Designing of a Microelectrode Sensor-Based Label Free Milk Adulteration Testing System

A novel hand held micro-electrode sensor based on a label free impedance spectroscopy is fabricated for the detection of adulteration in milk. The results showed remarkable impedance change for different concentrations of starch and detergent in the milk sample in the frequency range of 0.05-5 kHz. The impedance of reference milk sample at resonant frequency 4.75 kHz was found to be 8.01E + 02 Omega and that of model milk sample adulterated with 10% (w/v) detergent was found to be 56% of the original value while the impedance of milk sample adulterated with 10% (w/v) starch was found to be similar to 160% of the original value of 8.01E + 02 Omega. Also, it was found that the change in the concentration of starch and detergent in milk samples changes the overall impedance of the sensor remarkably. The measured impedance values were inversely proportional to the concentration of detergent and directly proportional to the concentration of starch in the model milk samples. The observed trend is explained and highlights the selectivity and sensitivity of the device. The device requires only 0.2 mL of the sample and gives response within 10 s. The real and simulated data were fitted in an ac equivalent circuit model of the device operation.