Densitometric determination of diclofenac, 1-(2,6-dichlorophenyl)indolin-2-one and indolin-2-one in pharmaceutical preparations and model solutions.

A chromatographic-densitometric method for identification and quantitation of diclofenac and its impurities, i.e. 1-(2,6-dichlorophenyl)indolin-2-one and indolin-2-one in pharmaceutical preparations and model solutions was developed. The effect of pH, temperature and ultra violet (UV) radiation on diclofenac's concentration was investigated. Chromatographic separation was performed on TLC silica gel coated plates with the mobile phase: cyclohexane-chloroform-methanol (12:6:1, v/v/v). Densitometric detection was carried out in UV at lambda=248 nm. The conditions for good separation and the detection limit were established. The recovery for diclofenac was 99.20%, for 1-(2,6-dichlorophenyl)indolin-2-one--92.34% and for indolin-2-one--95.85%. The method was used for quality assessment of diclofenac in pharmaceutical preparations. Reliable results comparable to those determined by high performance liquid chromatography (HPLC) were obtained.