双波长等吸收点紫外可见分光光度法测定口蘑中微量铜(Ⅱ)离子的研究

Determination of copper(Ⅱ) content in tricholoma by dual-wavelength isobestic point UV-visible spectrophotometry

以3,5-二甲酸-4'-羟基偶氮苯(DAH)为显色剂,建立了双波长等吸收点紫外可见分光光度法对口蘑中微量铜(II)(Cu 2+)离子的定量分析方法。在pH 9.18四硼酸钠缓冲溶液中,DAH与Cu 2+发生反应形成DAH-Cu 2+,该体系在紫外光区的吸收强度会发生变化,利用双波长等吸收点法的定量理论对铜元素进行定量分析。研究表明,双波长法中铜的标准曲线为ΔA=0.092c+0.0109,相关系数(R 2)为0.9979,双波长法的摩尔吸光系数为5.8×104 L/(mol·cm),而单波长法的摩尔吸光系数为4.3×104 L/(mol·cm);与单波长法相比,双波长等吸收点法灵敏度提高了将近1.4倍。双波长等吸收点紫外可见分光光度法的相对标准偏差(RSD)为0.87%(n=11),检出限为0.072μg/mL,定量限为0.22μg/mL,回收率在99.0%~100.7%之间,与国标中的电感耦合等离子体发射光谱法(ICP-OES)相比,2种方法的结果较接近,相对误差为1.53%。

A quantitative analysis method for the determination of Cu 2+with 3,5-dicardoxylic acid-4'-hydroxyazobenzene(DAH)as chromogenic reagent was developed.In an alkaline sodium tetraborate buffer media of pH 9.18,DAH reacts with Cu 2+to form DAH-Cu 2+complex,and quantitative analysis of Cu 2+content was carried out by using the quantitative theory of dual-wavelength isosbestic point method.The results showed that the regression equation of Cu 2+through the dual-wavelength spectrophotometry wasΔA=0.092c+0.0109,and the correlation coefficient(R 2)was 0.9979.The molar absorptivity of the dual-wavelength spectrophotometry can be achieved 5.8×104 L/(mol·cm),1.4 times higher than that of single-wavelength spectrophotometry(4.3×104 L/(mol·cm)for the single-wavelength method).The repetitive experiment indicated that the relative standard deviation(RSD)of dual-wavelength spectrophotometry was 0.87%(n=11),the limit of detection was 0.072μg/mL,the limit of quantitation was 0.22μg/mL and recoveries were 99.0%-100.7%,respectively.The content of Cu 2+in tricholoma determined by dual-wavelength spectrophotometry is close to that determined by inductively coupled plasma optical emission spectroscopy(ICP-OES),the relative error of two methods was 1.53%.