In this work, a method for multiclass determination of 70 pesticides residues with different properties in drinking water using solid phase extraction (SPE) with polymeric sorbent and determination by gas and liquid chromatography coupled to tandem mass spectrometry (GC-MS/MS and LC-MS/MS) was developed and validated. Different sample volumes, sorbents and elution solvents were evaluated. The best results were obtained using the sorbent Oasis® HLB, sample acidified at pH 2.5 and a mixture of dichloromethane/methanol as eluent. The limit of quantification (LOD) of the method was 0.02 µg L-1 for aldrin, dieldrin and chlordane and 0.5 µg L-1 for the other compounds. Satisfactory accuracy, with recoveries between 70 and 117.3%, and good precision, with relative standard deviation (RSD) values below 19.7% for most of the compounds, were achieved. The validated method was applied to real water samples and results indicated that the proposed method is suitable for the determination of pesticide residues in water samples.

In this study, a well-studied synthetic faujasite X (FAU-X) zeolite and a recently discovered natural zeolite material from Kenya (NZ-K) were compared for their efficiency in removal of clomazone, a herbicide and water contaminant, from aqueous solution. The adsorption kinetics, isotherms and thermodynamics parameters were investigated. Equilibrium sorption data were describable by both the Langmuir and Freundlich models. The adsorption kinetics obeyed the pseudo-second-order kinetic law while pore diffusion was not the sole operating rate determining step. The derived thermodynamic parameters, namely AG and AH, indicated the adsorption process was feasible, spontaneous and exothermic for the natural zeolite and non-spontaneous for the synthetic zeolite via a physical and chemical process, respectively. The natural zeolite proved to be a suitable low-cost adsorbent for clomazone removal with removal efficiency above 70 %, five-fold more efficient than faujasite X.

O mel pode apresentar resíduos de pesticidas devido à contaminação das abelhas durante a coleta de pólen e néctar ou por tratamento das colmeias. Assim, a determinação de resíduos de pesticidas em mel é de grande importância, apesar da dificuldade devido à complexidade da matriz. Neste estudo, um novo método para a determinação de pesticidas de diferentes grupos químicos em mel foi desenvolvido e validado. Amostras de mel foram extraídas pelo método QuEChERS modificado e analisados por cromatografia gasosa com detecção por captura de elétrons (GC-ECD). Os resultados de recuperação, avaliados em três níveis de fortificação, foram entre 71 e 119% para a maioria dos compostos, com valores de desvio padrão relativo (RSD) < 20%. O método proposto permite a determinação com limites de detecção entre 3 e 6 µg kg-1, combinando a extração e limpeza do extrato de forma efetiva, com boa sensibilidade e seletividade, e foi aplicado com sucesso na análise de amostras comerciais de mel.

Honey can present pesticide residues due to the contamination of bees during the collection of pollen and nectar or by treatment of hives. Thus, the determination of pesticide residues in honey is of great importance, despite the difficulty due to the complexity of the matrix. In this study a new method for the determination of pesticides from different chemical groups in honey was developed and validated. Honey samples were extracted by modified QuEChERS method and analyzed by gas chromatography with electron capture detection (GC-ECD). Recovery results, evaluated at three spike levels, were between 71 and 119% for most of the compounds, with relative standard deviation (RSD) < 20%. The proposed method enables the determination at limits of detection between 3 and 6 µg kg-1, combining effective extraction and clean-up steps with good sensitivity and selectivity, and was successfully applied to the analysis of commercial honey samples.