用于纳米气溶胶质谱仪的毛细管进样接口传输特性研究

采用自制的X射线离子诱导成核纳米颗粒物生成装置，通过纳米扫描迁移率颗粒物粒径谱仪（Nano-SMPS）测量纳米颗粒物通过毛细管之前、之后的粒谱分布，获得了纳米颗粒物穿透率随毛细管的内径、长度及进样流量的变化曲线，并对纳米颗粒物在毛细管中的传输损耗进行实验探究。同时，结合气溶胶颗粒物传输沉积模型，对纳米颗粒物的穿透率进行理论计算，并与实验测量值进行比较和讨论。结果表明，对于粒径小于10 nm的纳米颗粒物，受布朗运动等因素的影响，其穿透率与毛细管的尺寸及进样流量有较强的相关性。此外，采用毛细管进样接口结合激光电离气溶胶飞行时间质谱仪对部分纳米颗粒物的化学成分进行检测，获得了初步的实验结果。

Transmission Characteristics of Capillary Sampling Interface for Nano-Aerosol Mass Spectrometer

Aerosol mass spectrometer as a powerful and on-line device has been widely utilized to probe the chemical composition of aerosol particles in the atmosphere. Several kinds of interfaces to transfer particles from air into vacuum have been employed in aerosol mass spectrometers. Among them capillary was developed as an interface to deliver large particles with a limited size distribution before. We proposed here to use capillary as a sampling interface for nano-aerosol mass spectrometer and the penetration efficiency of nano-particles in capillary was investigated and presented. A home-made reactor was employed to generate nano-particles through X-ray ion-induced nucleation of gaseous mixture. The size distributions of the nano-particles at the inlet and the outlet of capillaries were measured, respectively, by using a commercial nanometer scanning mobility particle sizer (Nano-SMPS) and then the penetration efficiency was obtained. The size distribution of the particles generated from ion-induced nucleation was measured to be around 3-20 nm, where the lower detection limit was limited by the commercial Nano-SMPS. The penetration efficiency was dependent on the length and the inner diameter of capillary, in particular for the nano-particles with size of less than 10 nm due to the influences of Boltzmann diffusion et al. The penetration efficiency would decrease with the length and the bore size of the capillary as the particle diameter was less than 10 nm. The dependence of the penetration efficiency on the length and the bore size of capillary becomes insignificantly as the particle diameter is close to 20 nm. In addition, the penetration efficiency can be benefited from a large flow rate with a short transmission time in capillary. Then the penetration efficiency of the nano-particles in the capillaries was theoretically calculated by the aerosol transport and deposition model. The results showed that the obtained theoretical data could be comparable with the experimental results and their discrepancies were also discussed. As a representative example, a laser-based photoionization aerosol time-of-flight mass spectrometer (ATOF-MS) combined with the capillary interface was utilized to probe the chemical components of nano-particles and the initial results have also been presented in the article. These results have demonstrated that the capillary can be used as the sample interface of nano-aerosol mass spectrometer to deliver nano-particles. Also, on the basis of these results, it is of very interest to study the formation and evolution of atmospheric fine particles below 100 nm by nano-aerosol mass spectrometer in the future.