Protocols and algorithms for gas chromatographic/mass spectrometric analysis of multicomponent environmental samples

The characterization of a manual GC/MS method for total petroleum hydrocarbon (TPH), BTEX (benzene, toluene, ethyl benzene, o-xylene, m-xylene, p-xylene) and naphthalene in gasoline and diesel contaminated soils is described. Multiple ion selected ion monitoring (SIM) was employed to retain the high sensitivity of single ion SIM while permitting identification of solutes. Spiked soil samples containing gasoline and diesel with TPH concentrations in the range of 0.5 to 5000 ppm were used to evaluate the method. Ethyl ether and methylene chloride gave quantitative recoveries for both TPH and BTEX from spiked soils. The method presented here also eliminates time-consuming sample preconcentration steps for diesel range components.; The implementation of an algorithm for selecting multiple groups of ions in varying retention time ranges in multicomponent GC/MS analyses is described. From an initial chromatogram of a high concentration standard of target components the algorithm produces a list of retention time windows and ions to be monitored in each window. The resulting multiple group selected ion monitoring (MGSIM) chromatogram exhibits low background ion abundance and selectively high target peak ion abundances. These high signal-to-noise ratio conditions also produce improved detection limits, mass spectral quality, and linearity of peak integration compared to scan mode data acquisition. Mass spectra taken from MGSIM chromatograms also exhibit library match quality as good as or better than scan mode spectra.; An algorithm was developed to reduce noise in full scan GC/MS data. The approach removes noise from extracted single ion chromatograms, which are then recombined to form a new "total ion" chromatogram. Improvements in signal-to-noise-ratios, spectral quality of mass spectra, and linearity of integration are demonstrated. Very low target signals which are difficult to be distinguished visually from noise backgrounds can be processed by this program, and good chromatographic and mass spectral results are obtained.; A software filter using component similarity designed for deletion of undesired peaks in multicomponent chromatograms has been demonstrated. Pattern matching can simplify interpretation of complex chromatograms and enhance quantitation and identification of multiple components in samples that contain interfering peaks. The successful use of this algorithm suggests pattern template matching may be useful in designing analysis strategies for selected compounds or classes of compounds in complex samples.