Determinação de hidroquinona em formulações farmacéuticas por titulação condutométrica

Abstract

One of the most common skin problems is associated with hyperpigmentation of the same, caused mainly by the increase in the formation of melanin. One of the most frequently used active principles in the treatment of hypigmentation is hydroquinone (benzene-1,4-diol), it is present in more than 130 pharmaceutical formulations, similar to this has melanin precursor chemical structure and inhibits the oxidation of tyrosine as well as participating other metabolic processes in melanocytes. Due to the great importance of this substance is an undeniable need new analytical methodologies that allow quality control of this substance. In this context, the present research show a simple and rapid conductometric method for hydroquinone determination using copper phosphate solution as titrant was developed. The method was based on the chemical reaction between hydroquinone and Cu(II) ions. The conductance of the solution was monitored as a function of the added volume of titrant. The method was applied with success for hydroquinone determination in two pharmaceutical formula-tions. The relative standard deviation for the successive measurements was smaller than 10%. One of objective was to quantify the samples by conductometric titration and compare to the results obtained by atomic absorption spectrophotometry in the UV. Firstly copper phosphate solutions were standardized, all standardizing proce-dures and quantitative analysis were performed in triplicate. Some tests to optimize the analysis parameters were performed as well as, test of titrant concentration, teste of sample dissolution in ethanol and teste stability time. The proposed method was successfully applied in the determination of hydroquinone in two pharmaceutical for-mulations with results similar to those obtained by absorption spectrophotometry in the UV at 95% confidence level.