A magnetic material based on polyaniline coated zerovalent iron-silica (Fe@SiO2@PANI) was simply synthesized using a facile manner under low energy consumption and applied for magnetic solid phase extraction of phenolic pollutants prior to analysis by high performance liquid chromatography-photodiode array detection (HPLC-PDA). The parameters which affected the extraction efficiency, i.e., sorbent amount, extraction time, sample volume and pH, desorption solvent and its volume, were optimized. Wide linear dynamic range of 0.012-10.000 μg mL-1 and the coefficients of determination better than 0.9926 were achieved. The limits of detection and the limits of quantitation were found in the ranges of 0.001-0.030 and 0.012-0.090 μg mL-1, respectively. The precision, expressed as relative standard deviation (RSD), was better than 11%. The synthesized sorbent exhibits good adsorption affinity and reusability up to 16 cycles. Applicability of the proposed methodology for analysis of phenolic residues in environmental and wastewater samples showed the recoveries in the range of 83.4-118.9%.

A method using micellar precipitation process using cationic surfactant cetyltrimethyl ammonium bromide at ambient temperature was investigated for simultaneous determination of benzimidazoles coupled with high-performance liquid chromatography (HPLC) analysis. The studied benzimidazoles was selected as model compounds including thiabendazole, albendazole, mebendazole, and fenbendazole. The experimental parameters affected the extraction efficiency, including the kind and concentration of salt, pH, concentration of CTAB, volume of 1-octanol, and the centrifugation extraction time, was optimized. The optimum extraction condition: 0.030 mol L-1 CTAB, 10% (m/v) NaCl, pH 4.0, 300 µL 1-octanol and centrifugation time 10 min. Under optimum conditions, enrichment factors of between 60 and 90 fold were obtained, leading to lower limit of detection in the range of 0.5-0.7 µg L-1, depending on the analytes. The calibration range of the method was linear over the wide range of 0.5-1000 µg L-1, with correlation coefficients more than 0.999. Finally, the proposed method was successfully applied in the analysis of benzimidazoles in milk samples.

Diferentes sorventes sólidos modificados com surfactantes foram investigados comparativamente para a retenção de pesticidas carbamato em solução aquosa. Três sorventes modificados, incluindo alumina tratada com dodecil sulfato de sódio (SDS), sílica revestida com brometo de cetil trimetil amônio (CTAB) e zeólita revestida com CTAB foram preparados usando diferentes concentrações de surfactante. Os pesticidas carbamato estudados incluíram oxamil, metomil, aldicarb, carbofurano, carbaril, isoprocarb, metiocarb, promecarb e carbosulfano e foram analisados por cromatografia líquida de alta eficiência (HPLC) com UV. A adsorção de pesticidas carbamato (faixa de concentração de 0,5-5,0 mg L-1) nos sorventes modificados com surfactante, seguiu regressão linear com os coeficientes de correlação na faixa de 0,857-0,995. A zeólita modificada com CTAB apresentou alta captação para carbofurano, carbaril, metiocarb e carbosulfano. Alumina modificada com SDS demonstrou alta captação de carbaril, isoprocarb, metiocarb, promecarb e carbosulfano. Sílica modificada com CTAB apresentou alta captação de metiocarb, promecarb e carbosulfano. A dessorção dos pesticidas de carbamato dos sorventes modificados com surfactantes usando metanol foram melhores que as obtidas dos sorventes não modificados. O estudo provou que os sorventes modificados com surfactantes são efetivos para a extração de pesticidas carbamato.

Different surfactant-modified solid sorbents have been comparatively investigated for retention of carbamate pesticides in aqueous solution. Three modified-sorbents, including sodium dodecyl sulfate (SDS) treated alumina, cetyltrimethyl ammonium bromide (CTAB) coated silica and CTAB coated zeolite, were created using different surfactant concentrations. The studied carbamate pesticides including oxamyl, methomyl, aldicarb, carbofuran, carbaryl, isoprocarb, methiocarb, promecarb and carbosulfan were analyzed by HPLC/UV. Adsorption of all carbamate pesticides (concentration range between 0.5-5.0 mg L-1) onto surfactant-modified sorbents followed linear regressions with the correlation coefficients in the range of 0.857-0.995. CTAB-modified zeolite showed high uptake values for carbofuran, carbaryl, methiocarb and carbosulfan. SDS-modified alumina demonstrated high uptake values for carbaryl, isoprocarb, methiocarb, promecarb and carbosulfan. CTAB-modified silica gave high uptake values for methiocarb, promecarb and carbosulfan. Desorption of carbamate pesticides from surfactant-modified sorbents using methanol were better than that obtained from unmodified sorbents. The study clearly proved that the surfactant-modified sorbents are effective for carbamate pesticides extraction.