Ultra-fast determination of caffeine, dipyrone, and acetylsalicylic acid by capillary electrophoresis with capacitively coupled contactless conductivity detection and identification of degradation products

Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) was used for fast, simultaneous determination of dipyrone (DIP), caffeine (CAF), and acetylsalicylic acid (ASA). In the same run and in less than 1 min, the degradation products from DIP and ASA were also detected. In addition, the usage of the CE-C4D system allowed, for the first time, the detection of methylamine as a degradation product of DIP. Capillary electrophoresis with electrospray mass spectrometry experiments were carried out in order to confirm the formation of methylamine. The limits of detection by CE-C4D were 5, 5, and 6 μmol L−1 for CAF, DIP, and ASA, respectively. The proposed method was applied to the analysis of these compounds in pharmaceutical formulations with similar results to those achieved by HPLC (p < 0.05).