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A COMPARISON OF URINARY ARSENIC SPECIATION VIA DIRECT NEBULIZATION AND ON-LINE PHOTOOXIDATION-HYDRIDE GENERATION WITH DETECTION BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY
Citation:
Wei, X., C A. Schwegel, AND J T. Creed. A COMPARISON OF URINARY ARSENIC SPECIATION VIA DIRECT NEBULIZATION AND ON-LINE PHOTOOXIDATION-HYDRIDE GENERATION WITH DETECTION BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY 16(1):12-19, (2001).
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:
Arsenic speciation continues to be important in assessing human and environmental exposure risk. Urinary arsenic analysis provides information on recent arsenic exposure. In this study, two sample introduction pathways: direct nebulization (DN) and hydride generation (HG) were utilized and compared for urinary arsenic analysis via IC-ICP-MS. In the DIN method, the retention characteristics of arsenobetaine (AsB), arsenite (As(III)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenate (As(V)) and Cl were systematically evaluated with respect to column temperature and the (NH4)2CO3 eluent molarity. This evaluation indicated that the three early eluters (AsB, As(III) and DMA) were best separated at a higher column temperature and lower eluent molarity, whereas MMA, As(V) and Cl were best separated at a lower column temperature and higher eluent molarity. From this obsdervation, a gradient elution program was developed using 40mM and 70mM (NH4)2CO3(pH 10.5) at 69oC. This gradient condition produced satisfactory resolution for all five arsenic species with a Cl tolerance up to 0.3% (w/w). In the hydride generation (HG) configuration, a membrane based liquid-gas separator was used. A photo reactor interface was installed between the ion chromatography and the hydride gneration device to facilitate the oxidation and detection of non-hydride active arsenic species. Optimum photo-oxidation efficiency was achieved using a thin walled PTFE reaction coil braided around the UV lamp. Isocratic elution using 40mM (NH4)2CO3 was found adequate to resolve all five arsenic species while 40Ar35Cl nterference was eliminated. The HG method offers high sensitivity and wide eluent selection compared to DN, but has added experimental complexity and reagent background contamination. NIST SRM 2670 freeze dried urine was analyzed via both methods and the resuls from DN were within the 95% confidence bound calculated for HG.