Investigations into the initial composition of latent fingermark lipids by gas chromatography-mass spectrometry.

A more comprehensive understanding of the variability of latent fingermark composition is essential to improving current fingermark detection capabilities in an informed manner. Gas chromatography-mass spectrometry was used to examine the composition of the lipid fraction of latent fingermarks collected from a population of over 100 donors. Variations in the appearances of chromatograms from different donors were apparent in the relative peak sizes of compounds including free fatty acids, squalene, cholesterol and wax esters. Principal component analysis was used as an exploratory tool to explore patterns in this variation, but no correlation to donor traits could be discerned. This study also highlights the practical and inherent difficulties in collecting reproducible samples.

A comparative study of the adsorption of amino acids on to calcium minerals found in renal calculi.

To assess the binding of individual amino acids to the principal calcium minerals found in human kidney stones, the adsorption of 20 amino acids on to calcium oxalate monohydrate, CaHPO4*2H2O, Ca3(PO4)2 and Ca5(PO4)3OH crystals was determined over the physiological urinary pH range (pH 5-8) in aqueous solutions. All amino acids adsorbed most strongly at pH 5, and this decreased in all cases as the pH was increased. The amino acids which adsorbed most strongly were aspartic acid, glutamic acid and gamma-carboxyglutamic acid, with the last displaying the strongest affinity. All amino acids bound more avidly to calcium oxalate monohydrate than to any of the phosphate minerals. Adsorption on to CaHPO4*2H2O was generally higher than for Ca3(PO4)2 and Ca5(PO4)3OH, for which all amino acids, with the exception of gamma-carboxyglutamic acid, had only a weak affinity. The binding affinity of these acids is thought to be due to their zwitterions being able to adopt conformations in which two carboxyl groups, and possibly the amino group, can interact with the mineral surface without further rotation. The strong binding affinity of di-and tri-carboxylic acids for calcium stone minerals indicates that proteins rich in these amino acids are more likely to play a functional role in stone pathogenesis than those possessing only a few such residues. These findings, as well as the preferential adsorption of the amino acids for calcium oxalate monohydrate rather than calcium phosphate minerals, have ramifications for research aimed at discovering the true role of proteins in stone formation and for potential application in the design of synthetic peptides for use in stone therapy.

Quantitative determination of silicon in silica dust by FT-Raman spectroscopy.

Silicon was quantitatively determined in respirable silica dusts and silica fume by FT-Raman spectroscopy using barium sulfate as an internal standard. Barium sulfate was selected as the standard as its Raman spectrum does not overlap with that of silicon and its scattering cross-section is significantly lower. This allowed silicon admixed with barium sulfate in ratios as low as 0.00003 to be detected. The laser beam was defocussed to cover the sample area. 128 scans at 4 cm(-1) resolution with 600 mW of power at the sample achieved a detection limit of 0.1 mug of silicon in a 5 mg sample. Silicon to BaSO(4) ratios in the range 0.00003-0.06 showed a near linear response with any decade change being linear. The RSD for this analytical method was +/-2%. Silica fume and respirable silica dust showed silicon concentrations to be in the range 2.6-51.5 ppm and 0.05-0.7 mg m(-3) respectively.