Development and Evaluation of Mass Spectrometric Sampling Techniques and CBVapors and Aerosols

摘要

During the first year, three different configurations of capillary transfer linegas chromatography (TLGC) inlets for mass spectrometry (MS) were assembled and tested. Configuration 1 directly coupled an automated vapor sampling (AVS) device connected to a short capillary GC column to the MS ion source. Mathematical modeling techniques were used extensively to predict the behavior of the AVS-TLGC/MS system in order to optimize chromatographic performance with regard to resolving power, carrier gas flow, column length, retention time, and sampling pulse duration. A computer controlled, programmed TLGC module, capable of achieving heating rates up to 25 K/sec, was successfully designed and tested. The feasibility of extending the dynamic range of TLGC based spectroscopic techniques by up to 2 orders of magnitude through a corresponding decrease in AVS pulse duration was demonstrated using an AVS-TLGC/MS system. The second configuration tested consisted of a microvolume Tenax absorption/ desorption trap with inductive heating coupled directly to an AVS-TLGC/MS system. By absorbing from 300 ml/min flow for 100 sec and desorbing for 3 sec an effective enrichment factor of 10(3) appears achievable. The third and final configuration tested incorporated a permeable membrane interface between the TLGC column outlet and the high vacuum of the mass spectrometer to reduce vacuum pumping requirements. A mathematical model was developed to describe the absorption/diffusion/desorption behavior of membranes. Atmospheric monitoring, Fieldable instrumentation, ion Transfer line gas chromatography, Gas chromatography, Automated vapor sampling, Membrane inlet mass spectrometry.