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为减少对臭氧层的破坏,控制消耗臭氧层物质(简称ODS)及其他受控卤代烃的生产和消耗至关重要. 为此国际间先后通过了《关于消耗臭氧层物质的蒙特利尔议定书》及其相关修正案,定期开展科学评估,我国作为成员国之一,积极承担国际履约责任和义务,在消减ODS及其他受控卤代烃方面作出较多努力[1]. 目前,在我国除特殊用途外已禁止生产和消费ODS,但因ODS及其他受控卤代烃具有较长的大气寿命,部分可长达数万年,大气浓度存在滞后性,致使现今大气环境中仍可观测到相关物质[2] . 因此我国亟需开展以实际观测数据为基础的减排成效评估,通过大气浓度观测数据说明我国在履约工作方面作出的努力.
ODS及其他受控卤代烃在大气中含量较低,体积浓度大多数为10−12数量级,对方法的检出限、精度等要求较高,全球背景浓度水平较为稳定,不同城市浓度水平差异较大[3]. 目前美国、欧盟及日本等发达国家开展ODS及其他受控卤代烃的长期观测,监测点位多为人类活动较少的背景点位,所用观测设备以在线观测为主,主流设备为美国AGAGE自制的medusa/GC-MS、美国GML自制CATS-GC/ECD和HATs/GC-MS、欧盟SOGE在线GC/MS、日本自制的低温预浓缩-GC/MS,目前国际上所用的多为自制设备,方法的普及难度较大[4-8] . 中国在该方面的研究起步相对较晚,仅有较少的科研机构和高校开展了部分ODS及其他受控卤代烃观测和研究,采用的主流方法是基于环境空气中VOCs分析方法开发的罐采样-预浓缩-GC-MS/ECD[3, 9-12]。国内已有研究中方法检出限过高,导致样品无法检出,前处理需要大量的液氮制冷,气相色谱的柱箱初始温度较低(-50℃),种种原因导致开展相关监测工作的难度增大[9,12]. 环境空气中ODS及其他受控卤代烃的浓度较低、沸点较低,前处理装置的富集效率是该监测技术的关键环节[13],本文着重对前处理部分开展优化研究,采用电子制冷预浓缩系统-GC/MS方法对环境空气中33种ODS及其他受控卤代烃开展监测,无需液氮制冷,操作方法简单,检测成本低,监测目标物更多,检出限更低,分辨率、精密度、准确度均可满足环境大气浓度监测需求.
Determination of ODS and other controlled halogenated hydrocarbons in ambient air by electronic refrigeration preconcentration-GC/MS
- Available Online: 27/08/2022
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Key words:
- ozone-depleting substances /
- greenhouse gases /
- halogenated /
- electronic refrigeration preconcentration /
- GC/MS /
- ambient air.
Abstract: A method for the determination of 33 ozone-depleting substances (ODS) and other controlled halogenated hydrocarbons in air was established by using electronic refrigeration preconcentration-gas chromatography/mass spectrometry (GC/MS).The experiments include the optimization of focusing cold traps and pretreatment conditions, the comparison and conditioning experiments of the separation effects of different chromatographic columns. The optimal cold trap configuration scheme and experimental conditions were obtained, and the applicability of the method was investigated through the measurement of actual samples. The results of experiment showed that the correlation coefficients of calibration curves were above 0.99; their precisions were 0.5%—6.2%; When the injection volume was 800 mL, the method detection limits ranged from 0.07 pmol·mol−1 to 0.57 pmol·mol−1, and the lower limit of quantification was in the range of 0.28—2.28 pmol·mol−1. Through the analysis of actual samples of ambient air, it is suitable to analyse 33 ODS and other controlled halogenated hydrocarbons in ambient air.