OTIMIZAÇÃO DE METODOLOGIAS ANALÍTICAS PARA A DETERMINAÇÃO DE BENZODIAZEPÍNICOS EM AMOSTRAS AMBIENTAIS: AVALIAÇÃO DO COEFICIENTE DE DISTRIBUIÇÃO SEDIMENTO/ÁGUA

Abstract

Contaminants of emerging concern as drugs are widely consumed and their entry into the environment, even at low concentrations, is constant. When they reach rivers and lakes, their permanence, behavior and fate are not yet fully known. Thus, the present work aimed to develop analytical methodologies for the determination of clonazepam, alprazolam and diazepam, psychoactive drugs of the benzodiazepine class (BDZs) in envionmental samples and to study the behavior of these drugs in enriched systems. Voltammetric methods using the hanging mercury drop electrode for the determination of diazepam and clonazepam and spectrometric method using matrix assisted laser desorption ionization with time-of-flight detection (MALDI-TOF) for the determination of the three benzodiazepines were developed. Voltammetric parameters such as accumulation potential, scan rate, pulse amplitude, pulse time and equilibration time, in addition to pH and purge time were optimized for both drugs. The figures of merit studied for the DIAZ and CLO by voltammetry were respectively: linearity (0.5 to 20.1 μg L-1 and 0.49 to 96.12 μg L-1), limit of detection (0.081 μg L-1 and 0.149 μg L-1), quantification limit (0.271 μg L-1 and 0.646 μg L-1), accuracy by recovery studies (72 ± 4 to 108 ± 7 μg L-1 and 87 ± 6 to 120 ± 13 μg L-1), precision (RSD < 10% and RSD < 15%). For the MALDI-TOF analyzes, experimental conditions such as the ionization matrix and solvents were studied, as well as sample preparation procedures for water and sediments. Extraction forms of BDZs in sediments were also optimized for voltammetric determinations. Sediment and water samples were collected in Brazil and Canada and analyzed by voltammetry and MALDI-TOF. However, the BDZs studied were not determined in any of the samples collected. The voltammetric methods developed were also used to study the distribution coefficient (Kd) of these drugs in several samples enriched with the analytes. The Kd determined varied from 1.41 to 21.99 L Kg-1 being generally higher for DIAZ and lower for CLO. The Kd presented great variability among the samples. A relation between the physicochemical characteristics of the samples and the Kd obtained was observed and confirmed through Principal Component Analysis (PCA). The highest values of Kd were obtained in systems that contained higher levels of clay and organic matter probably due to the greater interaction between the drugs and the sediments.