Ultra-trace level determination of hydroquinone in waste photographic solutions by UV-vis spectrophotometry

A simpler UV-vis spectrophotometric method was investigated for hydroquinone (HQ) determination using KMnO₄ as oxidizing agent for conversion of HQ to p-benzoquinone (BQ) as well as signal enhancer. Various parameters such as analytical wavelength, stability time, temperature, pH, solvent effect and interference of chemicals were checked and parameters optimized by using 1 μg ml⁻¹ standard solution of HQ. Beer's Law was applicable in the range of 0.07-2 μg ml⁻¹ and 0.005-0.05 μg ml⁻¹ at 245.5 nm and at 262 nm for aqueous standard solutions of HQ with linear regression coefficient value of 0.9978 and 0.9843 and detection limit of 0.021 μg ml⁻¹ and 0.0016 μg ml⁻¹ HQ, respectively. Standard deviation of 1.7% and 2.4% was true for 1 μg ml⁻¹ and 0.03 μg ml⁻¹ HQ solution (n = 11) run at respective wavelengths. The method was successfully applied to dilute waste photographic developer samples for free HQ determination.