STABILITY – INDICATING SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF LAMOTRIGINE IN PURE FORM AND PHARMACEUTICAL PREPARATIONS

Three simple, sensitive, accurate, and precise methods were developed for determination of lamotrigine (LTG) in bulk powder and pharmaceutical preparations. The first method depends on charge transfer complexing of LTG with chloranilic acid (CA) as will as with 2,3-Dichloro-5,6-Dicyano-1,4-benzoquinone (DDQ) to produce purple color measured at 520 and 588 nm for CA and DDQ respectively. Beer’s low was obeyed in the range of 25 –200 and 6- 42 µg ml^-1 with LOD of 3.06 and 0.498 µg ml^-1 and LOQ of 10.19 and 1.66 µg ml^-1 respectively. The second method depends on ion pairing of LTG with bromothymol blue (BTB), bromophenol blue (BPB) and bromocresol green (BCG) to  produce red colored complexes measured at 419, 417 and 417 nm for the three reagents respectively. Beer’s low was obeyed in the range of 2 – 12 µg ml^-1 for all reagents. LOD was found to be 0.56, 0.18 and 0.13 µg ml^-1 while LOQ was 1.66, 1.86 and 0.53 respectively. The third method is the adopting of the first derivative spectrophotometry at 291 nm for direct determination of lamotrigine in presence of its degradation product. A linear relationship between peak height and drug concentration was obtained in the range of 10 – 70 µg ml^-1.LOD and LOQ were found to be 0.68 and 2.26 µg ml^-1 respectively. The percent recoveries ± RSD% of these methods were 99.52-100.36 ± 0.78-1.34, 99.65-100.48 + 0.85-1.38, and 99.62-100.26 ± 1.17-1.22 % respectively. The obtained results were compared with those of the reported method and no significant difference was observed regarding accuracy and precision