大气有机物热脱附-全二维气相色谱-火焰离子化分析方法

Analysis of atmospheric organic compounds by thermal desorption-comprehensive two-dimensional gas chromatography-flame ionization detection

全二维气相色谱(GC×GC)是20世纪90年代发展起来的具有高分辨率、高灵敏度、高峰容量等优势的分离技术,在我国将其用于大气挥发性有机物(VOCs)研究方面才刚刚起步.本文将GC-GC与氢火焰离子化检测器(FID)联用,构建了用于测量大气有机物的热脱附-全二维气相色谱-氢火焰离子化分析系统(TD-GC×GC-FID).采用HP-5MS和HP-INNOWAX色谱柱,建立了C5-C15大气有机物分析方法,实现了一次分析过程同时分离非甲烷烃(NMHCs)、含氧挥发性有机物(OVOCs)和卤代烃等多种组分.利用标准物质和四级杆质谱(qMS)进行定性,外标法结合FID质量校正因子定量.目标物在GC-GC谱图中第一和第二维保留时间变化分别小于0.6s和0.02s,峰体积平均相对标准偏差为14.3%,其中烷烃和芳香烃为4.5%.标准曲线r2均值大于0.99,平均检出限为6.04ng,平均回收率为111%.利用该方法检测到2010年1月北京市区大气中400多种有机物(信噪比大于50),鉴定了其中的103种物质,包括烷烃、烯烃、芳香烃、卤代烃、醛、酮、酯、醇和醚等.所测定有机物平均总浓度为51.3×10-9V/V,其中OVOCs约占51%,芳香烃约占30%,烷烃约占15%,卤代烃和烯烃分别占3%和1%.平均浓度最高的前3个组分是乙醇(9.84×10-9V/V)、丙酮(6.72×10-9V/V)和甲苯(3.48×10-9V/V).

As a new separation technology developed in the 1990s,comprehensive two-dimensional gas chromatography（GC？GC） has many advantages,such as high resolution,high sensitivity,and large peak capacity.In this work,a GC-GC system coupled with a flame ionization detector（FID） was set up for the measurement of atmospheric organic compounds.Using a thermal desorption（TD） as injector and a cold/hot jet modulator for the GC×GC modulation,the TD-GC×GC-FID system is able to separate various types of C5-C15 atmospheric organic compounds within only one chromatographic run,including non-methane hydrocarbons（NMHCs）,oxygenated volatile organic compounds（OVOCs） and halogenated hydrocarbons.Qualitative analysis was made using a quadruple mass spectrometer in combination with standard gases,and quantitative analysis using external standards combining with FID mass correction factors.The mean standard deviations of the first and second dimension retention times of the target compounds are less than 0.6 s and 0.02 s,respectively.The mean relative standard deviations of the peak volumes are 4.5% for NMHC and 14.3% for all compounds.The average r2 of the calibration curve exceeds 0.99.The average detection limit is 6.04 ng and the average recovery is around 111%.In the analysis of air samples from an urban site in Beijing January,2010,more than 400 peaks of organic compounds was detected,of which 103 compounds have been identified including alkanes,alkenes,mono-and poly-aromatics,aldehydes,ketones,alcohols,esters,halogenated hydrocarbons,etc.The total concentration of the quantified constituents averaged 51.3×10-9 V/V.The proportions of OVOCs,aromatics,alkanes,halogenated hydrocarbons,and alkenes were approximately 51%,30%,15%,3%,and 1%,respectively.The top 3 components was ethanol（9.84×10-9 V/V）,acetone（6.72×10-9 V/V）,and toluene（3.48×10-9 V/V）.The TD-GC×GC-FID system can be used as a platform for simultaneous measurements of different groups of atmospheric organic compounds.