Under optimal conditions the increase of oxidation peak currents was proportional to concentration of Xa in the range from 4.0 ∙ 10-8 mol/dm3 to 1.0 ∙ 10-4 mol/dm3 (R2=0.996), of A from 3.0 ∙ 10-7 mol/dm3 to 1.0 ∙ 10-4 mol/dm3 (R2=0.996), and of T from 1.0∙10-5 to 1.1∙10-3 mol/dm3 (R2=0.999).