Triplex-wavelength spectrophotometric methods using diphenylcarbazide as a chromogenic reagent was established to eliminate the interference of turbidity for determining Cr( VI) in waste water. However, this method could not be used to eliminate the effect of other factors on Cr( VI) except for turbidity. In the triplex-wavelength spectrophotometric method, the measuring wavelength was 540 nm, and the reference wavelengths were 460 run and 660 nm. The triplex-wavelength spectrophotometric method had a good correlation coefficient ( r = 0. 9998 ) and precision (RSD 1.44% , for seven 8. 0 μg/L standard samples). The detection limit (LD =3. 143s) was 0. 3 μg/L. The average value of recoveries in waste water samples were in the range of 84. 8% - 93. 8% using an internal standard. Compared with the single-wavelength spectrophotometric method, the triplex-wavelength spectrophotometric method had better precision and accuracy. Furthermore, the triplex-wavelength spectrophotometric method had better precision and less workload than the turbidity compensation spectrophotometric method. This method is suitable for the determination of Cr( VI) in low turbidity waste water when the absorbency is lower than 0. 1000 at 540 nm. High turbidity waste water needs to be diluted before spectrophotometric measurements can be made.%建立了二苯碳酰二肼分光光度法测定废水中Cr(Ⅵ)的三波长法,减小了水样浊度的影响,但不能减小除浊度之外的其他干扰对Cr(Ⅵ)测定结果的影响.三波长法的测定波长为540 nm,460 nm和660 nm为参比波长,方法检出限为0.3 μg/L(3.143s),拟合方程的线性关系为0.9998,8.0 μg/L标准点水样测定结果的相对标准偏差( RSD,n=7)为1.44％,实际样品加标回收率均值为84.8％～93.8％.与单波长法相比,三波长法提高了二苯碳酰二肼分光光度法测定水中Cr(Ⅵ)的精密度和准确度,与浊度补偿法相比具有较好的精密度,可减轻分析人员的工作量.三波长法适用于较低浊度废水(显色后样品本底在540 nm处的吸光度小于0.1000)中Cr(Ⅵ)的直接比色分析,浊度较高的样品应适当稀释后显色测定.
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