Proficiency testing for determination of metals in tomato paste

In this study, the mass fractions of Cd, Cu, Fe, Pb, Sn and Zn in tomato paste were determined by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). For this purpose, samples were digested with mixture of HNO 3 (65 %, w/w), HCl (30 %, w/w) and H 2O 2 (30 %, w/w). In order to validate a method, some parameters such as limit of detection and quantification, linear range, repeatability, intermediate precision and recovery were investigated. The mass fractions with uncertainties of Cd, Cu, Fe, Pb, Sn, and Zn in the tomato paste with uncertainties were (5.12 ± 0.28) mg/kg, (11.94 ± 0.27) mg/kg, (64.40 ± 3.61) mg/kg, (5.31 ± 0.39) mg/kg, (25.72 ± 0.61) mg/kg, (39.19 ± 1.27) mg/kg, respectively. Homogenized samples were sent to different laboratories for proficiency testing (PT) that was organized in order to evaluate the results and to control the quality of laboratories. As a result of the PT schemes, the participating laboratories can compare their analytical results with those from other laboratories and can improve their method for better measurement accuracy and reliability of their results.