Highly-sensitive quantification of carbamazepine and identification of its degradation and metabolism products in human liver by high performance liquid chromatography – High resolution mass spectrometry

A method for the qualitative and quantitative determination of carbamazepine in human <i>post mortem</i> liver tissues using high-performance liquid chromatography coupled with high-resolution mass spectrometry has been developed. Validation has been carried out and the main analytical characteristics of the developed method have been determined. The limit of detection (LOD) is 1 ng/g, and the lower limit of quantification (LLOQ) is 5 ng/g. The range of working concentrations for the calibration curve is 5-2000 ng/g. When assessing analyte carryover, the analyte signal of the sample does not exceed 20 % of the signal at the LLOQ level. Degradation products of carbamazepine in model solutions were studied under the presence of hydrochloric acid, sodium hydroxide, and hydrogen peroxide oxidation. Twenty-two degradation products were identified. It was found that the most intensive degradation process of carbamazepine, resulting in various degradation products, is observed during its oxidation with an acidified solution of 3 % hydrogen peroxide at pH= 1-2. The stability of carbamazepine in liver tissues was studied during storage under ambient conditions over various periods. The maximum concentration decline is observed during the first week of storage (on average by 20 %), and then the concentration approximately halves over 8 weeks. Based on the analysis of forensic samples from human liver, 2 out of the 22 carbamazepine degradation products described in this study were detected.