Determinação condutométrica de benzofenona em formulações farmacêuticas empregando nitrato de prata como titulante

Abstract

The benzophenone has the ability to absorb and dissipate ultraviolet radiation (UV) and it is widely used as a UV filter in the pharmaceutical and cosmetics industry. The present work a simple and rapid conductometric method for benzophenone determi-nation using silver nitrate solutionas titrant was developed. The method was based on the chemical reaction between benzophenone and Ag(I) ions. The conductance of the solution was monitored as a function of the added volume of titrant. The method was applied with success for benzophenone determination in two pharmaceutical formulations. One of objective was to quantify the samples by conductometric titra-tion and compare to the results obtained by atomic absorption spectrophotometry in the UV-vis. Firstly silver nitrate 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 conductance values were corrected by equation: Lcorr. = Lexp. x ((Vi + Va) / Vi) where: Lcorr is the cor-rected conductance; Lexp is the measurements of conductance during analysis, Vi is the initial volume of the sample and Va is volume added of titrant. The proposed method was successfully applied in the determination of benzophenone in two phar-maceutical formulations with results similar to those obtained by absorption spectro-photometry in the UV-vis in 320 nm at 95% confidence level.