Application of normalized spectra in resolving a challenging Orphenadrine and Paracetamol binary mixture

Normalized spectra have a great power in resolving spectral overlap of challenging Orphenadrine (ORP) and Paracetamol (PAR) binary mixture, four smart techniques utilizing the normalized spectra were used in this work, namely, amplitude modulation (AM), simultaneous area ratio subtraction (SARS), simultaneous derivative spectrophotometry (S(1)DD) and ratio H-point standard addition method (RHPSAM). In AM, peak amplitude at 221.6nm of the division spectra was measured for both ORP and PAR determination, while in SARS, concentration of ORP was determined using the area under the curve from 215nm to 222nm of the regenerated ORP zero order absorption spectra, in S(1)DD, concentration of ORP was determined using the peak amplitude at 224nm of the first derivative ratio spectra. PAR concentration was determined directly at 288nm in the division spectra obtained during the manipulation steps in the previous three methods. The last RHPSAM is a dual wavelength method in which two calibrations were plotted at 216nm and 226nm. RH point is the intersection of the two calibration lines, where ORP and PAR concentrations were directly determined from coordinates of RH point. The proposed methods were applied successfully for the determination of ORP and PAR in their dosage form.