ABSTRACT
Volatility can influence the lifetime of particles in the atmosphere, and provide useful information on the formation of secondary aerosol. The previous studies generally utilized thermodenuder ( TD ) to investigate the volatility behavior of particles. Using TD, semivolatile species are vaporized at different temperature, and the vaporized gas is adsorpted by activated charcoal. However, carbon might be emitted from activated charcoal under high temperature or activated charcoal ageing. In this study, a new method was developed for the measurement of particle volatility by coupling a thermodiluter system to an online single particle aerosol mass spectrometer ( SPAMS) . Aerosol particles were passed into two different channels, and then analyzed by SPAMS. Through Channel 1, aerosol particles were heated to different temperature by heating tube, then non-volatile particles and volatile gas entered into the diluter. After diluting and cooling by diluent air, the non-volatile particles were analyzed by SPAMS. Through Channel 2, aerosol particles were analyzed directly by SPAMS without the heating process. Particle volatility was obtained by comparing the information ( particle size, particle number and mass spectrum ) of particles through Channels 1 and 2. Laboratory tests showed that the diluter could avoid the re-condensation of volatiles to the particles. This developed method was applied in the real time measurement of individual particle volatility in the spring of Guangzhou. The results showed that these particles were primarily comprised of highly volatile and moderate volatile species.
ABSTRACT
Background contamination is a major problem in the analysis of organophosphate esters (OPEs). In this study, the possible sources of OPEs pollution were screened and several different ways were applied to minimize the blank contamination. Under the strict quality control measures, the cleanup efficiency of different solid phase extraction (SPE) was investigated for OPEs in different environmental matrices. A method was developed for the detection of 7 OPEs in dust, soil and sediment samples by gas chromatograph coupled with mass spectrometry ( GC / MS). Target compounds were extracted by hexane:dichloromethane (1 : 1, V/ V) followed by aminopropyl silica gel SPE column cleanup for dust, and target compounds in soil and sediment were Soxhlet extracted and cleanuped by two-step SPE. The results showed that the aminopropyl silica gel SPE column displayed the best purification performance among the three employed columns. Instrumental detection limits among the 7 OPEs ranged from 2. 5 to 25. 8 μg / L, and the method limits of quantification (MLOQs) in dust and soil sample ranged from 1. 4 to 15. 7 ng / g and 0. 3 to 2. 9 ng / g, respectively. The average recoveries of 7 OPEs in different matrices ( dust and soil) at two spiked concentration levels ranged from 67. 9% to 117. 4% . The proposed method was successfully applied to detect OPEs in different environmental matrices collected in Shanghai.