A novel multielemental scanning thermal analysis (MESTA) method for the identification and characterization of solid substances.

Identification and characterization of solid samples has been relatively difficult due to the limited separation techniques available. Reported here is the development of a multielemental scanning thermal analysis (MESTA) method that provides a simple, rapid, and sensitive alternative for routine examination of solid samples. A MESTA system heats up a sample in an enclosed quartz tube from ambient to 800 degree C at a constant heating rate and under a given atmosphere. The volatile components in the sample are carried to a high-temperature combustion tube where the C, N, and S are oxidized to their respective oxides and detected by the detectors. The result is the simultaneous C, N, and S thermograms of a sample that can be used as chemical signatures for identification and characterization purposes. Sample heating rate, oxygen content of the carrier gas, and the possible interactions among the ingredients of a sample would all affect the outcome of an analysis. These effects need to be understood for a specific application. The general instrumentation, technique, usefulness, and interpretation of the MESTA are presented with examples. The simplicity and cost-effectiveness of the MESTA make it a promising tool for routine chemical analysis of solid substances.

A review of the analysis of vegetable oil residues from fire debris samples: spontaneous ignition, vegetable oils, and the forensic approach.

This paper reviews the literature on the analysis of vegetable (and animal) oil residues from fire debris samples. The process of self-heating and spontaneous ignition is well-known by fire investigators and causes many fires. Vegetable oils are often the chemicals that originate such phenomenon. Vegetable oils are composed of lipids, which contain fatty acids. The autooxidation of the double bonds present in unsaturated fatty acids is the exothermic reaction at the origin of the self-heating process. The degree of unsaturation of fatty acids directly influences the propensity of an oil to undergo self-heating and, eventually, spontaneous ignition. When fire debris samples are collected, it is possible to examine them at the laboratory to extract and identify vegetable oil residues. This is typically performed by solvent extraction, followed by gas chromatographic(-mass spectrometric) analysis of the extract. Such analyses differ from ignitable liquid residue analyses, so a different forensic approach is necessary.

Air-activated chemical warming devices: effects of oxygen and pressure.

Air-activated chemical warming devices use an exothermic chemical reaction of rapidly oxidizing iron to generate heat for therapeutic purposes. Placing these products in a hyperbaric oxygen environment greatly increases the supply of oxidant and thus increases the rate of reaction and maximum temperature. Testing for auto-ignition and maximum temperatures attained by ThermaCare Heat Wraps, Playtex Heat Therapy, and Heat Factory disposable warm packs under ambient conditions and under conditions similar to those encountered during hyperbaric oxygen treatments in monoplace and multiplace hyperbaric chambers (3 atm abs and > 95% oxygen) revealed a maximum temperature of 269 degrees F (132 degrees C) with no spontaneous ignition. The risk of thermal burn injury to adjacent skin may be increased significantly if these devices are used under conditions of hyperbaric oxygen.