High-resolution mass spectrometry applications (HRMS)

Mass spectrometry has been traditionally used for the determination of molecular mass, which in turn, does or does not confirm the presence of a compound. Identification of compounds using MS techniques can be straightforward if reference mass spectra or standards are available. But in most cases, either identifying metabolites in biological samples or looking for new environmental contaminants, identifying impurities in pharmaceutical formulations, etc. the only available information for a mass spectrometrist is the mass spectrum i.e., a set of digits. The quality of a mass spectrum (accuracy and resolution) is critical for the successful identification of a compound. 

Here are demonstrated examples of the high-resolution mass spectrometry (HR-MS) applications successfully used for the analysis and structure elucidation and identification of "known-unknowns" and "unknown-unknowns".

First, let's consider the meaning of mass accuracy and resolution in mass spectrometry. The resolution (R) of the mass spectrometer is calculated as M/ΔM, where M is the mass of an ion, and ΔM is the full width at half maximum (FWHM). In the Orbitraps, R depends on the measured mass range and decreases as the m/z increases.  In TOF instruments R is constant throughout the full mass range.

Mass accuracy is the ability of a mass spectrometer to measure mass against the known standard, accuracy is often calculated in ppm in high-resolution mass spectra. Why is it so important? Only the mass of the 12C isotope is equal to 12.00000 (and only while it is neutral because the electron also weight), whereas all other elements and isotopes have so-called "mass defect", for example, the exact mass of 1H is 1.007825, 16O - 15.994914, 14N - 14.00307.  Having an accurate mass spectrum, possible atomic compositions of detected ions can be calculated.

1. Analysis of potato glycoalkaloids

2. Isotopic labeling in biochemical studies

3. Analysis of Lipid A

4. Analysis of tryptophan in spinach after hydrolysis

5. Oligosaccharides in human milk 

6. Analysis of mono-, di- and oligosaccharides in plants

7. Polar organic acids and inorganic anions (IC-MS)

8. Soy saponins and isoflavones 

9. Fenugreek saponins

10. Polyphenols in red wine

11. Analysis of resveratrol in red wine.

12. Polyphenols in green tea

13. Artemisinin in plants

14. Tropane alkaloids

15. Fake case of Oriental medicine