Application of computerized differentiation technique to remote- sensing Fourier transform infrared spectrometry for analysis of toxic vapors.
Anal Chem 1993 Sep; 65(17):2262-2269
A computer assisted procedure for minimizing background fluctuations in Fourier transform infrared (FTIR) spectra of toxic vapors obtained by remote sensing was described. A single beam FTIR spectrum of the analyte was obtained using an open path remote sensing FTIR spectrophotometer. A computer program was used to generate a wavelength shifted spectrum by introducing an arbitrary wavelength increment at each data point in the spectrum. A differential spectrum was created by calculating the ratio of the intensity at each data point in the wavelength shifted spectrum to the intensity at each data point in the single beam spectrum. The differential spectral intensities were arranged in a K-matrix. The K-values were computed by least squares analysis of calibration data obtained using known concentrations of the analytes. Once this was done, the concentrations of the analyte in an unknown sample could be determined from a similarly constructed matrix. Applying this technique to 26 single organic vapors indicated that their detection limits were higher than when the traditional method of spectrum analysis was used; however, each substance could be readily detected and quantitated. The differential method was used to analyze test mixtures in a pilot scale chamber. Field measurements were made in a pharmaceutical facility. The authors conclude that the differential technique has the requisite sensitivity to detect and quantify individual vapors as well as mixtures of toxic substances in the workplace.
Organic-vapors; Analytical-methods; Infrared-spectrophotometry; Mathematical-models; Workplace-monitoring
Environmental & Indust Health University of Michigan 1420 Washington Heights Ann Arbor, MI 48109-2029
Other Occupational Concerns; Grants-other
University of Michigan at Ann Arbor, Ann Arbor, Michigan