A new QCM sensor characterization technique based on the phase/mass sensitivity concept

Quartz crystal microbalance (QCM) technique is widely used in in-liquid biochemical applications. The main challenges remain on the improvement of sensitivity and limit of detection, as well as multianalysis capabilities and reliability. The improvement of sensitivity has been addressed in the last decades by increasing the sensor fundamental frequency; following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of limit of detection. A new concept of sensor characterization has been recently proposed based on the phase/mass sensitivity equation: Δφ/Δm ≈-1/m_L, where m_L is the liquid mass perturbed by the resonator in its oscillatory movement; this mass reduces proportionally with the frequency square root. The validation of the new concept is presented in this work. An immunosensor application for the detection of the very low molecular weight insecticide, carbaryl, has been chosen for the validation of the characterization technique.