The Temperature Control System Research Of Micro GC For Pesticide Residues Detection

GC technology occupies an important position in the field of Analytical Chemistry. With the ability to separate and detect complex mixtures, it has been widely used in petroleum industry, chemical industry, agriculture and other industries. In recent years, portable and micro gas chromatographs have become a hot issue for rapid in-situ detection because of traditional GCs’complex structure and large size. As core of the GC control system, the study of portable and micro temperature control system is also an emphasis for Micro GC.In this work, two kinds of heating method are designed for heating chromatographic columns. The first one is to heat columns with miniature chromatographic box. Another one is to straightly heat columns by stainless steel capillary. For the first heating structure, an embedded system of GC temperature control was developed, which is based on the Micro2440 board and Linux. This structure simplifies the temperature control circuits and greatly reduces its size.This temperature control hardware system consists of Micro2440 board, its three ADC ports and three GPIO ports. Three ADC and GPIO ports are applied to control temperature system of injector, chromatographic columns box and detector. The main program gets the current temperature by the sampling module, which is used as a parameter to calculate the heating time through PID with single neuron algorithm, and then turns on heating circuits to heat controlled unit for the calculated time. The Proportion, Integral and Derivative coefficient of PID are dynamic adjusted by the single neuron algorithm based on supervised Hebb rule.Finally, the heating experimental results show that the temperature control system meets the required accuracy of ±0.5℃, and can realize process heating function. And the Micro GC equipped with this temperature control system successfully detects dichlorvos, trichlorfon and other organophosphorus pesticide residue in laboratory.