Solid-phase extraction of melamine from aqueous samples using water-compatible molecularly imprinted polymers

A method for molecularly imprinted SPE of the melamine from environmental water samples was investigated. Cyromazine-imprinted polymers were synthesized in water-methanol systems for the selective extraction of melamine from aqueous samples, followed by HPLC analysis. Molecular recognition properties and binding capability to melamine were evaluated by adsorption test and Scatchard analysis, which showed the dissociation constant (KD) and the maximum binding quantity (Q(max)) were 0.032 mu mol/L and 4.77 mu mol/g for high affinity binding site, and 0.26 mu mol/L and 19.10 mu mol/g for lower affinity binding site, respectively. Under the optimum extraction protocol, the method can be successfully applied to selectively extract and enrich melamine in environmental water. The linearity was ranged from 0.500 to 100.0 ng/mL (r > 0.999) in tap water, lake water, and seawater analysis. When 50 mL of the water samples loaded, the LODs of the method were ca. 0.1 ng/mL, and the LOQs were ca. 0.5 ng/mL. The mean recoveries of melamine from blank water samples spiked at 0.5, 5.0, and 50 ng/mL were more than 86.3%, with the RSD less than 8.8%.