| Popis: |
The United States Environmental Agency permits the use of 39 organophosphate pesticides. Many of these pesticides are acutely toxic and have lasting effect on human health. Organophosphates quickly metabolize in the body, therefore currently human exposure is studied by measuring the metabolic products in urine. In this work a suite of analytical methods was developed to determine the presence of un-metabolized organophosphate pesticides in human serum. First mass spectroscopic detection methods were evaluated. Gas chromatograph coupled tandem mass spectrometer was used to compare the detection limits using chemical and electron impact ionization. Positive chemical ionization was selected, because it provided better detection limits for this set of analytes. Liquid chromatograph coupled tandem mass spectrometry was also evaluated and was found advantageous over the gas chromatographic method for approximately 50% of the compounds. Positive atmospheric pressure chemical ionization was chosen for this group of compounds. Once the analytes were separated by detection methods, analytical separation methods were compared: column and eluent was selected for liquid chromatography, column alone was selected for gas chromatography. Last step of the method development was to produce a suitable sample cleanup process. Solid phase extraction was not suitable because the very wide range of solubility characteristics and hydrolytic stability of the analytes. Lyophilization, liquid-liquid extraction methods were tested and compared. A multi step cleanup method was produced, which starts with liquid-liquid extraction using high pressure ethyl acetate in accelerated solvent extractor, solvent exchange and a lipid removal step. The concentrated extract then injected in a HPLC-MS-MS system then the same extract either directly injected in GC-MS-MS or further purified using headspace solid phase micro extraction before the GC-NS-MS step. The method was used with good results for analyzing samples collected from farm workers using OP pesticides. |
