Simple, quantitative headspace analysis by cryoadsorption on a short alumina PLOT column.
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 alumina-coated 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 microg TNT per gram of substrate (determined with a 60 min sweep with the sample held at 60 degrees C). Moreover, for quantitative results, we can achieve a percent standard deviation (coefficient of variation) of 10% with samples as low as 0.064 microg TNT per gram of substrate.
Bruno
Thomas J
TJ
Physical and Chemical Properties Division, National Institute of Standards and Technology, Boulder, CO, USA. bruno@boulder.nist.gov