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Sequential Injection Magneto Chromatography Determination of Non-Steroidal Anti-Inflammatory Drugs in Pharmaceutical Formulations

A magnetic separation method based on the use of magnetic silica as the stationary phase in sequential injection chromatography was used for simultaneous determination of nonsteroidal anti-inflammatory drugs (acetaminophen, naproxen, diclofenac, and ibuprofen) in tablets. The method is based on a thin layer paramagnetic stationary phase retained on the inner wall of a mini-column through the action of an external magnetic field. The influence of the variables involved was evaluated and the optimal conditions were found to be: a methyl-silica magnetic adsorbent was used as the stationary phase, the mobile phase was methanol-water (60:40, v/v), pH 2.5 adjusted with 98% phosphoric acid, a flow rate 0.60 ml min−1, and UV detection at 225 nm. Under these conditions, the linear range of the calibration curve ranged from 3–6 mg L−1 to 100 mg L−1 with limits of detection ranging between 1 to 2 mg L−1. The proposed method was validated by comparing the results obtained against those provided by high performance liquid chromatography; no significant differences were seen.