A new method for determining ternary mixtures of vitamin B1; B6 and B12 using second derivative
spectrophotometry is described. The procedure is accurate, nondestructive and does not require any
separation step or the solving of equations. Calibration graphs were linear up to 20 gml
−1 of vitamin B1 at 228.9 nm (r=0.9999), vitamin B6 at 309.6 nm (r=0.9999) and vitamin B12 at 361.7 nm (r=0.9998).
The method was successfully applied for analyzing synthetic mixtures and commercial pharmaceutical