If it becomes possible to analyze trace elements within a single cell, it is expected to improve the induction of differentiation of iPS cells and elucidate the mechanism of cancer cell development. To enable high-selectively single cell elemental analysis, a method for introducing droplets containing single cells into an inductively coupled plasma (ICP) spectrometer has been developed by our group using a cell sorter and analysed by ICP-time of flight-mass spectrometer (ICP-TOF-MS). Since the solvent of droplets load the ICP and reduces the analytical sensitivity, droplets are desolvated, and the dried samples are introduced into the ICP by carrier gas flow. The carrier gas flow rate affects the transport of cells into the ICP, desolvation effects and the stability of the ICP. In this study, the effect of the carrier gas flow rate on the analytical sensitivity was investigated.

The experimental setup consists of a droplet nebulizer which eject droplets with diameter of 70 µm at a frequency of 10 Hz, a desolvation device, and an ICP-TOF-MS (icpTOF R, TOFWERK). Droplets of standard solution (Multi-element Calibration Standard 2A, Agilent Technologies Japan, Ltd) are ejected and introduced the desolvation system with a carrier gas. Argon was used as the carrier gas at a flow rate of 1.00 L/min. In the desolvation system, the droplets are evaporated the water by infrared rays, and removed in the cooling section. After the desolvation, the dried sample was introduced into the ICP with the additional gas. In the experiments, argon was used as the additional gas and the flow rate was varied from 0.5 to 1.5 L/min to compare the intensity of the droplet-derived mass signals.

As the carrier gas flow rate increased, analytical sensitivity decreased. The analytical sensitivity at an additional gas flow rate of 1.50 L/min was approximately 1/11 of that observed at 0.50 L/min. In the presentation, results from the analyses using helium as the carrier gas will also be discussed.