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7250 GC/Q-TOF: The Quickest Way to Your Molecular Ion

Martin Perkins

11th October 2018

7250, Accurate Mass, Camilla Liscio, Design of Experiments, DoE, GC-MS, GC-MSD, GC-QQQ, GC/Q-TOF, HES, High Efficiency Source, LC-MS, Low Energy EI Source, Molecular Ion,


This is Big News!

When you are doing product characterisation, or looking for unknowns in your samples, would you like to know how to quickly and easily create molecular ions and get accurate mass data for them?

Whilst accurate mass LC-MS has been hitting the headlines for a while, the last few years have seen the accurate mass GC-MS beginning to catch up.

The Agilent 7250 GC/Q-TOF is the latest addition to their GC Accurate Mass portfolio; we installed one in our own lab recently and have now been fully trained.

In addition to offering increased sensitivity and higher resolution than the previous 7200 model, the 7250 GC/Q-TOF is also equipped with a Low Energy EI source.

Personally, I don’t have much experience with Chemical Ionisation (CI) and so the idea of having a more user-friendly way to enhance molecular ions, was very appealing indeed.

Low Energy EI alone, is not a ground-breaking concept; it has been done before. However, there are two very important things that set this instrument above other Low Energy EI machines:

Firstly, this instrument combines a Low Energy EI capability with High Resolution Accurate Mass. This means that when you generate a molecular ion, you can be more certain of its identity.

Secondly, while conventional EI sources can, potentially, operate at low electron energy and perform a softer ionisation (to increase the relative intensity of the molecular ion), this would typically result in a drastic drop in sensitivity levels.

In this case, the new source is based upon the High Efficiency Source (HES) available on the GC/MSD and GC/QQQ models. Low energy EI spectra, do indeed, show a loss in total ion current at lower electron energy values, but the high ionisation of the HES nicely compensates for that, and you end up with usable levels of sensitivity.

Of course, I couldn’t let this Low Energy EI method development opportunity slip away without trying out my beloved Design of Experiments (DoE) approach to finding the optimum settings.

I wasn’t disappointed, DoE turns out to work very well and you find the optimum source settings quickly and easily. Low Energy EI is one of my new favourites!

If you are interested in the details of what I did, check out this technical note ‘The Power of Low Energy EI Ionisation in GC/Q-TOF MS‘.

How about you? Would you like a quicker way to your molecular ion?