Dissolution monitoring of diclofenac sodium and codeine phosphate tablets using fibre optic chemical sensor assisted by dual-wavelength isosbestic point spectrophotometry.

The purpose of this investigation was to establish a mathematical model for determining the dissolution of diclofenac sodium and codeine phosphate simultaneously. Based on the dual-wavelength isosbestic point spectrophotometry, the dissolution of diclofenac sodium and codeine phosphate tablets was determined using Fiber-Optic Dissolution Test (FODT) instrument capable of real-time measurement. Dissolution curves showed that the dissolution process of diclofenac sodium was similar to that of codeine phosphate. The dissolution profile of diclofenac sodium and codeine phosphate at 45 min was concordant with that stated in Chinese pharmacopoeia. There was no significant difference between results obtained from FODT and HPLC (p>0.05). A fibre-optic dissolution test system assisted by the mathematical separation model of linear equations was able to detect the dissolution of diclofenac sodium and codeine phosphate simultaneously. The dissolution profiles and overall data, which can directly reflect the dissolution speed at each time point, can provide the basis for establishing standards for the quality evaluation of drugs.