Rapid Determination of Multi-Elements in Herb Tea by Semi-Quantitative XRFS and Quantitative ICP-MS

Semi-quantitative XRFS without standard sample was used to screening all of the elements in samples of five kinds of herb tea to obtain the types and content ranges of the elements contained after using powder pressed method to prepare the sample slice of herb tea. After microwave digestion of herbal tea sample, ICP-MS was applied to quantitative determination of multi-elements. XRFS could detect those metal elements and nonmetal elements which mass fraction more than 1 μg·g^-1 in five kinds of herb tea samples. 10 elements, i.e. K, P, S, Mg, Ca, Cl, Si, Fe, Zn and Mn in five kinds of herb tea samples were all detected. The element with the highest mass fraction was K. According to XRFS determination results, the sample pretreatment method and instrument working conditions of ICP-MS were optimized. Linear relationships between values of signal intensity and mass concentration of multi-elements were kept in definite ranges. Detection limits (3s) of the method ranged from 0.001 8 to 35.27 μg·kg^-1. Determination results of ICP-MS were consistent with XRFS. 4 heavy metal elements, i.e. As, Pb, Cd and Cr could be detected. The national reference material of citrus leave (GBW 10020) was determined by XRFS and ICP-MS, and determination results of XRFS and ICP-MS were all within the range of the certified values with RSDs (n=6) of determination results of XRFS and ICP-MS were less than 5.0%, 3.0% respectively. Determination results of 6 elements, i.e. Mg, K, Ca, Mn, Fe and Zn by XRFS and ICP-MS were compared. Slopes of trend lines were in the range of 0.761 2-1.306, and correlation coefficients ranged from 0.910 8 to 0.999 8. The two methods were good in comparability.