Nitrate in food stuff can be reduced to nitrite and may form nitrosamines which are known as carcinogenic substances. Thus, its concentration has to be controlled by highly sensitive methods. In this work a new and fast differential pulse polarographic (DPP) method is established for the determination of nitrate. According to the reduction potentials V(II) was found most suitable for the reduction of nitrate. The product of this reaction is V(III) and its polarographic peak is high and sharp, it also displays very good performance in regard to reproducibility. Thus, with this method it is possible to determine low concentrations of nitrate. This reaction has been used first time in this work. The optimum conditions for the quantitative reaction between nitrate and V(II) has been studied. This method is applied to potato samples and nitrate is determined.