The Construction And Application Of Sensor Array For Raw Milk Detection Based On Electrochemical Method

The sensor array system for raw milk detection based on electrochemical methods consisted of a sensor array, a signal acquisition system and process control software based on computer or microcomputer operation. Through detecting and gathering electrochemical properties information of raw milk, constructed a standard raw milk database. And calculated the Mahalanobis distance (di) between sample xi to the center of the database, then the max one (dmax) was chosen to be reference standard, which was compared with the Mahalanobis distance (dj) between sample xj to the center of the database. If dj≤dmax, the ample was in the range of standard. If not, the suspicious samples need to be verified through follow-up testing. This paper mainly included the construction of voltammetric sensor array, optimization of the sensor array, investigation on diversity discrimination to several kinds of liquid milk with sensors and sensor array and application of the rapid detection system of raw milkThe first chapter summarized the current situation of raw milk and its adulteration, and nowadays commonly used detection technique; preliminary analyzed the advantages and defects of these methods. This chapter introduced the detection technical principle of the sensor array, and its research status in food, environment and other various study fields. And it summarized the technical route of constructing the rapid detection system for raw milk.The second chapter studied the constructing techniques and methods of voltammeric sensor array. Under the differential pulse voltammetry excitation signal, studied the characterization of the array on electrochemical active substances, and through the result, screened the arrays and preliminarily constructed the sensor array; using raw milk as object, studied the stability and data reproducibility of multi-sensor array. The result showed that three-electrode system, used platinum, gold, palladium, titanium, tungsten and silver inert precious metal bare electrode as the working electrode, platinum disk electrode as auxiliary electrode, and reference electrode of aqueous Ag/AgCl, the multi-sensor array had a good detection stability and data reproducibility in raw milk detection.The third chapter studied the combinatorial optimization, and performance verification of the optimize sensor array. Using fresh raw milk, pasteurized milk, stale milk, rancid milk and two types of adulterated stale raw milk as the study object, Under the differential pulse voltammetry excitation signal, calculated the coefficient of variation (CV) through the response current signal on the above six categories of samples collected by the sensor array, and obtained the mean value of coefficient of variation. Regarding CV<5as a standard, re-screened sensors to construct the array, then combined the selected sensors and studied the combination performance of the sensor array by principal component analysis, to select the optimal array combination as the sensor array of detection system of raw milk. And verified its performance under cyclic voltammetry excitation signal. The results showed that using palladium, platinum, gold and titanium electrode as working electrodes, the array had the best distinguish effect among different samples, so it was the most optimal array combination.The fourth chapter stated investigation on diversity discrimination to raw milk and several kinds of liquid milk with sensors and sensor array based on the interactive sensitivity-relative selectivity theory. And to detect the electrochemical properties changes of different kinds of liquid milk during its’storing and manufacturing. Dealing with the data gathered from different kinds of liquid milk with sensors and sensor array in PCA and CA pattern recognition methods. The result showed that the single sensor can, in a degree, discriminate the diversities between different kinds of liquid milk. And the discrimination efficiency of different sensors the samples mentioned upon have some non-relativity. The construction of sensor array could improve its discrimination capability. And all the diversities between different types of liquid milk demonstrated the processes of different kinds of liquid milk get its’ electrochemical properties changed at the meantime.The fifth chapter mainly studied the practical application of the new system. First detected the physical and chemical indicators of raw milk by GB methods, selected the qualified samples and removed some samples whose index data had a large deviation. The left samples were used for the electrochemical response signal acquisition to established standard raw milk database. Under differential pulse voltammetry excitation signal, collected electrochemical response signal of selected samples by the optimized sensor array, then analyzed the data and established database model by distance discrimination analysis. The results showed that the sensors were able to correctly detect qualified raw milk, and the construction of sensor array could effectively improve the detection system classification rate of qualified raw milk samples. The application of rapid detection system for raw milk detection achieved initial success.The sixth chapter is the summary and outlook of this study. It stated constructing a new detecting system for raw milk, which is a judge system based on sensor array. It also described the application future of this sensor array system.