Summary of Data for Quality Assessment Materials Analyzed

from January 1994 through November 1998 using the NAWQA

Program Bed-Sediment Analytical Protocol

By

Richard F. Sanzolone*

Open-File Report 99-588

1999

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards 

and stratigraphic nomenclature. Any use of trade names is for descriptive purposes only and does not imply

endorsement by the U.S. Government.

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

*U. S. Geological Survey, Box 25046, MS 973, DFC, Denver, CO 80225-0046
Table of Contents

List of tables.......................................................................................3

Introduction.........................................................................................4

Quality Assessment Program.....................................................................4

Analytical Protocol................................................................................ 5

Assessment Data................................................................................... 5

References .......................................................................................... 11
List of Tables

Table 1. Analytical Protocol................................................................ 7

Table 2. GXR-2 values compared to literature values .................................. 8

Table 3. GXR-2 results compared to number of standard deviations from mean... .9

Table 4. Average relative percent difference for within job analytical duplicates... 10
Introduction

This report contains a summary of the analytical data for quality assessment materials 

analyzed concurrently with bed-sediment samples collected by the National Water 

Quality Assessment (NAWQA) Program of the U.S. Geological Survey (Hirsch and 

others, 1988). The NAWQA bed-sediment samples were analyzed from January 1994 

through November 1999 by the analytical laboratories of the Central Region Mineral 

Resource Surveys Team (formally the Branch of Geochemistry) of the U.S. Geological 

Survey. The assessment materials were analyzed to provide enhanced quality assurance 

for samples analyzed for the NAWQA Program.

Quality Assessment Program

Quality assurance is a critical component of a program of the scope and duration of 

NAWQA. The purpose of an analytical quality assurance program is to assure the 

reliability (precision and accuracy) of reported laboratory data, and to provide a 

permanent record to assure data integrity. Two concepts are involved: (1) quality control, 

which is the mechanism established to control errors, and (2) quality assessment, which is 

the mechanism to verify that the system is operating within acceptable limits (Taylor, 

1981).

The approach of the quality assessment program is based on traceability, through 

concurrent analysis of sample duplicates and reference materials. This approach assesses 

both precision and accuracy but has some limitations since the ability to achieve a good 

result for a reference material or sample split does not guarantee a similar result for all of 

the natural samples analyzed. The quality assessment materials reported in this document 

include a geochemical reference material and sample analytical duplicates. The 

geochemical reference material, GXR-2, is an enriched gray-brown loam soil from a 

mining area (Alcott and I/akin, 1975), which was selected to provide concentrations for 

most constituents that are above the lower reporting limits of the analytical techniques 

used for determination. The sample analytical duplicates were randomly selected samples 

split after pulverizing to provide a duplicate sample. One reference material and one 

analytical sample split were inserted as double blind samples in each batch (job) of up to 

38 samples submitted to the laboratory. Data from the reference material are used to 

assess the accuracy and long-term precision of the analysis. Data from the within batch 

analytical splits are used to assess the short-term precision of the analysis.

The use of assessment materials submitted along with NAWQA bed-sediment samples is 

in addition to the standard quality control and quality assurance practices used by the 

laboratory. The Laboratory QA/QC Program included the use of reference materials, 

duplicates, and analytical blanks. Reference materials are plotted using x~(mean)-quality 

control charts to assess analytical bias and duplicate samples are plotted on R (range)- 

quality control charts to evaluate precision. The warning and control limits are set at 2 

and 3 standard deviations respectively from the mean for these charts. All data released
for samples analyzed for the NAWQA Program meets the criteria of the Laboratory 

QA/QC Program. The publication "Quality assurance manual for the Branch of 

Geochemistry, U.S. Geological Survey" (Arbogast, 1990) describes the Laboratory 

QA/QC Program as well as protocols for written documentation, sample handling, 

sample preparation, instrumental procedures, safety protocols, and other standard 

procedures used by the laboratory. The laboratory also participates in various 

international round-robin exercises to further assess the reliability of laboratory data.

Analytical Protocol

Bed -sediment samples were wet sieved to <63 micron in the field according to the 

NAWQA protocol (Shelton and Capel, 1994). Samples were submitted to the laboratory 

where they are dried in a forced air oven at ambient temperature. Dried samples were 

processed using ceramic plate grinders and the pulverized material was put into 3 oz 

cylindrical containers. The containers are then placed on mechanical rollers to 

homogenize the material. Table 1 shows the analytical protocol used to analyze bedsediment samples from the NAWQA Program (referred to as Schedule 2400 by Water 

Resources Division of the U.S. Geological Survey, National Water Quality Laboratory). 

This table includes the constituents determined, lower reporting limits, decomposition 

procedures and detection techniques used by the laboratory. A description and validation 

of the chemical techniques used for the NAWQA Program analytical protocol are 

documented in "Analytical methods manual for the Mineral Resource Surveys Program, 

U.S. Geological Survey" (Arbogast, 1996). The digestion procedures used are meant to 

be "total" for the constituents of interest. The 4-acid digestion [nitric (HNO3), 

hydrochloric (HC1), perchloric (HC1O4), and hydrofluoric (HF)] procedure used for the 

inductively coupled plasma -atomic emission spectrometric (ICP-AES) technique is 

considered a 'total" digestion, however as with any decomposition technique dealing 

with natural materials there are exceptions. The digestion may not fully dissolve specific 

refractory, resistant, or secondary minerals. Instances of low recoveries for some 

elements such as Ba in barite, Cr in chromite, Ti in rutile, Sn in cassiterite, Al in 

corundum, and rare earth elements in monazite may be encountered.

Assessment Data

Table 2 shows the mean, standard deviation, percent relative standard deviation, and 

range of values produced by the laboratory for reference material GXR-2 along with 

mean consensus values from the literature and percent recovery. The data shown in table 

2 addresses both accuracy and long-term precision. Percent relative standard deviation 

(%RSD) 1 is less than 10% for 75% of the constituents determined. Most of the

1 %RDS is calculated by dividing the mean for a particular constituent by its standard deviation and 

multiplying by 100.
constituents with poorer recoveries are those with concentrations near the lower reporting 

limit as expected. Over 85% of the constituents in GXR-2 quantified by the laboratory 

show a percent recovery value of 85% or greater. Notable exceptions include Al with 

only a 36% recovery level. This incomplete recovery is attributed to the presence of 

corundum, a fact verified by independent x-ray diffraction analysis. As stated above the 

multi-acid procedure used by the laboratory is not designed to completely dissolve 

corundum. It should also be noted that while GXR-2 is well characterized for a large 

number of constituents, consensus values for this material may not be "true" values. 

Criteria such as the number and type of determination used to produce consensus values 

may not meet criteria needed to qualify as a **true" or certified value.

Table 3 shows long term precision of the GXR-2 analysis. The table lists the number of 

times the values from the analysis of GXR-2 are within plus or minus 1,2, and 3 standard 

deviations of the laboratory meaa The means and standard deviations used for these 

tables were calculated from the laboratory data presented in table 2. The table also lists 

the number of less than the lower reporting limit values (qualified values) for each 

constituent. Where the number of samples under the <=3s column plus the number of less 

than values is less than the total number of determinations (i.e. Cr) the difference is the 

number of samples outside of 3 standard deviations from the mean. Molybdenum and 

Sulfiir show 2 and 5 unqualified values respectively which are not tabulated because of 

insufficient unqualified data to determine mean and standard deviation values.

Table 4 shows within job sample duplicate data to evaluate short-term precision. The 

average relative percent difference (ARPD) and the average mean (mean of all duplicate 

means) of duplicate samples are presented. The average mean is presented to give an 

indication of the concentration level at which the ARPD is calculated. ARPD is a statistic 

often used to evaluate the precision of sample duplicates. It is calculated using the 

formula:

* xlOO

Where: r is the difference between the duplicate 

x is the mean of the duplicate 

n is the number of pairs of duplicates

The table also shows the number of less than values and the number of times the 

duplicates were both reported as less than values. In instances where duplicate analysis 

resulted in an unqualified and a qualified value (the number of less than values is not 

twice the number of less than pairs) the less than indicator was ignored for the qualified 

value in order to calculate the mean (x) and difference (r). The ARPD is less than 10% 

for 90% of the constituents and less than 5% for more than 68% of the constituents.
Table 1. 

Analytical Protocol Used for the Analysis of NAWQA Bed-Sediment Samples

CONSTITUENT

Al

Au

Ba

Be

Bi

Ca

Ce

Co

Cr

Cu

Eu

Fe

Ga

Ho

K

La

Li

Mg

Mn

Mo

Na

Nb

Nd

Ni

P

Pb

Sc

Sn

Sr

Ta

Ti

V

Y

Yb

Zn

As

Sb

Se

Hg

Ag

Cd

Th

U

Total C

Organic C

Carbonate C

S

DECOMPOSITION

TECHNIQUE

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HN03, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCL04, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCL04, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HN03, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HN03, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCL04, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCL04, HF)

(HCL, HNO3, HCL04, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCL04, HF)

(HCL, HNO3, HCLO4, HF)

L (HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCL04, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HN03, HCL04, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HN03, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HCL, HNO3, HCLO4, HF)

(HF, HNO3, HCLO4)

(HF, HNO3, HCLO4)

(HF, HNO3.HCIO4, H2SO4)

(HNO3, NA2CR2O7)

(HF, HCL, H2O2)

(HF, HCL, H2O2)

(NONE)

(NONE)

(COMBUSTION)

(HCL04)

(COMBUSTION)

DETECTION

TECHNIQUE

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(ICP-AES)

(HYDRIDE-AAS)

(HYDRIDE-AAS)

(HYDRIDE-AAS)

(COLDVAPOR-AAS)

(AAS)

(AAS)

(DNA)

(DNA)

(INFRARED)

(BY DIFFERENCE)

(TITRATION)

(INFRARED)

LOWER REPORTING

LIMIT

0.005%

8 PPM

1 PPM

1 PPM

10 PPM

0.005%

4 PPM

1 PPM

1 PPM

1 PPM

2 PPM

0.005%

4 PPM

4 PPM

0.005%

2 PPM

2 PPM

0.005%

4 PPM

2 PPM

0.005%

4 PPM

4 PPM

2 PPM

0.005%

4 PPM

2 PPM

10 PPM

2 PPM

40 PPM

0.005%

2 PPM

2 PPM

1 PPM

4 PPM

0.1 PPM

0.1 PPM

0.1 PPM

0.02 PPM

0.1 PPM

0.1 PPM

1 PPM

0.1 PPM

0.01%

0.01%

0.01%

0.01%

ICP-AES = Inductively coupled plasma-atomic emission spectrometry

AAS = Atomic absorption spectrometry

DNAA = Delayed neutron activation analysis 7
Table 2. 

Comparison of laboratory values for reference material GXR-2 to literature concensus values (n=44)

CONSTITUENT

Al*

Au

Ba

Be

Bi

Ca*

Ce

Co

Cr

Cu

Eu

Fe*

Ga

Ho

K*

La

Li

Mg*

Mn

Mo

Na*

Nb

Nd

Ni

P*

Pb

Sc

Sn

Sr

Ta

Ti*

V

Y

Yb

Zn

As

Sb

Se

Hg

Ag

Cd

Th

U

Total C*

Organic C*

Carbonate C*

S*

Mean

6.68

X

2181

1.24

X

0.90

51.8

9.2

34.3

79.8

X

1.92

17.8

X

1.30

28.4

59.8

0.845

995

X

0.569

11.9

20.9

18.4

0.072

681

6.2

X

158

X

0.269

50.9

15.2

1.2

537

23.5

42.8

0.625

3.03

18

3.95

8.90

3.03

2.95

2.94

0.014

X

LABORATORY VALUES

s

0.42

X

91

0.43

X

0.04

3,3

0.8

2.7

3.7

X

0.07

2.4

X

0.07

2.4

3.2

0.035

27

X

0.032

3.6

1.7

0.9

0.004

46

0.4

X

8

X

0.013

2.2

1.3

0.4

25

3.1

5.1

0.076

0.25

2.6

0.2

1.24

0.15

0.056

0.059

0.009

X

% RSD

6.3

X

4.2

34.7

X

4.4

6.4

8.7

7.9

4.6

X

3.6

13.5

X

5.4

8.5

5.4

4.1

2.7

X

5.6

30.3

8.1

4.9

5.6

6.8

6.5

X

5.1

X

4.8

4.3

8.6

33.3

4.7

13.2

11.9

12.2

8.3

14.4

5.1

13.9

4.4

1.9

2

64.3

X

Range

5.8 to 7.6

<8 to <8

2000 to 2400

1 to 2

<10to<10

0.80 to 1.00

45 to 59

8to11

30 to 44

71 to 91

<2 to <2

1.8 to 2.1

13 to 22

<4 to <4

1.1 to 1.5

25 to 40

54 to 67

0.76 to 0.96

950 to 11 00

<2to2

0.52 to 0.68

<4 to 20

18 to 25

17 to 20

0.07 to 0.08

580 to 790

6 to 7

<5 to <5

140 to 180

<40 to <40

0.24 to 0.30

47 to 58

14 to 20

1 to 2

480 to 600

18 to 35

0.50 to 0.80

32 to 53

2.1 to 3.6

16 to 24

3.3 to 4.1

6.35 to 11. 30

2.51 to 3.30

2.77 to 3.07

2.76 to 3,07

<0.01 to 0.05

<0.05 to 0.06

CONSENSUS VALUES1

Mean

16.46

0.036

2240

1.7

0.7

0.93

51.4

8.6

36

76

0.81

1.81

37

no data

1.37

25.6

54

0.85

1010

2.1

0.556

11

19

20

0.105

690

6.88

1.7

160

0.9

0.29

52

17

2.04

530

25

49

0.61

2.9

17

4.1

8.8

2.9

2.5

2.59

0.025

0.0313

% Recovery

40.6

97.4

72.9

96.8

100.8

107.0

95.3

105.0

104.3

48.1

94.9

110.9

110.7

99.4

98.5

102.3

108.2

110.0

92.0

68.6

98.7

90.1

98.8

92.8

97.9

89.4

58.8

103.1

94.0

87.3

102.5

104.5

105.9

96.3

101.1

104.5

118.0

113.5

56.0

All values ppm except * in percent

x = Insufficient unqualified data

n = number of samples

s = standard deviation

% R = percent recovery

%RSD = percent relative standard deviation 1 Gladney and Roelandts, 1990
Table 3. 

Fit of results of GXR-2 reference material to number of standard deviations from the laboratory means

CONSTITUENT

AL

Au

Ba

Be

Bi

Ca

Ce

Co

Cr

Cu

Eu

Fe

Ga

Ho

K

La

Li

Mg

Mn

Mo

Na

Nb

Nd

Ni

P

Pb

Sc

Sn

Sr

Ta

Ti

V

Y

Yb

Zn

As

Sb

Se

Hg

Ag

Cd

Th

U

Total C

Organic C

Carbonate C

S

No. of samples

<=1 s

34

X

36

44

X

37

34

35

34

30

X

38

29

X

29

38

37

35

37

X

36

31

29

35

35

31

34

X

36

X

34

35

36

36

32

33

35

30

36

37

35

28

29

36

35

27

X

No. of samples

<=2s

41

X

43

0

X

41

42

43

42

42

X

43

44

X

42

43

43

42

42

X

42

42

43

44

44

42

44

X

41

X

42

42

42

44

41

42

41

43

42

39

39

43

39

41

42

27

X

No. of samples

<=3s

44

X

44

0

X

44

44

44

43

43

X

44

44

X

44

43

44

43

43

X

43

43

44

44

44

44

44

X

44

X

44

43

43

44

44

43

44

44

43

44

43

44

43

43

44

27

X

No. of less

than values

0

44

0

0

44

0

0

0

0

0

44

0

0

44

0

0

0

0

0

42

0

1

0

0

0

0

0

44

0

44

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

16

39

x = insufficient unqualified data
Table 4. 

Average relative percent difference and average mean for within job sample duplicates (n = 44 pair)

CONSTITUENT

AL

Au

Ba

Be

Bi

Ca

Ce

Co

Cr

Cu

Eu

Fe

Ga

Ho

K

La

Li

Mg

Mn

Mo

Na

Nb

Nd

Ni

P

Pb

Sc

Sn

Sr

Ta

Ti

V

Y

Yb

Zn

As

Sb

Se

Hg

Ag

Cd

Th

U

Total C

Organic C

Carbonate C

S

Average Relative

Percent Difference

2.3

X

2.0

4.2

X

3.0

3.7

3.7

2.7

5.1

X

1.3

5.9

X

3.1

4.4

2.9

1.2

1.6

X

2.7

8.5

5.8

3.1

4.6

11.4

1.2

X

1.5

X

3.8

2.5

3.0

8.6

2.8

6.3

22.4

7.2

17.7

3.6

8.5

14.2

7.6

0.7

2.7

4.2

3.4

Average Mean

6.6*

<8

526

2

<10

4.3*

73

16

68

29

<2

3.5*

16

<4

1.5*

39

36

1.08*

1112

<2

0.8*

14

36

32

0.09*

28

12

<5

285

<40

0.42*

99

23

2

114

8.7

0.90

0.72

0.090

0.32

0.400

10.8

3.95

3.11*

1.86*

1.44*

0.13*

No. Less Than Values

0

88

0

8

88

0

0

0

0

0

85

0

2

88

0

0

0

0

0

86

0

4

4

0

0

1

2

88

0

88

0

0

0

4

2

0

4

4

13

11

3

4

0

0

0

12

25

No. Less Than Pairs

0

44

0

4

44

0

0

0

0

0

42

0

1

44

0

0

0

0

0

43

0

2

2

0

0

0

1

44

0

44

0

0

0

1

1

0

1

2

5

4

1

2

0

0

0

5

12

All values in ppm except * in percent 

x = insufficient unqualified data 10
References

Alcott, G. H., and Lakin, H. W., 1975, Geochemical exploration 1974: in Elliott, I. L., 

and Fletcher, W. D., Editors, Elseveir, Amsterdam, 659 p.

Arbogast, B. F., 1990, Quality assurance manual for the Branch of Geochemistry, U. S. 

Geological Survey: U.S. Geological Survey Open-File Report 90-668,184 p.

Arbogst, B. F., 1996, Analytical methods manual for the Mineral Resource Surveys

Program, U.S. Geological Survey: U.S. Geological Survey Open-File Report 96- 

525, 248 p.

Gladney, E. S., and Roelandts, L, 1990,1988 compilation of elemental concentration data 

for USGS geochemical reference materials GXR-1 to GXR-6: Geostandards 

Newsletter, 14, p. 21 - 118.

Hirsh, R. M, Alley, W. M, and Wilber, W. G., 1988, Conceptual design of a National 

Water Quality Assessment Program: U.S. Geological Survey Circular 1021,42p.

Shelton, L. R., and Capel, P. D., 1994, Guideline for collecting and processing samples of 

stream-bed sediment for analysis of trace elements and organic contaminants for 

the National Water Quality Assessment Program: U.S. Geological Survey OpenFile Report 94-458, 20p.

Taylor, J. K., 1981, Quality assurance of chemical measurements: Analytical Chemistry, 

v. 53, no. 14,p.l588-1596.

11