热解析-GC／MS方法测定大气中的羰基化合物

MEASUREMENT OF AMBIENT CARBONYLS BY THERMAL DESORPTION-GC/MS METHOD

本文发展了五氟化苯肼(PFPH)衍生化-热解析-GC/MS方法,质谱采用SIM扫描方式,可实现对大气中23种羰基化合物的测定,并建立了方法相应的质量控制和质量保证(QA/QC)程序.采用美国环保局TO-15标准气体测量了这些羰基化合物衍生化采集测定的相对误差.方法检测限为0.01—0.25nmol,对大气样品采集测定的相对误差为-7.8%—-40.2%.在2007年"好运北京"奥运测试赛的机动车限行前后和限行期间对大气中的羰基化合物进行实际观测,测得的羰基化合物的总平均浓度为31.47±11.53μg·m-3,主要组分为2,5-二甲基苯甲醛、乙二醛、乙醛、正癸醛和苯甲醛.结果表明,2007年车辆限行期间,大气中羰基化合物浓度水平较2005年观测有显著降低.

Ambient carbonyls are important volatile organic compounds contributing to the formation of ground-level ozone. However, the roles of carbonyls in air chemistry are not well understood due to the measurement difficulties. This work improved the method of PF PH derivatization-thermal desorption followed by GC/MS analysis by using SIM （selected ion monitoring） mode. 23 carbonyls in the atmosphere were measured and QA/QC procedure of this method was established. Relative errors of these carbonyls were checked by using TO-15 standard gas from U. S. Environmental Protection Agency. The method detection limits ranged between 0. 01 and 0. 25nmol, the relative errors of ambient carbonyls concentrations were -7.8%- -40. 2%. The ambient levels of earbonyls were measured during before and after the vehicle-limiting campaign in 2007. The average concentrations of measured carbonyls were 31.47 ± 11.53 μg · m^-3. The major compounds were 2,5-dimethyl- benzaldehyde, glyoxal, acetaldehyde, decanal and benzaldehyde. The results showed that the concentration levels of ambient carbonyls during the 2007 vehicle-limiting campaign had decreased significantly comparing to the levels obtained in the summer of 2005.