Simple, quantitative headspace analysis by cryoadsorption on a short alumina PLOT column

Abstract

The use of purge and trap methods for sampling volatile organic compounds prior to chromatographic analysis is a mature technology. Application to low volatility compounds has been far less facile and sensitive. Especially problematic has been applications that require precise quantitative analysis and analyses as a function of sample temperature, especially for low volatility analytes. In this paper, we have applied short lengths of aluminacoated PLOT columns as purge traps and operate the traps at low temperature during the collection cycles to improve efficiency in a method called cryoadsorption. We have applied the method as a function of temperature to a medium volatility solid, coumarin, as a demonstration, with further application to the pure explosive compound 2,4,6-trinitrotoluene (TNT) and the practical explosive C-4. We estimate that by use of mass spectrometry, the sampling method discussed in this paper can provide a detection limit of 0.0019 μg TNT per gram of substrate (determined with a 60 min sweep with the sample held at 60°C). Moreover, for quantitative results, we can achieve a percent standard deviation (coefficient of variation) of 10% with samples as low as 0.064 μg TNT per gram of substrate.