Development and comparative analysis of single-drop and solid-phase microextraction techniques in the residual determination of 2-phenoxyethanol in fish.

Solid-phase microextraction (SPME) and single-drop microextraction (SDME) in headspace mode, were used in the residual determination of the anesthetic 2-phenoxyethanol in fish fillets, to ensure food safety. For the optimization of the methodologies the experimental central composite design (CCD) was used, resulting in accurate evaluations with less amount of analysis. The developed methodologies presented good precision in the evaluated range, o limits of detection (LD) and quantification (LQ) for SDME were 0.2 and 0.62 µg mL-1 and for SPME were 0.18 and 0.56 µg mL-1, respectively. In the analyzed samples the determined elimination time of post-anesthesia 2-phenoxyethanol was 12 h for the SDME and 24 h for the SPME, at the anesthesia concentrations evaluated (450-1050 µg mL-1). The two techniques presented viability of application for the residual determination of 2-phenoxyethanol in fish, SPME being more sensitive and automated and SDME with lower operation cost.

Effect of the acid treatment conditions of kaolinite on etheramine adsorption: A comparative analysis using chemometric tools.

The present work evaluated the effect of the acid treatment conditions of natural kaolinite (NK) regarding its efficiency in removing etheramine. The treatment was conducted using sulfuric acid at the concentrations of 1 mol L-1 (KA-01), 2 mol L-1 (KA-02) and 5 mol L-1 (KA-05) at 85 °C. The obtained adsorbents were characterized by X-ray fluorescence, X-ray diffraction, N2 adsorption/desorption isotherms, zeta potential analysis and infrared spectroscopy. The Response Surface Method was used to optimize adsorption parameters (initial concentration of etheramine, adsorbent mass and pH of the solution). The results, described by means of a central composite design, were adjusted to the quadratic model. Results revealed that the adsorption was more efficient at the etheramine concentration of 400 mg L-1, pH 10 and adsorbent mass of 0.1 g for NK and 0.2 g for KA-01, KA-02 and KA-05. The sample KA-02 presented a significant increase of etheramine removal compared to the NK sample. The adsorption kinetics conducted under optimized conditions showed that the system reached the equilibrium in approximately 30 min. The kinetic data were better adjusted to the pseudo-second order model. The isotherm data revealed that the Sips model was the most adequate one. The calculation of Eads allowed to infer that the mechanism for etheramine removal in all the evaluated samples was chemisorption. The reuse tests showed that, after four uses, the efficiency of adsorbents in removing etheramine did not suffer significant modifications, which makes the use of kaolinite to treat effluents from the reverse flotation of iron ore feasible.