在线富集-光纤传感分光光度法测定胶囊壳中六价铬含量及评价

目的：建立一种在线富集-光纤传感分光光度法测定胶囊壳中六价铬含量。方法：在碱性条件下，硝酸铈为沉淀剂、用聚四氟乙烯滤膜管对六价铬进行在线富集、以HNO₃为洗脱剂、二苯基碳酰二肼为显色剂、采用自制流通池与光纤光谱仪连接构成的流动注射分析系统对胶囊壳中六价铬进行含量测定。考察了沉淀剂、洗脱剂、流速、富集时间、显色剂浓度、反应管长度和共存离子的影响。结果：在最佳实验条件下测定六价铬的线性范围是0.5~3.5 μg·L^-1，六价铬摩尔浓度与吸光度呈良好的线性关系，相关系数r=0.999、检出限为76.64×10^-3 μg·L^-1、相对偏差为1.4%、加标回收率为96.7%~103.7%。结论：本实验测定胶囊中六价铬的方法简单，样品通过在线富集排除干扰因素的影响，无需前处理，可以用于直接测定胶囊中Cr （Ⅵ）的含量及评价。

Objective: To establish a method for the determination of hexavalentchromium in capsule shell by on-line preconcentration and optical fiber sensing spectrophotometry.Methods: Under alkaline conditions,cerium nitrate as precipitant,on-line enrichment of hexavalent chromium by PTFE membrane tube,HNO₃ as the eluent and diphenylcarbazide as chromogenic agent,the flow injection analysis system composed of self-made flow cell with fiber spectrometer was used to determine the content of hexavalent chromium in capsule shell.The effects of precipitant,eluent,flow rate,concentration time,concentration of chromogenic agent,length of reaction tube and coexisting ions were investigated.Results: Under the optimal experimental conditions,linear range of Cr(Ⅵ) was 0.5-3.5 μg·L^-1 and Cr(Ⅵ)concentrations and absorbance was in good linear relationship with correlation coefficient r=0.999.The detection limit was 76.64×10^-3 μg·L^-1;the relative deviation was 1.4% and the recovery rate was 96.7%-103.7%.Conclusion: The experimental method for the determination of hexavalent chromium in capsule shell is simple.The samples can be excluded interference by on-line preconcentration without pretreatment.It can be used to directly determine the content and evaluation of Cr(Ⅵ) in capsules.