A New Method for Determination of Mg, Ca, Zn, and Na in Cocoa Butter by FAAS Employing Extraction Induced by Emulsion Breaking and Multivariate Optimization

This study aims to develop of a method based on extraction induced by emulsion breaking (EIEB) to determine Mg, Ca, Zn, and Na in cocoa butter by flame atomic absorption and emission spectrometry. The method has been optimized using Box-Behnken design as a response surface methodology for the variables: nitric acid concentration, extraction time, and surfactant concentration. Optimal conditions were the following, for 1.00 g of sample: 1.0 mL of solution extractor containing 0.7% (w v(-1)) Triton X-114 surfactant in 1.8 mol L-1 nitric acid, and 7 min for extraction, being the emulsion breaking promoved by heating to 96 degrees C in a water bath followed of centrifugation. Under this conditions, quantitation limits were 0.33, 0.67, 0.05, and 0.33 mg kg(-1) for Mg, Ca, Zn, and Na, respectively; precision, obtained by values of RSD%, was less than 9.6%; accuracy, evaluated by addition and recovery test on three different cocoa butter samples and comparison of extraction with a reference method established in the literature, was between 90 and 117%. The proposed method of EIEB has been applied to cocoa butter samples, and the found concentrations (mg kg(-1)) varied between 15.8 and 37.1 (Mg), 1.20 and 5.18 (Ca), 0.20 and 1.05 (Zn), and 0.60 and 1.93 (Na). Therefore, the EIEB method is simple, efficient, with low cost and reagent consumption, presents good precision and accuracy, and is an excellent alternative for the element determinations in cocoa butter.