A PRACTICAL T

ESTABLISHING TRACEA

CHEMICAL MEASU

Gregory C. Turk and Marc L

NIST
Specifically, a tool to establi

traceability of the value of aelemental solution standard NIST SRM 3100 Series

N

S

3

C

o

Calibration

Standard
The NIST SRM 3100 

Spectrometric S

• NIST produces and 

certifies 69 Spectrometric Solution SRMs

• Typical mass 

fraction is 10 ± 0.03 mg/g

• Serve as national 

standards
An important link in the c

infrastructure for elementa

Elemental

Analysis

Lab

a

Elemental

Analysis

Lab

b

Standards

Producer

A

Elemental

Analysis

Lab

c

Standards

Producer

B

Elemental

Analysis

Lab

d

Elemen

Analys

Lab

e

Standards

Producer

C

NIST

SRM 3100 Series

NIST

Primary Materials

BIPM

CCQM
We have de

“Traceability Tool” for E

Solution S

• a spreadsheet

– an experimental design with replicat

critical measurements and preparatio

» to assess measurement uncertainty

– a ratio-based method

» interactively designs the correct “spike”

– optional drift correction and diagnost– calculates the traceable value– full uncertainty budget
What you need to use 

• An instrument that gives a sig

linearly proportional to the mafraction of the analyte and an standard mixed in a solution 

– Designed for ICP-OES, but not 
• 10 g of SRM• 4 units of Test 

Solution

• Rough setup 

solutions for analyte and IS

• Stock solution of IS• One 250 mL bottle

• Eight 30 

for spike

• Eight mo

for dilutesolutions

• A 1 mg b• A digital 
The tool does NOT 

• Any instrumental operating pa

– Wavelengths, background correction 

integration times .........

• Choice of internal standard
ICP-OES is a great do

balance for comparing 

solution s

• spectroscopic elemental selectivity• simultaneous detection of analyte 

internal standard emission

– highly correlated noise

• excellent precision

– better than 0.03 % in most cases– thus adds negligible uncertainty to tr

values
Ratio-Based Meas

SRM IS

SRM

Test

SRM

Test

Test

IS

IS

R

R

g

mg 







= 





SRM

Internal

Standard

Working

SRM

Test

Solution

Spiked

Test

Solution

Spiked

SRM

Working

Test

Solution

Test IS

gTest

gSRM
Start

select internal standard, analyte and internal 

emission lines

determine sensitivities

prepare Internal Standard Spike Soluti

weigh and spike aliquots of SRM and Test S

prepare Working Solutions

measure Working Solutions, repeat 5 tim

copy measurements to spreadsheet, review 

Finish
Example Cobalt S

10.305 g of SRM 3113

@ 9.996 mg/g

+ 0.046 g water

= 9.9
Step 1. Experimen

In

Experiment related information 

Date of analysis Element 

Identification label of the Test Sample Lot number of the Test Sample Nominal mass fraction of Test Sample (mg/g) SRM 3100 series number SRM lot number Certified Mass Fraction (mg/g) of SRM 3113, lot 000630 Uncertainty of Certified Mass Fraction (mg/g) Coverage Factor, k, for the SRM Certified Uncertainty 

http://srmcatalog.nist.gov/

SRM Certificates of Analysis can be found at
Step 1 (continued). In

Related In

Instrument related information 

Instrumental comparison method Working Response Level Mass of Working Solutions (g) Internal standard element Mass fraction of Internal Standard Stock Solution (mg/g) 
Step 2. Sensiti

5 2.20E+07 4408475.2 

Sc (Int. Std.) Sensitivity Solution

10 1.67E+06 167086.9 

Co (Analyte) Sensitivity Solution

Sensitivity 

(response/(μg/

g))

HP-ICP 

response ug/g

measure instrument response for t

) Solutions of the analyte and intern

HP-ICP Comparison of Example (lot 1) to NIST SRM 3113 (lot 00
Step 3. Solution Pr

))

Target Target Tar

Tare Gross Net Tare Gross Net 

SRM 1 2.5 6.275 8.882 2.607 2SRM 2 2.5 6.277 8.931 2.654 2SRM 3 2.5 6.241 8.889 2.648 2SRM 4 2.5 6.162 8.536 2.374 2

Test Sample 1 2.5 6.305 8.961 2.656 2Test Sample 2 2.5 6.230 8.884 2.654 2Test Sample 3 2.5 6.259 8.922 2.663 2Test Sample 4 2.5 6.272 8.585 2.313 2

)

Actual

g of Test Sample

0.32

SRM Samples

Test Samples

g of spiked solution 

to dilute to 60 g

0.32

HP-ICP Comparison of Example (lot 1) to NIST SRM 3113 (lot 000630), 1

g of Sc Internal Standard

Stock Solution to dilute 

to 200g

Into labeled bottles, prepare spiked Test Samples and SRMs following tbelow:Prepare Working Solutions by dilution of spiked solutions.

0.95

Actual

Prepare Sc Internal Standard Spike Solution.

g of SRM 3113 
Step 4. Pa

Analyte 1137374.55

IS 1113068.13

Analyte 1141089.78

IS 1099376.97

Analyte 1196692.63

IS 1123082.64

Analyte 1108934.27

IS 1068717.37

Analyte 1208361.01

IS 1114122.94

Analyte 1243910.54

IS 1137017.31

Analyte 1038993.8

IS 1092479.25

Analyte 1077577.54

IS 1188758.02

Analyte 1126370.41

IS 1102142.82

Analyte 1132849.54

IS 1092214.67

Analyte 1207295.28

IS 1132187.5

Analyte 1111136.64

IS 1069968.02

Analyte 1214994.39

IS 1119541.71

Analyte 1231031.77

IS 1122825.22

Analyte 1051854.31

IS 1107376.21

Analyte 1075063.37

IS 1186723.38

Analyte 1139182.62

IS 1115025.26

Analyte 1128984.33

IS 1088690.61

Analyte 1197496.24

IS 1124042.41

Analyte 1107071.47

IS 1066707.79

Analyte 1214189.49

IS 1119554.66

Analyte 1233749.11

IS 1128012.72

Analyte 1040693.68

IS 1096859.49

Analyte 1067269.46

IS 1179873.52

Analyte 1140342.82

IS 1118347.55

Analyte 1116463.3

IS 1077175.94

Analyte 1207101.01

IS 1133854.78

Analyte 1106567.61

IS 1067109.36

Analyte 1215341.11

IS 1123379.19

Analyte 1240087.04

IS 1135925.69

Analyte 1037383.85

IS 1094632

Analyte 1063956.92

IS 1177214.46

Analyte 1123252.23

IS 1103387.89

Analyte 1128926.16

IS 1092771.06

Analyte 1196393.54

IS 1124993.86

Analyte 1106270.51

IS 1069921.32

Analyte 1215945.61

IS 1123944.01

Analyte 1235961.65

IS 1132041.02

Analyte 1042308.55

IS 1099013.19

Analyte 1073005.15

IS 1186736.11 Test Sample 4

543

Test Sample 2

SRM 3

Test Sample 3

SRM 4SRM 1

Test Sample 1

SRM 2

2

SRM 3

Test Sample 3

SRM 4

Test Sample 4

SRM 1

Test Sample 1

SRM 2

Test Sample 2

SRM 3

Test Sample 3

SRM 4

Test Sample 4

SRM 1

Test Sample 1

SRM 2

Test Sample 2

SRM 3

Test Sample 3

SRM 4

Test Sample 4

SRM 1

Test Sample 1

SRM 2

Test Sample 2

1

SRM 1

Test Sample 1

SRM 2

Test Sample 2

SRM 3

Test Sample 3

SRM 4

Test Sample 4

Repeat # ID Element Rea

Analyte 113

IS 111

Analyte 114

IS 109

Analyte 119

IS 112

Analyte 110

IS 106

Analyte 120

IS 111

Analyte 124

IS 113

Analyte 10

IS 109

Analyte 107

IS 118

1

SRM 1

Test Sample 1

SRM 2

Test Sample 2

SRM 3

Test Sample 3

SRM 4

Test Sample 4
Correlation D

Analyte:Internal Standard Correlation

959799

101103105

95 97 99 101 
Drift D

Drift Pattern

y = 4E-11x6 - 5E-09x5 + 2E-07x4 - 4E-06x3 + 3E-05x2 + 9E-0

0.9960.9970.9980.999

1

1.0011.0021.003

0 5 10 15 20 25 30 

Run Order

Relative Drift
Results (without drift co

HP-ICP Comparison of Example (lot 1) to NIST SRM 3113 (lot 000630), 10/26/2001.

Mass Ratio

Slope of 

Calibration 

Curve

Apparent 

Mass 

Fraction

sd

(mg analyte/g

IS)

(signal

ratio/mass mg/g mg/g

SRM 1 1.0209 0.0015 0.14% 1.2741 0.8013 9.995 0.014SRM 2 1.0649 0.0015 0.15% 1.3293 0.8011 9.993 0.015SRM 3 1.0843 0.0017 0.16% 1.3527 0.8016 9.998 0.016SRM 4 0.9489 0.0015 0.15% 1.1838 0.8016 9.999 0.015

Average slope 0.80138

sd of slope 0.00023

Observed 

Mass 

Fraction

sd

mg/g mg/g

Test Sample 1 1.0364 0.0018 0.17% 9.951 0.017 99.99%Test Sample 2 1.0377 0.0019 0.18% 9.952 0.018 100.00%Test Sample 3 1.0933 0.0019 0.17% 9.945 0.017 99.92%Test Sample 4 0.9051 0.0013 0.15% 9.952 0.015 100.00%

Average mass fraction 9.950

sd of mass fraction 0.003

Source (mg/g) relative df coverage factor, k

SRM 3113 Measurements

0.001 0.01% 3

Example Measurements 0.002 0.02% 3

Certified Value of SRM

3113 0.010 0.10% 8

Combined Uncertainty 0.010 0.10% 9

Coverage Factor, k 2.26

Expanded Uncertainty 0.023 0.23%

rsd

SRM 3113 

Measurements rsd

Example 

Measurements

Determined Traceable Value >> 9.9496 mg/g ± 0.0230 mg/g

Observed 

/Nominal

Average 

Signal Ratio sd

Uncertainty Budget

Average 

Signal Ratio sd

9.995

9.9609.9709.9809.990

10.00010.01010.020

SRM 1 SRM 

mg/g

9.951 9

9.9009.9109.9209.9309.9409.9509.9609.970

Test Sample 1 Test Sam

mg/g
Results (with drift co

HP-ICP Comparison of Example (lot 1) to NIST SRM 3113 (lot 000630), 10/26/2001.

Mass Ratio

Slope of 

Calibration 

Curve

Apparent 

Mass 

Fraction

sd

(mg analyte/g IS) (signal ratio/mass mg/g mg/g

SRM 1 1.0207 0.0002 0.02% 1.2741 0.8011 9.992 0.002SRM 2 1.0649 0.0002 0.02% 1.3293 0.8011 9.992 0.002SRM 3 1.0843 0.0003 0.03% 1.3527 0.8016 9.999 0.003SRM 4 0.9491 0.0005 0.06% 1.1838 0.8017 10.000 0.006

Average slope 0.80136

sd of slope 0.00034

Observed 

Mass Fraction sd

mg/g mg/g

Test Sample 1 1.0362 0.0004 0.04% 9.950 0.004 99.98%Test Sample 2 1.0377 0.0005 0.05% 9.952 0.005 100.00%Test Sample 3 1.0934 0.0005 0.05% 9.946 0.005 99.94%Test Sample 4 0.9052 0.0003 0.03% 9.953 0.003 100.01%

Average mass fraction 9.950

sd of mass fraction 0.003

Source (mg/g) relative df coverage factor, k

SRM 3113 Measurements

0.002 0.02% 3

Example Measurements 0.002 0.02% 3

Certified Value of SRM

3113 0.010 0.10% 8

Combined Uncertainty 0.010 0.10% 9.00

Coverage Factor, k 2.26

Expanded Uncertainty 0.023 0.23%

SRM 3113 

Measurements rsd

Example 

Measurements

Observed 

/Nominal

Average 

Signal Ratio sd

Average 

Signal Ratio sd rsd

Determined Traceable Value >> 9.9501 mg/g ± 0.0232 mg/g

Uncertainty Budget

9.992 9.992

9.9809.9859.9909.995

10.00010.00510.010

SRM 1 SRM 2 

mg/g

9.950

9.952

9.9359.9409.9459.9509.9559.960

Test Sample 1 Test Sample 2 

mg/g
Uncertain

(without drift c

Source (mg/g) relative df coverage factor, 

k

SRM 3113 Measurements

0.001 0.01% 3

Example Measurements 0.002 0.02% 3

Certified Value of SRM

3113 0.010 0.10% 8

Combined Uncertainty 0.010 0.10% 9

Coverage Factor, k 2.26

Expanded Uncertainty 0.023 0.23%

Determined Traceable Value >> 9.9496 mg/g ± 0.023

Uncertainty Budget
Uncertain

(with drift c

Source (mg/g) relative df coverage factor, 

k

SRM 3113 Measurements

0.002 0.02% 3

Example Measurements 0.002 0.02% 3

Certified Value of SRM

3113 0.010 0.10% 8

Combined Uncertainty 0.010 0.10% 9.00

Coverage Factor, k 2.26

Expanded Uncertainty 0.023 0.23%

Determined Traceable Value >> 9.9501 mg/g ± 0.02

Uncertainty Budget
SRM

1234

Mass Fraction (g/kg)

9.929.949.969.98

10.0010.02

Test Sample

1234

SRM

1234

Drift Corrected

reference value for 

Test Sample

Summary o
The uncertainty of the 

value is identical to the un

of 

• SRM 3113: 9.996 ± 0.023 mg/g• Test Solution: 9.950 ± 0.023 mg/g