Catalysts prepared by co-precipitation of iron and titanium were evaluated in heterogeneous photo-Fenton degradation of the azo dye Acid Red 8 under blacklight irradiation. Materials with different titanium contents (0 < Ti/Fe < 0.6) were characterized using X-ray diffractometry, scanning electron microscopy, X-ray fluorescence spectroscopy, specific surface area and X-ray photoelectron spectroscopy. Hematite was identified as main phase in materials with lowest Ti content, while titanomaghemite was predominant at high Ti content. Highest degradation was obtained using titanium free catalyst due to iron leaching, which promoted a homogeneous reaction. Addition of Ti led to a heterogeneous process with a maximum when Ti/Fe = 0.40 achieving 0.76 mol of dye mineralized per mol of soluble iron after 90 min, using 10 mmol L-1 H2O2 at pH 5.6, value at least three times higher than that observed for catalysts with lower Ti content. The results indicate that Ti stabilizes the catalyst and increases its heterogeneous activity in photo-Fenton process.

Esse estudo descreve o desenvolvimento e otimização de um método de extração em fase solida (SPE) para análise dos filtros ultravioletas (UV): benzofenona-3 (BP-3), etilhexil salicilato (ES), etilhexil metoxinamato (EHMC) e octocrileno (OC) em matrizes ambientais. Um planejamento fatorial fracionário (PFF) 2(5-1) foi empregado na avaliação das variáveis significativas do método de extração. As condições experimentais otimizadas da avaliação estatística foram: capacidade do cartucho de 500 mL, eluente acetato de etila, metanol como solvente de lavagem (10% em água, v/v) and volume do eluente de 3 × 2 mL e pH 3. Os parâmetros analíticos avaliados foram satisfatórios, apresentando linearidade de 100 a 4000 ng L-1, recuperações para os quatro níveis de fortificação (Limite de Quantificação do Método, 200, 1000 e 2000 ng L-1) entre 62 e 107% com desvio padrão relativo menor que 14%. Os limites de quantificação foram encontrados na faixa de ng L-1, variando entre 10 e 100 ng L-1. O método proposto foi aplicado para a determinação dos quatro filtros UV em amostras de águas naturais.

This study describes the development and optimization of a solid-phase extraction (SPE) method for analysis of ultraviolet (UV) filters, benzophenone-3 (BP-3), ethylhexyl methoxycinnamate (EHMC), ethylhexyl salicylate (ES) and octocrylene (OC), in environmental matrices. A 2(5-1) fractional factorial design (FFD) was used to evaluate the significant variables for the extraction method. The optimized experimental conditions determined from the statistical evaluation were: breakthrough volume of 500 mL, eluent of ethyl acetate, wash solvent of methanol (10% in water, v/v), eluent volume of 3 × 2 mL and pH 3. The evaluated analytical parameters were satisfactory for the analytes and showed linearity between 100 and 4000 ng L-1, recoveries for four fortification levels (Method Quantification Limit, 200, 1000 and 2000 ng L-1) were between 62 and 107% with relative standard deviations less than 14%. Limits of quantification were in the ng L-1 range and were between 10 and 100 ng L-1. The proposed method was used to analyze four UV filters in natural water samples.

O objetivo deste trabalho foi desenvolver um método analítico por microextração em fase sólida (SPME) para a determinação de resíduos dos pesticidas pirimetanil, pirimicarbe e buprofezina em águas superficiais de áreas de irrigação por cromatografia a gás acoplada a espectrometria de massas (GC-MS). O método SPME foi otimizado apresentando os seguintes valores: tipo de fibra (polidimetilsiloxano, PDMS 100 µm), velocidade de agitação da amostra (900 rpm), pH 7, tempo de extração (30 min) e tempo de dessorção (7 min). A linearidade foi estabelecida na faixa de 0,1 a 4,0 µg L-1 com coeficientes de determinação (R²) > 0,991. A precisão apresentou valores de desvio padrão relativo (RSD) < 15% para os pesticidas com limites de detecção (LOD) e quantificação (LOQ) variando de 0,04 a 0,1 µg L-1 e 0,1 a 0,2 µg L-1, respectivamente. Amostras de águas superficiais do Platô de Neópolis em Sergipe (Brasil) e do Distrito de Irrigação Senador Nilo Coelho de Petrolina em Pernambuco (Brasil) foram analisadas, encontrando valores para buprofezina de até 0,14 µg L-1 e pirimicarbe abaixo do limite de quantificação. Pirimetanil não foi detectado nas amostras.

The objective of this work was to develop a solid-phase microextraction (SPME) technique for the determination of residues of the pyrimethanil, pirimicarb and buprofezin pesticides in surface waters from irrigated areas, with analysis by gas chromatography-mass spectrometry (GC-MS). The optimized method used a 100 µm polydimethylsiloxane (PDMS) fiber, agitation speed of the sample of 900 rpm and pH 7.0. Extraction and desorption times were 30 and 7 min, respectively. Linearity was achieved in the concentration range 0.1-4.0 µg L-1, and coefficients of determination (R²) were > 0.991. Precision, expressed as relative standard deviation (RSD), was < 15%, and limits of detection (LOD) and quantification (LOQ) were in the ranges 0.04-0.1 µg L-1 and 0.1-0.2 µg L-1, respectively. Surface water samples were collected from irrigated regions of the Platô de Neópolis in Sergipe State (Brazil) and from Distrito de Irrigação Senador Nilo Coelho in Pernambuco State (Brazil). Concentrations of buprofezin were < 0.14 µg L-1, while those of pirimicarb were lower than the limit of quantification (LOQ). Pyrimethanil was not detected in the samples.