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Developing repeatable measurements for reliable ambient surface characterisation using DESI.

Green, F M; Stokes, P*; Hopley, C*; Seah, M P; Gilmore, I S; O'Connor, G* (2009) Developing repeatable measurements for reliable ambient surface characterisation using DESI. Anal. Chem., 81 (6). pp. 2286-2293.

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Desorption electrospray ionisation (DESI) is a powerful new ionisation technique that can provide highly sensitive mass spectrometry information from surfaces at ambient pressure. The potential of DESI has been demonstrated in a wide range of application areas, including forensics, homeland security, counterfeit detection of pharmaceuticals and biological analysis. Although a growing amount of research has been carried out exploring applications, there are presently few studies studying the basic parameters and metrology to improve robustness and repeatability. An understanding of these are crucial to develop DESI as a robust and reliable technique, increasing uptake into industry.

In this study, we begin with a systematic study of the parameters affecting the repeatability, sensitivity and rate of consumption of material in DESI. Using an evaporative sample preparation method, thin films of Rhodamine B on glass were produced as a model system. This was used to optimise the instrument parameters for DESI and an absolute intensity repeatability of better than 15% can be achieved over a days use. In addition, the model system provides valuable insight into the electrospray-sample interaction and the desorption mechanism. Confocal microscopy of areas analysed by DESI allow droplet size, distribution and spot size to be determined. The erosion also gives the consumption rate of material, analogous to the sputtering yield in secondary ion mass spectrometry. The results of the study provide a clear description that explains the differences observed with changing electrospray parameters allowing optimisation of the technique, for both spatial resolution and sensitivity.

Item Type: Article
Keywords: DESI, ambient mass spectrometry, direct analysis, erosion
Subjects: Nanoscience
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4399

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