Quantifying uncertainty in the measurement of arsenic in suspended particulate matter by Atomic Absorption Spectrometry with hydride generator

Nahar Singh,Prabhat K Gupta,Tarushee Ahuja,Vn Ojha,Nijhuma Kayal

doi:10.1186/1752-153x-5-17

Abstract

Arsenic is the toxic element, which creates several problems in human being specially when inhaled through air. So the accurate and precise measurement of arsenic in suspended particulate matter (SPM) is of prime importance as it gives information about the level of toxicity in the environment, and preventive measures could be taken in the effective areas. Quality assurance is equally important in the measurement of arsenic in SPM samples before making any decision. The quality and reliability of the data of such volatile elements depends upon the measurement of uncertainty of each step involved from sampling to analysis. The analytical results quantifying uncertainty gives a measure of the confidence level of the concerned laboratory. So the main objective of this study was to determine arsenic content in SPM samples with uncertainty budget and to find out various potential sources of uncertainty, which affects the results. Keeping these facts, we have selected seven diverse sites of Delhi (National Capital of India) for quantification of arsenic content in SPM samples with uncertainty budget following sampling by HVS to analysis by Atomic Absorption Spectrometer-Hydride Generator (AAS-HG). In the measurement of arsenic in SPM samples so many steps are involved from sampling to final result and we have considered various potential sources of uncertainties. The calculation of uncertainty is based on ISO/IEC17025: 2005 document and EURACHEM guideline. It has been found that the final results mostly depend on the uncertainty in measurement mainly due to repeatability, final volume prepared for analysis, weighing balance and sampling by HVS. After the analysis of data of seven diverse sites of Delhi, it has been concluded that during the period from 31st Jan. 2008 to 7th Feb. 2008 the arsenic concentration varies from 1.44 ± 0.25 to 5.58 ± 0.55 ng/m3 with 95% confidence level (k = 2).

Highlights

In chemical metrology most of the important decisions are based on the quality and the reliability of results of quantitative analysis
A generalized scheme for planning a measurement and a simple, practical approach to estimate and combining uncertainties has been demonstrated for the determination of arsenic in suspended particulate matter (SPM) samples
The results show that the arsenic concentration varies 1.44 ± 0.25 ng/m3 to 5.58 ± 0.55 ng/m3 with variation of sites with 95% confidence level

Summary

Background

In chemical metrology most of the important decisions are based on the quality and the reliability of results of quantitative analysis. In this context it is important to have reliability of the results in the international trade and analytical results should be acceptable to all users within the country or outside the country This can be achieved by the estimation of uncertainty in the measurements as per ISO/EURACHEM guidelines [1,2,3,4,5]. An attempt has been made to choose such a complex matrix for the evaluation and expression of uncertainty in measurement of arsenic in SPM samples by AAS-HG, following documents published by ISO/IEC 17025:2005, EURACHEM guideline and GUM document

Results and discussion

Conclusion

Experimental Section

International Organization for Standardization