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Speciation and preservation of CrVI and CrIII in finished drinking water matrices using collision cell ion chromatography-inductively coupled plasma-mass spectrometry
Citation:
Wilson, R., P. Creed, T. Pinyayev, L. Wymer, AND J. Creed. Speciation and preservation of CrVI and CrIII in finished drinking water matrices using collision cell ion chromatography-inductively coupled plasma-mass spectrometry. JOURNAL ASSOCIATION OF OFFICIAL ANALYTICAL CHEMISTS. AOAC International, Gaithersburg, MD, 97(3):956-962, (2014).
Impact/Purpose:
To develop a technique to speciate CrIII and CrVI
Description:
The polyatomic background at the major isotope of Cr was evaluated as a function of collision cell gas flow rate using three different mobile phases. The stability of CrVI was evaluated as a function of solution pH using an enriched 53CrVI. The recovery was ≥ 95% at pH 7.8 but by pH 6.2 a significant amount of the enriched spike was recovered as 53CrIII-EDTA. The instability of CrIII at pHs above 7.8 required that CrIII be chelated prior to speciation. The concentration of EDTA was optimized by evaluating CrIII recoveries in six drinking waters from across the US, an USGS reference water and a challenge water fortified with competing matrix cations. If the CrIII was allowed to precipitate (characteristic of shipping a sample without field preservation) acceptable recoveries of CrIII required the sample be heated to 70oC in 10mM EDTA to quantitatively produce the CrIII-EDTA complex. The overall preservation / speciation approach was evaluated using an enriched 53CrVI and natural CrIII in seven drinking water matrices over a 46 day period. A linear least squares analysis was performed on each water, and the corresponding p-values were estimated. The method detection limits for CrIII-EDTA and CrVI were 0.06 and 0.1 µg/L, respectively.
