光离子化传感器在全二维气相色谱仪检测环境VOCs中的应用

Photo-ionization Sensors as Detectors in GC×GC Systems for Ambient VOCs Measurements

热脱附-气相色谱-质谱仪(TD-GC-MS)和热脱附-气相色谱-氢火焰离子化检测器(TD-GC-FID)是目前检测大气挥发性有机化合物(volatile organic compounds,VOCs)的常用仪器,但这些仪器比较笨重、昂贵且能耗高。本研究采用低成本的微型光离子化检测器(photo-ionization detector,PID)检测VOCs气体,其中对异戊二烯(C5H8)体积分数的检出限(limit of detection,LOD)可低至0.02×10-9。采用PID作为自主研制的微型全二维气相色谱仪(GC×CC)的检测器进行环境VOCs检测,所检测的结果与常规TD-GC-FID检测的结果非常一致。自制的微型GC×CC更便携、成本更低、能耗更低,适用于野外大气环境VOCs的检测。使用PID作为气相色谱-四极杆飞行时间质谱仪(GC-Q-TOF-MS)的第二检测器,并比较了PID与质谱仪在检测VOCs时的性能。结果显示PID的检测结果与质谱仪的检测结果非常一致,但PID的检测灵敏度略逊于质谱仪。进一步研究发现PID传感器可用于有毒有害物质的快速检测,并且不同电离能的灯源对PID传感器的检测性能有影响。装有11.7 eV电离灯的PID可检测出8种有机硫化物和4种有机磷酸盐物质,而装有10.6 eV电离灯的PID只能检测出2种物质。本研究证明低成本的PID可作为微型GC×CC和常规GC的检测器,应用在环境VOCs的检测领域。与其他检测器(FID或MS)相比,PID传感器体积小、价格低廉、工作条件简单、能耗低,更适合作为便携式检测器。

Thermal desorption-gas chromatography-mass spectrometry(TD-GC-MS)and thermal desorption-gas chromatographyhydrogen flame ionization detector(TD-GC-FID)are commonly used instruments for the detection of volatile organic compounds(VOCs)in the atmosphere.This study used a low-cost miniature photo-ionization detector(PID)to detect isoprene,and the detec⁃tion limit was as low as volume fraction of 0.02×10-9.The PID was used as the detector of the self-developed compact two-dimen⁃sional gas chromatography(GC×GC)to detect ambient VOCs.The detection result was consistent with that of the conventional TDGC-FID detection.However,the self-made miniature GC×GC was more portable,with lower cost and energy consumption,and suit⁃able for the detection of VOCs in the field.The PID was also used as the second detector of gas chromatography-quadrupole-time of flight-mass spectrometer(GC-Q-TOF-MS),and the performance of PID and mass spectrometer in detecting VOCs was com⁃pared.The results show that their detection results were consistent,but the detection sensitivity of PID was slightly inferior to that of mass spectrometer.The application of PID sensor for rapid detection of poisonous and harmful substances was further studied,and the influence of different ionization energy of light source on the PID detection performance was examined.It was found that PID with lamp of 11.7 eV ionization can detect eight kinds of organic sulfide and four kinds of organic phosphate material,but only two kinds of material with lamp of 10.6 eV ionization.This study proves that low-cost PID can be used as a detector for micro GC×GC and conventional GC,especially applied in the field detection of ambient VOCs.Compared with other detectors(FID or MS),PID sensor is more suitable for portable instruments due to its small size,low price,simple working condition and low energy con⁃sumption.