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Determination of arsenic species in soils
The objective of this study was to develop new methods for the determination and speciation of arsenic in soils. Ion-pairing chromatography was used for the separation of 4 toxicologically important arsenic species (As(III), As(V), monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA)). Hydride generation atomic absorption spectrometry (HG-AAS) or inductively coupled plasma mass spectrometry (ICP-MS) was used for detection. Extraction of arsenic species from soils was achieved using various techniques such as shaking, sonication, and microwave-assisted extraction. Even though As(V), DMAA and MMAA were quantitatively extracted from spiked soils, the recoveries for As(III) were low due to its irreversible adsorption into the soil. ^ In order to determine acid-extractable arsenic in soils, a procedure based on flow injection and slurry sampling with on-line microwave extraction (SS-MW-HG-AAS) was developed. The on-line microwave extraction increases the recovery of the adsorbed arsenic from 30 to 70%. The manifold was also successfully coupled to an ICP-MS for the multielemental analyses of soils. ^ In order to eliminate the use of liquid nitrogen for the speciation of arsenic using cryo trapping, a thermal desorption instrument equipped with a Peltier cooler was utilized. The arsines from the HG manifold were directed into the U-tube of the instrument, which is kept at −30°C. At this temperature, arsine eluted with little retention but the organo-arsines were trapped and then released after arsine completely eluted. ^ A new nebulizer design that provides better sensitivity than commercially available nebulizers are described. This nebulizer is constructed by inserting one fused silica capillary into another and then inserting this double capillary system into a PEEK tube (Double Capillary Nebulizer-DCN). Unlike the conventional concentric nebulizers where the argon delivery is from the outer area, the uniqueness of this nebulizer was the delivery of the argon from the inner and outer parts of the liquid flow to increase the efficiency of the interaction between the liquid and the gas. The performance of the DCN was comparable to the Meinhard nebulizer and some of the DCNs prepared were found to perform even better. The cost of a DCN is approximately 15% of the price of a Meinhard nebulizer. ^
"Determination of arsenic species in soils"
(January 1, 2001).
Electronic Doctoral Dissertations for UMass Amherst.