Electrochemical behaviors and determination of melamine in neutral and acid aqueous media

The electrochemical behaviors of melamine (MEL) were studied at paraffin-impregnated graphite electrode in PBS (pH?7.0) and 0.5?M H₂SO₄. Various methods including UV?Cvis thin-layer spectroelectrochemistry, infrared spectra (IR) and electrochemicatry have been performed to investigate the characteristics. In 0.1?M PBS (pH?7.0), MEL loses two electrons to form a dication, which couples head-to-head with a neutral molecule of MEL to form a dimer accompanying the production of azocompound, the dimer plays a role of a monomer in the following polymerization. In 0.5?M H₂SO₄, unstable MEL mostly hydrolyzes to form ammeline, ammelide, s-triazine-2,4,6-trion, and tricyanic acid, respectively; The hydrolysis could be accelerated by electrochemical method; Meanwhile, MEL associates tricyanic acid to give a plane molecule cake by hydrogen bonding. The spectra responses of MEL at 205 and 234?nm are linearly increasing in a same concentration range of 1.0?×?10^?7?C1.0?×?10^?5?M in 0.5?M H₂SO₄ (determination limit, 1?×?10^?8 and 3?×?10^?8 (3??)). The proposed method was successfully applied to the determination of MEL in real sample.