Formation of triazene from sulphonamide and nitrite in acidic solution

Formation of triazene derivatives from sodium nitrite and sulphanilamide, sulphamethizole or sulphamethoxazole in acidic solution containing saliva or canned vegetable juice was studied using reverse-phase high-performance liquid chromatography with ultraviolet light detection at 365 nm. At the optimal pH of 3.2-3.7, the mean yield of the triazene formed by reaction of sulphanilamide and nitrite in saliva was 28.8%, calculated on the nitrite content, and there was a high positive correlation (r = 0.993) between the nitrite concentration in the saliva and the triazene yield. In contrast, at the optimal pH values for triazene formation from sulphamethizole and sulphamethoxazole (3.0-3.5 and 2.5-2.9 respectively), triazene yields were much lower, accounting for only 0.9 and 1.0%, respectively, of the nitrite present. Triazene formation was partly inhibited in the presence of vegetable juice.