Quantification of 10,11-dihydro-10-hydroxy carbamazepine and 10,11-epoxycarbamazepine as the main by-products in the electrochemical degradation of carbamazepine

Carbamazepine (CBZ) is one of the most widely used antiepileptic drugs in Malaysia. It was detected frequently in wastewater. The electrochemical treatment process has been applied for the degradation of CBZ using graphite-PVC as an anode under these conditions: 0.5 g sodium chloride (NaCl)) as supporting electrolyte, 5 V and 0-60 min electrolysis time in 100 mL of solution. However, 10,11-dihydro10-hydroxy carbamazepine (HDX-CBZ) and 10,11-epoxycarbamazepine (EPX-CBZ) as the main by-product have been analysed and quantified using liquid chromatography-time of flight/mass spectrometry (LC-TOF/MS). Both by-products were analysed in positive ionization mode, and they were separated on a chromatographic C18 column (5 mu m, 2 mm x 150 mm) at a flow rate of 0.3 mL/min. Solid-phase extraction (SPE) was applied as a preconcentration step for the enhancement of the sensitivity and detectability for both HDX-CBZ and EPX-CBZ by-products. Methanol (MeOH) has been selected as the best elution solvent for both by-products compared to methyl tertiary butyl ether (MTBE) and acetone (AC). However, the recovery was 85% and 92% for HDX-CBZ and EPX-CBZ by-products, respectively. The limit of quantification (LOQ) was 0.588 and 0.109 mu g/L for HDX-CBZ and EPX-CBZ by-products, respectively. After 20 min of electrolysis time, both by-products HDX-CBZ and EPX-CBZ appeared at maximum concentrations of 343 and 144 Rg/L then they were decreased to 17.2 and 9.8 mu g/L, respectively, after 40 min. At the end of electrochemical treatment, both by-products were completely eliminated after 60 min.

Automated summary

This study investigated the degradation of carbamazepine, one of the most widely used antiepileptic drugs in Malaysia, using an electrochemical treatment process. The main by-products, 10,11-dihydro10-hydroxy carbamazepine (HDX-CBZ) and 10,11-epoxycarbamazepine (EPX-CBZ), were analyzed and quantified using liquid chromatography-time of flight/mass spectrometry (LC-TOF/MS). The results showed that both by-products could be completely eliminated after 60 minutes of electrolysis.