Abstract: Considering the impact of oxygen in the air on the measurement results of ICP-MS, the air direct injection measurement could lead to the reduction of ionization degree for nuclides to be measured, which may decrease the sensitivity of ICP-MS or even cause an outage. Therefore, in order to measure air aerosol samples by ICP-MS directly, a set of aerosol direct injection device was designed to achieve the exchange between air and working argon, so as to make sure that aerosol can be carried into ICP-MS for measurement by argon. Conversion efficiency of the device was measured and analyzed. Analyzing the system background levels measured by the on-line system of ICP-MS, and estimating the operating costs the whole system, the optimum programme was chosen while the inlet flowrate of air sample was 0.8 L/min, and the inlet flowrate of argon was 10 L/min. According to study on the aerosol loss rate, it is proved that the aerosol loss does not need to be considered when aerosol passes the direct injection device. With the development and performance test of the aerosol direct injection device, air aerosol can be measured directly and fast by ICP-MS, laying a foundation for rapid and quantitative measurement of various long-life radioactive nuclides in air aerosol by ICP-MS in the future, and providing a new method to measure aerosol continuously and rapidly in sites and effluents.

Key words: ICP-MS, aerosol direct injection device, sample introduction flow rate, aerosol loss rate