The effect of chlorophyll on the enzyme‐linked immunosorbent assay (ELISA) of procymidone in vegetables and the way to overcome the matrix interference

BACKGROUND There is now an increasing demand for the immunoassay of procymidone residue in foodstuffs. However, the matrix interference could significantly affect the analysis. Till now there is no detailed information on the source of the interference and the mechanism involved, which greatly limits the real application of these techniques. RESULTS Significant matrix effect was observed in the enzyme‐linked immunosorbent assay (ELISA) of procymidone in negative vegetable samples (leek, broccoli and cucumber). By the investigation with both vegetable extracts and standard solutions, the chlorophyll was confirmed as an important source of the matrix effect. Therefore, a new strategy was proposed for the pretreatment based on the exploitation of 5‐sulfosalicylic acid. It was demonstrated to effectively eliminate chlorophyll and exhibited little effect on procymidone and the competitive indirect ELISA (ci‐ELISA) performance. The established technique was validated with different vegetables. With the spiking concentration of procymidone investigated, the recovery rate of ci‐ELISA was 71.52–120.37%, and the relative standard deviation was 4.05–17.61%. CONCLUSION Chlorophyll was for the first time illuminated as an important source of matrix interference to the immunoassay of procymidone in vegetables. A new pretreatment based on 5‐sulfosalicylic acid was established to remove chlorophyll and therefore eliminate the matrix effect. Validated with different vegetable samples, the new technique was demonstrated much better efficiency in comparison to conventional methods, which indicated its promising application for the development of immunoassays of herb‐origin samples. © 2021 Society of Chemical Industry.