http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
study of qualitative and quantitative aspects of particle desorption mass spectrometry
The goal of this study has been to expand the analytical scope of ²⁵²Cf particle desorption mass spectrometry (PDMS). The technique has a unique set of features: simple spectra, usually with a predominant parent ion peak and little fragmentation; shallow escape depth (less than 10 layers); minimal sample damage (less than 20 ppm); and dependence of the desorption yield on concentration. Furthermore, quantitative analysis is possible through the use of an internal standard. To demonstrate the ability of PDMS to analyze mixtures without prior separation and isolation, two types of samples were examined: a mixture of three arylmethane dyes (Methylene Blue, Methyl Violet, and Rhodamine B) and a natural carotenoid extract. Approximately 18 pmol of each synthetic dye were sampled to obtain the mass spectrum. In addition, the Crystal Violet contaminant and the deethylation and demethylation photoproducts were detected. The analysis of complex and insulating surfaces was demonstrated for three glasses (National Bureau of Standards Standard Reference Materials 611 to 617, a microscope slide, and a commercial float glass sample) and for four surface treatments (untreated, cleaned with 10% nitric acid, etched with 10% HF acid, and soaked overnight in water). The lithium dopant (35 to 350 ppm) was also detected in the NBS standards. The sample damage to the glass by the fission fragments was observed on an electron micrograph after etching with HF acid. Implanted fission fragments were detected with a GeLi detector. Finally, in order to quantify the results, several parameters that affect the yield were determined: field strength, the local environment on the surface, and the performance of the time-of-flight detection system. Quantitative analysis can be obtained with the use of an internal standard; in this study, the desorption of picomoles of ⁶Li and ⁷Li were compared. Reproducibility was ± 12%. In the course of these analyses, a start detector based on microchannel plates was added. This detector gives more reproducible results and a faster signal than the surface barrier detector. The mass resolution (Δm/m) of the time-of-flight system was 71 at 133 daltons.
Ph. D. in Chemistry Texas A & M University 1987
Includes bibliographical references (leaves 92-98).