光离子化检测器的电离室结构优化与实验研究

针对光离子化检测器(Photo Ionization Detector),通过原理研究,利用COMSOL进行了气流场和静电场的仿真,在仿真结果的指导下,进行了结构优化,使气室死体积大幅度缩减,并得出偏置电压与收集效率之间的关系.使光离子化检测器的带电离子收集效率大幅提升.开发了低干扰和快速响应的电离室.在确定最佳流量为50 mL,紫外灯电离能为10.86 eV的情况下,针对VOC气体(甲苯)进行实验,确定偏置电压为150 V时,离子收集效率可达到85%,且光离子化检测器线性度良好,相关系数为99.84%,最低检测限可达到ppb级.其检测结果符合仿真结果中偏置电压与响应值的关系.

The Experimental Study and Structural Opitimzation of Ion Chamber in Photo-ionization Detector

The simulation of gas flow field and electrostatic field in the Photo Ionization Detector by COMSOL was conducted in the present study based on principle investigation,and by the results of which to achieve the target of structural optimization so as to have the dead volume significantly reduced,and finally the relationship between offset voltage and collection efficiency was obtained. Which led to a remarkable increase of collection efficiency by the charged ions in the Photo Ionization Detector. And an ionization chamber with both low interference and fast re-sponse was then developed. Then experiment performed with toluene as a VOCs gas under the condition of optimal gas flow rate of 50 mL,ionization energy of 10.86 eV of the UV lamp,and the results showed that,in the case of off-set voltage of 150 V,the ion collection efficiency reached 85%,moreover,a preferable linearity of 99.84% of the Photo Ionization Detector was obtained,and the a ppb level of LOD can be achieved. The determination results well fitted the relationship between offset voltage and the response value obtained in the simulation.