Development of a reference material for the composition of 0.1 m potassium dichromate solution. Certified reference material GSO 10992-2017

This paper describes key stages in the development and investigation of a high-precision certified reference material (CRM) for the composition of potassium dichromate solution. The proposed reference material (RM) exhibits metrological traceability to the units of the International System of Units (SI). Not requiring additional preparation before use, the CRM is convenient for use as a titrant in redox titration.

The metrological characteristics of the developed CRM were determined by the direct primary method of coulomet-ric titration using the State Primary Standard GET 176. The interval of permissible certified values of the molar concentration of potassium dichromate in the CRM under study is found to vary from 0.098 mol/dm³ to 0.102 mol/ dm³. The relative expanded uncertainty (k = 2) of the certified value ofpotassium dichromate molar concentration is calculated to be 0.024 %, with relative standard uncertainties caused by long-term and short-term instability each being equal to 0.0044 %. The shelf life of the developed CRM is found to be 1 year, provided that storage conditions are ensured. A procedure for measuring the molar concentration ofpotassium dichromate is described, along with the equipment used. A comprehensive uncertainty budget for the measurements is assembled.

The developed CRM is included into the State Register of Certified Reference Materials under the number GSO 10992-2017. The CRM can be used for transferring the mass (molar) concentration unit of a component to RMs and chemical reagents via oxidation-reduction reactions; the verification and calibration of measuring instruments (MI), as well as control of metrological characteristics during MI trials including type approval; MI graduation; validation of measurement procedures; control of measurement results when determining the mass (molar) fraction and mass (molar) concentration of components in liquid and solid substances and materials.

1. Milton M. J.T., Quinn T. J. Primary methods for the measurement of amount of substance. Metrologia. 2001;38(4):289—296. https://doi.org/10.1088/0026—1394/38/4/1

2. Mariassy M., Pratt K. W., Spitzer P. Major applications of electrochemical techniques at national metrology institutes. Metrologia. 2009;46(3):199-213. https://doi.org/10.1088/0026—1394/46/3/007

3. Terentiev G. I., Sobina A. V., Shimolin A. J., Zyskin V. M. Application of coulometric titration for the certification of primary reference materials of pure substances. AJAC. 2014;5:559-565. https://doi.org/10.4236/ajac.2014.59063.

4. Borges P. P., Silva Junior W. B., Gonzaga F. B., Sobina A. V., Shimolin A. Yu., Terentiev G. I. Сoulometric determination of amount content of potassium dichromate for comparability assessment through a bilateral comparison. Proc. XX IMEKO World congress metrology for green growth. Busan, 9—14 September 2012. (In Korea).

5. Mariassy M et all. Key comparison CCQM-K96 Determination of amount content of dichromate. Draft B report. Bratislava, February 2013.

6. Terentiev G. I., Gerasimova N. L., Mamonova I. S., Borozdina N. F., Zyskin V. M., Marina N. V. Transfer of standard titres to the category of certified reference materials is a new step in metrological assurance of analytical measurements. Reference materials 1(2):17-22. (In Russ.)

7. Sobina A. V. Development of State primary standard units of mass fraction and mass concentration of the component in the liquid and solid substances and materials based on coulometric titration. Dissertation, D. I. Mendeleyev Institute for Metrology (VNIIM). Available at: http://vniim.ru/files/dis-sobina. pdf

8. Marinenko G., Taylor J. K. Precise coulometric titrations of potassium dichromate. Journal of research of the National Bureau of Standards - A. Physics and Chemistry 1963;67A(5): 453-459.

9. Atomic weights of the elements 2013 (IUPAC Technical Report). Pure Appl. Chem. 2016;88(3):265-291. https://doi.org/10.1515/pac-2015-0305.

10. Mohr P. J., Newell D. B., Taylor B. N. CODATA recommended values of the fundamental physical constants: 2014. Rev. Mod. Phys. 2016;88(3):035009-70. https://doi.org/10.1103/RevModPhys.88.035009.

11. Shimolin A. J., Sobina A. V., Zyskin V. M. Potassium iodate purity determination by high precision coulometric titration: new measurement procedure implementation. Chelyabinsk, 16-19 Oct. 2017. IEEE, 17410812. https://doi.org/10.1109/URALCON.2017.8120729

12. Perelman V. I. Chemist quick reference. Scientific and technical publishing house of chemical literature, 1963, Moscow. (In Russ.).

13. GOST 4220-75 Reagents. Potassium bichromate. Specifications. Standartinform Publ., 2010. 6 p. (In Russ.).

14. JCGM 100:2008 Evaluation of measurement data - guide to the expression of uncertainty in measurement. JCGM, 2008. http://www.bipm.org/utils/common/documents/jcgm/JCGM_100_2008_E.pdf

15. ISO Guide 35:2017 Reference materials - Guidance for characterization and assessment of homogeneity and stability. Available at: https://www.iso.org/standard/60281.html

16. Р.50.2.058-2007 State System for Ensuring Uniform Measurement. Evaluation of certified values uncertainties of reference materials. Standartinform Publ., 2008. 28 p. (In Russ.).

17. GOST 23683-89 Petroleum paraffin waxes. Specifications. Standartinform Publ., 2008. 14 p. (In Russ.).

18. GOST 8.736-2011 State system for ensuring the uniformity of measurements. Multiple direct measurements. Methods of measurement results processing. Main principles. Standartinform Publ., 2008. 24 p. (In Russ.).