A new homogeneous liquid-liquid extractive- spectrophotometric method for determination of diclofenac in urine

A new, simple and reliable extractive-spectrophotometric method for the preconcentration and determination of diclofenac (DCF) was developed. In a strong nitric acid medium, diclofenac produced a yellowish compound in a water / tetrahydrofuran / perfluorooctanoic acid homogeneous phase that could be extracted into a sedimented microdroplet. The concentration of the extracted colored compound in the microdroplet was determined by measuring its absorbance at 376 nm. The effective experimental parameters for spectrophotometric determination of diclofenac in water and methanol were optimized, so that DCF could be sensitively determined in an aqueous or organic medium. The maximum absorbance was achieved in 1.5 and 7.0 M aqueous and methanolic solutions of nitric acid. The absorbance of DCF solutions in water and methanol obeyed Beer’s law, over the range of 1.0 30.0 μg cm-3 and 0.5 40.0 μg cm-3, with molar absorptivities of 7.4×103 and 1.3×104 dm3 mol-1 cm-1 respectively. Additionally, different experimental parameters for homogeneous liquid-liquid extractions of diclofenac were investigated. The limit of detection (LOD) achieved with the proposed method was 0.03 ng cm-3. The maximum concentration factor obtained was 6667-fold. The reproducibility of 10 replicate measurements was found to be 2.3%. Finally, the proposed method was successfully applied to the extraction and determination of diclofenac in pharmaceutical preparations and urine samples.