HPLC, Densitometric and Visible-Spectrophotometric Determination of Triclabendazole and Ivermectin

Two methods were developed for simultaneous determination of triclabendazole and ivermectin, in addition to a Vis-spectrophotometric method for the analysis of ivermectin only. The first one was HPLC method in which efficient separation of two drugs was achieved on a C18 column with isocratic elution and a mobile phase composed of acetonitrile-methanol-0.005M KH2PO4 in a ratio of (60:30:10, v/v/v), pH 6. The linearity range was found to be 2.5-50 µg mL-1 for triclabendazole and 1-20 µg mL-1 for ivermectin with mean accuracy of 100.11% ± 0.99 and 100.08% ± 0.53, respectively. The second method was a densitometric evaluation of thin-layer chromatograms of the two drugs using a mobile phase of chloroform-acetone (8: 2, v/v). The plates were visualized under UV lamp at 254 nm where spots appeared at Rf 0.79 and 0.33 for triclabendazole and ivermectin, respectively. The chromatograms of the two drugs were measured densitometrically at 306 nm in the range 2.5-25.0 µg/spot for triclabendazole and at 245 nm in the range of 0.5-5.0 µg/spot for ivermectin with mean accuracy of 100.38% ± 0.52 and 100.05% ± 0.41, respectively. The Vis-spectrophotometric method was applied for the determination of ivermectin depending on its reducing character on tetrazolium red to give highly colored red product absorbing maximally at 485 nm in the range of 10-200 µg mL-1 with mean accuracy of 100.61% ± 0.43. The first two methods provided selective recovery of triclabendazole and ivermectin (100.53% ± 0.97 and 100.03% ± 0.82, 99.94% ± 1.60 and 98.77% ± 0.72; respectively). While the third Vis-spectrophotometric method provided selective recovery of ivermectin (100.86% ± 0.93) in presence of triclabendazole. Successful application of the methods for analyzing triclabendazole and ivermectin in their pharmaceutical formulations was obtained. The validity of the method was evaluated in terms of linear regression analysis, precision, accuracy and selectivity.