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

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.

Assay for the simultaneous determination of acetaminophen–caffeine–butalbital in human serum using a monolithic column

A fast and sensitive high performance liquid chromatography (HPLC) assay was developed on a C18 monolithic column for the simultaneous determination of acetaminophen-caffeine-butalbital in human serum. Serum samples were treated with a solid phase extraction procedure. The analytes were separated using a mobile phase of 95:5 (v/v) 0.1M potassium phosphate monobasic (pH 2.41)-acetonitrile on the C18 monolithic column with detection at 220 nm. Benzoic acid was used as the internal standard (IS). The method was validated over the range of 1.25-100 microg/ml for each drug and found to be linear (r > 0.995, n = 12) with RSD less than 8.3%. The method proved to be accurate (percent bias for all calibration samples varied from -14.6 to -1.3%) and precise (ranged from 2.9 to 13.4%). The mean percent absolute recoveries from serum were 89.7 +/- 3.6 for acetaminophen, 95.5 +/- 4.5 for caffeine, 99 +/- 5.2 for butalbital and 83.4 +/- 3.9% for the internal standard.