Abstract: The possibility of employing the method of mass spectrometry with matrix-assisted laser desorption/ionization (MALDI) for the rapid detection of carboxyl-containing nonsteroidal anti-inflammatory drugs has been studied. Comparison of the results obtained using the previously described and newly proposed as matrix compounds 4-(dimethylamino)benzaldehyde and N,N-dimethyl-p-phenylenediamine, showed that the latter provide the registration of mass spectra containing intense peaks of deprotonated molecules of all drugs used in the work. Comparison of the time required for their detection by various mass spectrometric methods has shown that MALDI mass spectrometry provides the highest performance in streaming analysis. © 2020, Pleiades Publishing, Ltd.