Multivariate analyses of element concentrations revealed the groupings of propolis from different regions in China

The concentrations of 15 kinds of elements (Ca, Al, Mg, K, Fe, Na, Zn, Mn, Sr, Cu, Cr, Ni, As, Cd and Pb) of 31 propolis samples collected from China and one sample from the United States were determined by inductively coupled plasma atomic emission spectrometry after microwave digestion. The results showed that the average contents of Ca, Al, Mg, K, Fe, Na, Zn, Mn, Pb, Sr and Cd in propolis were 1449.1 mg kg−1, 971.2 mg kg−1, 552.5 mg kg−1, 1137.4 mg kg−1, 1188.4 mg kg−1, 497.5 mg kg−1, 160.8 mg kg−1, 36.93 mg kg−1, 19.92 mg kg−1, 8.70 mg kg−1 and 0.60 mg kg−1, respectively, while the As, Cu, Cr and Ni were not detected in many samples. Thirty-two propolis samples were classified into five groups by principal component analysis. Cluster analysis resulted in the similar groupings. Linear discriminant analysis showed that 90.6% and 88.4% of the propolis samples are predicted correctly as the groupings identified by the colour and climatic zone, respectively.