National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan.
Int J Cosmet Sci. 2011 Apr;33(2):132-7. doi: 10.1111/j.1468-2494.2010.00599.x.
A highly sensitive, simpler, faster and economical UV/visible spectrophotometric method has been established for the estimation of hydroquinone (HQ) in dilute organic matrices. The method is based on using ammonium meta-vanadate as an oxidizing catalyst for conversion of HQ to p-benzoquinone (BQ) in the presence of oxygen. As a result of higher absorption of UV light by BQ than by HQ, its signal has been utilized for determining HQ at the trace level. The effect of various parameters such as amount of oxidizing agent, stability time, temperature, acids and bases, solvents and interference by various compounds has been studied upon the absorption of BQ as HQ. Under optimized conditions, Beer's Law was obeyed in the range of 0.025-2.00 μg ml(-1) HQ at 245.5 nm using 1 : 1 (V/V) 2-propanol/water system with a lower detection limit of 7 ng ml(-1) and linear regression coefficient of 0.9998. Relative standard deviation of 1.5% was observed for 0.5 μg ml(-1) HQ solution (n = 11). The newly developed method has been successfully applied to diluted samples of various skin lightening creams for free HQ determination at the trace level. Comparison of the results obtained by the proposed method with those by a previously reported method proved its validity.
已建立了一种高灵敏度、简单、快速且经济的 UV/可见分光光度法，用于估算稀有机基质中的对苯二酚 (HQ)。该方法基于在氧气存在下使用偏钒酸铵作为氧化催化剂，将 HQ 转化为邻苯醌 (BQ)。由于 BQ 比 HQ 吸收更多的紫外光，因此可以利用其信号来测定痕量 HQ。研究了各种参数（如氧化剂用量、稳定时间、温度、酸和碱、溶剂以及各种化合物的干扰）对 BQ 作为 HQ 吸收的影响。在优化条件下，在 245.5nm 处使用 1：1（V/V）异丙醇/水体系，在 0.025-2.00μg ml(-1) HQ 范围内遵守比尔定律，检测限为 7ng ml(-1)，线性回归系数为 0.9998。对于 0.5μg ml(-1) HQ 溶液（n=11），相对标准偏差为 1.5%。该新方法已成功应用于各种皮肤美白霜的稀释样品，用于痕量 HQ 的测定。与之前报道的方法相比，所提出的方法的结果证明了其有效性。
