Determination of ibuprofen and paraben in pharmaceutical formulations using flow-injection and derivative spectrophotometry

A flow-injection UV spectrophotometric method for the determination of ibuprofen in tablets was developed. The proposed method was achieved by using a flow cell which was located in a UV spectrophotometer and a peristaltic pump helped maintaining the carrier solvent, 0.1 M NaOH. During the study, flow rate, loop volume and the number of injections per hour were 15 mL/min, 193 μL and 100, respectively. The analytical signal of ibuprofen was linear in the concentration range of 400–1200 μg/mL. The detection limit and limit of quantification were determined as 27 and 91 μg/mL, respectively. Results for the determination of ibuprofen in tablets, 600 ± 2 mg/tablet (mean ± SD), were in good agreement with the labeled quantities, 600 mg/tablet. A relatively high recovery value, 100.4 ± 0.6%, proves the accuracy of the proposed method. The spectro-photometric method and reference HPLC method were shown to be comparable when Student’s t -test and Fisher test were applied to both methods. In addition, a fourth order derivative UV spectrophotometric method (at 268.8 nm and n = 9) for the determination of ibuprofen and a first order (at 271 nm and n = 1) derivative UV spectrophotometric method for the determination of paraben in pediatric syrups were developed. Recovery values for the determination of ibuprofen and paraben were 102.4 ± 1.1% and 100.2 ± 2.3%, respectively.