分光光度法测定萃余液中氯仿浓度

用NaOH-吡啶比色法可以测定水或某些废水中的微量CHCl3浓度,但测定N,N-二甲基甲酰胺(DMF)废水经CHCl3萃取DMF后的萃余液中CHCl3浓度时,DMF对显色的有严重的干扰。采用蒸馏预处理后,再用比色法测定蒸馏所得的馏液中CHCl3浓度的方法,可以消除废水中DMF对显色的干扰。研究了水样中DMF浓度、蒸馏汽化率等因素对比色时显色的影响,建立了蒸馏-比色法测定DMF废水萃余液中微量或大量CHCl3浓度的分析方法。对含10g/LDMF水样的测定,CHCl3的线性范围为0～0.75g/L;与顶空色谱法测定结果对比,测定CHCl3浓度为5g/L和0.16g/L水样的相对误差分别为2.1%和1.2%;对CHCl3浓度为0.575g/L的水样进行7次平行测定,相对标准偏差为6.6%。对含DMF<15g/L水样的分析,结果令人满意。

Determination of Chloroform in Extraction Raffinate by Distillation-Spectrophotometric Method

When spectrophotometric method was applied to determine the concentration of chloroform of raffinate left by extraction of N,N-dimethylformamide(DMF) from an leather manufacturing industrial waste water with chloroform as an extractant,the DMF in wastewater seriously interferes in the Fujiwara coloured reaction.This interference can be obviously eliminated by distillation pretreatment of sample before spectrophotometry detection.So,the distillation-spectrophotometric method was utilized for the determination of chloroform concentration in extraction raffinate,and was proved to be very efficient,and the effects of DMF concentration of the samples and of the distils,the percent vaporization of the samples were investigated,and a distillation-spectrophotometric analysis procedure or method were developed.The experimental results showed that a linear calibration plot(R=0.9983) for the distillation-spectrophotometric method was obtained within a chloroform concentration range of 0-0.75 g/L,and this method is an accurate one for determination of chloroform concentration in DMF containing wastewater or extraction raffinate with relative errors of 2.1% and 1.2% for initial chloroform concentration 5 g/L and 0.16 g/L respectively by comparison with static head-space gas chromatography and relative standard deviation of 6.6% in repeated determination chloroform concentration of 0.575 g/L by 7 times.The results of determination of chloroform concentration in wastewater containing DMF]<15 g/L were satisfactory.