Decitabine is chemically unstable at physiological temperature and pH. In addition, the bioanalysis of decitabine is easily interfered by endogenous 2-deoxycytidine. A simple, sensitive and specific LC–MS/MS method was developed for the analysis of decitabine in rat plasma. No exogenous stabilizers were used to prevent the degradation of decitabine in rat plasma. After deproteinized with acetonitrile at room temperature, rat plasma samples were analyzed on a Hypersil APS-2 NH2 column interfaced with a triple quadrupole tandem mass spectrometer in positive electrospray ionization mode. Decitabine was completely separated from 2-deoxycytidine using gradient elution of water (solvent A) and acetonitrile (solvent B) at a flow rate of 1 mL/min. To quantify decitabine and daidzin (internal standard), respectively, multiple reaction monitoring (MRM) transitions of m/z 251.1 → 134.7 and m/z 417.3 → 255.3 was performed. The assay was linear over the concentration range of 5.0–2000 ng/mL. The intra- and inter-day precision was within 12.0% in terms of relative standard deviation (RSD%) and the accuracy within 5.9% in terms of relative error. The LC–MS/MS method was fully validated for its sensitivity, selectivity, stability study, matrix effect and recovery. The data indicate that this LC–MS/MS method is a specific and effective method for the pharmacokinetic study of decitabine in rat plasma. Compared with the previously reported analytical methods, this method showed easy and economic sample preparation, good specificity and high sensitivity with less plasma (50 μL).

A selective, rapid and sensitive liquid chromatography tandem mass spectrometry method has been developed for the simultaneous determination of ramipril and ramiprilat in human plasma using enalapril as the internal standard via one-step extraction with ethyl acetate under acidic condition. The analysis was carried out on a Diamonsil C18 column (150 mm × 4.6 mm i.d., 5 μm) with a mobile phase consisting of 1% formic acid-acetonitrile (25:75, v/v) at a constant flow rate of 0.5 mL min−1. The detection was performed on a triple-quadruple tandem mass spectrometer by selective reaction monitoring mode via electrospray ionization. Linear calibration curves of ramipril and ramiprilat were obtained in the concentration range of 0.107–107.0 and 0.262–105.0 ng mL−1, respectively. The intra- and inter-day precision (RSD) values were below 8.2 and 4.8% for ramipril, 10.4 and 12.3% for ramiprilat, and accuracy (RE) were within ±5.5 and ±3.2%, respectively at all QC levels. The method was utilized to support clinical pharmacokinetic studies in healthy volunteers following oral administration of ramipril tablets.

A rapid and sensitive liquid chromatography–tandem mass spectrometry method was developed and validated for the quantification of cyclobenzaprine in dog plasma. After extracted with organic solvent, post-treatment samples were separated on an Agela C18 column interfaced with a triple quadrupole tandem mass spectrometer in positive electrospray ionization mode. Multiple reaction monitoring was performed using the transitions of m/z 276.2 → 216.1 and m/z 325.1 → 109.0 to quantify cyclobenzaprine and escitalopram (internal standard), respectively. The mobile phase consisted of acetonitrile: 5 mM ammonium acetate: formic acid (90:10:0.01, v/v/v) at a flow rate of 0.3 ml/min. The total analysis time was 2.4 min. The method was linear over the concentration range of 0.0200–10.0 ng/ml. The intra- and inter-day precision was within 12.8% in terms of relative standard deviation (RSD%) and the accuracy within 5.6% in terms of relative error. This method was successfully applied in a pharmacokinetic study of extended-release cyclobenzaprine in dogs.