Through ultraviolet-visible( UV-Vis) spectra, a strategy for the determination of cysteine(Cys) was established by simply assembling copper( II ) and 4-(2-pyridylazo)-resorcinol( PAR) in a molar ratio of 1 : 1 in aqueous solution. Cys could be detected in 10 mmol/L4-(2-hydroxyethyl)-l-piperazineethanesulfonic acid (HEPES) buffer(pH = 7. 0) system containing copper( II )-PAR due to coordination competition. The Cu2+-PAR ensemble was highly selective for Cys without interference from other amino acids. From the UV-Vis ab-sorbance value changes of Cu2+-PAR and Cu2+-PAR-Cys, the optimal coordinated ratio of PAR : Cu2+ was found to be 1:1 and Cu2+:Cys was 1:3. It is worthy mentioned that within the concentration range of 0-240 μmol/L in aqueous solution, the measurement of Cys conformed well with linear law, with an average coefficient of light extinction of 7519 L/(mol·Cm) and a correlation coefficient of 0. 9982. The whole recognition process for Cys gave rise to a rapid visual color change from pink to yellow which can be observed simultaneously with naked eye.%基于半胱氨酸(Cys)与二价铜离子的配位作用,发展了一种在纯水溶液中以4-(2-吡啶偶氮)间苯二酚(PAR)为指示剂,通过紫外-可见光谱定性定量检测半胱氨酸的方法.研究发现,在pH=7.0的含有PAR和二价铜离子(摩尔比为1∶1)的缓冲溶液中,当加入半胱氨酸后,由于配位竞争使PAR释放出来,实现了对半胱氨酸的识别,选择性研究结果表明,其它氨基酸不干扰体系对半胱氨酸的测定.通过紫外-可见光谱(UV-Vis)对识别过程进行了研究,确定了Cu2+与PAR的配位比为1∶1,Cu2+与Cys的配位比为1∶3；半胱氨酸的线性关系变化范围为0 ～ 240 μmol/L,ε=7519 L/( mol·cm),线性相关系数为0.9982.在检测过程中可观察到溶液颜色由桃红色变成了黄色.
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