The Application Of Electrospray Mass Spectrometry On Pharmaceutical Analysis And Reaction Mechanism

1. Tiopronin is an important thiol compound and is mainly used to remedy hepatitis. The thiol compounds can easily generate disulfides either as a dimmer or mixed forms with endogenous thiols in the biological matrices. For this reason, unless the thiol group can be stabilized in the biological sample, quantitative analysis of the tiopronin can be very problematic. A highly selective and sensitive LC-MS-MS method was developed and validated to quantify tiopronin in human serum, using fudosteine as the internal standard. L-Cysteine and 1, 4- Dithiothreitol were used as the reducer and the stabilizer to release and stabilify tiopronin from a dimmer and mix forms with endogenous thiols in the treatment of serum samples. After a simple liquid-liquid extraction with ethyl acetate in acidic condition, the post-treatment samples were analyzed on a C18 column interfaced with a tripe-quadruple tandem mass spectrometer using negative electrospray ionization. Methanol and water (40:60, v/v) were used as the isocratic mobile phase, with 0.2 % formic acid and 1.0 mM tris (hydroxymethyl) aminomethanein water. The method was validated to demonstrate the specificity, lower limit of quantification, accuracy and precision of measurements. The method was employed in a pharmacokinetic study after oral administration of 200 mg tiopronin tablets to 24 healthy volunteers.2. L-proline which is a small molecular catalyst is used to catalyze aldol reaction. The aldol reaction is recognized as a powerful tool for the construction of new carbon-carbon bonds. The catalytic cycle currently accepted for this reaction has been proposed to proceed via the formation of an adduct intermediate between the L-proline and the acetone producing an enamine intermediate by elimination of water. ESI-MS is a technique that allows the ions presents in solution to be transferred into the gas phase, where they can be analyzed and eventually characterized, with minimal fragmentation. ESI-MS has been used as an effective method for the characteristic of organic intermediates, thus providing direct evident for the mechanism of organic reactions. The aldol reaction catalyzed by L-proline has been monitored and the accepted mechanism confirmed by intercepting and characterizing, all the proposed intermediates by ESI-MS/MS.