Gas chromatography-mass spectrometry and nuclear magnetic resonance spectrometry of some toxic environmental contaminants.

摘要

oupled gas chromatograph-mass spectrometers including quadrupole mass spectrometers and an ion trap mass spectrometer were used in this study to identify and quantitate alkylated aromatic hydrocarbons and some chlorinated pesticides such as heptachlor epoxide isomers.;It is well recognized that some polynuclear aromatic hydrocarbons (PAH's) are highly carcinogenic. The alkylated PAH's pose even greater health risks partly due to the ease by which these compounds are oxidized to compounds containing hydroxyl groups. Identifications and quantifications of the specific compounds are important.;Qualitative identification of PAH's was performed by analyzing standards and samples under the same conditions and by comparing resultant mass spectra and GC retention times. Calibration using individual standards for alkylated PAH's is frequently impossible because not all of the standards are available. The use of a single or a limited set of standards for the analysis of related alkylated compounds was evaluated using both electron impact (EI) and chemical ionization (CI). Comparison of relative response factors for a number of alkylated polycyclic aromatic compounds showed a smaller relative standard deviation for CI mode than EI mode.;Gas chromatography-mass spectrometry analysis may not allow differentiation among isomers due to their spectral similarity. Therefore the more selective technique of gas chromatograph-mass spectrometry-mass spectrometry (GC/MS/MS) was applied to the identification of alkylated PAH's, including alkylated naphthalenes, phenanthrenes and anthracenes. We clearly differentiated alkylated isomers using isobutane CI GC/MS/MS.;Both chlordane and heptachlor, were formerly used as soil plant pesticides. Chlordane consists of a series of different chlorinated hydrocarbons. Oxychlordane and heptachlor epoxide are found in the environment as metabolites of these pesticides. They are very persistent and therefore common environmental contaminants. Coelution is a particular problem for the identification of these environmental contaminants with the EI/GC/MS technique. These two compounds mutually interfere with one another. Ion trap GC/MS/MS was used to identify and quantitate the two heptachlor epoxide isomers and oxychlordane in environmental samples. Heptachlor epoxide isomer A was detected in a walrus fat sample in addition to the usual finding of isomer B. Isomer A had not been previously reported in environmental samples.;The structures of endo-epoxy and exo-epoxy isomers of heptachlor epoxide were confirmed by