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In this research, we developed and validated a liquid chromatography coupled to mass spectrometry (LC-QToF-MS) method for simultaneous quantification of the antituberculosis drugs ethambutol, isoniazid, pyrazinamide and rifampicin in human plasma. Plasma samples spiked with cimetidine (internal standard) were extracted using protein precipitation with acetonitrile containing 1% formic acid. Separation was performed using a C 18 column under flow gradient conditions with water and acetonitrile, both containing 5 mM ammonium formate and 0.1% formic acid. The method was validated according to the ANVISA and US Food and Drug Administration guidelines for bioanalytical method validation. The calibration curve was linear over a concentration range of 0.2-5 μg ml −1 for ethambutol, 0.2-7.5 μg ml −1 for isoniazid, 1-40 μg ml −1 for pyrazinamide and 0.25-2 μg ml −1 for rifampicin, all with adequate precision and accuracy. The method was reproducible, selective and free of carryover and matrix effects.The validated LC-QToF-MS method was successfully applied to real samples and shown to be applicable to future therapeutic and pharmacokinetic monitoring studies. K E Y W O R D Santi-tuberculosis drugs, human plasma, LC-QToF-MS, validation

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The honey produced by stingless bees has been of increasing interest for the pharmaceutical, food, and cosmetic industries because it presents an unusual degree of acidity, sweetness, slow crystallization, a fluid texture, and medicinal value that are all associated with its bioactive constituents (

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A stability-indicating HPLC-DAD method was developed and validated for the simultaneous determination of dasabuvir and its degradation products in the pharmaceutical formulation. The proposed method utilized a Symmetry ® C18 (4.6 x 75 mm, 3.5 µm) column, and the mobile phase consisted of an isocratic elution of formic acid (0.1%) and acetonitrile (55:45, v/v), at a flow of 1 mL min -1 ; analytes were detected at 244 nm. Dasabuvir was submitted to different stress degradation conditions, such as acidic, alkaline, neutral, thermal, oxidative and photolytic, and the structural elucidation of degradation products was performed using LC-QToF-MS/MS. The HPLC-DAD stability-indicating method was validated for selectivity, linearity, limit of detection and quantification, accuracy, precision and robustness, according to ICH guidelines. Dasabuvir produced two degradation products (DP 1 and DP 2 ) from the alkaline stress conditions, which were characterized in negative ion mode. Dasabuvir was linear in the range 9.78 to 136.92 µg mL -1 , and DP 1 and DP 2 were linear in the range 2.9 to 20.2 µg mL -1 and 1.3 to 14.9 µg mL -1 , respectively. The recovery ranged between 99.16 and 100.86%, while precision ranged from 1.02 to 2.89%. As the method can effectively separate the dasabuvir from its degradation products and quantitate them, it may be employed as a stability-indicating method for the pharmaceutical formulation.

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