Validated spectrophotometric and spectrodensitometric methods for determination of a ternary mixture of analgesic drugs in different dosage forms

Accurate, sensitive and precise methods have been developed for determination of aspirin, caffeine, and paracetamol, in their ternary mixture with minimum sample pretreatment and without previous separation.Method (A) is a spectrophotometric one that depends on determination of aspirin and paracetamol using the successive derivative of the ratio spectra and measuring the amplitudes at 241.2 and 228.2 nm, respectively. Caffeine is indirectly determined using a calculated equation by measuring the amplitude of the third derivative spectra at 285.6 at which there is no interference from paracetamol and interference from aspirin was removed by subtraction as aspirin was selectively determined at 241.2 nm, where CAF showed no absorbance.Method (B) depends on quantitative TLC-Densitometric separation of the ternary mixture using silica gel 60 F254 plates and scanning at 230 nm using chloroform:methanol:acetic acid:ammonia solution (95:5:0.5:0.2, by volume) as a developing system.The proposed methods have been validated as per ICH guidelines and USP requirements. Moreover the developed methods have been applied for determination of the above mentioned drugs in different pharmaceutical formulations where no interference from the excipients has been detected.Statistical comparison of the results obtained from the suggested methods with those of the reported HPLC method showed no significant difference. The developed methods can be considered sensitive, accurate, and cost-effective methods.