氯酸钾氧化分光光度法测定水体中总铬浓度

Determination of total chromium in water using potassium chlorate oxidation spectrophotometry

为了克服GB 7466—87水质总铬的测定法中测定总铬浓度的不足之处,采用氯酸钾作为氧化剂建立一种新的测定方法。对国标法的消解预处理步骤进行了部分改进,简化操作过程,避免总铬成分的损失。在酸性溶液中以二苯碳酰二肼（DPC）为显色剂测定总铬时,研究显色剂配制方法、显色体系稳定性及饱和氯酸钾溶液用量对测定的影响。结果表明：用乙醇代替丙酮配制显色剂对吸光度没有影响,显色液放置100 min吸光度无变化,0.5 mL饱和氯酸钾溶液可满足氧化3价铬的要求,过量的氯酸钾无须另加还原试剂消除。该方法测定总铬质量浓度的线性范围是0.02～1.0μg/mL,相关系数r=0.9999。将新方法应用于测定几种水体的总铬浓度,加标回收率为95.0%～102.0%,测定含铬废水的平均浓度值与国标法无显著性差异。

A novel method was set up for the determination of total chromium in water using potassium chlorate as an oxidant to overcome the disadvantage of the national standard method（GB7466-87）.The digestion pretreatment procedure was improved in this method compared with that of the standard method,which made for a simplified analysis process and prevented the loss of total chromium.With 1,5-diphenylcarbazide（DPC） as the color development reagent used to determine the content of total chromium in the acidic solution,the formation method of the color development reagent,the stability of color development system,and the dosage of the saturated solution of potassium chlorate used in the oxidation process were studied.The results showed that the absorbency with alcohol as the solvent in the color development reagent was the same as that with propanone as the solvent;absorbency of this colored development system was constant over 100 minutes;and 0.5 mL of saturated potassium chlorate was enough to oxidize all of the Cr3＋ in the water,without the need to eliminate excessive potassium chlorate in the solution with other reductants.The linear range of determination of total chromium in this method was 0.02 to 1.0 μg/ml,and the correlation coefficient was 0.9999.Using this method to determine the content of total chromium in several kinds of water,the recoveries were in the range of 94.70% to 102.1%.The mean value of the waste water containing chromium was not significantly different from that of the national standard method.