ABSTRACT:
Two simple, accurate and sensitive spectrophotometric methods for determination of Lamotrigine and Minoxidil in bulk and dosage forms are described. Method A depends on the reaction of the mentioned drugs with either bromocresol purple or bromothymol blue to form ion pair complex with characteristic absorption maxima at 592 nm and 618 nm, respectively. Effect of anionic, cationic and nonionic surfactants on the absorption was studied. Beer’s law was obeyed in the range of 10-50 µg/ml and 10.2-81.6 µg/ml for lamotrigine and minoxidil with bromocresol purple respectively and in the range of 10-40 µg/ml for lamotrigine with bromothymol blue and in the range of 10.2-71.4 and 30.6-81.6 for minoxidil in presence of cationic and anionic surfactant, respectively. Method B is based on formation of charge transfer complex between 2,3-dichloro-5,6-dicyano-1,4-benzoquinone(DDQ) and the studied drugs. The colour produced has absorption maxima at 590 nm and 457 nm for Lamotrigine and Minoxidil, respectively. Different experimental parameters were studied and incorporated into the procedure. The molar absorptivity (e), sandell sensitivity, detection (LD) and quantitation limits (LQ) were calculated. The proposed methods were applied for determination of Lamotrigine and Minoxidil in pharmaceutical preparations and were validated and obtained results were compared with reference methods.