A simple, precise and accurate high performance thin layer chromatographic method has been developed for the simultaneous estimation of Isotretinoin and Erythromycin in pharmaceutical gel. The separation was carried out on Merck TLC aluminum sheets of silica gel 60 F 254 , (20 × 10 cm) with 250 µm thickness using toluene: DMSO: methanol (6.5:0.2:2.5, v/v/v) as a mobile phase. HPTLC separation of the two drugs followed by densitometric measurement of their spots at 340 nm for Isotretinoin before

more »

... derivatization and 410 nm for Erythromycin after derivatization with 10% H 2 SO 4 and heating at 100C for 15 min. The drugs were satisfactorily resolved with R F values of 0.38 ± 0.02 and 0.55 ± 0.02 for Isotretinoin and Erythromycin, respectively. The accuracy and reliability of the method was assessed by evaluation of linearity (30-150 ng spot -1 for Isotretinoin and 1200-6000 ng spot -1 for Erythromycin), precision (intra-day RSD 0.62-0.79% and inter-day RSD 0.43-0.71% for Isotretinoin and intra-day RSD 0.47-1.71% and inter-day RSD 0.42-1.49% for Erythromycin), accuracy (98.91 ± 0.92% for Isotretinoin and 99.27 ± 0.72% for Erythromycin), and specificity, in accordance with ICH guidelines. Figure 3. (a) Densitogram of Isotretinoin 60 ng spot -1 before derivatization at 340 nm; (b) Densitogram of Erythromycin 400 ng spot -1 after derivatization at 410 nm. 2