Effect of acidic mobile phase additives on the TLC behaviour of some alkaloids

The effect of two acids (phosphoric and acetic) and their derivatives (hydrogen di(2-ethylhexyl)orthophosphoric, chloroacetic, dichloroacetic, trichloroacetic, and trifluoroacetic acids) on the retention of selected alkaloids on silica gel plates has been investigated. The dependence of the chromatographic behaviour of the alkaloids on mobile phase diluent and on the concentration of the acids in mobile phase (0.001, 0.005, or 0.01 M) was also investigated. Higher concentrations of acid resulted in reduced adsorption and larger RF values.