Determinação simultânea de carbamazepina, fenitoína e fenobarbital em amostras de sangue seco em papel, coletadas post-mortem, por cromatografia gasosa acoplada a espectrometria de massas

Abstract

The examinations carried out in biological samples, in the scope of legal medicine, have the purpose of identifying intoxication as a qualifying circumstance of the offense or as a cause of danger or imputability. In cases of suspected death from intoxication, this will be framed within the framework of violent deaths. For this type of death there is a legal obligation to perform necropsy, followed by the withdrawal of biological material for the chemical-toxicological expertise. The presence or absence of the antiepileptic drug may be a key element in determining the cause of death of an individual or the explanation of the behavior of an individual linked to an event investigated by the competent entity. According to some studies carried out by expert groups of the Belo Horizonte Medical Institute (IML-BH), it was possible to observe that the antiepileptic drugs with the higher incidences in post-mortem individuals in the institute are: carbamazepine, phenytoin and phenobarbital. This study optimized an analytical method using dried blood spot to quantify phenobarbital, carbamazepine and phenytoin simultaneously. The analytes were separated by gas chromatography and identified by mass spectrometry. The running time of the chromatographic analysis was 15 minutes and it was possible to obtain intra-assay and inter-assay precision in the range of 6.1 13,16% and 5,0 14,7% respectively. The accuracy presented a range of 61,5 84,7%. The limits of detection and quantification were respectively 2,98 and 9,80 ìg/mL for phenobarbital, 1,77 and 5,90 ìg/mL for carbamazepine and 5,46 ìg/mL and 18,2 ìg/mL for phenytoin. The method presented the merit parameters appropriate to the proposed objectives, when a set of 10 anonymous samples of postmortem blood were detected, which had been qualitatively detected in Labtox (IML / BH) phenobarbital, carbamazepine and phenytoin. In the determination of these samples in the methodology proposed in this study, a concentration of 71.6 ìg / mL was presented; 52.8 ìg / mL and 61.8 ìg / mL for phenobarbital and 27.1 ìg / mL for carbamazepine, another sample showed detection for carbamazepine, but with an area below the limit of quantification, all other samples presented results below limit of detection for this method.