Abstract:

Based on cafalexin monoclonal antibody, an indirect competitive enzyme-linked immunosorbent assay (ELISA)
to determine cefalexin residues in milk was established. The linear detection range of the ELISA method in milk was 1.0
to 50.0 ng/mL, with limit of detection of 1.0 ng/mL, and IC50 value of 4.1 ng/mL. The recovery rates for spiked milk with
50, 100 ng/mL and 200 ng/mL of cafalexin were 96.0%, 98.2% and 93.3%, respectively. Satisfactory cross-reactivity of the
antibody with cefradine, cefadroxil, cefaclor and cefixme was also observed (160.0%, 80.0%, 28.4% and 3.7%, respectively).
In addition, a simple and effective sample extraction method was established. The ELISA assay was validated by comparing
its results with those obtained by using UPLC-MS-MS, with a good correlation (R2) of 0.9988.

Key words: cefalexin, monoclonal antibody, indirect competitive ELISA, milk, residue detection, UPLC-MS-MS