在pH为4.8的乙酸-乙酸钠缓冲溶液中，卡托普利能将Cu（Ⅱ）还原为Cu（Ⅰ），Cu（Ⅰ）与SCN^-反应生成硫氰酸亚铜粒子后体系呈现较强的共振光散射信号，反应体系在波长398 nm处的共振散射信号增强程度（ΔI_RS）与卡托普利的质量浓度在一定范围内呈线性关系，据此采用硫氰化亚铜共振散射光谱法测定药物中卡托普利的含量。优化的试验条件如下：①0.50 g·L^-1硫酸铜溶液的用量为1.50 mL；②0.50 g·L^-1硫氰化钾溶液用量为2.00 mL；③反应时间为10 min。卡托普利的线性范围为0.40~24.00 mg·L^-1，检出限（3σ）为0.14 mg·L^-1。在1.00 mg·L^-1浓度水平进行加标回收试验，回收率为97.0%~104%，测定值的相对标准偏差（n=5）为1.6%~2.7%。

In HOAc-NaOAc buffer solution of pH 4.8, Cu(Ⅱ) was reduced by captopril to form Cu(Ⅰ), and then Cu(Ⅰ) reacted with SCN^- to form CuSCN particles, which made the resonance scattering (RS) signal increase drastically. The enhanced RS intensity (ΔI_RS ) at 398 nm was proportional to mass concentration of captopril in definite range. Based on the fact, resonance scattering spectrometry was applied to the determination of captopril in drugs based on CuSCN particles. The optimized conditions found were as follows:① amount of 0.50 g·L^-1 CuSO₄ solution was 1.50 mL;② amount of 0.50 g·L^-1 KSCN solution was 2.00 mL;③ time of reaction was 10 min. Linearity range of captopril was found in the range of 0.40-24.00 mg·L^-1, with detection limits (3σ) of 0.14 mg·L^-1. Tests for recovery were made by standard addition method at the concentration level of 1.00 mg·L^-1, giving values of recovery and RSDs (n=5) in the ranges of 97.0%-104% and 1.6%-2.7% respectively.