A quantitative t.l.c. densitometric method for the simultaneous determination of the water-soluble vitamins B1, B2, B6, and B12 is proposed. The four vitamins are determined on one and the same plate by direct densitometry of the t.l.c. spots. A preliminary separation of the vitamins one from another, as well as a preliminary separation from other pharmaceuticals is not necessary. The determination is performed quickly and easily. The relative standard deviations of a single determination are the followingfor thiamine 6,6%, for riboflavin 5,5%, for pyridoxine 6,4%, and for cyanocobalamin 5,8%.

The proposed method is applied to the determination of B-vitamins in three pharmaceutical preparationsampoules B12 with B1, ampoules B-complex, and antisclerol dragee. The presence of other pharmaceuticals (vitamins C and PP, urethane, aminophenazone, phytin, rutin, theobromine, etc.) does not interfere with the determination.