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