Direct Chemical Analysis Of Solids By Laser Ablation In An Ion Storage Time Of Flight Mass Spectrometer

Author : David Brian Aeschliman
Publisher :
ISBN 13 :
Total Pages : 188 pages
Book Rating : 4.:/5 (544 download)

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Download or read book Analysis of Solids by Laser Ablation Inductively Coupled Plasma Mass Spectrometry written by David Brian Aeschliman and published by . This book was released on 2003 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation manuscript concentrates on methods to improve the utility of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a rapid and accurate technique for quantitative analysis, forensic matching, and source attribution of solid samples. A solution calibration method for LA-ICP-MS is described that does not require matrix-matched solid standards or prior knowledge of sample composition. Desolvated particles from a microconcentric nebulizer and particles ablated from a localized position on a solid sample are mixed and introduced simultaneously to the ICP-MS. The transport of sample particulates from the ablation cell is measured online with piezoelectric microbalance to provide signal normalization. The relative accuracy of the quantitative analysis of NIST 612 glass and NIST 1264a steel is 3% and 12%, respectively, except for the elements Pb and Bi in steel. LA-ICP-MS is also used with principal components analysis (PCA) to simplify routine comparisons of forensic materials without time-consuming and destructive sample dissolution. The relative concentrations of trace elements in a solid sample are examined to provide a "fingerprint" composition that can be used for definitive identification and source matching of the material. Residue samples are matched to bulk materials using PCA. Variation of laser focus and PCA are also used to diagnose the presence and severity of elemental fractionation, which remains the most significant limitation for accurate quantitative analyses by LA-ICP-MS. High-speed photographs and video of an ICP are used to examine the validity of solution calibration for LA-ICP-MS and to study the trajectories, lifetimes, and emission behavior of particles traversing the plasma under a variety of conditions. No red emission clouds from YO are visible in the ICP when a 20-[mu]L min−1 nebulizer is used to spray a 2000 ppm aqueous yttrium solution, suggesting that the wet droplets from this nebulizer desolvate almost completely before entering the ICP. These desolvated particles appear to atomize and ionize like the small dry particulates from laser ablation. However, some large ablated particulates are observed to fly through the plasma intact, possibly contributing to elemental fractionation. Nevertheless, accurate calibration results using solution standards can be obtained for elements not affected by fractionation.