| AVS 55th International Symposium & Exhibition | |
| Applied Surface Science | Wednesday Sessions |
| Session AS-WeA |
| Session: | Frontiers of Analysis and Combined Materials |
| Presenter: | I.S. Gilmore, National Physical Laboratory, UK |
| Authors: | F.M. Green, National Physical Laboratory, UK P. Stokes, LGC Ltd., UK G. O'Connor, LGC Ltd., UK I.S. Gilmore, National Physical Laboratory, UK |
| Correspondent: | Click to Email |
There has been an explosion in the growth of ambient surface mass spectrometries with new ionisation and desorption methods developing rapidly. Surface chemical analytical techniques such as SIMS are extremely powerful providing high-sensitivity molecular information at better than 200 nm spatial resolution. However, the requirement for analysis in vacuo is for many applications a severe drawback. This is, of course, particularly important in biology. In the vanguard of these ambient methods is Desorption Electrospray Surface Ionisation (DESI) developed by the Cooks group.1,2 DESI has already been shown to have great potential in a wide range of application areas from forensics and homeland security, through to counterfeit detection of pharmaceuticals and biological analysis. Of the wide variety of desorption methods it is clear that DESI has one of the strongest uptakes and so it is with DESI that we begin the development of a metrological approach, similar to that developed for SIMS and XPS. The objective is to improve repeatability and reproducibility and consequently confidence in the method and uptake into industry. A first step in the development of a metrological framework is to measure and improve repeatability. Here we conduct a systematic study of the parameters affecting spectral intensities and the interaction of the electrospray jet with the material surface. We have developed a well-controlled model system of Rhodamine B on glass that allows the effect of key experimental parameters such as geometry and spray conditions to be studied and optimised. Using this approach we have improved the repeatability of spectral intensities to 20%. In addition, we have studied the surface crater and surrounding disrupted material which gives insights into the interaction mechanism of the electrospray jet and the surface. This is important to allow future improvements in resolution and to understand the rate at which material is removed.
1 Z. Takats, J. Wiseman, B. Gologan, G. Cooks; Science, 306 (2004) 471
2 G. Cooks, Z. Ouyang, Z. Takats, J. Wiseman, Science, 311 (2006) 1566.