High Resolution Mass Spectrometry

High resolution mass spectrometry uses instruments capable of measuring the mass of chemicals to the 3rd of 4th decimal place, i.e. highly accurately. This accurate mass measurement, along with the pattern of isotopes, allows the exact chemical composition of small chemicals to be deduced with high confidence and even narrows down the elemental composition of biological molecules to a small range of potential formulas. Combined with fragmentation of the chemicals and accurate mass measurement of the pieces, HRMS is invaluable to prove the identity of a chemical.

A solution of the analyte is infused into the mass spectrometer directly or else is passed first through an online chromatography column, which allows mixtures of analytes to be analysed. Analytes molecules are ionised and vapourised by electrospray ionisation and enter the orbitrap mass spectrometer where they move move on eliptical trajectories between outer and inner electrodes - their motion depends on the mass and the charge of the ions. The ions are detected because they induce an oscilatory electric current in the outer electrode as they circle and the current can be deconvoluted by Fourier transform to a mass/charge scale. Resolving powers of up to 140,000 are possible with our instrument which also has a high energy collision cell with which to fragment ions.

As well as routine mass measurements of purifed and semi-purified chemicals, the Exactive orbitrap is also used for proteomics and metabolomics workflows.

Our HRMS system is interfaced to a UPLC system that can operate at micro- or nanoflow ranges. Thus, our HRMS is optimal for:

Purity and elemental compositions of small chemicals

Purity and narrowing down the elemental composition of small biomolecules and peptides

Analysis of larger proteins including binding partners

Relative quantification of small and large molecules in complex mixtures, such as cell lysates, by use of metabolomics and proteomic pipelines.

Mass spectrometry is highly sensitive and typically micro- to nanorgram levels of analyte is all that is required.

Typically the analyte is dissolved in a suitable solvent or buffer system.

The inclusion of detegents is discouraged but can sometimes be acceptable by use of sample clean up procedures pre-analysis.