| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Biomaterial Surfaces & Interfaces | Tuesday Sessions |
| Session BI-TuM |
| Session: | Bioimaging and Bionanotechnology |
| Presenter: | Peter Cumpson, Newcastle University, UK |
| Authors: | J. Hood, Newcastle University, UK P. Cumpson, Newcastle University, UK I. Fletcher, Newcastle University, UK S. Sheraz, Ionoptika Ltd, UK |
| Correspondent: | Click to Email |
Increasing the secondary ion yield from organic and biological molecules has been a key pursuit in the development of secondary ion mass spectrometry (SIMS) since the inception of the technique, with novel primary ion sources a promising avenue of research. The development of a water cluster primary ion beam has offered improvement in this regard, with ion yield enhancements of the order of 100 to 1000 times observed for beams with water cluster size 7,000, relative to argon cluster beams of size 2,000 [1] [2].
We demonstrate that exploiting larger cluster sizes, in excess of (H2O)10,000+, with higher beam energy of 40 keV, offers further enhancement of the secondary ion yield, including for large fragments.
To complement the increased secondary ion yield of higher mass fragments, higher mass resolution is desirable. One way to achieve this is through the coupling of a high resolution Fourier transform mass spectrometer (FT-MS) to a SIMS instrument. One form of such hybrid instrumentation utilizes an orbital trapping mass analyser [3] [4], which we have designed and fabricated for our J105 SIMS instrument [3]. However, as with ion cyclotron resonance (FT-ICR MS) techniques, orbital trapping analysers operate at a much slower repetition rate than time-of-flight (ToF) variants, with acquisition dwell times per pixel of the order of 100ms to several seconds, as opposed to as little as 10µs for modern ToFSIMS instruments such as the Ionoptika J105[5].
In FT-MS the field which governs ion motion can potentially be manipulated by applying different voltages to the component electrodes, a process known in ICR-MS as Stored Waveform Inverse Fourier Transform (SWIFT)[6]. The time-domain excitation waveform is formed from the inverse Fourier transform of the appropriate frequency-domain excitation spectrum, which is chosen to excite the resonance frequencies of selected ions. The application of a SWIFT signal to the orbital ion trap improves the speed of acquisition, making high mass resolution SIMS practical.
The combination of a water cluster primary ion beam with high mass resolution orbital ion trapping offers considerable potential for analyzing the molecular chemistry in organic and biological systems.
References
[1] S Sheraz née Rabbani et al. Analytical chemistry 85, 2013, 5654–5658
[2] S Sheraz Nee Rabbani et al. Analytical Chemistry 87(4), 2015, 2367–2374
[3] JC Hood et al. Int. J. of Modern Engineering Research 6(10), 2016, 76–83
[4] A Pirkl et al. Microscopy and Microanalysis 22(Suppl 3), 2016, 340–341
[5] JS Fletcher et al. Analytical Chemistry 80(23), 2008, 9058–9064
[6] RB Cody et al. Rapid Communications in Mass Spectrometry 1(6), 1987, 99–102