大气中气相和颗粒相三氟乙酸浓度测定

Determination of Gaseous and Particulate Trifluoroacetic Acid in Atmosphere Environmental Samples by Gas Chromatography-Mass Spectrometry

建立了我国大气中气相和颗粒相三氟乙酸(Trifluoroacetic acid,TFA)的采集和分析方法。采用环形扩散管-滤膜联用装置分离气相和颗粒相,利用环形扩散管的碱性涂层吸附气相TFA,石英滤膜吸附颗粒相物质。对气相和颗粒相样品分别处理,以2,4-二氟苯胺作为衍生剂,与TFA反应生成TFA的苯胺产物,采用GC/MS进行分析。本方法在0.31～4.91μg/L浓度范围内呈线性关系(R2=0.9991),检出限为66 ng/L。采样装置回收率为(101±3)%,当采样量为48 m3,TFA大气浓度检出限为31 pg/m3。于2012年4～10月在北京大学采样点采集大气,测得其中TFA总浓度在501～7447 pg/m3范围,TFA在气相中的浓度大于在颗粒相中的浓度,气固分配系数Kp随温度变化。

Trifluoroacetic acid（TFA） concentration was measured in air samples by a sampling device composed of annular denuders coupled with a quartz filter,which was efficient for collection and separation of gaseous and particulate TFA.Gaseous TFA was performed by means of annular denuders coated with alkaline solution,while particulate TFA was absorbed by quartz filters.TFA can be determined by gas chromatography-mass spectrometry after derivation with 2,4-difluoroaniline.Calibration curves were linear with a correlation coefficient of 0.9991.Detection limit of TFA was 66 ng/L,which was 31 pg/m3 when sampling volume was 48 m3.Recoveries of the TFA sampling device ranged between 98% and 105% with relative standard deviation（RSD） ≤ 3%.The developed method was applied for the determination of TFA in atmosphere samples collected in Peking University in Beijing in 2012.Total TFA concentrations ranged between 501 and 7447 pg/m3.Concentrations of gaseous TFA were significantly higher than those of particulate,and the gas-particle partition coefficient of TFA decreased as air temperature rose.