Determination of aromatic arsines in environmental solids by direct thermal desorption gas chromatography

Abstract

To quantify aromatic arsines in the environment, such as World War I era chemical warfare agents and degradation products of arsenicals used in agriculture, a sensitive, selective, and direct method is needed. We describe the development and optimization of a method for the measurement of trace levels of triphenylarsine used as a model aromatic arsenic compound. Triphenylarsine was determined at low µg/g levels in sand, soil, and lake sediment by thermal desorption before gas–liquid chromatography (GC) with mass spectrometric and pulsed flame photometric detection. The dithiol derivative of phenylarsonic acid was used as an internal standard, thereby significantly improving the precision of the method. The desorption conditions were studied and found to be optimal at 350°C for 15 min. Significant improvement in precision was realized by preparing the solid samples as slurries in acetone and by inserting a small (∼100 mg) quartz wool plug into the sample vial. The method was applied to determine triphenylarsine in authentic soil and sediment samples that had been fortified with triphenylarsine and aged for at least 15 days. Recoveries for soil samples ranged from 84.3 � 2.3 to 87.7 � 1.3%, while lower recoveries were obtained for sediment samples (75.1 � 3.0%). The detection limit for triphenylarsine in soil was 3.14 ng with a precision of 7.10% (n ¼ 4). Using these optimized conditions, the performance of the direct thermal desorption GC method for sample introduction was greatly improved compared to methods that have been reported in the literature.