Development of infrared desolvation device for single cell element analysis using droplet sample injection inductively coupled plasma spectrometry

Microdroplet injection systems, which introduce single cells into an inductively coupled plasma by encapsulating them in droplets, have been developed by several research groups, including our group. In our laboratory, to improve the analytical sensitivity, a droplet desolvation system using a ribbon heater has achieved an approximately tenfold improvement in sensitivity. However, the desolvation throughput was limited to 100 Hz because of the low heat-transfer efficiency associated with indirect of indirect heating via heated gas. In this paper, a novel desolvation device using infrared radiation was developed to improve the desolvation throughput. Infrared radiation enables direct and efficient droplet heating. The developed device comprises a heating section and a cooling section. An infrared lamp with a luminous length of 140 mm was used in the heating section. Infrared radiation was focused on the flight axis of the droplets to enhance irradiation efficiency. The cooling section was placed downstream of the heating section to condense and remove vapor. With a power of 1000 W applied to the lamp and a carrier gas flow rate of 0.1 L min^-1, the carrier gas temperatures at the bottom of the heating section remained below 71 °C for both argon and helium. Under these conditions, the cells remained intact without rupture. Helium exhibited superior throughput compared to argon and when the carrier gas flow rate was above 0.5 L min^-1, the desolvation at a throughput of 1000 Hz could be achieved with an applied power of 150 W to the lamp.