Direct photodegradation of carbamazepine followed by micellar electrokinetic chromatography and mass spectrometry.

Carbamazepine, a widely consumed psychotropic pharmaceutical, is one of the most commonly detected drugs in the environment. To better assess the environmental persistence of carbamazepine in aqueous matrices, the effect of pH and dissolved oxygen on the direct photodegradation rate of this pharmaceutical was evaluated in this study, using simulated solar irradiation. In order to follow the degradation and the emergence of photoproducts, a micellar electrokinetic chromatography based method was developed, consisting on the use of a dynamically coated capillary column. The developed methodology showed good repeatability and efficiency in the separation of carbamazepine and photoirradiation products. Also, seven photodegradation products were identified by electrospray mass spectrometry (ESI-MS), including the known carcinogenic acridine that was produced under all the pH and oxygenation levels studied and one newly identified photoproduct. This paper gives new insights into the role of dissolved oxygen on the photodegradation rate of carbamazepine. The results indicate that acidic pH, combined with the absence of dissolved oxygen in the aqueous matrix, results in very high direct photodegradation rates. At basic pH, dissolved oxygen does not interfere with the process and very low rates were observed. At environmentally relevant conditions, carbamazepine was shown to persist in the environment from 4.5 to 25 days.