Selective spectrophotometric methods for determination of ternary mixture with overlapping spectra: A comparative study

• Selective determination of ternary mixture with severe spectral overlap.
• More convenient and easier spectrophotometric methods are presented.
• Newly designed area under curve of derivative ratio spectra spectrophotometry.
• Difficult ratio of pharmaceutical formulation was handled by spiking technique.

Comparable double divisor ratio spectra derivative, area under curve of derivative ratio and mean centering of ratio spectra spectrophotometric methods were introduced for determination of orphenadrine citrate (ORPH), caffeine (CAF) and aspirin (ASP); a combination for symptomatic relief of mild to moderate pain of acute musculoskeletal disorders; with evident accuracy and precision. The suggested methods have the advantage over the previously published spectrophotometric method for determination of the same combination in that they did not require a preliminary separation step and able to resolve the ternary mixture, with severe overlapping spectra, with competent sensitivity and selectivity. The recommended methods allow the determination of ORPH, CAF and ASP in the range of 2–32, 2–28 and 3–28 μg mL−1, respectively. The validity of the proposed methods was examined by analysis of different laboratory prepared mixtures of ORPH, CAF and ASP and assay of their tablet formulation where reliable results were obtained. Statistical analysis between the suggested spectrophotometric methods and the reported HPLC method using student’s-t and F-ratio tests reveals that the suggested methods are as accurate and precise as the reported one.

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