Traceability Tool for Elemental Solution Standards Using 

 Ratio-Based Instrumental Comparison 

Version 1.2

March 7, 2005

Designed and written by G.C. Turk and M.L. Salit of the NIST Analytical Chemistry Division 

Intended Use 

This spreadsheet has been designed as an aid for establishing traceability of a batch of an 

elemental solution standard to the corresponding elemental spectrometric solution from 

the NIST SRM 3100 Series. It will work only with ratio-based instrumental comparison 

data, i.e. data from instrumental methods capable of utilizing internal standards. It has 

been tested using ICP-OES data, but should also be applicable to other multi-element 

methods. A spreadsheet with ICP-OES example data is included in this package. The 

measurements for that example took 95 minutes. When all required input data fields are 

filled, the spreadsheet will calculate the traceable mass fraction and uncertainty of the 

batch elemental solution standard. 

Prior to using this tool, the user must develop an appropriate measurement method for the 

analyte. This includes the selection of an appropriate internal standard element, 

verification that the analyte and internal standard are free of any interferences or solution 

cross-contamination, and verification that there are no blank contamination or instrument 

memory issues. The instrument must have a linear response to analyte and internal 

standard. For ICP-OES measurements, the publication by Salit, et al.

1

 should be 

consulted. 

Overview 

The batch elemental solution standard for which traceability to an SRM is being sought is 

referred to as the Test Sample. Four weighed aliquots of the Test Sample and four 

weighed aliquots of the SRM will each be spiked with weighed aliquots of an Internal 

Standard Spike Solution. The mass fraction of the Internal Standard Spike Solution and 

the spike aliquot mass are chosen to yield an analyte/internal standard instrument 

response ratio near unity. Since this depends on the relative sensitivity of the analyte and 

internal standard, the procedure begins with the determination of the instrument 

sensitivity for the analyte and internal standard under the instrument operating conditions 

to be used for the measurement. This is done by recording the instrument response of an 

analyte Sensitivity Solution and an internal standard Sensitivity Solution. With this 

information, instructions are given for the preparation of the Internal Standard Spike 

Solution by dilution of an Internal Standard Stock Solution. Spiked Test Samples and 

SRMs are then prepared according to instructions. In most cases, it is expected that the 

spiked solutions will be too concentrated for direct instrumental analysis, and therefore 

Working Solutions must be prepared by dilution. Dilution instructions are given based on 

the mass of Working Solutions to be prepared and a user-specified instrument Working 

Response Level. A reasonable Working Response Level is one which is significantly 

above the blank and background level, and which is comfortably within the linear range 

of the detection system. Five measurements of the analyte and internal standard response 
of each Working Solution of Test Sample and SRM are made in a specified run order. 

The traceable analyte mass fraction of the Test Sample is calculated based on the relative 

analyte/internal standard response of Test Sample to SRM, and the relative masses of 

Test Sample, SRM and Internal Standard Spike Solution. The uncertainty of the traceable 

mass fraction is calculated based on the observed variability of the measurements and 

uncertainty of the certified value of the SRM. 

This process is diagrammed below. 

Start

develop method

determine sensitivities

prepare Internal Standard Spike Solution

weigh and spike aliquots of SRM and Test 

Samples

prepare Working Solutions

measure Working Solutions, repeat 5 

times 

copy measurements to spreadsheet, 

review results

Finish
Equipment and Supplies 

3⁄4 One ampoule, or 10 mL, of the appropriate SRM 3100 solution. 

3⁄4 Four units of the Test Sample. Each unit must contain at least 2.5 g at 10 mg/g, or 

25 g at 1 mg/g (assuming the usual situation of a 10 mg/g SRM). Each unit should 

be chosen from a different section of the batch to achieve a good sampling of the 

batch. 

3⁄4 A solution containing the analyte at a known concentration that will yield an 

instrument response signal in a good working range of the instrument. This is the 

analyte Sensitivity Solution. The mass fraction of this solution need not be 

accurately known. 

3⁄4 A solution containing the internal standard at a known concentration that will 

yield an instrument response signal is a good working range of the instrument. 

This is the internal standard Sensitivity Solution. The accuracy of this solution is 

not important. 

3⁄4 A bottle of the Internal Standard Stock Solution. A 10 mg/g solution is best. The 

mass fraction of this solution need not be accurately known. 

3⁄4 A 250 mL bottle for the preparation of the Internal Standard Spike Solution. 

3⁄4 8 bottles for spiked SRM and Test Samples. In most cases, 30 mL bottles will be 

suitable when the Test Sample has a nominal mass fraction of 10 mg/g. If the 

nominal mass fraction of the Test Sample is 1 mg/g, 60 mL bottles will be 

appropriate. 

3⁄4 8 containers for the Working Solutions. Autosampler tubes are convenient. 

3⁄4 A balance with 1 mg precision (i.e. a “3-place top loader”). 

3⁄4 An adjustable digital pipette is useful to deliver solution mass near the specified 

target values. 

Instructions 

1. Open and complete the Descriptive Information worksheet. In this and all 

subsequent worksheets, cells requiring input information are shown with gold 

backgrounds. 

2. Using the analyte and internal standard Sensitivity Solutions, measure the analyte 

and internal standard instrument response signal for these solutions. Enter the 

known mass fractions and the measured response signals in the Instrument 

Sensitivity Test worksheet. 

3. Open and print the Solution Preparation worksheet. Following the target mass 

values given, prepare the Internal Standard Spike Solution, the spiked samples of 

the SRM and Test Sample, and the Working Solutions. Enter the exact mass 
values for the preparation of the spiked Test Samples and SRMs into the 

worksheet. The exact mass values for the preparation of the Internal Standard 

Spike Solution and the Working Solutions are not used in any subsequent 

calculations, and are not entered into the spreadsheet. 

4. Collect instrumental data following the experimental design in the Instrumental 

Measurements worksheet, recording between 1 and 10 replicate readings of each 

specified measurement. Enter the data into the spreadsheet. 

5. The spreadsheet includes the possibility of using the Salit and Turk drift 

correction method.2 The drift correction function should be visually inspected in 

the Drift Pattern spreadsheet to confirm that a reasonable model of observed drift 

has been calculated. 

6. Final results can be found in either the Final Results (with Drift Correction) 

worksheet, or the Final Results (without Drift Correction) worksheet. 

 

1. M.L. Salit, G.C. Turk, A.P. Lindstrom, T.A. Butler, C.M. Beck II, and B. 

Norman, “Single-element Solution Comparisons with High-Performance ICPOES,” Anal. Chem. 73, 4821-4829 (2001).

2. M.L. Salit and G.C. Turk, “A drift correction procedure,” Anal. Chem. 70, 3184-

3190 (1998).