Abstract
A polyacrylamide-based molecularly imprinted hydrogel (MIH) doped with positively charged gold nanoparticles (Au NPs) has been synthesized via a free radical polymerization of acrylamide (AM) aqueous solution containing positively charged Au NPs as a Raman active substrate, New Red colorant as a template molecule, N,N’-methylenebis(acrylamide) as a crosslinking agent, and potassium persulfate as an initiator. The Au NPs-doped MIHs were subsequently explored as a Raman active substrate for the sensitive and selective detection of New Red colorant via surface-enhanced Raman spectroscopy (SERS). The logarithmic intensity of the characteristic peak of New Red at 1572 cm−1 was proportional to the logarithmic concentration of New Red with a detection linear range of 1.64 × 10−6 to 1.64 × 10−4 M and a limit of detection (LOD) of 1.64 × 10−7 M. The recoveries ranged from 86.3% to 100.6% with a relative standard deviation (RSD) in the range of 2.3% to 7.7%. The RSD and recovery rates for the detection of New Red spiked in a sports drink sample were 1.8% to 7.7% and 91.0% to 97.1%, respectively. These results showed that SERS combined with MIHs as Raman active substrates could provide a sensitive, selective, and effective approach for the detection of the New Red colorant in beverage matrix.
Highlights
New Red is a water-soluble azo synthetic colorant, which was synthesized by Chinese researchers [1] and permitted for use only in China
N = 3). standard deviation (RSD) of the detection of New Red spiked in water samples
The molecularly imprinted hydrogel (MIH) which were synthesized via a free radical polymerization of acrylamide aqueous solution containing positively charged Au NPs, New Red, and N,N’-methylenebis(acrylamide) exhibited high selectivity and specificity to New Red
Summary
New Red is a water-soluble azo synthetic colorant, which was synthesized by Chinese researchers [1] and permitted for use only in China. New Red can be used in beverages, decorative fruits and vegetables, candies, and other foods in China according to Chinese national standard GB2760-2014. The maximal addition limit for New Red is 50.0–100 μg/kg in foods and beverages in China according to GB2760-2014. New Red might be illegally used because of its advantages of low price, high solubility, effective tinting, and good stability. In order to prevent food fraud and for food safety reasons, there remains an urgent need to develop a sensitive, selective, rapid, and effective analytical method for detection of New Red in food and beverage matrix
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