| AVS 61st International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS+BI+VT-TuM |
| Session: | Ambient Ionization Mass Spectrometry |
| Presenter: | Ian Gilmore, National Physical Laboratory, UK |
| Authors: | I.S. Gilmore, National Physical Laboratory, UK T.L. Salter, National Physical Laboratory, UK J. Bunch, National Physical Laboratory, UK |
| Correspondent: | Click to Email |
Plasma sources for ambient mass spectrometry are of increasing importance owing to their ability to analyse a wide range of organics including polymers. Some industrially important molecules are not successfully analysed by electrospray based methods and here plasma methods are making an important contribution. For analysis in industry, it is essential to understand the fundamental mechanisms so that predictions can be made of which types of materials can and cannot be detected. In this study, we develop a metrology framework to understand the sensitivity of PADI to different substances and material form. We study in detail, the effect of sample temperature on the signal intensity and show that the intensity is proportional to the vapour pressure. Importantly, we also show the sample form, as a film or powder, has a strong effect of sensitivity. For the analysis of thin films at room temperature and using a low plasma power, a vapour pressure of greater than 10-4 Pa is required to achieve a sufficiently good quality spectrum. Using thermal desorption we are able to increase the signal intensity of materials with vapour pressures less than 10-4 Pa, in thin film form, by between 4 and 7 orders of magnitude. This is achieved by increasing the temperature of the sample up to a maximum of 200 °C. Thermal desorption can also increase the signal intensity for the analysis of powders. Prospects for imaging PADI and sub-micron imaging ambient mass spectrometry imaging will also be discussed.