微波消解-离子选择电极法测定植物样品中氟离子的实验条件优化

Optimal Conditions for Determination of Fluoride in Plant Samples by Microwave Digestion Coupled with Ion Selective Electrode Method

准确检测植物体内的氟含量有助于预测氟化物的生态环境效应。植物中的氟含量低,通常不超过300μg/g,应用离子选择电极法测量氟需选择样品分解效率高的前处理方法使氟不受到损失,获得离子成分简单、空白低的溶液,同时加入适量的缓冲液增强氟离子的强度和掩蔽干扰。本文采用微波消解法处理植物样品,离子选择电极法测定氟的含量,通过优化实验条件确定了缓冲液的浓度。结果表明,在25℃、p H=6.5的样品溶液中加入147 g/L总离子强度缓冲溶液（TISAB）10 m L,避免了溶液中的阳离子与氟离子生成稳定的不溶絮状物,显著降低了沉淀物的产生。本方法检出限为0.242μg/g,精密度（RSD）小于8.5%,回收率为92.0%-108%,能满足地球化学样品分析中对植物样品中低含量氟的检测要求。

It is helpful to predict the ecological and environmental effects of fluoride by accurately detecting the fluorine content in plants. Fluoride in plant samples is commonly lower than 300 μg / g. The chemical separation method with good separation effect should be selected to avoid the loss of F and determine the resulting solution with simple components and low blank when the method of microwave digestion coupled with Ion Selective Electrode Method is applied. Appropriate buffer solution is added to increase the intensity of fluoride ions and reduce screen interferences. Plant samples are digested by microwave,and fluoride is determined by Ion Selective Electrode Method,as reported in this paper. The concentration of buffer solution is defined by optimal conditions.Results show that the addition of 10 m L TISABⅡ solution of 147 g / L to the sample solution at 25℃ and p H of 6. 5can avoid the formation of stable insoluble floccule due to the reaction between cation and fluoride ions. The method has a relative standard deviation（ RSD） of less than 8. 5%,a detection limit of 0. 242 μg / g and a recovery of92. 0%-108%,which meets the determination requirement of the low-content fluoride in plant samples.