The advances in material sciences in the fabrication of nanostructures and the increasing interest in the biological sciences to characterize intracellular compartments have posed a great challenge for chemical analysis: most traditional chemical analysis techniques are far from having the required nanoscale resolution and most traditional techniques used for nanoscale characterization give little chemical information.
To achieve nanoscale resolved chemical analysis an instrument was developed in our laboratory that couples mass spectrometry to laser ablation atmospheric pressure sampling via near field techniques. The approach involves delivering a laser pulse through an optical fiber near field probe to ablate the analyte from the surface. The ablation plume is then transferred through a capillary to a mass spectrometer. In this fashion molecular analysis of the sample surface is allowed where the spatial resolution is limited by the near field probe aperture.
The current instrument has several key features to overcome the limitations of similar near field ablation mass spectrometry techniques [1]. For example, it has a differentially pumped interface to allow atmospheric pressure sampling as opposed to requiring the sample to be in high vacuum [2]. In addition, it has an ion trap coupled to a time-of-flight mass spectrometer which allows for "preconcentration" of the sampled material and, in contrast to scanning mass spectrometers [3], allows for simultaneous detection of a wide range of mass-to-charge ratios.
A characterization of the instrument performance with different samples will be presented. The near field laser ablation craters with their corresponding mass spectrometry signatures will be demonstrated. In addition, the chemical imaging capabilities will be explored with model samples.
[1] P. D. Setz, T. A. Schmitz, R. Zenobi, Rev. Sci. Instrum. 77, 024101 (2006).
[2] D. A. Kossakovski, S. D. O`Connor, M. Widmer, J. D. Baldeschwieler, J. L. Beauchamp, Ultramicroscopy 71, 111 (1998).
[3] R. Stöckle, P. Setz, V. Deckert, T. Lippert, A. Wokaun, R. Zenobi, Anal. Chem. 73, 1399 (2001). |