在弱碱性乙醇溶液中，溴甲酚绿与盐酸米多君以静电引力结合生成具有1个较强正吸收峰和1个较强负吸收峰的二元离子缔合物，最大正吸收峰位于553 nm，最大负吸收峰位于444 nm，表观摩尔吸光系数（κ）分别为2.06×10⁴ L/（mol·cm）（553 nm）和2.07×10⁴ L/（mol·cm）（444 nm）。当用双波长法测定时，表观摩尔吸光系数（κ）可达4.13×10⁴ L/（mol·cm），线性范围均为0.2~8.7 mg/L，检出限分别为0.15 mg/L（单波长法，553 nm）、0.14 mg/L（单波长法，444 nm）和0.072 mg/L（双波长法）。据此建立了测定盐酸米多君的双波长可见吸收光谱法，该方法用于盐酸米多君片剂中盐酸米多君的测定，回收率和相对标准偏差RSD（n=5）分别为98.4%~102%和1.8%~2.3%。

In a weak-alkaline ethanol solution,bromocresol green combines with midodrine hydrochloride by electrostatic attraction to form a binary ionic association complex with a strong positive absorption peak and a strong negative absorption peak.The maximum positive absorption peak locates at 553 nm and the minimum negative absorption peak locates at 444 nm.The apparent molar absorptivity (κ) are 2.06×10⁴ L/(mol·cm) for 553 nm peak and 2.07×10⁴ L/(mol·cm) for 444 nm peak,respectively.When the dual-wavelength absorption spectrophotometry is used to determine the content of midodrine hydrochloride,its apparent molar absorptivity (κ) can achieve 4.13×10⁴ L/(mol·cm),their linear ranges both are in the range of 0.2 to 8.7 mg·L^-1,and their detection limits are 0.072 mg·L^-1.When the single-wavelength method is used,the detection limits are 0.15 mg·L^-1 (for 553 nm) and 0.14 mg·L^-1 (for 444 nm).Accordingly,a dual-wavelength visible absorption spectrometric method for the determination of midodrine hydrochloride is established.The recovery rate and relative standard deviation RSD(n=5) are 98.4%-102% and 1.8%-2.3%,respectively when the method is applied to determine the content of midodrine hydrochloride in commercially available midodrine hydrochloride tablets.

卢俊伶(1998-),女,本科,研究方向为分子光谱分析,lujunlin2018@163.com