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APPLICATION OF SAMPLE PRE-OXIDATION OF ARSENITE IN HUMAN URINE PRIOR TO SPECIATON VIA ON-LINE PHOTO-OXIDATION WITH MEMBRANE HYDRIDE GENRATION AND ICP-MS DETECTION
Citation:
Wei, X., C A. Schwegel, AND J T. Creed. APPLICATION OF SAMPLE PRE-OXIDATION OF ARSENITE IN HUMAN URINE PRIOR TO SPECIATON VIA ON-LINE PHOTO-OXIDATION WITH MEMBRANE HYDRIDE GENRATION AND ICP-MS DETECTION. ANALYST 125(6):1215-1220, (2000).
Impact/Purpose:
Investigate the occurrence of Aeromonas bacteria in potable water derived from both surface and ground water sources. Develop improved method(s) for the detection of culturable H. pylori in environmental samples and investigate the occurrence of H. pylori in potable waters.
Description:
A pre-oxidation procedure which converts arsenite (AS(III)) to arsenate (As(VVV)) was investigated in urinary arsenic speciation prior to on-line photo-oxidation hydride-generation with ICP-MS detection. This sample pre-oxidation method eliminates As(III) and As(V) preservation concerns, simplified & facilitates chromatographic separations. Four oxidants were investigated. Chlorine and MnO2 selectively convErted As(III) to As(V) in pure water samples, but conversion was inefficient in complex urine matrix. Oxidation of As(III) by H202 was least affected by urine matrix, but removal of excess H2O2 at pH 10 proved difficult. The most appropriate oxidant for selective conversion of As(III) to As(V) with minimal interference from urine matrix is I3 at pH 7. Unlike H202, excess oxidant can be easily removed by addition of S2032. The I3/S2032 treatment on a fortified sample of reconstituted NIST SRM 2670 freeze dried urine indicated arsenobetaine (AsB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and As(V) were not chemically degraded with percent recoveries ranging from 95-102% for all arsenicals. Sample clean-up involved pH adjustment prior to C18 filtration in order ot achieve efficient (As(III) conversion and quantitative recoveries of AsB and DMA. The concentrations determined in NIST SRM 2670 freeze dried urine were AsB 17.2+/-0.5, DMA 55.6+/-4.1, MMA 10.3+/-0.3 with a combined total of 8.31+/-5.0 (ug/L+/-2o).