Selective spectrofluorimetric determination of two corticosteroids along with their co-formulated drugs and degradation products in ophthalmic solution and aqueous humour.

Prednisolone acetate (PNO) and fluorometholone (FRT) are corticosteroids, co-formulated with moxifloxacin HCl (MFX) and cromolyn sodium (CML), respectively. PNO has a negligible quantum yield and its hydrolytic degradation products have enhanced fluorescence, which is 250-fold greater. FRT is a nonfluorescent drug, but its hydrolytic degradation products show reasonable fluorescence; MFX and CML have native fluorescence. Two methods were proposed based on the determination of PNO and FRT via their hydrolytic degradation products in the presence of other degradation products. Method (A) was developed for simultaneous determination of PNO and MFX in the presence of PNO degradation products by measuring peak amplitudes of the first derivative ( D) of its enhanced fluorescence; PNO and MFX were measured at 345 and 473 nm, respectively. Method (B) is a synchronous fluorescence spectroscopic method for simultaneous determination of FRT and its co-formulated drug CML in the presence of its degradation products. Fluorescence intensities were measured at λ 283 and 347 nm for FRT and CML, respectively, using Δλ = 99.20 nm. Validation of the proposed methods was conducted as per International Council for Harmonisation (ICH) guidelines. The proposed methods were successfully applied for the determination of the proposed drugs in bulk powder, ophthalmic solution, and rabbit's aqueous humour.