A stable and sensitive enzyme-linked immunosorbent assay (ELISA) for the determination of metsulfuron-methyl residues in foods

A hapten of metsulfuron-methyl was successfully designed and synthesized from 2-methylester-phenylsulfonamide and succinic anhydride, and the polyclonal antibody against metsulfuron-methyl was prepared by immunization procedure with the hapten-bovine serum albumin conjugate. A stable and sensitive direct competitive enzyme-linked immunosorbent assay (dcELISA) method had been developed under the optimal conditions. The sensitivity (IC50) was 37.03 +/- 1.87 mu g/L, and the detection line (IC15) was 1.57 +/- 0.11 mu g/L. Rice, wheat, oat, flaxseed, milk, and water were chosen to study the recovery test and the recovery rates were 83.11%-117.44% . The matrix effect was eliminated by a simple dilution of the sample extracts. The results from dcELISA were well agreement with the results from HPLC-MS. It was indicated that the developed method had good accuracy and stability. It could be applied for the detection of metsulfuron-methyl residues. It was worth mentioning that the antibody could recognize metsulfuron-methyl and tribenuron-methyl with cross-reactivities of 100% and 49.72%, respectively. In order to understand the cross-reactivity, molecular modeling including molecular alignment and electrostatic potential surfaces were introduced. It was found that the special group of metsulfuron-methyl played an important role, especially on C3 position of the phenyl group. Practical Application A stable, sensitive, and low-cost dc ELISA method had been developed with good accuracy and applied in the determination of metsulfuron-methyl in foods. Molecular simulation was introduced to understand the specificity between the antibody and the analyst. It was a good method to study the cross-reactivity between the antibody and the analyst or analogue.