Liquid chromatography-mass spectrometric determination of rufinamide in low volume plasma samples.

Quantification of rufinamide in plasma was achieved using a selective and sensitive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method. The chromatographic separation was achieved on a reversed phase column (Zorbax SB-C18 100mm×3mm, 3.5µm) under isocratic conditions. The mobile phase consisted of a mixture of water containing 0.1% formic acid and methanol (50:50, v/v). The mass spectrometric detection of the analyte was in multiple reaction monitoring mode (MRM) using an electrospray positive ionization (ESI positive). The monitored ions were 127m/z derived from 239m/z rufinamide and 108m/z derived from 251m/z the internal standard (lacosamide). Protein precipitation with methanol was applied for sample preparation using only 50µl aliquots. The concentration range was 40-2000ng/ml for rufinamide in plasma. The limit of detection was 1.25ng/ml and the lower limit of quantification was established at 5ng/ml rufinamide concentration. Selectivity and matrix effect was verified using individual human, rat and rabbit plasma samples. Short-term, post-preparative and freeze-thaw stability was also investigated. The proposed method provides accuracy, precision and high-throughput (short runtime 4.5min) for quantitative determination of rufinamide in plasma. This is the first reported liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for analysis of rufinamide from low volume plasma samples. The LC-MS/MS method was validated according to the current official guidelines and can be applied to accurately measure rufinamide level of large number of plasma samples from clinical studies or therapeutic drug monitoring.

[Qualitative determination of flavonoids and phenol-carboxylic acids of indigene Stachys species using HPLC method]. / Analiza calitativa a flavonoidelor si a acizilor fenol-carboxilici din specii indigene ale genului Stachys prin cromatografie de lichide de înalta performanta.

Indigene Stachys species have a high content in interesting compounds as iridoids, but also high quantities of flavonoids and phenol-carboxylic acids. These compounds present vasorelaxing effect on smooth vascular muscle interfering with metabolic degradation of nitric oxide pathways (inhibition of peroxynitrites formation) and by inhibition of phosphodiesterase. This work shows flavonoids spectrum of 3 Stachys species using HPLC methods. We identified quercetol, rutoside, miricetin and phenol-carboxylic acids (chlorogenic, caffeic and ferulic acids).

Validation of an HPLC method for the determination of ciprofloxacin in human plasma.

A simple HPLC method with fluorescence detection of ciprofloxacin in human plasma was developed and validated. After protein precipitation, chromatographic separation of ciprofloxacin in plasma was achieved at 35 degrees C with a C18 column and acetonitrile-phosphate mixture, pH 3, as mobile phase. Quantitative determination was performed by fluorimetry after excitation at 278 nm. The method was specific and validated with a limit of quantification of 41 ng/ml. The intra- and inter-day coefficients of variation were between 0.5 and 6.6% and accuracy between -2.02 and 7.04%. Ciprofloxacin was stable in plasma for 40 days at -20 degrees C and after three freezing-thawing cycles. The method has been applied in a bioequivalence study of two formulation of 500 mg ciprofloxacin.