植物样品消解后残留颗粒物元素组成研究

分别采用干灰化法和湿消化法处理植物标准参考物质灌木枝叶组合样(杨树叶和茶叶)，用扫描电镜(SEM)对消解液中残留的不溶性颗粒物微观形貌进行了观察，并用SEM附属的X能谱仪研究了颗粒物的主要元素组成。另外，还用BCR法对茶叶残留颗粒物进行了分级萃取, 相关元素在四种存在形态中的含量分布状况由AAS和ICP-AES给出。研究结果表明：不同消解方法对颗粒物微观形貌有较大影响，其中植物样品经干灰化法处理后残留的颗粒物多呈灰黑色，表面疏松多孔;经湿消化法处理后残留的颗粒物均呈白色，多数结构紧密，数量也相对较少。不同植物样品残留的颗粒物元素组成均大同小异，主要为Si和Al，此外还有少量的Ca, Fe, K, Ti等。这些元素在颗粒物中存在形态不一，致使在进行植物样品分析时某些元素含量测定结果大为偏低。

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 elemental 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.