The Detection Of Heavy Metal Pb(Ⅱ) In Fruit Based On QCM

At present, with the development of industrialization, the whole community is facing heavy metal pollution is more and more serious, especially in the food industry, which has put forward higher requirements on the detection of heavy metals in food. Compared with other detection methods, quartz crystal microbalance(QCM) as a new type of sensor technology has reach nanogram level measurement accuracy, simple device, convenient operation, good portability and low cost advantages in many fields has been deeply researched and widely used.With the rapid development of electronic information industry and gradually improvingof the measurement requirements,quartz crystal microbalance gradually towards the direction of digital,portable,high frequency stability develop.which put forward higher requirements upon frequency measurement accuracy, stability, and operability etc.Quartz crystal microbalance is based on the characteristics of piezoelectric quartz crystal, the oscillation of the quartz crystal caused by the differential frequency circuit; The surface quality of adsorption arised in the piezoelectric material can cause the change from the frequency of the sensor. Micro changes in quality can be measured by the measurement of frequency, which can be used to measure the content of heavy metal ions in fruits.theresonant frequency of quartz crystal will vary with the size of the adsorption material quality.The core component of the QCM sensor is a quartz crystal sandwiched between in the electrodes,when the electrode is connected with the oscillator and exert the electric field,quartz crystal is because the piezoelectric effect and the resonant frequency of the oscillation.First of all,this paper briefly introduces the present of the development history and application area of the QCM,at present all kinds of heavy metal ions in food detection method, and then through the quartz crystal piezoelectric characteristics and vibration mode arised the measuring principle of the QCM sensor in the liquid phase,and briefly introduces the various factors affecting with the operation of the QCM sensor system,and then the electrode and substrate of the QCM probe is designed on the basis of trap theory; combined with the design need to choose a modified Pearce oscillation circuit in order to make the system better maintain resonance, processing of sensor system frequency measurement signal; design a frequency meter,which can directly show the frequency, and burn the program; construct a QCM testing platform completely. Finally using Sauerbrey equation as the theoretical basis for detecting heavy metal lead ion in fruits.The experiment results show that:demonstrated the feasibility of using the QCM sensor detection heavy metal ions in fruit,the measurement have a goodresult,but still needs to be improved in many aspects if you want to put into practical application.For example: the measurement results have mainly difference and bad veracity compared to measured data of the standard method;film material can only measure one substance,only one measurement indicators;theoretical study on selection of membrane materials have to be strengthened;Because the micro measurement of material, the higher requirement to the operator.