Eight solvents were compared for their relative efficiency in removing nitroglycerine from the hands of persons handling explosives. The amount of interfering material also removed from the hands by the cotton swabs and the stability of the nitroglycerine in the solvent used were also investigated. Aqueous solvents yielded the best recoveries, when the extracts were partially purified by thin-layer chromatography before analysis, but the explosive was degraded rapidly by microorganisms that grew in the solutions. Of the aqueous, organic, and polar solvents tested, ethanol was found to offer the most complete, consistent, and stable recovery.
The techniques of thin-layer chromatography, gas chromatography with electron capture detection, and gas chromatography/mass spectrometry were used to analyze hand swab extracts for the presence of nitroglycerine. Both the amount of nitroglycerine transferred to the hands after handling commercial explosives and its persistence were measured. Gas chromatography-electron capture detection was found to be the most accurate and sensitive technique for making such determinations, especially if the extract was partially purified by thin-layer chromatography prior to analysis. The lowest limit of detection was 10 ng of nitroglycerine, and residues could be detected over 20 h after handling the raw explosive.
The more general methods for the separation of boron from associated elements, and for its estimation, are briefly considered.Work carried out in adapting Tschischewski's method to the estimation of boron in boronised iron, nickel, cobalt and copper is described, in which these metals are removed by mercury cathode electrolysis. In addition, a rapid method for the estimation of boron in boronised molybdenum is described in which the metal is separated as the sulphide. The boron after conversion to mannitoboric acid is finally determined by potentiometric titration with sodium hydroxide, which obviates the difficulties inherent in the use of colour-change indicators.The methods as described have an accuracy of about 1.4 per cent. of the amount of boron present over the range 0.27 to 4.30 per cent., which may be extended with slight modification.
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