Experimental investigation of an atmospheric pressure plasma jet as an ion source for on-site mass-spectrometry analysis of nonvolatile solid samples: the integration effect of thermal desorption and ionization

This work reported an air atmospheric pressure plasma jet served as an ion source for nonvolatile solid analysis, which allows a unique capability to achieve thermal desorption and ionization simultaneously without complex devices, inert gas, or solvents. Owing to precise amount of heat generated by plasma jet, nonvolatile analytes were thermally released from solid surfaces without the assistance of secondary desorption equipment. According to the mass spectra and Fourier transform infrared spectrum, [M + H]+ and [M + NO3]− ions were the major analyte ions in the positive-ion and negative-ion modes, respectively. The applied voltages, discharge currents, and gas temperatures of plasma jet were measured, and found to be positively correlated with the mass spectra signal intensity of the samples, while the added resistances and gas flow rate were negatively correlated with the signal intensity. The influence mechanisms of analytes natures coupling physical parameters of plasma jet on detection performance were revealed. The prospect of quantitative testing was confirmed by the linear relationship between the peak intensity and sample mass.