It is recommended that low, mid, and high CCCs be used to verify

the calibration curve over time.

10.3.1 Low-CCC - the concentration range may vary from as low as 2 times the

OCDL up to 0.7 mg/L OC. The Low-CCC is used to verify the low end of the

calibration and must be at or below the MRL, which may depend on system

sensitivity. The recovery for the Low-CCC must be within + 50% of the true

value. 

10.3.2 Mid-CCC - the concentration is varied between 1.0 mg/L to 5.0 mg/L OC. 

The purpose of this CCC is to verify the precision and accuracy at the

calibration range where critical source water treatment decisions are made. 

The Mid-CCC concentration may be varied to meet changing regulatory

requirements. The Mid-range CCC must be within ±20% of the true value. If

it is not, the TOC instrument system must be recalibrated.

10.3.3 High-CCC - the concentration range is varied between 5 to 50 mg/L OC. The

selection of the High-CCC should be near the concentration of the highest OCCAL standard used. The purpose of this CCC is to bracket the concentration

the samples that are typically analyzed and to verify the upper range of the

calibration curve. High-CCC must be within ±15% of the true value. If it is

not, the TOC instrument system must be recalibrated.

10.4 SPECTROPHOTOMETER PERFORMANCE CHECK - The performance of the

spectrophotometer is initially demonstrated using the procedure in Section 9.4.1. The

day-to-day performance of the spectrophotometer is checked using KHP-SCS (Sect.

7.10) or a commercially available SCS (COMM-SCS, Sect. 7.9) prior to analyzing any

UVA samples using the procedure described below.

10.4.1 Using a transfer pipet fill the spectrophotometer cell with the COMM-BKS or

KHP-SCS-BLANK (Sects. 7.9.1, 7.10.1). Use this solution to zero the

spectrophotometer.

10.4.2 After the spectrophotometer is zeroed, empty the cell, clean with LRW, rinse

with methanol, dry with N2 or reagent grade air, and fill it with the KHP-SCS

or COMM-SCS. 

10.4.3 Read the UVA of the KHP-SCS or COMM-SCS. The reading must be within

10% of the expected absorbance value. Record the absorbance of the KHPSCS or COMM-SCS in the spectrophotometer instrument logbook. Empty the
415.3 - 34

cell, clean with LRW, rinse with methanol, and dry with N2 or reagent grade

air. 

10.4.4 If the SCS absorbance criteria stated above cannot be met, discard the COMMSCS or the KHP-SCS and purchase new COMM-SCS or remake the KHPSCS. Repeat Section 10.4.

11.0 PROCEDURE

11.1 TOC/DOC SAMPLE INTEGRITY EVALUATION - It is important to analyze a TOC

or DOC sample as directly and as soon as possible. Sample handling and preparation

should be minimized. Upon receiving the sample from the field, the analyst must

determine if the sample was treated and stored according to instructions found in

Section 8.

11.2 OPTIONAL TREATMENT FOR TOC/DOC SAMPLE MATRIX LOSS - Aquatic

humic substances precipitate at pH below 2 16, and may move to glass vessel walls or

instrument tubing. If the analyst suspects that humic substances have precipitated

(which sometimes occurs in blackwaters)14 or flocked to the bottom of the sample

container, the sample is degassed by sparging to remove IC as directed in Section 11.5. 

The sample is then split into two portions. One portion is left at a pH #2, and the pH

of the second portion is adjusted to pH 5 to 7 in order to increase the solubility of

hydrophobic matter in the sample. Both samples are allowed to sit capped for 1⁄2 hour

before further sample processing. These samples are treated in the same manner as

field duplicates (FD), Section 9.6. The results of both split samples and corresponding

pH values should be reported to the data user. 

11.3 TOC SAMPLE PREPARATION - Remove the TOC sample from cold storage and

allow the sample to come to room temperature. Determine if the sample has been

preserved by acidification to a pH #2 by placing some drops on pH paper or by

pouring some of the sample into a small beaker and checking it with a glass or solidstate pH electrode. Do Not put the pH paper or electrode into the sample bottle. If the

pH is greater than 2, discard the sample. 

11.3.1 TYPICAL TOC SAMPLE PRE-TREATMENT - Samples that appear to be

low in particulate and suspended material are generally transferred directly to

the 40-mL injection vial. If the sample appears to contain sediment or floating

material, allow the sample to sit for a minute or two to allow sediment material

to settle back to the bottom of the bottle. After allowing the sample to settle, 

transfer the sample from the middle of the bottle using a disposable pipet to the

injection vial. Add 40 μL of H3PO4, HCl, or H2SO4 depending upon instrument

requirements (Sect. 8.0) to the 40-mL injection vial and label it.

11.3.2 Proceed to Section 11.5, for IC removal.
415.3 - 35

11.4 SUVA SAMPLE PREPARATION - If SUVA is not being determined, proceed to

Section 11.5. The SUVA determination consists of paired sample analyses composed

of a DOC sample and a UVA sample. DOC and UVA samples may be taken from the

same bottle, or may be taken from separate field duplicate bottles. Remove the DOC

and UVA sample(s) from cold storage and allow them to come to room temperature. 

The laboratory is required to document any use of alternative filters, apparatus (see

note, Sect. 6.1), or changes in the SUVA sample preparation procedure. All QC

requirements (Sect. 9) must be met.

11.4.1 Samples for DOC and UVA analysis are NOT acidified in the field. The DOC

sample is acidified after filtration as described below and the UVA sample is

not acidified at all. Determine if the sample(s) was accidentally preserved by

placing a few drops from the sample on pH paper or by pouring some of the

sample into a small beaker and checking it with a glass or solid-state pH

electrode. Do Not put the pH paper or electrode into the sample bottle. 

Placing the pH paper or electrode into the sample bottle will contaminate the

sample solution with organic carbon. If this happens, the sample must be

discarded. If the UVA sample pH is #2, check to make sure that the sample is

actually for the UVA determination. It is possible that this sample is a TOC or

filtered DOC sample and was mislabeled as a UVA sample. If the sample set

was not mislabeled or switched but accidentally preserved, the sample must be

discarded. The analyst must check the date and time of collection to ensure

that the sample holding times listed in Section 8.1 have been met. 

11.4.2 Filter Cleaning - Cleaning the filter apparatus, including the filter, removes

trace organic compounds that may have been left behind in the manufacturing

process. This cleaning must be done immediately prior to sample filtration. 

Rinse the filter with LRW, using the cleaning procedure used to determine

filter membrane suitability (Sect. 9.3.2.2), including the cleaning of the prefilter if a pre-filter is necessary.

11.4.3 Filter Blank (FB) - Use a clean filter apparatus (prepared in Sect. 11.4.2) and

filter an aliquot of LRW into an injection vial for the DOC analysis and another

aliquot of LRW into a vial for UVA analysis (Figure 1). FB volume must be

the same as the sample volume collected in Section 11.4.4. During the

development of this method, approximately 250 mL of LRW was filtered and

aliquots were poured into two 40-mL injection vials and labeled as the DOC

and UVA FBs. If the DOC and UVA analyses are coming from two separate

bottles, a filter apparatus will be needed for each bottle and an FB should be

prepared from each apparatus. Add 40 μL of H3PO4, HCl, or H2SO4 (as

required by the various instrument types, Sect. 8.0) to the 40-mL DOC-FB

injection vial. Do not acidify the UVA-FB injection vial. These vials are

paired with the respective SUVA sample and retained for DOC-FB and UVAFB analyses.
415.3 - 36

11.4.4 Sample Preparation - Reassemble the filter apparatus. Pour enough sample

onto the filter to saturate any adsorption sites, as determined according to the

filter-to-waste procedure in Section 9.3.2.3. Apply vacuum until no visible

water remains on the filter. Remove the vacuum, swirl the apparatus with

sample filtrate, disassemble, and discard the sample filtrate rinse. Reassemble

the filter apparatus and pour an additional aliquot of sample into the top of the

filter apparatus. Attach the vacuum and retain the filtrate. Pour one aliquot

into a 40-mL injection vial and label it to identify it as the DOC sample. Pour

a second aliquot into a 40-mL injection vial and label it to identify it as the

UVA sample. Add 40 μL of H3PO4, HCl, or H2SO4 to the 40-mL DOC

injection vial. Do not acidify the UVA injection vial. As with the DOC and

UV FBs (Sect. 11.4.3), separate filter apparatus may be used for the DOC and

UVA samples, in which case the filtrate need not be split into two aliquots. 

For a sample that is difficult to filter, an additional filter apparatus or the

optional pre-filter insert apparatus may be used. The use of additional filters

may require the collection of additional FBs, collected as specified in Section

11.4.3. The resulting additional DOC-FB, UVA-FB sample filtrates are

collected, their volumes composited and then placed into their respective

injection vials.

11.5 INORGANIC CARBON REMOVAL - All OC-CALs, TOC and DOC samples,

DOC-FBs, and LRBs must be treated to remove IC prior to OC analysis. UVA

samples and UVA-FBs are not sparged with nitrogen gas or otherwise treated to

remove IC prior to analysis (See Figure 2). The laboratory is required to document

any use of alternative IC removal apparatus (Sects. 6.9, 11.5.2) or changes in the IC

removal procedure. All quality control requirements (Sect. 9.2.4) must be met. 

NOTE: If a sparging apparatus is used, it should be isolated from the organic

laboratory and be free of organic contaminants. 

11.5.1 CLEANING SPARGING APPARATUS: Before initial use and immediately

after each use, the sparging apparatus must be cleaned. With the nitrogen

turned off, dip the stainless steel needles in a 40-mL injection vial containing

dilute acid (40 μL H3PO4, HCL, or H2SO4 per 40 mL LRW). Take the needles

out of the dilute acid and turn the nitrogen back on to flush out any residual

dilute acid. If disposable pipettes are used as part of the sparging apparatus,

discard the pipettes after each use instead of attempting to clean and reuse 

them.

11.5.2 SPARGING PROCEDURE: Submerge the apparatus needles used to sparge

the samples near the bottom of the 40-mL sample injection vial. Data

generated for this method were generated by externally sparging the acidified

samples with nitrogen gas, at 100 to 200 mL/minute, for 20 minutes per 40-mL

sample injection vial. Some instrument companies provide optional inorganic
carbon removal apparatus that may produce an efficient means for the removal of 

IC. The laboratory must demonstrate sparging efficiency by the performance of 

the IC removal sparging efficiency test (Sect. 9.2.4 ) and meeting the LRB 

requirements as stated in Section 9.9. 

11.6 SAMPLE ASSAY 

11.6.1 TOC/DOC Sample Analysis - This is accomplished by placing into the 

injection vial tray a series of 40-mL injection vials usually containing any or all of 

the following types of samples: LRB, DOC-FB, CB, OC-CAL(s), CCC s (Low, 

Mid or High concentration), field samples, FD1 & FD2, LRB between samples if 

needed as specified in Section 9.2.3, LFB, LFM, and the QCS. The DOC-FB 

maximum allowable background concentration is 0.35 mg/L OC. The 

injection tray is placed into the instrument, the run is initiated, and the results of 

analyses are recorded. 

11.6.2 UVA ANALYSES - If the spectrophotometer performance meets the SCS 

absorbance criteria as stated in Section 10.4, fill the cell with LRW and zero 

the instrument. Rinse and fill the cell with LRW from a second source. Verify 

UVA ≤ 0.01 cm-1 for second source LRW. Next fill the cell with the UVA-FB 

and read the absorbance. The UVA-FB’s maximum allowable background 

absorbance is 0.01 cm-1 UVA. If 0.01 cm-1 UVA for the UVA-FB is exceeded, 

the cause must be identified and any determined source of contamination must 

be eliminated. The spectrophotometer performance must then be rechecked 

(Sect. 10.4). The laboratory should also check the initial zero each time 10 

samples have been read. Rinse the spectrophotometer cell with a small amount 

of the UVA sample or UVA-FB by directly pipetting or pouring the sample 

into the spectrophotometer cell and discarding the rinse. Refill the 

spectrophotometer cell, carefully clean the cell window, and place in the 

spectrophotometer cell holder. Alternatively, flow cells maybe used, filled and 

flushed as needed. Measure the UVA and record. If field duplicates are 

collected, the FD1 & FD2 sample filtrates are also read and recorded. 

12.0 DATA ANALYSIS AND CALCULATION

12.1 TOC DIRECT READING: The TOC concentration is calculated by the automated 

instrument system’s software. Follow the instrument manufacturer’s operation manual 

when making instrument response adjustments for instrument system blank 

corrections. The TOC calculation assumes that the sample has been properly 

preserved, that only a trace amount of IC remains following the IC removal procedure, 

and that any remaining IC will not contribute to the TOC measurement and result in a 

calculation error. Some instrument systems calculate TOC from the difference of the 

total carbon (TC) minus the IC. The analyst is reminded that the IC in the sample is 

removed prior to sample analysis. Therefore, the reported TC is equal to, and the same 

415.3 - 37 
415.3 - 38

as, the TOC value (TOC =TC) and is read directly from the instrument’s computer or

printout.

12.2 SUVA CALCULATION: Follow the instrument manufacturer’s operation manual

instructions when making instrument response adjustments for instrument system

blank correction. As in the above TOC calculation, the analyst is reminded that the IC

of the DOC sample is removed prior to analysis. After filtration, the TOC instrument

value is equal to the DOC. The SUVA is then calculated from the DOC & UVA data

that results from the procedure as described above (Sects. 11.6.1, 11.6.2). The UVA of

the sample in cm-1 is divided by the DOC of the sample, multiplied by 100 cm/M and

either reported in units of L/mg-M or as “SUVA”. The SUVA is calculated as follows:

SUVA (L/mg-M) = UVA(cm-1) / DOC (mg/L) * 100 cm/M 

UVA Calculation: UVA = A /d 

where: 

UVA = The calculated UV absorbance of the sample in

absorbance units (cm-1).

 

A = The measured UV absorbance at 254 nm of the

sample that is filtered through a 0.45-μm filter

media.

 d = The quartz cell path length in cm.

NOTE: A Filter Blank (FB) is used to monitor background carbon

contamination (Sect. 11.4.3) and is not subtracted from the DOC and

UVA measurements.

12.3 Calculations should utilize all available digits of precision, but final reported

concentrations should be rounded to two significant figures (one digit of uncertainty). 

The final calculation is rounded up or down according to Standard Method 1050B.15

13.0 METHOD PERFORMANCE

NOTE: Data presented in Section 17 are from single-laboratory determinations. All

available digits were used for calculation and the calculations were rounded prior to

entry in the tables. The data were reported to as many as three significant figures to

give the reader a better understanding of method performance.

13.1 Table 17.1 summarizes the 3-day organic carbon detection limit (OCDL) study for five

TOC instruments systems. The DOC determination ranged from 0.02 to 0.08 mg/L

OCDL and the TOC determination ranged from 0.04 to 0.12 mg/L OCDL. All source
415.3 - 39

water samples reported in Section 13 and the Section 17 Tables were sparged for 20

minutes to remove inorganic carbon interferences.

13.2 Table 17.2 and associated sub-tables illustrate the single instrument precision and

accuracy for each of the five TOC instrument technologies.

13.3 Tables 17.3 and 17.4 illustrate the instrument differences and performances for five

TOC instruments analyzing seven different source water matrices.

13.4 In all cases, the TOC instruments had difficulty in analyzing the Saint Leon well water. 

The Saint Leon well water had a moderately high inorganic carbon content of

approximately 100 mg/L IC, and a low organic carbon content of 0.2 to 0.6 mg/L OC. 

The Saint Leon well water organic carbon content was near the organic carbon

detection limit. The low OC concentration produced the greatest differences between

instrument responses. For low TOC samples with high IC, differences between

instrument responses may be more apparent due to possible IC interference.

13.5 The TOC, DOC and SUVA procedures of this method are dependent on the operation

manual for the TOC instrument system and the UV spectrophotometer as provided by

the respective instrument manufacturers. However, all performance criteria and

quality control requirements described in this method, as summarized in Tables 17.5

and 17.6, must be met.

14.0 POLLUTION PREVENTION

14.1 Pollution prevention encompasses any technique that reduces or eliminates the

quantity or toxicity of waste at the point of generation. Numerous opportunities for

pollution prevention exist in laboratory operations. The EPA has established a

preferred hierarchy of environmental management techniques that places pollution

prevention as the management option of first choice. Whenever feasible, laboratory

personnel should use pollution prevention techniques to address their waste generation. 

When wastes cannot be feasibly reduced at the source, the Agency recommends

recycling as the next best option.

14.2 For information about pollution prevention that may be applicable to laboratories and

research institutions, consult Less is Better: Laboratory Chemical Management for

Waste Reduction, available from the American Chemical Society's Department of

Government Relations and Science Policy, 1155 16th Street N.W., Washington D.C.

20036, (202)872-4477. 

14.3 For recycle information, contact the US EPA, Pollution Prevention and WasteWise

program, http://www.epa.gov/wastewise/ .
415.3 - 40

1. Glaser, J. A.; Foerst, D. L.; McKee G. D.; Quave, S. A.; Budde, W. L. Trace Analyses

for Wastewaters. Environ. Sci. Technol. 1981, 15 (12), 1426-1434.

2. Benner, R.; Storm, M. A Critical Evaluation of the Analytical Blank Associated with

DOC Measurements by High-Temperature Catalytic Oxidation. Mar. Chem. 1993, 41,

153-160.

3. Standard Method 5910B: Ultraviolet Absorption Method. In Standard Methods for the

Examination of Water and Wastewater, Eaton, A. D.; Clesceri, L. S.; Greenberg, A. E.,

Eds.; American Public Health Association; Washington, DC, 1995; 19th ed.

4. Aiken, G.R. Chloride Interference in the Analysis of Dissolved Organic Carbon by the

Wet Oxidation Method. Environ. Sci. Technol. 1992, 26 (12), 2435-2439.

5. Sakamoto, T.; Miyasaka, T. TOC Analysis Study Confirming the Accuracy of a Method

for Measuring TOC by Wet Oxidation. Ultrapure Water 1987, 24-31.

6. Potter, B. B.; Wimsatt, J. C. Preprints of Extended Abstracts, Vol 42 (1), 223rd National

Meeting of the American Chemical Society, Orlando, FL, April 7-11, 2002; American

Chemical Society Division of Environmental Chemistry: Cape Girardeau, MO, 2002;

Paper 60, 559-564.

7. Aiken, G.; Kaplan, L. A.; Weishaar, J. Assessment of Relative Accuracy in the

Determination of Organic Matter Concentrations in Aquatic Systems. J. Environ. Monit.

2002, 4, 70-74.

15.0 WASTE MANAGEMENT

15.1 The U.S. Environmental Protection Agency requires that laboratory waste management

practices be conducted consistent with all applicable rules and regulations. The

Agency urges laboratories to protect the air, water, and land by minimizing and

controlling all releases from hoods and bench operations, complying with the letter and

spirit of any sewer discharge permits and regulations, and by complying with all solid

and hazardous waste regulations, particularly the hazardous waste identification rules

and land disposal restrictions. For further information on waste management, consult

The Waste Management Manual for Laboratory Personnel, available from the

American Chemical Society at the address listed in Section 14.2.

15.2 The laboratory should consult with local authorities prior to disposal of any waste to 

publicly owned treatment works (POTW) and receive permission for that disposal.

16.0 REFERENCES
415.3 - 41

8. American Chemical Society, Committee on Chemical Safety. Safety in Academic

Chemistry Laboratories, Vol. 2, Accident Prevention for Faculty and Administrators, 7th

ed.; American Chemical Society: Washington, DC, 2003.

9. Occupational Exposure to Hazardous Chemicals in Laboratories. Code of Federal

Regulations, Part 1910.1450, Title 29, 2001.

10. Karanfil, T.; Erdogan, I.; Schlautman, M. A. Selecting Filter Membranes for Measuring

DOC and UV254. J. Am. Water Works Assoc. 2003, 95 (3), 86-100.

11. Standard Method 1080: Reagent-Grade Water. In Standard Methods for the Examination

of Water and Wastewater, Eaton, A. D.; Clesceri, L. S.; Greenberg, A. E., Eds.; American

Public Health Association; Washington, DC, 1995; 19th ed.

12. Schaffer, R. B.; Van Hall, C. E.; McDermott, G. N.; Barth, D.; Stenger, V. A.; Sebesta,

S. J.; Griggs, S. H. Application of a Carbon Analyzer in Waste Treatment. J. Water

Pollut. Control Fed. 1965, 37 (11), 1545-1566.

13. Van Hall, C. E.; Barth, D.; Stenger, V. A. Elimination of Carbonates from Aqueous

Solutions Prior to Organic Carbon Determination. Anal. Chem. 1965, 37 (6), 769-771. 

14. Kaplan, L.A. Comparison of High-Temperature and Persulfate Oxidation Methods for

Determination of Dissolved Organic Carbon in Freshwaters. Limnol. Oceanogr. 1992, 37

(5), 1119-1125.

15. Standard Method 1050B: Significant Figures. In Standard Methods for the Examination

of Water and Wastewater, Eaton, A. D.; Clesceri, L. S.; Greenberg, A. E., Eds.; American

Public Health Association; Washington, DC, 1995; 19th ed.

16. Standard Method 5510: Aquatic Humic Substances. In Standard Methods for the

Examination of Water and Wastewater, Eaton, A. D.; Clesceri, L. S.; Greenberg, A. E.,

Eds.; American Public Health Association; Washington, DC, 1995; 19th ed.
415.3 - 42

17.0 TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA

17.1 ORGANIC CARBON DETECTION LIMIT (OCDL)a

Dissolved Organic Carbon (DOC), mg/L

Instrument Fortified 

Conc.b

Mean

Recovered

Conc.

%RSDc %RECd OCDL

1 0.130 0.155 11 119 0.054

2 0.125 0.116 22 93 0.082

3 0.250 0.249 4 100 0.035

4 0.130 0.125 5 96 0.018

5 0.250 0.233 9 93 0.068

Total Organic Carbon (TOC), mg/L

Instrument Fortified

Conc.

Mean

Recovered

Conc.

%RSDc %RECd OCDL

1 0.130 0.159 14 122 0.071

2 0.125 0.145 26 116 0.118

3 0.250 0.259 8 104 0.061

4 0.130 0.130 9 100 0.036

5 0.250 0.251 7 100 0.059

a

 Organic Carbon Detection Limits were determined by analyzing 7 replicates over 3 days.

b

 LRW fortified as specified in the table.

c

 %RSD = percent relative standard deviation

d

 %REC = percent recovery

INSTRUMENT:

1: UV/Persulfate/Wet Oxidation with Permeation/Conductivity Detection

2: Elevated Temperature/Catalyzed/Persulfate/Wet Oxidation/Nondispersive 

 Infrared Detection (NDIR)

3: UV/Low Temperature/Persulfate/Wet Oxidation/NDIR

4: Catalyzed/Combustion Oxidation(680 °C)/NDIR

5: High Temperature Combustion Oxidation/NDIR
415.3 - 43

17.2 SINGLE TOC INSTRUMENT PRECISION AND ACCURACY

17.2.1 TOC Instrument 1: UV/persulfate wet oxidation with

permeation/conductivity detection

Dissolved Organic Carbon, mg/La

Source

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.63 1.62 12.2 105

Shingobee R. 2.98 0.19 13.5 105

Bolten Well 1.27 0.00 12.0 107

Ohio R. (Fernbank) 2.79 0.36 13.6 108

Muddy Creek 3.81 0.15 14.6 108

Great Miami R. 3.18 0.00 13.7 104

Saint Leon Well 0.53 0.97 11.0 104

Total Organic Carbon, mg/La

Source 

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.73 0.33 12.1 103

Shingobee R. 3.16 0.18 13.0 98

Bolten Well 1.32 0.44 11.4 100

Ohio R. (Fernbank) 3.02 0.57 13.2 102

Muddy Creek 4.24 0.00 14.6 103

Great Miami R. 3.51 0.33 13.8 102

Saint Leon Well 0.66 0.52 11.1 104

a N = 3, samples fortified at 10mg/L OC using KHP
415.3 - 44

17.2 SINGLE TOC INSTRUMENT PRECISION AND ACCURACY, cont’d.

17.2.2 TOC Instrument 2: Elevated temperature/catalyzed/persulfate wet

oxidation/NDIR

Dissolved Organic Carbon, mg/La

Source

Water

Unfortified

Sample Conc. Fortified Sample Conc.

Mean Mean %REC

Boulder Creek 1.40 11.8 104

Shingobee R. 2.58 13.3 106

Bolten Well 1.04 12.6 105

Ohio R. (Fernbank) 2.41 13.3 108

Muddy Creek 3.25 14.3 110

Great Miami R. 2.68 13.4 107

Saint Leon Well 0.40 10.6 101

Total Organic Carbon, mg/La

Source 

Water

Unfortified

Sample Conc. Fortified Sample Conc.

Mean Mean %REC

Boulder Creek 1.38 11.2 98

Shingobee R. 2.62 12.7 100

Bolten Well 1.05 11.4 103

Ohio R. (Fernbank) 2.46 13.1 106

Muddy Creek 3.41 13.8 104

Great Miami R. 2.89 13.2 103

Saint Leon Well 0.38 10.5 102

 

a N = 2, samples fortified at 10mg/L OC using KHP
415.3 - 45

17.2 SINGLE TOC INSTRUMENT PRECISION AND ACCURACY, cont’d.

17.2.3 TOC Instrument 3: UV/low temperature/persulfate wet oxidation/NDIR

Dissolved Organic Carbon, mg/La

Source

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.52 1.81 11.5 100

Shingobee R. 2.71 1.10 13.2 104

Bolten Well 1.18 1.76 11.3 101

Ohio R. (Fernbank) 2.50 0.74 13.1 106

Muddy Creek 3.38 0.81 14.0 106

Great Miami R. 2.91 0.64 13.1 102

Saint Leon Well 0.56 0.88 10.7 101

Total Organic Carbon, mg/La

Source 

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.47 1.77 11.2 97

Shingobee R. 2.72 0.02 12.7 99

Bolten Well 1.16 2.45 11.0 98

Ohio R. (Fernbank) 2.58 1.01 12.6 100

Muddy Creek 3.18 1.28 13.5 103

Great Miami R. 2.92 1.01 13.0 101

Saint Leon Well 0.45 1.57 10.7 102

a N = 3, samples fortified at 10 mg/L OC using KHP
415.3 - 46

17.2 SINGLE TOC INSTRUMENT PRECISION AND ACCURACY, cont’d.

17.2.4 TOC Instrument 4: Catalyzed, 680 °C combustion oxidation/NDIR

Dissolved Organic Carbon, mg/La

Source

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.54 5.75 11.4 98

Shingobee R. 2.71 3.18 12.4 97

Bolten Well 1.24 1.25 12.4 98

Ohio R. (Fernbank) 2.52 5.73 12.4 98

Muddy Creek 3.56 3.17 13.3 98

Great Miami R. 3.00 6.94 12.7 96

Saint Leon Well 0.38 27.4 10.1 98

Total Organic Carbon, mg/La

Source 

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.46 2.86 11 100

Shingobee R. 2.84 2.19 13 97

Bolten Well 1.12 1.70 11 100

Ohio R. (Fernbank) 2.81 1.79 13 100

Muddy Creek 4.04 2.02 14 96

Great Miami R. 3.42 1.66 14 101

Saint Leon Well 0.28 7.64 10 100

a N = 3, samples fortified at 10 mg/L OC using KHP
415.3 - 47

17.2 SINGLE TOC INSTRUMENT PRECISION AND ACCURACY, cont’d.

17.2.5 TOC Instrument 5: High temperature combustion oxidation/NDIR

Dissolved Organic Carbon, mg/La

Source

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.21 1.18 11.0 98

Shingobee R. 2.29 1.15 12.0 97

Bolten Well 0.90 2.93 11.5 106

Ohio R. (Fernbank) 2.11 0.28 12.3 102

Muddy Creek 2.89 1.09 13.1 102

Great Miami R. 2.43 0.77 12.3 99

Saint Leon Well 0.38 27.4 10.0 96

Total Organic Carbon, mg/La

Source 

Water

Unfortified Sample

Conc. Fortified Sample Conc.

Mean %RSD Mean %REC

Boulder Creek 1.26 6.02 11.0 97

Shingobee R. 2.45 0.84 12.1 97

Bolten Well 0.93 1.02 10.8 98

Ohio R. (Fernbank) 2.31 1.19 12.1 98

Muddy Creek 3.34 3.40 13.1 98

Great Miami R. 2.72 0.78 12.3 96

Saint Leon Wellb0.32 N/A 10.0 97

a N = 3, samples fortified at 10 mg/L OC using KHP

 

b N = 2 for this sample, N/A = not applicable
415.3 - 48

17.3 PRECISION AND ACCURACY DATA FOR DOC AND SUVA MEASURED IN

SEVEN SOURCE WATERS ON FIVE INSTRUMENTSa

17.3.1 DOC Measurements for Seven Source Waters, Three Replicate

Instrument Injections on Five Instruments 

Dissolved Organic Carbon, mg/L, Unfortified Samples

Source Water Inst

#1

Inst

#2

Inst

#3

Inst

#4

Inst

#5 Mean Std

Dev %RSD

Boulder Creek 1.64 1.40 1.52 1.54 1.21 1.46 0.17 11

Shingobee R. 2.98 2.58 2.71 2.71 2.29 2.66 0.25 9

Bolton Well 1.27 1.04 1.18 1.24 0.90 1.13 0.15 14

Ohio R. (Fernbank) 2.79 2.41 2.50 2.52 2.12 2.47 0.24 10

Muddy Creek 3.81 3.25 3.38 3.56 2.89 3.38 0.34 10

Great Miami R. 3.18 2.69 2.91 3.00 2.43 2.84 0.29 10

St. Leon Well 0.53 0.40 0.56 0.38 0.25 0.42 0.13 30

17.3.2 DOC Measurements for Seven Source Waters, Fortified with KHP, Three

Replicate Instrument Injections on Five Instruments

Dissolved Organic Carbon, mg/L, Samples Fortified at 10 mg/L OC

Source Water Inst #1 Inst #2 Inst #3 Inst #4 Inst #5 Mean Std

Dev %RSD %RECb

Boulder Creek 12.2 11.8 11.5 11.4 11.0 11.6 0.43 4 101

Shingobee R. 13.5 13.3 13.2 12.4 12.0 12.9 0.62 5 102

Bolton Well 12.0 11.5 11.3 11.2 11.5 11.5 0.31 3 104

Ohio R. (Fernbank) 13.6 13.2 13.1 12.4 12.3 12.9 0.54 4 105

Muddy Creek 14.6 14.3 14.0 13.3 13.1 13.9 0.62 5 105

Great Miami R. 13.7 13.4 13.1 12.7 12.3 13.0 0.55 4 102

St. Leon Well 11.0 10.5 10.7 10.1 10.0 10.5 0.40 4 100

a For instrument identification (by type) see Section 6.3.

b % Recovery calculated as described in Section 9.8.
17.3 PRECISION AND ACCURACY DATA FOR DOC AND SUVA MEASURED IN 

SEVEN SOURCE WATERS ON FIVE INSTRUMENTSa, cont’d. 

17.3.3 Mean SUVA Calculation Based on the DOC Data in 17.3.1 for Seven 

Source Waters 

SUVA b (L/mg-M) 

Source Water 

UVA 

(cm-1) Inst #1 Inst #2 Inst #3 Inst #4 Inst #5 Mean 

Boulder Creek 0.0432 2.62 3.08 2.84 2.97 3.58 3.02 

Shingobee R. 0.0744 2.50 2.88 2.75 2.77 3.25 2.83 

Bolton Well 0.0236 1.86 2.28 2.01 1.91 2.62 2.14 

Ohio R. (Fernbank) 0.0727 2.60 3.01 2.90 2.88 3.43 2.97 

Muddy Creek 0.1124 2.95 3.46 3.33 3.20 3.89 3.37 

Great Miami R. 0.0895 2.81 3.33 3.07 3.05 3.69 3.19 

St. Leon Well 0.0077 1.46 1.93 1.38 1.83 3.13 1.95 

a For instrument identification (by type) see Section 6.3. 

b SUVA calculated as described in Section 12.2. 

415.3 - 49 
415.3 - 50

17.4 PRECISION AND ACCURACY DATA FOR TOC MEASURED IN SEVEN

SOURCE WATERS ON FIVE INSTRUMENTSa

17.4.1 TOC Measurements for Seven Source Waters, Three Replicate Instrument

Injections on Five Instruments

Total Organic Carbon, mg/L, Unfortified Samples

Source Water Inst #1 Inst #2 Inst #3 Inst #4 Inst #5 Mean Std

Dev %RSD

Boulder Creek 1.73 1.38 1.47 1.46 1.26 1.46 0.17 12

Shingobee R. 3.16 2.62 2.72 2.84 2.45 2.76 0.26 10

Bolton Well 1.32 1.05 1.16 1.12 0.93 1.12 0.14 13

Ohio R. (Fernbank) 3.02 2.46 2.58 2.81 2.31 2.64 0.28 11

Muddy Creek 4.24 3.41 3.18 4.04 3.34 3.64 0.47 13

Great Miami R. 3.51 2.89 2.92 3.42 2.72 3.09 0.35 11

St. Leon Well 0.66 0.39 0.45 0.28 0.32 0.42 0.15 35

17.4.2 TOC Measurements for Seven Source Waters, Fortified with KHP, from

Replicate Instrument Injections on Five Instruments 

Total Organic Carbon, mg/L, Samples Fortified at 10 mg/L OC

Source Water Inst #1 Inst #2 Inst #3 Inst #4 Inst #5 Mean Std

Dev %RSD %RECb

Boulder Creek 12.1 11.3 11.2 11.4 11.0 11.4 0.43 4 99

Shingobee R. 13.0 12.7 12.6 12.5 12.1 12.6 0.32 3 98

Bolton Well 11.4 11.4 11.0 11.2 10.8 11.1 0.28 3 100

Ohio R. (Fernbank) 13.2 13.1 12.6 12.8 12.1 12.8 0.45 4 101

Muddy Creek 14.6 13.8 13.5 13.7 13.1 13.7 0.54 4 101

Great Miami R. 13.8 13.2 13.0 13.6 12.3 13.2 0.59 5 101

St. Leon Well 11.1 10.5 10.7 10.2 10.0 10.5 0.41 4 101

a For instrument identification (by type) see Section 6.3.

b % Recovery calculated as described in Section 9.8.
415.3 - 51

17.5 INITIAL DEMONSTRATION OF CAPABILITY (IDC) REQUIREMENTS

(SUMMARY) 

Method

Reference

Requirement Specification and

Frequency

Acceptance Criteria

Sects. 9.2.1,

9.9

Initial

Demonstration of

Low System

Background

Analyze LRB prior to

any other IDC

samples.

LRBs must be < 0.35 mg/L OC

and < 0.01 cm-1 UVA. 

Sects. 9.2.2,

9.11

Initial Calibration

Verification

After initial calibration

of TOC instrument

system a QCS sample

is used to verify

accuracy.

The analyzed value of a 1-5 mg/L

calibration standard must be

within ±20% of the true value

before proceeding with the

method.

Sect. 9.2.3 Initial Organic

Carbon Flow

Injection Memory

Check

Analyze after Low

System Background 

requirement, but

before any other TOC

or DOC IDC samples. 

LRB injections after the highest

OC-CAL injection must be 

< 0.35 mg/L TOC.

Sect. 9.2.4 Inorganic Carbon

Removal

Prior to first analysis

of samples and

whenever the IC

removal procedure is

modified.

Analysis of the IC-TEST solution

after IC removal must result in a

concentration of < 0.35 mg/L IC,

measured as OC interference.

Sect. 9.2.5 Initial

Demonstration of

Accuracy

Analyze 5 replicate

LFBs (at 2-5 mg/L

OC). 

The average recovery must be

+20% of the true value.

Sect. 9.2.6 Initial

Demonstration of

Precision

Calculate precision of

the accuracy samples.

The %RSD must be < 20%.

Sect. 9.2.7 Organic Carbon

Detection Limit

(OCDL)

Determination

Analyze 7 replicate

LFBs over a period of

at least 3 days at a

concentration

estimated to be near

the DL.

The calculated OCDL must not

exceed 0.35 mg/L. The mean

recovery of the LFBs used in the

OCDL determination must be

+50% of the true value. 
Method

Reference

Requirement Specification and

Frequency

Acceptance Criteria

415.3 - 52

Sect. 9.3.2 Initial

Demonstration of

Filter Membrane

Suitability

Prior to the first use of

filters and whenever a 

manufacturer or filter

type is changed.

FB < 0.35 mg/L OC and/or 

< 0.01 cm -1 UVA. Sample

filtrate OC within + 15% of

unfiltered sample OC.

Sect. 9.4.1 Initial

Spectrophotometer

Check

Prior to first

instrument use and

annually thereafter.

Test two wavelengths between

220 and 340 nm. Check

manufacturer’s operation manual

for acceptance limits.

Sects. 9.4.2,

10.4

Spectrophotometer

Performance Check

Prior to analysis of

samples.

UVA within 10% of expected

absorbance value. 
415.3 - 53

17.6 QUALITY CONTROL REQUIREMENTS (SUMMARY) 

Method

Reference

Requirement Specification and

Frequency

Acceptance Criteria

Sect. 9.9 Blanks One LRB with each TOC

analysis batch. One FB

with each DOC and UVA

analysis batch.

TOC LRBs and DOC-FBs

must be < 0.35 mg/L OC. 

The UVA-FB must be < 0.01

cm-1 UVA.

Sect. 8.1 Holding Time,

SUVA

DOC - filtered and then

acidified within 48 hours of

collection. Analyzed

within 28 days of time of

collection.

Stored at < 6 °C; preserved

with acid to pH < 2 after

filtration. 

UVA - filtered and

analyzed within 48 hours of

time of collection.

Not preserved with acid,

stored at < 6 °C.

Sect. 8.2 Holding Time,

TOC

TOC - analyze within 28

days from time of

collection.

Preserved at pH < 2 at the

time of collection, stored at 

< 6 °C. 

Sects. 9.2,

9.3, 9.4

Initial

Demonstration of

Capability (IDC) 

Performed whenever a new

instrument is set up or

when a new analyst is

trained. 

See Table 17.5.

Sects. 9.5,

10.3

Continuing

Calibration Checks

Analysis of Low-CCC (at

the MRL or below) at the

beginning of each analysis

batch. Subsequent CCCs

analyzed after every 10

samples and after the last

sample in the analysis

batch, rotating

concentrations to cover the

calibrated range of the

instrument. Mid-CCC

required during each

analysis batch.

Low-CCC: + 50% of true

value.

Mid-CCC: + 20% of true

value.

High-CCC: + 15% of true

value.
Method Requirement Specification and Acceptance Criteria 

Reference Frequency 

Sect. 9.6 Field Duplicate One FD is collected and FD > 2 mg/L OC < 20% 

(FD) Analyses analyzed with each analysis 

batch. 

RPD. UVA < 1 0% RPD. 

Sect. 9.7 Laboratory One LFB is analyzed with Concentration of 1-5 mg/L 

Fortified Blank 

(LFB) analysis 

every DOC analysis batch. OC using KHP. Recovery 

must be within + 20% of true 

value. 

Sect. 9.8 Laboratory One LFM is analyzed with Recovery outside 70-130% 

Fortified Matrix every TOC or DOC warrants investigation of 

(LFM) analysis batch. Spike 

concentration should result 

in an increase in the LFM 

concentration of 50 to 

matrix effect. 

 200% of its measured or 

expected concentration. 

Sect. 9.11 Quality Control The QCS is analyzed The analyzed value of a 1-5 

Sample (QCS) during the IDC, after each 

new calibration curve, each 

time new calibration 

solutions are prepared, or at 

least quarterly. 

mg/L QCS must be within 

±20% of the true value. 

Sec t. 10.2 Calibration Curve A new calibration curve is Calibration curve must have 

generated when fresh 

standards are made and/or 

when CCCs are out of QC 

limits. 

r2 > 0.993 before proceeding 

with analyses. 

Sect. 10.4 Spectrophotometer The day to day performance The UVA of the KHP-SCS or 

performance check of the spectrophotometer is 

checked using the COMMSCS and/or KHP-SCS prior 

to analyzing any UVA 

sample(s). 

COMM-SCS reading must be 

within 10% expected 

absorbance values. 

Sect. 11.6.2 Spectrophotometer 

Blank 

A second source LRW is 

analyzed each time 

spectrophotometer is zeroed.

Analysis of second source 

LRW must result in UVA ≤

0.01 cm-1. 

415.3 - 54
415.3 - 55

FIGURE 1: FILTER BLANK PREPARATION 

LRW

WASH FILTER*,

DISCARD

FILTER LRW*,

 DISPENSE INTO

40-ML VIALS

DESIGNATE AS

FILTER BLANK (FB)

 

DOC - FB

ADD ACID

SPARGE

ANALYZE

UVA - FB

NO ACID

NO SPARGE

ANALYZE

*Using volume as determined in Section 9.3.2.
415.3 - 56

FIGURE 2 : SAMPLE PREPARATION

WATER SAMPLE

 

 

TOC DOC UVA

 

USING PRE - WASHED FILTERS

FILTER AND DISCARD FIRST PORTION* 

TO WASTE

 

 FILTER REMAINING SAMPLE

 

DISPENSE INTO 40ML VIALS

 

TOC AND DOC-SAMPLE

ADD ACID

 SPARGE

ANALYZE

UVA-SAMPLE

NO ACID

NO SPARGE

ANALYZE

* Using volume as determined in Section 9.3.2.3.