MS-1000 SPECTRA

High mass resolution and accuracy-for better mass identification

Some degree of organic contamination is to be found on nearly all samples taken for analysis by static SIMS. In samples where inorganic species are of interest, this contamination can lead to difficulties in spectral interpretation. MS-1000 has been designed with sufficient mass resolution to sort out most of the organic versus inorganic ambiguities. The inset shows an example where two peaks at the same nominal mass are resolved. Uniquely for such a small instrument, MS-1000 maintains a high mass resolution in the low mass range - such performance could not be matched using a quadrupole analyser. In a conventional TOF-SIMS of similar size, the width of the primary ion gun pulse would limit mass resolution at such low masses.

In addition, as mass accuracy is typically very high in TOFMS, (approximately 100ppm for MS-1000), the centroid mass value of a single peak can be checked so that it can be assigned with confidence to either an organic or inorganic molecule.

Organic molecules

MS-1000 can be used to detect low traces of organic contamination in pharmaceuticals production. The spectra below is from a dilute solution of a steroid in methanol, evaporated onto clean aluminium to result in about a monolayer of sample. The M+H peak at 373 also M+H-O at 357 and M+Na at 395 can be seen.

Insulating samples

Charge neutralisation is achieved in MS-1000 using low-energy electrons, typically under 10 eV. The low electron energy minimises unwanted sample damage from electrons and makes insulator analysis with MS-1000 very straightforward. The spectrum below was taken from fresh photocopying paper with no preparation.

Polymer surfaces can also be examined with ease in MS-1000. Below is a spectrum of a polythene bag showing the same characteristic peaks obtainable from TOF-SIMS instruments costing 10 times more!

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Last updated: Thursday, September 15, 2005, 10:56

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