A procedure based on the selective retention of either Cr(III) or Cr(VI) on alumina is evaluated and modified, and some mechanistic investigations made. Problems were encountered in selectively and quantitatively retaining either Cr(VI) or Cr(III) in the presence of the other, or in the presence of modest concentrations of various interferents. Evidence is presented that the poor recovery and selectivity were a function of chromatographic adsorption on alumina, a secondary retention mechanism which limits the practicality of the method. A modified and improved version of a plasma source atomic fluorescence spectrometer is described. Control of the spectrometer has been completely transferred to a PC-AT, which uses a control software package (LabVIEW, version 3.1) and two programmable circuit boards (AT-MIO-16DL and PC-TIO-10, both from National Instruments) to control lamp pulsing and data processing circuitry. A series of printed circuit boards have been constructed to process the photomultiplier tube current signal using a modified gated integration (boxcar integration) technique. Greater reproducibility and a two order of magnitude improvement in sensitivity were observed. Microwave assisted extraction, and sonication are compared to methanolic-HCl modified supercritical fluid extraction both quantitatively and qualitatively for the removal of organoarsenic species from National Institute of Standards (NIST) SRM1944 New York Harbor Sediment), SRM2704 (Buffalo River Sediment), and SRM2710 (Montana Soil). The extracted arsenic species were separated by ion exchange chromatography and introduced on-line into a hydride generation manifold prior to determination by plasma source mass spectrometry. Six different arsenic species were observed, and monomethyl arsonic acid (MMA) was quantified in each reference material. The determination of arsenic in soil and lake sediment samples taken in close proximity to CCA-treated wood structures revealed a highly elevated level of arsenic in soils and non-elevated arsenic level in the sediment. Though the level of arsenic in the exposed lake sediment was not elevated, the exposed sediments contained proportionally more monomethyl arsonic acid, (about 1.2% arsenic as MMA) than did the soil samples taken near pressure treated decks (from 0.02-0.30%, depending on sampling depth). The proportion of arsenic as MMA in the CCA exposed soils increased with the sampling depth.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-2903 |
| Date | 01 January 1997 |
| Creators | Yehl, Peter Michael |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
Page generated in 0.0015 seconds