<p num="35">FIELD: chemistry.</p> <p num="36">SUBSTANCE: invention relates to analytical chemistry. A method for controlling the content of anti-tuberculosis preparations (ATP) of the main line and their toxic metabolites in blood plasma involves preparation of blood plasma for chromatographic analysis by adding an antioxidant in form of ascorbic acid, precipitating proteins with an organic solvent, diluting the sample with deionized water at ratio of 1:10, performing analysis by reversed-phase liquid chromatography in a gradient elution mode, detecting ATP signals using a triple quadrupole tandem mass spectrometer with electrospray ionization, as controlled ATP pyrazinamide, isoniaside, ethambutol and rifampicin are determined, as toxic metabolites – pyrazine acid, 25-O-deacetyltrifampicin, acetyliso-niazine and isonicotinic acid, measuring analytical parameters of the analyzed sample and comparing them with analytical parameters of chromatographic analysis of the solution of ATP standards with known conce