Cuantificación de cadmio en cacao ecuatoriano mediante LIBS : Definición sistemática de la metodología de cuantificación de cadmio en cacao.

Abstract

The LIBS technique for its application in the analysis of cadmium in cocoa beans (cocoa powder as the final product), an important export product of Ecuador, was evaluated. The quantification of cadmium concentration is of interest to public health, environmental protection, and agriculture. A systematic methodology for pellet preparation was established to carry out the analysis, in which cocoa powder was mixed with known amounts of cadmium nitrate. Subsequently, LIBS plasmas were generated in standard and nitrogen-rich atmospheres, focusing a pulsed Nd: YAG laser on the sample surface (1064 nm, 8 ns; energy: 75 mJ/pulse; delay time: 3 µs, LTSD: 82 mm). The spectral emission of cadmium atoms, neutral ions, and other elements present in the pellets were studied to find the best experimental conditions for measurement. Additionally, a baseline correction algorithm was implemented, proving suitable for the type of samples and avoiding spectral distortions in the analyzed emission lines. Appropriate calibration curves were generated, including exponential and linear models, to determine the inherent cadmium concentration in cocoa powder. Although the results did not fully agree with previous studies due to differences in the concentrations used, the developed technique qualitatively revealed the presence of a detectable amount of cadmium.