High-throughput determination of carbocysteine in human plasma by liquid chromatography/tandem mass spectrometry: application to a bioequivalence study of two formulations in healthy volunteers

The characterization of selected drugs with infrared laser desorption/tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

Some selected drugs including captopril, fudosteine and racecadotril have been analyzed by infrared (IR) laser desorption/tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS). The molecular ions of captopril and racecadotril are exclusively observed without any fragments at near threshold single-photon ionization (SPI). However, fudosteine easily forms fragments even at a photon energy near the ionization threshold, indicating the instability of its molecular ion. For these drugs, a number of fragments are yielded with the increase of photon energy. The structures of such fragments proposed by IR LD/VUV PIMS are supported by electron ionization time-of-flight mass spectrometry (EI-TOFMS) results. Fragmentation pathways are discussed in detail.

Study of tanshinone IIA tissue distribution in rat by liquid chromatography-tandem mass spectrometry method

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated for determining tanshinone IIA in rat tissues. After a single step liquid-liquid extraction with diethyl ether, tanshinone IIA and loratadine (internal standard) was subjected to LC/MS/MS analysis using positive electro-spray ionization under selected reaction monitoring mode. Chromatographic separation of tanshinone IIA and loratadine was achieved on a Hypersil BDS C(18) column (i.d. 2.1 x 50 mm, 5 microm) with a mobile phase consisting of methanol-1% formic acid (90:10, v/v) at a flow rate of 300 microL/min. The intra-day and inter-day precision of the method were less than 10.2 and 12.4%, respectively. The intra-day and inter-day accuracies ranged from 99.7 to 109.7%. The lowest limit of quantification for tanshinone IIA was 1 ng/mL. The method was applied to a tanshinone IIA tissue distribution study after an oral dose of 60 mg/kg to rats. Tanshinone IIA tissue concentrations decreased in the order of stomach > small intestine > lung > liver > fat > muscle > kidneys > spleen > heart > plasma > brain > testes. Tanshinone IIA still could be detected in most of the tissues at 20 h post-dosing. These results indicate that the LC/MS/MS method was rapid and sensitive to quantify tanshinone IIA in different rat tissues.