| Liquid chromatography-mass spectrometry is a sensitive, specific and powerful method for many organic compounds. The mass analyzers at present are mainly ion trap detector and quadrupole detector. Both of them have their characteristics. Triple stage quadrupole mass spectrometer has good accuracy and precision, and increased both selectivity and sensitivity. With the function of MS", ion trap mass spectrometer has confidently power in qualitative analysis of compounds. In this thesis, the quantitative and qualitative analyses were carried out with these two LC/MS instrumentss.Determination of residues of four tetracyclines in milk by high-performance liquid chromatography-electrospray mass spectrometryThe tetracycline antibiotics are widely used in modern agricultural practice. Such a wide use may lead to residue problems in milk.The aim of the experiment was to develop a precise liquid chromatographic determination with high sensitivity and a reliable ESI mass spectrometric confirmation of tetracycline antibiotics in milk, and interpret the pathways of mass fragmentation of metacycline. The tetracyclines were extracted from milk and concentrated using solid-phase extraction with a Bond Blut C18 cartridges. HPLC separation was carried out on a Hypersil BDS C18 column with a mobile phase of acetonitrile-water-formic acid (37.5:62.5:1.2, V/V), and the tetracyclines were detected using a ESI ion trap LC/MS/MS. With this method, the calibration curves were linear from 0.05 μg/mL to1.0 μg/mL for tetracycline, oxytetracycline, metacycline, and from 0.1 ug/mL to 2.0 ug/mL for chlortetracycline. The analytes were detectable at levels as low as 0.05 ug/mL for tetracycline, oxyletracycline, metacycline, and 0.1μg/mL for chlortelracycline. This method achived the required sensitivity to detect the residues of tetracyclines in milk. It also been found that tetracyclines have different pathways of mass fragmentation. Tetracycline, oxytetracycline and chlortetracycline gave [M+H-H2O]+ as major product ions while metacycline gave [M+H-NH3]+ as major product ion, when [M+H]+ was selected as the precursor.Determination of plasma concentration of rimantadine by ESI LC/MS/MSRimantadine is a drug used in the treatment and prophylaxis of influenza caused by the type A strain of virus. A method was developed using liquid chromatography-mass spectrometry to determine the concentration of rimantadine in plasma sample. The analytes were separated by Kramasil C18 column after extracted by liquid-liquid extraction from plasma samples. The mobile phase used was methanol-water-formic acid (75:25:1, V/V). With this method, the calibration curves were linear from 2.0 ng/mL to 400 ng/mL of plasma sample (r = 0.9981) and the detection limit was 2.0 ng/mL of plasma concention. This method was used to assess the bioequivalence of rimantadine preparations.Identification of metabolites of rimantadine in urine by ESI LC/MS/MSRimantadine, which has an asymmetric center and is given as the racemate, is extensively metabolized in man to hydroxylated metabolites. In this study, the urinary metabolites generated by healthy volunteers who had taken rimantadine were assayed using ESI LC/MS/MS followed by solid phase extration and C18 column separation. Analysis of the experimental data showed that rimantadine undergoes extensive metabolism in humans. The metabolites include m-hydroxyrimantadine, epimers of two p-hydroxyrimantadine and their glucuronide conjugates. By MS/MS analysis, rimantadine and its unconjugated metabolites all losed an ammonia from their quasi-molecular ions and produced[M+H-NH3]+,and conjugated hydroxyrimantadine losed a glucuroniderest from its quasi-molecular ion and produced[M+H-C6H8O6]+.
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