Apart from the cool name, my post today will cover what is different and original about the Orbitrap Mass Spectrometer (MS) as compared to other types of mass analyzers. By the way, we are celebrating the 10th anniversary of the commercial release of the Orbitrap tandem MS this year!
Measuring Frequency of Movement
As with Fourier Transform-Ion Cyclotron Resonance (FT-ICR)-based mass spectrometers, a frequency of movement is measured. The FT-ICR technique is very accurate but requires huge and expensive superconducting magnets which are not needed for Orbitrap-based mass measurement. Other mass spectrometers, such as those based on Time-Of-Flight (TOF) technology, for example, use a time measurement to determine m/z but they are measuring a flight time, not a frequency, which is fairly accurate but not as accurate as an Orbitrap MS.
Frequency is the most measurable of things, if you will, and the very accurate measurement of frequencies involved in FT-ICR and Orbitrap MS is then converted to m/z via a Fourier transform giving a more accurate m/z measurement than is possible in a TOF.
Importance of High-Mass Resolution
Another key mass spectrometric quality that singles out the Orbitrap MS from most other mass spectrometers is high-mass resolution. In a relatively small amount of time, compatible with ultra high performance liquid chromatography (UHPLC), very high-mass resolutions can routinely be achieved with the Orbitrap MS. High resolution allows us to discriminate between compounds that have very similar masses when measured in the mass spectrometer.
Thus, for example, we can identify and quantify a compound even in the presence of something else (another compound or a background ion for example) almost identical in mass which with lower-resolution instruments we would not be able to discriminate and therefore couldn’t measure accurately.
Typically, an Orbitrap mass spectrometer can achieve very high resolution in a fraction of a second, considerably higher than, for example, TOF-based mass measurement. High resolution is not only important in qualitative applications, it can also be very significant in quantitative applications, for example, when quantifying the level of a pesticide or pharmaceutical product in your drinking water or waste water.
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High Resolution Leads to High Quality Data
A single m/z measured at >50,000 FWHM resolution is more selective than selected reaction monitoring (SRM) performed by a triple quadrupole mass spectrometer as described in this peer-reviewed article, Comprehensive comparison of liquid chromatography selectivity as provided by two types of liquid chromatography detectors (high resolution mass spectrometry and tandem mass spectrometry): “where is the crossover point?”.
So? High resolution leads to high-quality data. High mass accuracy leads to high confidence in identification. Thus, the performance of your mass spectrometer in these fundamental metrics really does matter (bad pun intended). The better the mass spectrometer, the better the data and the better the data the better your answer: more specific, more accurate, and more sensitive.
Forgive my personal bias as I answer my own question ‘What is the Orbitrap mass analyzer and why is it amazing?’ by saying that that this is possibly the best mass analyzer in the world so far invented! If you are still not convinced,do check out the huge impact it has had on the world of research in the last 10 years and the even bigger impact it is now just starting to have in the world of routine analysis by visiting our Planet Orbitrap website. Just last year, more than 200 peer-reviewed articles were published in the Science and Nature group of publications involving the use of an Orbitrap-based mass spectrometer.
Past, Present and Future of Orbitrap Mass Spectrometry
Listen to the Orbitrap MS inventor Alexander Makarov (LinkedIn profile) in this 30-min video where he describes how the Orbitrap MS works, its developmental history, and provides a comparison with other mass spectrometers.
Sometimes, I think we should have called it the AWE-BITRAP!
Do you use an Orbitrap MS in your lab? Tell us of your experiences; we look forward to hearing from you.