Validation of oxybutynin

In this study, we have developed two facile spectroscopic methods for quantifying oxybutynin hydrochloride in its pure form and tablets using design of experiments (DOE). The spectroscopic methods depended on the ion-pair complex formation between the tertiary amino group in the drug and in the 0.2-M acetate buffer of pH 4. Method I involves spectrophotometric measurement of the absorbance of the developed complex at 550 nm and showed linearity through 1.0–10.0 μg/mL. Method II involves spectrofluorometric measurement of the quenching influence of oxybutynin on the native fluorescence of eosin (λexcitation/λemission of 304/548 and showed linearity through 1.0–6.0 μg/mL. Critical parameters were identified through preliminary trials and optimized using the DOE. Additionally, the quenching mechanism was investigated, and the pathway of the reaction was postulated. The fluorescence-quenching constant and thermodynamic parameters were explored using the Stern– Volmer plot and Van't Hoff gr...