A vitamin B 1 ion-selective electrode based on 1,2-dichloroethane-water (DCE/W) and nitrobenzene-water (NB/W) interfaces supported at the tip of a dual-section micropipette was examined by using cyclic voltammetry, asymmetric sweep rate cyclic voltammetry and stripping voltammetry. We have determined trace vitamin B 1 down to 4.6 10 - 6 mol l - 1 in aqueous sample solution. The response mechanism has been discussed and some relevant data of vitamin B1 transfer across NB/W and DCE/W interfaces were also obtained.