Label-free impedimetric immunosensor for sensitive detection of fenvalerate in tea

•EIS was employed for the first time employed to determine fenvalerate.•Pre-treatment for the detection is simple in operation with this technique.•This method is label-free with high sensitivity and selectivity, rapidity and low cost. In this experiment, fenvalerate antibodies were immobilised on the electrode by the crosslinking with glutaraldehyde modified on the glassy carbon electrode (GCE) via chitosan. Fenvalerate was 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 1.0×10−3∼1.0×101mg/L (R=0.998) with a detection limit of 0.80μg/L. This method bears such merits as simplicity of operation, high sensitivity, wide linear range, specificity, reproducibility and good stability. The immunosensor was applied in the detection of real samples of tea, achieving satisfactory results, and it could be regenerated after being placed alternately in 0.5mol/L HCl and 0.5mol/L NaOH solutions.