Rapid assessment of metal contamination in commercial fruit juices by inductively coupled mass spectrometry after a simple dilution

A simple and fast method for the determination of Ca, Cd, Co, Cu, Fe, Mn, Mo, Na, Ni, Pb, Rb, Sr, V and Zn in fruit juices samples, by inductively coupled plasma mass spectrometry (ICP-MS) after only a sample dilution, is proposed. For comparison, the samples were also digested with nitric acid and hydrogen peroxide in a microwave oven. The same conditions could be used for aqueous standard solution and diluted sample and the sensitivity was similar in both media, thus external calibration against aqueous standard solutions could be used for quantification. The results were in agreement with those obtained after digestion, according to the t-test at a 95% confidence level. The good accuracy was also confirmed by the recovery test. The precision expressed by the relative standard deviation (RSD) was between 1 and 3%. The detection limits were between 0.1 (Pb) and 2000 μg L⁻¹ (Ca). Similar values for detection limits and RSD were obtained after sample digestion or when the internal standard was not used. The compositions of 20 samples were evaluated by multivariate analysis techniques: principal component analysis (PCA) and hierarchical cluster analysis (HCA), showing that samples are grouped by the brand and not by the fruit, what could be due to soil characteristics where the plant was grown and to the different processing and storage conditions used by the different brands, including water and additives.