Experimental Bias in the Thermal Desorbing Stage of Gaseous Aromatic Volatile Organic Compounds Analyses

초록

Sources of analytical bias in the gas chromatographic (GC) analysis of gaseous aromatic volatile organic compounds (VOC) were evaluated in relation to the thermal desorption (TD) technique. A series of calibration experiments were conducted using gaseous VOC standards containing benzene, toluene, xylene, and styrene (namely, BTXS) at various concentration ranges. Initially, standard gases of lower bound concentration ranges (50500 ppb) were analyzed to derive response factors under normal TD (N-TD) operation conditions. The second phase experiment was conducted by the modified injection through a TD (MI-TD) method that allowed for the expansion of the concentration ranges used for calibration (from 50 ppb to 10 ppm). Comparison of these calibration results showed that the recovery rate (or sensitivity) varies systematically in the TD-based analysis of low concentration (and large volume) samples. Evidence collected from this study suggests that the analytical properties of GC/TD operation can be modified considerably due to the variability introduced in the enrichment/delivery stage of TD operation.

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