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Fourier transform infrared least-squares methods for the quantitative analysis of multicomponent mixtures of airborne vapors of industrial hygiene concern.

Air monitoring methods suitable for use in the workplace, though accurate for monitoring individual compounds or classes of compounds, cannot be used to monitor several compounds or classes of compounds simultaneously. In the past few years, Fourier transform infrared (FT-IR) spectroscopy has been investigated for use as a method for multicomponent quantitative analysis. This work focuses on quantitative analysis of six mixtures in ambient air. The concentration ranges of the two- to six-component mixtures are from 50 ppm to 100 ppb. The optimal least-squares fit (LSF) method selected, background reference file chosen, and quantitative peak windows picked were evaluated in this effort. The quantitative results of six mixtures were accurate at the 50, 10, and 1 ppm levels. There were some components for which the analysis was also accurate at the 0.1 ppm level. The data indicate that the LSF program could be used to quantify strongly overlapping multicomponent mixtures. The results support the conclusion that the FT-IR spectrometer is appropriate for the direct quantification of multicomponent mixtures of many airborne gases and vapors of industrial hygiene concern.