Multivariate Optimization and Exploratory Analysis Applied to the Internal Standardization of Complex Matrices by Inductively Coupled Plasma Optical Emission Spectrometry

The presence of high concentrations of Na, K, Ca, and C in complex matrices such as beverages, foods, and pharmaceutical formulations may interfere in their analysis by inductively coupled plasma optical emission spectrometry (ICP-OES). The interference is amplified when it is associated with large variations in operating conditions. Internal standardization is indicated for the repair of this interference effect. Elements that present comparable behavior in similar conditions may be used as internal standards (IS) for other elements. The behavior of 31 analytical lines in the presence of Ca, K, and Na (250 and 1000 mg L-1) in 8% urea, to simulate pharmaceuticals, beverages, and foods, was evaluated under different operating conditions by hierarchical cluster analysis (HCA) and principal component analysis (PCA). The HCA and PCA methods formed four element groups with similar behavior. In these groups, some elements were tested as IS from the other groups. It was possible to choose the best IS for the element groups, and the recoveries were close to 100% with simulated samples. This study amplified the possibility of selecting internal standards for the analysis of complex matrices, thus promoting better precision and accuracy of the results.