Nutrient and Contaminant Quantification in Solid and Liquid Food Samples Using Laser-Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS): Discussion of Calibration Strategies

The quality and safety of food samples always require strict control. From an analytical perspective, many techniques can be used for this type of monitoring, one of which involves the application of laser pulses in laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). LA-ICP-MS has great advantages such as simplicity of operation, versatility, and high analytical capability for multielement determinations. One of the difficulties and challenges associated with this technique involves quantitative analyses because of problems in the process of ablation, plasma formation and/or matrix effects. In this case, calibration strategies combining internal standards, standard addition methods, and chemometric tools can help improve the results. Food samples are among the most variable samples in terms of their matrix and composition, which can further complicate analysis by laser ablation and require the development of ablation strategies. This study describes the use of calibration strategies and the determination of Ca, Cd, Cr, Cu, Fe, Mg, Pb and Zn in food samples, including liquid (i.e., orange juice) and solid (i.e., dietary supplements) samples. The calibration curve for the solid samples was constructed using microcrystalline cellulose and a proportional mixture of solid samples chosen according to their higher and lower concentrations of metals. The liquid samples were immobilized in a polymer film with the help of polyvinyl alcohol (PVA). Using these calibration strategies, it was possible to obtain accuracy values between 60 and 120 % for almost all samples, except for Ca, Mg, and Zn. These exceptions could be a reflection of unresolved matrix interferences. Carbon was used as the internal standard but did not show promising results.