Separation of Selected Bile Acids by TLC. IX. Separation on Silica Gel 60 and on Silica Gel 60F₂₅₄ Aluminum Plates Impregnated with Cu(II), Ni(II), Fe(II), and Mn(II) Cations

Abstract

Seven selected bile acids: cholic acid (C), glycocholic acid (GC), glycolithocholic acid (GLC), deoxycholic acid (DC), chenodeoxycholic acid (CDC), glycodeoxycholic acid (GDC), and lithocholic acid (LC) were separated using adsorption TLC on aluminum plates precoated with silica gel 60 and on aluminum plates precoated with silica gel 60F₂₅₄. The plates were impregnated with 1%, 2.5%, and 5% aqueous solutions of the following salts: CuSO₄, MnSO₄, NiSO₄, and FeSO₄. The mixtures of n–hexane–ethyl–acetate–acetic acid in the volume compositions: 22:20:5 and 25:20:2 (v/v/v) for both aluminum plates, 22:22:5 (v/v/v) only for #1.05554 plates and 25:20:5 (v/v/v) for #1.05553 plates were used as mobile phases. These mobile phases were not effective for the separation of bile acids on non impregnated silica gel 60 and silica 60F₂₅₄ aluminum plates at 18°C. The plates impregnated with the salts whose application resulted in ΔR_F≥0.05 and R_S>1 for all neighboring pairs of examined bile acids were considered the most effective for bile acids separation. It was observed that impregnation of silica gel 60 and silica 60F₂₅₄ aluminum plates with aqueous solutions of CuSO₄, MnSO₄, NiSO₄, and FeSO₄ improved the separation of GC/GDC and C/GLC, which separated poorly on aluminum plates precoated with non impregnated silica gel 60 and 60F₂₅₄. Moreover, it was stated that the use of a mobile phase in volume composition 25:20:2 (v/v/v) and aluminum plates precoated with silica gel 60F₂₅₄ impregnated with a 5% aqueous solution of CuSO₄ made the separation of all neighboring pairs of investigated bile acids possible, in comparison with their separation on non impregnated aluminum plates.

Keywords:

• Bile acids
• Adsorption TLC
• Impregnation with metal cations
• Silica gel 60 aluminum plates
• Silica gel 60F₂₅₄ aluminum plates