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本文报告用镉试剂测定工业废水中微量镉的光度法。在聚乙烯吡咯烷酮存在下,镉试剂在碱性乙醇溶液中呈紫色,与镉离子生成桔红色络合物。干扰离子用抗坏血酸——酒石酸钾钠——氰化钾——氟化钾联合掩蔽并用甲醛解蔽,可不经分离在水溶液中直接测定镉。本法测定镉的灵敏度较常用的双硫腙比色法为高。在470毫米处克分子吸光系数ε～1.09×10~5,灵敏度(Sandell 法表示)为0.00103微克/厘米~2。在测定条件下,镉含量在8微克/25毫升以下符合比耳定律。用2厘米比色血,直接测定水样中镉量的下限为0.013毫克/升(相当于吸光度0.01)。予先浓缩水样可测定更低含量的镉。用本法对工业废水进行了测定,含镉量在0.05——18毫克/升范围内,测定的相对偏差不大于6.2%。
This paper reports the spectrophotometric determination of trace cadmium in industrial wastewater using cadmium reagents. In the presence of polyvinylpyrrolidone, the cadmium reagent is purple in alkaline ethanol solution and orange-red complex with cadmium ions. Interfering ions are ascorbic acid - potassium sodium tartrate - potassium cyanide - potassium fluoride combined masking and formaldehyde shielding, can be directly measured in aqueous solution without separation of cadmium. The sensitivity of this method for determination of cadmium is higher than the commonly used dithizone colorimetric method. The molecular extinction coefficient ε ~ 1.09 × 10 ~ 5 at 470 mm and the sensitivity (Sandell’s method) is 0.00103 μg / cm ~ 2. Under the conditions of the assay, Beer’s law is obeyed at cadmium levels below 8 μg / 25 ml. With a 2 cm colorimetric blood, the lower limit of direct determination of cadmium in water samples is 0.013 mg / l (equivalent to 0.01 absorbance). Pre-concentration of water samples can be measured lower levels of cadmium. The industrial wastewater was determined by this method. The relative deviation from the determination of cadmium content within the range of 0.05-18 mg / l was not more than 6.2%.