Synthesis and sorption performance of highly specific imprinted particles for the direct recovery of carminic acid

Carminic acid (CA) is a colorant of natural origin, which is demanded by the food, cosmetic, and pharmaceutical industries. In this work, a selective finite bath process was developed based on the utilization of molecularly imprinted polymeric particles. Such adsorbent was synthesized in a (porous) particle shaped form employing methacrylic acid (MAA) and 4-vinylpyridine (4Vpy) as monomers and ethylene glycol dimethacrylate (EDGMA) as a cross-linker. The imprinted particles were characterized by surface area, surface charge and pore size determination. The adsorption behavior of CA on such a material followed a Langmuir-Freundlich isotherm. Maximum capacity at equilibrium reached 0.64 mmol/g (316 mg/g) and maximum available binding sites 1.8 mmol/g (917 mg/g) were observed for an association coefficient value of 1.5 mM(-1). Further, the imprinting factor; showing the strength of interaction of CA to the polymer, was calculated as 13 while the selectivity factor depicted a value of 15. The data presented indicates that the imprinted adsorbent could be conveniently utilized for the recovery of CA, from cochineal extract, in the finite bath mode of operation. (C) 2012 Published by Elsevier Ltd.