A maximum wave which is observed ca. -1.5 V vs NCE in a solution containing 1mM CoCl_2,0.1 M NH_4Cl, 0.1 M NH_3,is usefull for determination of thiamine in multi-vitamin preparations. Niacin amide in such preparations can be determined by means of the reduction wave E1/2-1.86V in 0.1N NaOH. In such conditions the other vitamins do not disturb the determination.
