Evaluation of Gas Chromatography/Matrix Isolation Infrared Spectrometry for theDetermination of Semivolatile Organic Compounds in Air Sample Extracts

摘要

The capabilities of gas chromatography/matrix isolation-infrared (GC/MI-IR)spectrometry for determination of semivolatile organic compounds (SVOCs) in air sample extracts were evaluated. Systematic experiments, using xylene isomers as test compounds, were conducted to determine the repeatability of the steps involved in GC/MI-IR measurements and to identify parameters that affect the precision in quantitation. The repeatability of MI-IR net absorbance measurements for single and replicate depositions was determined. The MI-IR net absorbance was nonlinear at concentrations higher than 52.1 ng/microliters, probably due to an increase in the sample spot size relative to the IR beam focus or a decrease in the matrix-to-solute ratio to less than acceptable matrix isolation conditions. The method detection limit for xylene isomers was between 1 and 2 ng/microliters injected on-column for routine measurements. Extensive signal averaging was required to obtain spectra at concentrations less than 1 ng/microliters. The method was tested by determining target SVOCs in ambient air sample extracts. The MI-IR quantitative results were compared to those from the system's flame ionization detector(FID). The FID response exhibited a high bias when unknown compounds coeluted with target analytes. The ability of GC/MI-IR to quantify target compounds in the presence of interferents and to discriminate between coeluting isomers is demonstrated.