Label-free impedimetric immunosensor for sensitive detection of 2,4-dichlorophenoxybutyric acid (2,4-DB) in soybean

Electrochemical impedance immunosensor, with its high sensitivity from electrochemical impedance analysis and ideal specificity from the immunoassay, is increasingly used in the detection of a kind of phenoxy acid herbicides which is 2,4-Dichlorophenoxybutyric acid (2,4-DB). In this experiment, synthetic 2,4-DB antibodies were immobilized on the electrode by the crosslinking of l-Cysteine/glutaraldehyde, and 2,4-DB were measured by the increase of electron-transfer resistance when the immune reaction occurred, with Fe(CN)63−/Fe(CN)64− as the probe. Under optimal conditions, the change of resistance is in a linear relationship with the logarithm of the concentration in the range of 1.0×10−7–1.0×10−3 g/L (R=0.994) with the detection limit of 1.0×10−7 g/L (0.1 ppb). This method bears such merits as simplicity in operation, high sensitivity, wide linear range, specificity, reproducibility and good stability. The actual soybean samples were analyzed with the recovery of 82.8%–102.3%.