流动注射-火焰原子吸收光谱法测定水样中铬(Ⅲ)和铬(Ⅵ)

FI-FAAS for Determination of Chromium(Ⅲ) and Chromium(Ⅵ)

应用编结反应器(KR)在线富集,提出了测定水样中痕量铬(Ⅲ)和铬(Ⅵ)的流动注射-火焰原子吸收光谱法。取2份水样与络合剂吡咯烷二硫代氨基甲酸铵(APDC)溶液在线混合,分别与样品中铬(Ⅲ)及铬(Ⅵ)形成络合物并吸附于KR的内壁上,引入空气除去残留的溶液。泵入乙醇-盐酸(9+1)混合溶液将吸附于KR内壁上的络合物洗脱。按仪器工作条件测定洗脱液的吸光度(A_s)。另取1份水样,预先用抗坏血酸将其中铬(Ⅵ)还原为铬(Ⅲ),再按上述条件操作并测得吸光度(A_(Cr))。基于铬(Ⅲ)和铬(Ⅵ)富集系数的差异,推导了铬(Ⅲ)及铬(Ⅵ)含量的计算公式,将所测数据代入公式进行计算。所提出方法对铬(Ⅲ)及铬(Ⅵ)的检出限(3S/N)依次为8.9,5.3μg·L^(-1),相对标准偏差(n=5)分别为5.6%和2.8%。用标准加入法测得回收率在95.9%～98.9%之间。

FI-FAAS with on-line enrichment in knotted reactor（KR） was applied to the determination of Cr（ⅢandⅥ） in water.A portion of water sample was on-line mixed with the complexing reagent APDC solution to form complexes with the Cr（Ⅲ） and Cr（Ⅵ） present in the solution,which were adsorbed on the inner wall of the KR.After removing the residual solution by air-current,a mixed solution of ethanol and HCl（9＋1） was introduced into the KR to dissolve the adsorbed complexes of Cr（Ⅲ） and Cr（Ⅵ）,and the eluate was analyzed by FAAS,with the absorbance taken and nominated as A_s.Another protion of the sample was taken and after reduction of Cr（Ⅵ） to Cr（Ⅲ） by ascorbic acid,was analyzed in the same way as mentioned above.The absorbance obtained was denoted as A_（Cr）.These values were substituted into the formula which were derived on the base of the difference of enrichment factors between complexes of Cr（Ⅲ） and Cr（Ⅵ）,contents of Cr（Ⅲ） and Cr（Ⅵ） in the sample were found.Detection limits（3S/N） of Cr（Ⅲ） and Cr（Ⅵ） found were 8.9 and 5.3μg·L^（-1） and values of RSD＇s（n=5） found were 5.6%and 2.8%respectively.Test for recovery was performed by standard addition method,giving results in the range of 95.9%to 98.9%.