Methyltetrahydrophthalic anhydride in air--sampling and analysis.

Methyltetrahydrophthalic anhydride (MTHPA), an organic anhydride, is a sensitizing agent even at low air concentrations: no methods for its sampling and analysis have previously been reported. This paper outlines the use of Amberlite XAD-2 for sampling MTHPA vapour in air, followed by analysis using gas chromatography with flame ionization detection. The level of detection corresponds to a concentration in air of 10 micrograms m-3 for a 20 l. sampling volume. Up to 200 l. air has been sampled, at a sampling rate of 1 l. min-1, without detectable losses. The adsorption efficiency and the stability of the anhydride in the XAD-2 tubes were not influenced by a relative air humidity (RH) of 40%, but at RH 80% there was a loss of 18% at 50 l. air-sample volume. Results from sampling in XAD-2 tubes were 8% lower than those from parallel sampling in midget bubblers containing 10 ml 0.01 M sodium hydroxide.