Development and characterization of a thermal inkjet-based aerosol generator for micro-volume sample introduction in analytical atomic spectrometry

Abstract

A novel system for the introduction of liquid samples into analytical plasmas for atomic spectrometric analysis is presented in this manuscript for the first time. The proposed “drop-on-demand” (DOD) aerosol generator is based on the use of a modified thermal inkjet cartridge. This system employs a lab-built microcontroller, which allows accessing all parameters important for driving the dosing cartridge for the generation of pL-droplets from sample volumes in the μL range. The droplet generation frequency, thus the resulting liquid flow rate, is variable over a wide range from the generation of isolated droplets up to a theoretical flow rate of approximately 2 mL min⁻¹, with parallel operation of all 300 nozzles available on the employed device. The flow rate was investigated in the range from 20 nL min⁻¹ to 6.3 μL min⁻¹ and a new calibration strategy based on the droplet generation frequency instead of on the use of standard solutions of different concentrations is introduced. The new system is characterized and the achievable analytical figures of merit of such a DOD aerosol generator coupled to a quadrupole ICP-MS are outlined and compared to a commercially available pneumatic low-flow nebulizer, the MicroMist™. The new system offers a superior sensitivity by a factor of 8–18, improved limits of detection and better background equivalent concentrations for the investigated elements (Li, Cr, Mn, Co, Ga, Sr, Ag, Cd, In, Ba, Tl and Bi). The achievable precision in multi-elemental DOD-ICP-MS analysis was found to be comparable to the data gained with the corresponding commercial system.