Development And Application Of Portable Gas Chromatograph

Gas chromatograph, one of the most importantly general instrument in analysis field, plays a significant role for separation and detection of samples. However, the awkward features of the traditional gas chromatograph, such as big volume, heavy weight and long analysis time, impede the wide range application of analysis in situ.Compared with the traditional gas chromatograph, portable gas chromatograph has a broad market demand in the field of on-site rapid detection for the advantages of small volume, light weight and fast analysis speed. However, due to the reasons of weak foundation, lack of developers and the late start in domestic portable gas chromatograph related fields, the domestic market of portable gas chromatograph is monopolized by foreign analytical instruments, for example Agilent. For the purpose of elimination of technique monopoly and development of independent technique,an integrated portable gas chromatograph has been developed in this work, and the portable gas chromatograph which has the features of small volume, light weight,and fast analysis speed, has been successfully meeting the demand of the on-site rapid detection.Firstly, the distribution of airflow field in gasify room and the formation of electrostatic field in hydrogen flame ionization detector were modeled and simulated by COMSOL Multiphysics(a numerical simulation software), respectively. Basic on the guidance of simulation results, the geometry models of gasify room and hydrogen flame ionization detector were optimized, resulting in the reduction of dead volume in the gasify room and the improving of collection efficiency of charged particles in the hydrogen flame ionization detector.Then, on the basic of PID control principle, the temperature control module and gas control module were designed, respectively. The temperature control module,with accuracy of 0.1℃, was acquired by combination of Constant current source temperature measurement circuit, small power heating circuit and PID temperature control program. Also, the highly accuracy of pressure and flow rate, was achieved by combination of commercialized electronic pressure controller and PID pressure control program.Finally, the integrated platform of portable gas chromatograph was developed on the solid foundation of our previously studies, and the performance of gas chromatograph was tested. Preliminary test results showed as follows: a detection limit of 1.861×10-8 g/s, a qualitative repeatability of 2.152% and a quantitative repeatability of 10.401%. Also, a good correlation coefficient of 0.9966 wasobtained in range of 100-2000 mg/L. Subsequently, the detection of methylbenzene in seawater by combination of membrane extraction technology and our home-built gas chromatograph was demonstrated. The results showed that the detection concentration of methylbenzene in sea water reached 1 mg/L, and the detection range of methylbenzene in sea water was significantly expanded.