It is demonstrated that the oxidation peak currents of Xa, A and T increased linearly with their concentration in the range of 4.0 10-8 - 1 10-4 mol/dm3 for Xa, 3.0 10-7 – 1.0 10-4 mol/dm3 for A, and 1.0 10-5 – 1.1 10-3 mol/dm3 for T with correlation coefficients of 0.996, 0.996 and 0.999, respectively.