Phathalic anhydride as an impurity in industrial atmospheres: assay in air samples by gas chromatography with electron-capture detection

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Abstract
A gas-chromatographic method utilising a 63Ni electron-capture detector was developed for the measurement of phthalic anhydride in air samples. The limit of detection for the anhydride in solution was 5 pg µl–1 and in air samples 0.0004 mg m–3(0.00007 p.p.m.) with a sample volume of 12 l. This indicates a superior sensitivity in comparison with former techniques. Industrial phthalic anhydride processes take place at elevated temperatures. The anhydride vaporises (sublimes) and appears in the air as vapour, fume and dust. These impurities of factory air were collected both on membrane filters and in Tenax porous polymer tubes equipped with pre-filters. Phthalic anhydride was found partly to penetrate the membrane filters, which are also used in older methods. For Tenax tubes, a breakthrough of 6% was noted at an anhydride concentration of 2.5 mg per tube, when the sample volume was 12 l. Large particles were apparently retained by the filter whereas vapour and condensed fume were found partly in the adsorbent tube. Atmospheric phthalic anhydride concentrations measured during industrial processes did not exceed the current Western reference values. The present method has particular value for the evaluation of the working conditions of workers with suspected sensitisation.

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