CHARACTERIZATION OF NON-STEROIDAL ANTI-INFLAMMATORY DRUGS IN TABLETS BY DIRECT ANALYSIS IN REAL TIME/TIME OF FLIGHT/MASS SPECTROMETRY (DART/TOF/MS) WITHOUT SAMPLE PREPARATION

This powerful mass spectrometric technique was used to investigate four profen drugs which are widely used as non-steroidal anti-inflammatory drugs for treating pain, fever and inflammation: Ibuprofen (M = 206), Flurbiprofen (M = 244), Naproxen (M = 230) and Ketoprofen (M = 254). The DART ion source was operated in positive ion mode with helium as the ionizing medium heated to 250°C. A solution containing a mixture of poly (ethylene glycol) standards PEG 600 and PEG 200 was used for mass calibration. A standard solution of each pure standard was manually introduced by using a small glass rod. The high resolution mass spectra of Ibuprofen, Flurbiprofen, Naproxen and Ketoprofen showed the presence of an intense protonated molecular ion [M + H]+ at 207.13860, 245.09776, 231.10632 and 255.09966 Da, respectively. Moreover, a non-protonated molecular ion M+ was also observed except for Ketoprofen. On the other hand, an intense adduct ion [M + H2O]+ was also present in the four mass spectra. Since these profens are 2-arylpropionic acid derivatives they have a known tendency to form dimers; indeed, an intense protonated ion corresponding to this dimer [2M + H]+ was present in the spectrum of Ibuprofen, Flurbiprofen, Naproxen and Ketoprofen at 413.27102, 489.19944, 461.19266 and 509.19662 Da, respectively. The presence of profens as active ingredients was then investigated in various pharmaceutical tablets collected from the local market. A small piece of each solid tablet was submitted to the DART ion source without any sample preparation. The obtained mass spectrum showed the characteristic peaks corresponding to each profen as active principle, as well as the other ingredients of the tablet.