Application of factorial design to optimize cloud point extraction on the determination of metals in eye makeup

Abstract

Experimental design is an important chemometric tool for systemic optimization, allowing the study of a number of variables concomitantly, thus reducing the number of tests, time and reagents that are used in addition to reduce the amount of generated residues. In the present work the main objective was to use a factorial design 22 with central and axial points for optimization of cloud point extraction in order to determine cadmium, nickel, lead and cobalt by flame atomic absorption spectrometry. Variables that were studied in this factorial design were the amount of complexing agent, ammonium pyrrolidine dithiocarbamate (APDC) and the amount of surfactant (Triton X-100). Analysis of the math models that were developed from the design experiments demonstrated that in the case of nickel and cobalt these variables did not contributed significantly to increase absorbance readings. On the other hand, in the determination of cadmium the results have shown that it is necessary to reduce the amount of complexing agent, and for lead, it was shown to be necessary to increase both the amounts of complexing agent and surfactant. After optimization, the cloud point extraction was carried out using eye makeup samples, which presented concentrations for nickel and lead within 4.96 and 14.03 × 101 mg.kg-1. These values are within the allowed range of the Agência Nacional de Vigilância Sanitária (ANVISA), which establishes the limits of 20 mg.kg-1 and 100 mg.kg-1 respectively for lead and other metals in artificial organic dyes for cosmetics. Although the samples studied here have shown to be in a concentration range that would exempt them from a pre-concentration step, considering the analysis by atomic absorption spectrometry, the use of cloud point extraction has shown to be effective and also recommended in cases in which the analyzed metals are present in trace amounts.