The Study On The Key Technology Of Rapid Detection For Miniaturized Chromatograph

The gas chromatography is an important method for the separation and analysis of samples,As a modern analytical instrument,gas chromatograph plays an important role in food analysis,environmental analysis,petrochemical analysis,medicine and clinical analysis.However,due to the large volume,weight,power consumption and other factors,the traditional gas chromatograph can not meet the requirements of rapid analysis and detection on the spot.Because of its small volume,light weight,fast analysis speed and other factors,portable gas chromatography has a broader market demand.Due to the late start in China,the technology is not mature enough,so that domestic instruments in the domestic market share is very low.At present,the main problems of the portable gas chromatograph in China are that the separation efficiency is not high,the analysis speed is not fast enough,and the repeatability is poor.In order to solve these problems,a new type of portable rapid chromatographic system is developed in this paper.In order to realize the integration and intellectualization of the product,In the second chapter,the embedded hardware and software system are designed.Hardware includes circuit design,schematic drawing and PCB board production;Software includes driver programming,operating system porting and application and so on.In the aspect of improving the separation efficiency,to improve the peak overlap phenomenon in desorption by rapid heating means,invented a enrichment tube heating temperature measuring device.The utility model is characterized in that the platinum wire is used as a heating element and a temperature measuring element,to solve the problems caused by the traditional single point temperature measurement,such as uneven temperature,a patent has been granted,a patent has been granted.In the heating algorithm,through the improvement of temperature control algorithm to solve the problem caused by the rapid heating of the overshoot.The time delay curve of the sensor is fitted by studying the relationship between the heating rate and the overshoot,according to the delay time and the heating rate of the product to determine the size of the compensation value.In the aspect of increasing the heating rate,the LTM column with fast heating,small volume and low power consumption is adopted to replace the traditional column temperature box,according to the characteristics of the temperature sensor,a high precision differential amplifier circuit is designed.In the algorithm,the target temperature is divided into several sub intervals,and each interval is controlled by PID algorithm with first-order temperature compensation to improve the linearity of temperature rise.In the aspect of carrier gas control,the closed loop control method is adopted to improve the control accuracy of the carrier gas.The system consists of a mechanical gas flow control element proportional valve,a high precision flow sensor flow sensor and a flow acquisition and control circuit designed by the authors.According to the characteristics of proportional valve, the complex voltage and gas flow curve of proportional valve is fitted by means of inverse function.In the algorithm,the incremental PID algorithm is used to control the gas.