集束毛细管柱富集便携式光电离飞行时间质谱检测大气中苯系物

Determination of Benzenes in Atmosphere by Multi-capillary Column Enrichment Portable Photoionization TOF-MS

本研究利用集束毛细管柱研制了一种新型富集进样装置,并与便携式光电离飞行时间质谱(PI-TOF-MS)联用,实现了环境空气中苯系物的高灵敏检测。该富集进样装置无需制冷即可高效吸附苯系物,经过条件优化,样品经500 mL/min流速采样4 min,以2 mL/min载气流速进样3 min,捕集阱降温3 min,即可完成样品分析。与直接进样相比,富集进样后,苯、甲苯和对二甲苯的信号强度分别提高了130、220和255倍,相关系数(R^(2))均大于0.99,检出限分别达到0.23、0.19和0.23μg/m^(3),平行检测7个周期的相对标准偏差(RSD)小于6%。将研制的集束毛细管柱富集进样-便携式PI-TOF-MS应用于实际环境空气检测,结果表明,该仪器能够满足大气中痕量苯系物的检测需求,在现场环境快速检测领域具有广阔的应用前景。

Benzenes of wide sources can cause serious air pollution.In this study,a novel enrichment sampling device based on multi-capillary column was developed and coupled to portable photoionization time-of-flight mass spectrometer(PI-TOF-MS)to highly and sensitively detect benzenes in ambient air.The enrichment sampling device was composed of seven identical HP-PLOT Q capillary columns(0.10 m×0.53 mm×40μm)coated with polystyrene-divinylbenzene,which could achieve efficient adsorption of benzenes at room temperature.The homebuilt portable PI-TOF-MS has a volume of(0.47×0.35×0.38)m^(3),a weight of 35 kg,and a resolution of better than 1000(full width at half-maximum,FWHM)at m/z 92.Benzene,toluene and p-xylene gas diluted by nitrogen were used to optimize the operating parameters of the whole system.The optimal sampling flow rate was selected as 500 mL/min,the enrichment time was 4 min,the thermal desorption temperature was 160℃,and the analytical time for single sample was less than 10 min.Compared with direct sampling,the signal intensities of benzene,toluene and p-xylene were enhanced by 130,220 and 255 folds under the optimal conditions,respectively.The linearity,limit of quantitation(LOQ)and stability of the system were evaluated.As a result,the linear concentration range of 6.96-1741.05μg/m^(3)for benzene,8.21-2053.55μg/m^(3)for toluene,and 9.46-2366.05μg/m^(3)for p-xylene were obtained with the correlation coefficients(R^(2))of 0.9938,0.9997 and 0.9991,respectively.The limits of quantification(LOQs,S/N=10)were 0.78,0.63 and 0.76μg/m^(3),respectively.The relative standard deviations of the signal strengths for the three compounds were less than 6%during seven analytical cycles.Finally,the developed multi-capillary column enrichment portable PI-TOF-MS was used for comparative analysis of indoor and outdoor air in the laboratory.As a consequence,toluene and p-xylene were detected in both indoor and outdoor air of the laboratory.The indoor concentrations of the two compounds were 2.6 and 23.3μg/m^(3),respectively,which were much lower than the legal limit concentrations.Due to better ventilation,the outdoor concentrations of toluene and p-xylene were 0.5 and 16.4μg/m^(3),respectively.In addition,ethanol,methanthiol,acetone,etc.were also detected in indoor air of the laboratory,which may come from human exhalations or chemical reagent emissions.The results showed that the instrument can meet the requirements of trace benzenes detection in ambient air,and has broad application prospects in the field of on-site environmental analysis.