Integrated flow injection-solid phase spectrophotometric determination of minoxidil

A flow-through solid phase spectrophotometric (SPS) sensing device is propo sed for the determination of minoxidil. The analyte is concentrated on Seph adex SP-C25 ion-exchanger packed in a flow cell and it is monitored by UV-V is spectrophotometry at 282 nm, without derivatization reaction. When a HCl (10(-2) mol l(-1))/NaCl (5 x 10(-2) mol l(-1)) solution is used as carrier/ desorbing solution, the sensor responds linearly in the measuring range of 0.2-7, 0.1-4 and 0.05-2 mu g ml(-1) with detection limits of 60, 33 and 6 n g ml(-1) for 600, 1000 and 2000 mu l of sample, respectively. The relative standard deviations (%) for these volumes are 0.38, 1.06 and 2.63, respecti vely. The method was satisfactorily applied to the determination of minoxid il in pharmaceutical preparations and the results were compared with those obtained by high performance liquid chromatography (HPLC). (C) 1999 Elsevie r Science B.V. All rights reserved.