Use of ETAAS, FAAS and ICP-OES for production and post-certification monitoring of a multielemental certified reference material according to national regulation limits for elements in drinking water

This paper describes the development of a certified reference material (CRM), produced in the National Institute of Quality from Peru (INACAL) in order to provide a tool for assurance and quality control of nine elements in drinking water. Atomic absorption spectrometry (ETAAS or FAAS) allowed for measurements during the 18-month certification process. ETAAS or ICP optical emission spectrometry was used for 24-month post-certification monitoring measurements. CRM production took into account requirements of ISO Guides 34 and 35 for production of reference materials and criteria of the JCGM GUM and Eurachem QUAM Guides for uncertainty calculation. Mass fractions chosen for batch gravimetric preparation were based on the maximum permissible limits of the National Regulation for Drinking Water Quality in Peru. Characterization analytical measurements were performed using the bracketing calibration technique, applying a randomized 10-replicate measurement sequence and adjusting (matrix matching) the nitric acid concentration for all measured solutions. Characterization resulted from the combination of gravimetric preparation and analytical atomic absorption measurement results. Main sources of uncertainty were identified from the homogeneity study, characterization and the stability study. Expanded relative uncertainties for the assigned mass fractions (ng/g) of Pb, Cd, Ni, As, Cr, Cu, Zn, Mn and Al in the CRM produced were between 0.8 % and 1.9 %. INACAL’s capability to achieve the stated uncertainties has been confirmed through successfully participating in a comparison of the Inter-American Metrology System (SIM-QM-S2). All declared results (ETAAS and FAAS) were comparable to those declared by primary methods of other participants in this comparison.