Trends in vibrational overtone spectra associated with molecular structure in alkanes and sample preparation methods for ICP-AES and XRF

In Part I, overtone spectra of the sixth harmonic C-H stretch for a series of linear and branched alkanes were collected using intracavity dye laser photoacoustic spectroscopy. The spectra were deconvoluted into Lorentzian peaks. The non-equivalence of C-H stretches resulted in complex spectra with many broad peaks that were not statistically resolvable. Despite the complexity, comparisons of compounds based on structure, methyl position, and methyl additions were performed. The comparisons were based solely on the peak frequencies and peak widths as obtained from the deconvolution. From a series of dimethylpentanes, it was determined that the frequency of the strongest methyl C-H absorption peak is dependent on methyl position on a common carbon backbone.; Part II examines studies dealing with different aspects of sample preparation for trace metal analysis. Sample preparation is an essential part of trace metal analysis, regardless of instrumental method. Sample preparation methods can range from dissolution, extraction, or decomposition. For metal analysis, it is common to decompose the organic constituents of the analyte resulting in the dissolution of metals into an aqueous solution. Two methods that can be used would include microwave digestion and high pressure ashing. Nitric acid digestions of standard reference materials were carried out using these techniques covering a temperature range from 150-300{dollar}spcirc{dollar}C. The degree of organic matrix destruction was observed using HPLC while metal recovery was analyzed by ICP-OES.; One of the main advantages of using XRF for elemental analysis is the ease of sample preparation. Often no sample preparation is required. For solid samples, it may be necessary to grind, pelletize, or fuse samples prior to analysis. For liquids, there are various chemical and physical methods that can be used for sample preparation. A new method for trace metal analysis of drinking water has been proposed which combines solid phase extraction and XRF. A cation exchange solid phase extraction disk (3M Empore{dollar}sp{lcub}rm TM{rcub}){dollar} is used to capture the metals. The surface of the disk is subsequently analyzed by XRF. This method has the benefit of ease of use, preconcentration of analytes, and nondestructive analysis.