Simultaneous determination of Dimenhydrinate, Cinnarizine and Cinnarizine impurity by TLC and HPLC chromatographic methods

Two chromatographic methods have been established and validated for simultaneous determination of mixture of Dimenhydrinate (DMH) and Cinnarizine (CIN) in their pharmaceutical formulation and in presence of Cinnarizine impurity (1-(Diphenylmethyl) piperazine); CIN impurity. The first method was TLC-densitometric one, depends on separation and quantitation of DMH, CIN and CIN impurity on TLC silica gel 60 F₂₅₄ plates, using chloroform:methanol:glacial acetic acid:ammonia solution (9.5:0.5:0.1:0.1, by volume) as a developing system followed by densitometric measurement at 235 nm. Linear relationships were obtained in the range of 0.2–2, 0.4–1.6 and 0.1–1 μg/band for DMH, CIN and CIN impurity, respectively. The studied components were well resolved from each other with significantly different R_f values of 0.35, 0.52 and 0.04 for DMH, CIN and CIN impurity, respectively. The second method was RP-HPLC, separation on C8 column using 0.05 M KH₂PO₄ (pH = 3):methanol (35:65, v/v) as the mobile phase at a flow rate of 1 mL/min and DAD detection at 240 nm. Linear relationships were obtained in the ranges of 3–30, 2–20 and 1–10 μg/mL, with significantly different R_t values of 3.27, 6.95 and 2.87 min for DMH, CIN and CIN impurity, respectively. The developed methods were validated according to ICH guidelines demonstrating good accuracy and precision. The results were statistically compared with those obtained by reported HPLC method and no significant difference was obtained.