Highly sensitive and selective colorimetric sensing of antibiotics in milk

• A colorimetric strategy for sensing four antibiotics was proposed.
• Hydrogen bond between pyrocatechol violet and antibiotics played an important role.
• This strategy can be applied in the pretreated liquid milk products.

Antibiotics residues in foods are very harmful to human beings. Determination of antibiotics residues relies largely on the availability of adequate analytical techniques. Currently, there is an urgent need for on site and real time detection of antibiotics in food. In this work, a novel one step synthesis of gold nanoparticles (AuNPs) was proposed using pyrocatechol violet (PCV) as a reducer agent. Highly sensitive and selective colorimetric detection of four antibiotics kanamycin mono sulfate (KA), neomycin sulfate (NE), streptomycin sulfate (ST) and bleomycin sulfate (BL) was realized during the formation of AuNPs. PCV has OH groups and these antibiotics have OH, NH2, NH groups, so there may be some special hydrogen-bonding interactions between PCV and these antibiotics. Therefore, the presence of KA, NE, ST and BL would influence the synthesis of AuNPs, then the color and state of AuNPs would change, which could be observed with the naked eye or a UV–vis spectrophotometer. Results showed that A670 was linear with the logarithm of KA concentration in the range from 1.0 × 10−8 to 5.0 × 10−7 M and 5.0 × 10−7 to 5.5 × 10−5 M. The detection limit of KA was 1.0 × 10−9 M (S/N = 3). The coexisting substances including 1.0 × 10−5 M phenylalanine, alanine, glycerol, glucose, Mg2+, Ca2+, Na+, K+, CO32−, SO42−, NO3−, Cl− and Br− did not affect the determination of 1.0 × 10−7 M antibiotics. In particular, the proposed method could be applied successfully to the detection of antibiotics in the pretreated liquid milk products.

The presence of antibiotic substrates kanamycin mono sulfate, neomycin sulfate, streptomycin sulfate and bleomycin sulfate influence the synthesis of AuNPs, including the color and state of AuNPs, which could be used to detect antibiotic substrates with the naked eye or a UV–vis spectrophotometer.Figure optionsDownload as PowerPoint slide