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The purpose of this study was to demonstrate the feasibility of determining metals (Cr, Mn, Zn, Fe, and Cu) in commercial dietary supplements using microwave-induced plasma optical emission spectrometry (MIP OES) after fast ultrasound-assisted extraction. Various parameters affecting the extraction process, such as the nature and concentration of the extractant solution, sonication time, and sample mass, were evaluated. Under the optimal conditions, it was possible to quantitatively extract metals from the samples by sonicating 1.0 g of the supplement dispersed throughout 25 mL of a 1.0 mol L−1 HNO3 for only 5 min. The developed method was applied to determine the analytes in four dietary supplements available in the Brazilian market. The results obtained with the extraction method were compared with the values obtained when the samples were completely mineralized with concentrated HNO3 in a microwave oven. There were no statistical differences between the developed and reference methods when the paired Student's t-test was applied with a 95% confidence level. The application of ultrasound-assisted extraction was demonstrated to be advantageous compared to total sample digestion. This approach allowed the use of a higher mass of the sample, thereby enhancing the analytical capability of the method. Furthermore, employing less severe conditions, such as lower energy and a diluted acid solution, simplified and reduced the cost of the procedure compared to mineralization. [ABSTRACT FROM AUTHOR]

Permethrin is a synthetic pyrethroid insecticide that is largely used in the impregnation of fabrics employed for different purposes. This paper reports a detailed study on the conditions for its extraction from fabrics and for its determination by ultra-high performance liquid chromatography with diode array detection (UHPLC-DAD). Several parameters that could affect the extraction efficiency of permethrin were evaluated, such as the extraction time, agitating mode (mechanical or ultrasound-assisted), solvent type (methanol or acetonitrile), concentration, and volume. Under optimized conditions, the extraction was performed for 10 min using a 2 × 2 cm piece of impregnated fabric and 5 mL of pure methanol. The flask containing the sample and the solvent was shaken mechanically using a horizontal roller mixer. The accuracy of the method was assessed by a recovery test, which presented satisfactory results ranging from 86.8% to 95.2%. The method was employed in the analysis of nine samples of commercial fabrics of different colors and grammages that were impregnated with permethrin. The concentration of permethrin found in these samples varied between 25.6 ± 4.2 and 934 ± 119 mg m−2. [ABSTRACT FROM AUTHOR]

The goal of this work was to propose a novel method for the solid-phase extraction of the herbicides diquat (DQT2+) and difenzoquat (DFQT+) from aqueous medium using polymeric Amberlite XAD-2 and XAD-4 resins in the presence of sodium dodecylsulfate (SDS). The addition of SDS to the medium was of fundamental importance in order to allow the formation of a negatively charged surface able to sorb the cationic solutes. Several factors that could influence the sorption process, such as SDS concentration in the medium, sorbent mass, pH, ionic strength, and initial concentration of the solutes were investigated. Kinetic studies were also performed to model the system and to identify the mechanisms that operate the sorption process of the herbicides. SDS concentration in the medium presented remarkable influence on the extraction efficiency, achieving maximum values when the ratios [SDS]/[herbicide] were approximately 90, for XAD-2, and 22 and 11 for DQT2+ and DFQT+, respectively, for XAD-4. The sorption process followed a pseudo second-order kinetic in all cases studied. It was also found that an intraparticle diffusion process controlled exclusively the sorption of the herbicides by the Amberlite XAD-2 and XAD-4 resins in the first 15 min, becoming less active with time. [ABSTRACT FROM AUTHOR]

This work reports a study about the adsorption of Rhodamine B (RB) by unloaded polyether type polyurethane foam (PUF) in a medium containing sodium dodecylsulfate (SDS). The adsorption process was based on the formation of an ionic-pair between RB and SDS, which presented high affinity by PUF. Adsorption was characterized in relation to equilibrium, kinetic, and thermodynamic aspects and the results obtained showed that the ratio between the SDS and RB concentrations played an important role on the adsorption efficiency. A maximum adsorption capacity of 6.85 × 10-6 mol RB g-1 was observed at established experimental conditions. The adsorption process was spontaneous (negative ΔG) and presented an endothermic characteristic (positive ΔH). Also, its rate was regulated by an intraparticle diffusion process. Sequential extraction experiments were carried out by changing PUF plugs in 30 and 60 min time intervals, resulting in removal rates higher than 95%. [ABSTRACT FROM AUTHOR]

This paper presents a study about the sorption of the cadmium–diethyldithiocarbamate [Cd(II)–DDTC] complex onto polyurethane foam (PUF). It was observed that the maximum sorption of Cd(II) (80 or 150 µg L−1) was verified at pH 6.8 in the presence of 4.5 × 10−5 mol L−1 DDTC. The shaking time needed to achieve the equilibrium was 40 min. From these data, a kinetic characterization was performed by applying three models, which revealed that a film-diffusion process was a rate-determining mechanism. Results also indicated that an ether-like solvent extraction was the sorption mechanism. The investigation of many metallic ions as concomitants showed that the sorption by foam is relatively selective and it can be enhanced by using a suitable masking agent or incrementing the foam mass. [ABSTRACT FROM AUTHOR]