In this investigation a differential pulse polarographic method (DPP) is established to determine the electroinactive arsenic (V), which is formed after the wet digestion of the natural samples. For this purpose, As(V) formed is reduced into As(III) using Ti(III). According to the literature survey this redox reaction between As(V) and Ti(III) has been used first time in this work. In order to have the reaction quantitative the optimum reaction conditions such as Ti(III)/As(V) concentration ratio, reaction pH, waiting time for reaction and temperature had to be investigated. It was found that Ti(III)/As(V) concentration ratio had to be larger than 3-5 times, HCl concentration 0.4 to 1.0 M, reaction temperature 60 - 90 degrees C and waiting interval 3-5 minutes. Under the experimentally decided conditions the reduction was very fast and quantitative. No interference was observed from most common ions. The LOD was found as 1.5x10(-7) M. The newly developed method is applied for the determination of arsenic in beer. The reduction procedure takes place directly in polarographic cell. This newly developed method can safely be used for the speciation of As(III) and As(V) and for total arsenic quantity determination in natural samples.