提出以超声提取,单扫描极谱法测定植物和土壤中游离态铅的方法.实验发现,在酸性条件下,超声波能有效地分离提取豆芽和土壤样品中的游离铅,并用单扫描极谱法进行测定.分别以去离子水、2 mol/L HNO3、4 mol/L HNO3为溶液考察了超声介质及超声时间对铅提取量的影响.结果表明:豆芽和土壤样品在硝酸介质中分别超声80、50 min即达到饱和提取量,而在去离子水介质中超声的分离作用不大.与酸浸泡法相比,超声提取法具有更为显著的分离效果,表明超声促进了氢离子置换样品中铅离子的反应.该方法具有化学试剂消耗少、分析速度快、对环境污染小等优点,将其应用于实际样品的测定,结果满意.%A new method for determination of trace free lead in plant and soil by single sweep polarography with ultrasonic extraction was described. The results show that free lead in bean sprout and soil could be separated effectively by ultrasonic extraction in acidic solution and measured using single sweep polarography. The effects of ultrasonic medium and ultrasonic time on the extract amount of lead were investigated in deionized water,2 mol/L HNO3, and 4 mol/LHNO3 respectively. The results show that the extraction of lead in nitric acid medium reached the maximum amount with the ultrasonic time of 80 min for bean sprouts samples and the ultrasonic time of 50 min for soil samples respectively, while in deionized water media ultrasound extraction did not show any advantage in the separation of free lead from the samples. This indicates that ultrasound can accelerate the reactions of H + replacing Pb2+ in the samples.Compared with acid soak method, ultrasonic extraction is more effective, and of little chemical reagent consumption,simple procedure, rapid separation, and no environment pollution. The new method was applied to the determination of free lead in actual samples with satisfactory result.
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