Chromatographic behaviour of antibiotics on thin layers of an inorganic ion-exchanger

The chromatographic behaviour of amoxicillin, ampicillin, cepha-lexin, cloxacillin, doxycycline, tetracycline, erythromycin, gentamycin, stre-ptomycin, and co-trimoxazole has been studied on thin layers of titanic silicate inorganic ion-exchanger with organic, aqueous, and mixed aqueous–organic mobile phases. Rapid separations of one antibiotic from numerous other antibiotics have been achieved, as have many binary and ternary separations. Salting-out TLC using aqueous ammonium sulphate solutions revealed the dependence of RF values on the concentration of salt in the mobile phase, and the existence of a linear relationship between RM and molarity of (NH4)2SO4 for some antibiotics. The effect of varying the vo-lume ratio of the binary mobile phase methanol–0.1 M formic acid on the RF values of the antibiotics has also been studied.