A novel strategy based on in-syringe dispersive liquid-liquid microextraction for the determination of nickel in chocolate samples.

In this work, a novel approach was developed to perform dispersive liquid-liquid microextraction using a rapid pressure variation to disperse the extraction solvent in an aqueous medium. A glass syringe was used to produce an environment subject to a rapid pressure difference. The element used as a model was nickel and the approach was called pressure variation in-syringe dispersive liquid-liquid microextraction (PV-IS-DLLME). The extraction solvent used was 1-butyl-3-methylimidazolium hexafluorophosphate, and ammonium pyrrolidine dithiocarbamate was the complexing reagent. The variables pH, solvent volume, amount of complexing agent, extraction time and syringe volume were studied by a factorial 25-1 fractional design. All variables were significant. However, the two least significant, amount of complexing agent (50.0 µL) and syringe volume (20.0 mL) were fixed at their optimum levels, according to the generated Pareto chart. A Doehlert matrix was studied for the variables volume of solvent, pH and extraction time to obtain optimal levels of these factors, and the contour plots showed the following critical values: 120.0 µL, 2.0 and 60.0 s respectively. The developed method presented limits of detection and quantification of 0.1 and 0.3 mg kg-1, an enrichment factor of 17 and a precision of 4.8% (100.0 µg L-1). The developed method was applied to the analysis of samples of powdered chocolate and certified reference material.

Cascas de semente de cacau em chocolate em pó / Cocoa-seed shells in powdered chocolate

Foram analisadas 40 amostras de chocolate em pó, adquiridas no comércio da cidade de São Paulo, a fim de se determinar a porcentagem de cascas de semente de cacau, utilizando o método da contagem de vasos espiralados. Concluiu-se que todas as amostras continham cascas e que 47,50/0 das mesmas continha percentagem de cascas além dos limites tolerados por legislações internacionais. Foi strgerida modificação no Código Brasileiro de Alimentos a fim de permitir um limite de até 1,75% de cascas de semente de cacau em chocolate em pó. Essa tolerância poderia ser estendida à massa de cacau e a outros derivados do mesmo (AU).