The newly developed method is suitable for the determination of 8-AQ in the presence of 6-AQ in the concentration range of 8-AQ 2 – 10·10-6 mol·L-1 in the presence of 6-AQ of concentration from 0 to 4·10-6 mol·L-1 and for determination of 6-AQ in the presence of 8-AQ in the concentration range of 6-AQ 2 – 10·10-6 mol·L-1 in the presence of 8-AQ at concentration from 0 to 10·10-6 mol·L-1.