Synthesis of a molecularly imprinted polymer for the selective recognition of carmoisine (Azorubin E122) from pomegranate juice

Since natural pigments are lost during the processing of beverages such as pomegranate juice, carmoisine,
as an adulterant, is often added into the pure juice to improve color characteristics. In this study, molecularly
imprinted polymers, as an adsorbent of carmoisine, were synthesized using acrylamide, methacrylic
acid, and 4-vinylpyridine as functional monomers and then they were evaluated in terms of the separation
and detection of carmoisine. Experiments on the batch adsorption of carmoisine 10 ppm stock solution
revealed a better binding capacity for the 4-vinylpyridine-based polymer in comparison to methacrylic
acid and acrylamide polymers. The complexation of carmoisine with the 4-vinylpyridine-based polymer
was confirmed by Fourier transform infrared spectroscopy. The synthesized polymer exerted a high thermal
degradation point and average diameter of polymer particles were obtained to be 0.2 μm by dynamic
light scattering analysis. This work showed that detection of pomegranate juice adulteration with carmoisine
is not necessarily difficult, time consuming or expensive with selective separation techniques such as
molecularly imprinted polymers.