Detection of dichlorvos residue by flow injection calorimetric biosensor based on immobilized chicken liver esterase

A flow injection calorimetric biosensor for dichlorvos residue detection is developed. This biosensor consists of a peristaltic pump, an injection valve, a thermoelectric thermostat, two cells (an enzyme reaction cell and a reference cell), a thermopile sensor and a computer. The reaction temperature of mix solution is stabilized at 40 °C by the thermostat when the solution is pumped by the peristaltic pump. Chicken liver-esterase as an alternative of acetyl cholinesterase is used as the bio-recognition component. The enzymatic reaction takes place in the enzyme reaction cell when substrate is introduced into the system by injection valve. The identical reference cell is used to eliminate virtually the influence of unspecified heat, which is not produced by the enzymatic reaction. A thermopile sensor, containing 127 pairs of BiTe thermocouples, is used to measure the temperature difference of the two cells. Thermoelectric potential caused by enzymatic reaction without inhibition is about 5 mV. The enzymatic reaction is inhibited at 30.7% and 41.8% by 1 mg/L and 10 mg/L of dichlorvos respectively, when the flow rate is 1.0 mL/min, incubation time is 10 min and the activity of immobilized enzyme is 0.83 U/g. The experiments demonstrate that this calorimetric biosensor can be used as a simple and rapid method for on site pesticide detection.