[Study on the characteristics and compositions of fine particles left in the solution after decomposition of plant samples].

After decomposition of plant standard reference materials bush twigs and leaves (GBW07602, GBW07603), poplar leaves (GBW07604) and tea (GBW07605) with either dry ashing method or wet digestion method, all kinds of fine particles left in the solution were collected and examined carefully by a scanning electron microscope (SEM), and their chemical composition were investigated by a SEM-affiliated energy-dispersive X-ray spectrometer at the same time. Moreover, the concentrations of some metal elements distributed among four different tea SRM-originated particle fractions extracted following the BCR sequential extraction procedure were determined by AAS and ICP-AES. It was found that decomposition methods have a great influence on the structure of fine particles. When dry ashing method is used, grey-colored, fluffy and porous partices can be produced, whereas fewer white-colored, compact particles can be produced when another method is used. As for chemical composition, all kinds of fine particles are almost the same, with silicon and aluminium as their main constituents, and calcium, iron, potassium, titanium and so on as their minor ones. The elementaI distribution percentages in four different particle fractions in two kinds of plant-originated particles differ from element to element, which can result in severe negative errors when plant samples are decomposed and determined for elemental concentrations.

[Studies on the contents of twenty elements in different parts of garlic by using ICP-OES, AAS and AFS combined with microwave decomposition method].

The garlic plants sampled in the suburbs of Suzhou were rinsed thoroughly with deionized water, and divided into six different parts: root, low stem, middle stem, high stem, tender leaves and old leaves. After decomposition in a microwave oven, the contents of Al, As, B, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, S, Se, Sr and Zn in these parts were determined by using ICP-OES, AAS and AFS, and the contents of these 20 elements in garlic bulbs collected from the same location were also determined. It was found that the tender leaves or the bulbs of garlic should be chosen preferably for the extraction of active compounds, because they are much richer in Cu, Fe, Mn, S, Se and Zn elements and rather low in harmful As, Cd, Hg and Pb elements as compared with other parts of garlic. The contents of 20 elements are varied in six different parts of garlic, from which some useful conclusions can be drawn concerning either physiological properties of garlic or situations of atmosphere contamination.