Low temperature synthesis of carbon dots in microfluidic chip and their application for sensing cefquinome residues in milk

In this study, the N-doped carbon dots were continuously synthesized by a facile microfluidic strategy at 90 degrees C, and their quantum yields reached 19.2%. The characteristics of the obtained carbon dots could be real-time monitored in order to synthesize carbon dots with specific properties. By incorporating the carbon dots into a well-established enzymatic cascade amplification system, an inner filter effect-based fluorescence immunoassay was set up for ultrasensitive detection of cefquinome residues in milk samples. The developed fluorescence immunoassay provided a low detection limit of 0.78 ng/mL, which satisfied the maximum residue limit set by authorities. The fluorescence immunoassay had an 50% inhibition concentration of 0.19 ng/mL against cef-quinome and showed a good linear relationship from 0.013 ng/mL to 1.52 ng/mL. While, the average recovery values ranged from 77.8% to 107.8% in spiked milk samples, with relative standard deviations ranging from 6.8% to 10.9%. Compared with conventional methods, the microfluidic chip was more flexible on carbon dots synthesis and the developed fluorescence immunoassay was more sensitive and eco-friendlier for ultra-trace cefquinome residue analysis.

Automated summary

N-doped carbon dots were synthesized using a microfluidic strategy at 90 degrees C, with a quantum yield of 19.2%. The properties of the carbon dots were monitored in real-time to synthesize dots with specific properties. The carbon dots were incorporated into an enzymatic cascade amplification system, enabling ultrasensitive detection of cefquinome residues in milk samples. The developed fluorescence immunoassay had a low detection limit, good linear relationship, and high recovery values, making it more sensitive and eco-friendly compared to conventional methods for cefquinome residue analysis.