Sintesis hapten asam 4-(4, 6-diamino-1,3, 5- triazin- 2- ylamino) butanoat dan pembentukan konjugat hapten protein untuk deteksi selektif melamin = Synthesis of hapten 4- (4, 6- diamino- 1, 3, 5- triazine- 2- ylamino) butanoic acid and the formation of hapten protein conjugate for selective detection of melamine