甘薯不同氯离子测定方法的比较研究

摘要

采用加标回收率的方法,分析并比较了硝酸银滴定法、紫外分光光度法和自动电位滴定法测定甘薯(Ipomoea batatas L.)幼苗Cl-含量的结果,并初步探明不同甘薯品种地上部和根系C1-吸收和分布规律.结果表明:(1)硝酸银滴定法重复性差且难以判断滴定终点;紫外分光光度法测定Cl-回收率低(52.9％～81.4％),且受样品浸提液颜色影响;自动电位滴定法Cl-回收率为93.9％～105.5％,相对标准偏差(RSD)为0.6％～ 6.0％,该方法操作简单、重复性好且精确度高,因此是测定甘薯氯含量的最佳方法;(2)利用自动电位滴定法测定不同甘薯品种Cl-积累和分布,结果显示:甘薯幼苗地上部Cl-含量为0.067～0.096 mmol g-1DW,根系Cl-含量为0.038～0.087 mmol g-1 DW,品种间甘薯幼苗地上部和根系Cl-含量皆存在显著差异.不同品种向地上部转运Cl-选择性比率均大于1.0,表明Cl-向地上部聚集,以菜用型福薯7-6比率最高,紫心型徐紫20-1和浙紫1号次之,淀粉型泉薯9号最低.%Using the recovery (standard addition) method,analysis for comparison was done of the silver nitrate titration method,the ultraviolet spectrophotometry method and the automatic potentiometric titration method,used in determining chloride contents in sweet potato seedlings of six different cultivars,and chloride absorption and distribution in shoots and roots of these sweet potatoes explored.Results show that the silver nitrate titration method was low in reproducibility and it was also hard to determine when to end the titration; the ultraviolet spectrophotometry was low in chloride recovery,ranging from 52.9％ to 81.4％,and analysis of samples was influenced by the color of sample extraction solvent;whilst the automatic potentiometric titration method was high in chloride recovery rate,reaching high in the range from 93.9％ to 105.5％ with relative standard deviation being 0.6％～ 6.0％,and moreover,the method was simple to use,good in reproducibility and high in accuracy.Therefore,the automatic potentiometric titration method is the best one in determination of chloride in sweet potato.Chloride accumulation and distribution were determined of these sweet potato samples,using the automatic potentiometric titration method.Results show that chloride contents ranged from 0.067 to 0.096 mmol g-1 DW in shoot and 0.038 to 0.087 mmol g-1 DW in root.Significant differences were found between different cultivars in chloride contents in shoot and in root.The selectivity ratios of Cl-translocation from root to shoot of the sweet potatoes were all above 1.0 regardless of cultivars,indicating that chloride tends to accumulate in shoot.The cultivar of leafyvegetable sweet potato (Fushu No.7-6) was the highest in selectivity ratio,and followed by Xuzi No.20-1 and Zhezi No.1,and the cultivar of starchy sweet potato (Quanshu No.9) the lowest.