分光光度法测定化妆品中的甲醇

建立了一种1,2-萘醌-4-磺酸钠（NQS）分光光度法直接测定化妆品中甲醇的新方法。研究表明,在pH为13.00的KCl-NaOH缓冲溶液中,甲醇电离生成的甲氧离子（CH₃O^-）能够催化氢氧根离子（OH^-）与1,2-萘醌-4-磺酸钠反应形成橙红色的2-羟基-1,4-萘醌,其最大吸收波长为450nm。甲醇浓度在0.010mg/mL～4.000mg/mL范围内与吸光度呈现良好的线性关系。线性回归方程为A=0.0018+0.1714c（mg/mL）,相关系数为0.9998,检测限为0.005mg/mL。平均回收率在98.5%～105%。依本法取3份样品分别测7次,变异系数为2.5%～4.8%。该方法具有检出限低、快速、准确、灵敏度高以及经济实用等优点。

Determination of methanol in cosmetics by spectrophotometry

A novel and simple spectrophotometric method for the determination of methanol in cosmetics with sodium 1, 2-naphthoquinone-4- sulfonate as chromogenic reagent was developed. The method was based on 2-hydroxyl-l,4-naphthoquinone formed from hydroxyl ion and 1, 2-naphthoquinone-4-sulfonate in a buffe.r solution of pH = 13.00 with methoxy ion as a catalyst. Absorbency was linearly proportional to the concentration of methanol in a range of 0.010 mg / mL～4.000 mg / mL at the maximal absorption wavelength of 450 nm. The equation of linear regression was A= 0.0018 ＋ 0.1714c （mg / mL） , with a correlation coefficient of 0.9998. The detection limit was 0.005 mg/ mL, and the recovery was within a range of 98.5% - 105%. When detecting three samples for seven times, the variable coefficient was within 2.5% - 4.8%. The method is rapid, simple, accurate, economical as well as low in determination limit. This proposed method has been successfully applied to the determination of methanol in cosmetics with satisfactory results.