High Resolution GC MS

[MarkRob]

Hi there,

Small Environmental Lab Here.

I recently had a client ask me about High Resolution Gas Chromatography. I'm a newer chemist and I dont really understand the differences in the newer technologies. I called a vendor for these types of technologies and she really didn't know much either ( I know, I dont get it either) She tried to sell me Ion Trap GC-MS. I'm sure that's something different.

There's not really much general info out there about HR-GC-MS. Does anyone want to give a 30 second primer on it?

What is the difference between Ion Trap GC-MS and GC-MS/MS ????
What would you use each for???
Can HR-GC-MS replace all existing GC-MS procedures?

Any help is appreciated.

Thanks

-M

[HbJ]

Disclaimer: This post is to the best of my knowledge. Fell free to shred if incorrect Just adding this as I seem to have a talent for catching unpopularity.

The term HRGC (High resolution gas chromatography) is printed on one of my DANI boxes from 1984. It simply means chromatography with capillary columns (opposed to the packed columns used earlier).

The difference between Ion-Trap GC-MS and MS/MS is not really a question as it points to different things: Please look up Ion-Trap-MS in any textbook on the subject (MS collects ions in trap before analysis).
MS/MS means that the ions are not only one time, but several times fragmented. That way, you can look at the spectrum of ionization step 1 whose ions are then fragmented in a second step. That way you can distinguish very similar analytes (good thing for e.g. monoterpenes).

"Can HR-GC-MS replace all existing GC-MS procedures?" That question doesn't make much sense (see above). The mass spectrometers become more and more efficient and their resolution is increasing from generation to generation. So new units are often better than their predecessor. But you already knew that, right?

[Kostas Petritis]

Either the client didn't know much about GC and she was refering to what Hbj described (capillary vs packed columns) or maybe he/she meant a GC-TOF-MS (where you can achieve high resolution in the MS part). Not all vendors have GC-TOF's... I think Thermo and Waters have, others are on their way...

Was it for pesticide analysis?

[sindhu]

Mark,

First off all what is your application ?.

Since you said yours is a environmental lab , can I assume you want to analyze PCB's or pesticides?.

In either of the case you can use GC-MS/MS and you get good results.

If you wants to have a exact mass of your sample molecule then you can definetely look into High Resolution Mass Spec systems ( GC-TOF ).

Obviously the Mass Spec technology is now looking at HRMS and you can contact Waters , LECO and Jeol to buy GC-TOF.

Also Ion-Trap MS systems are not called HRMS and even GC-MS/MS too.

When you cant be able to buy a HRMS then my suggestion will be to buy GC-MS/MS ( Triple Quad system ) instead of Ion-Trap MS because of low-mass cut off disadvantage in Ion Trap systems.

[CE Instruments]

High resolution Gas Chromatography originally refered to Capillary as opposed to packed column. ( Carlo Erba HRGC 4000 series circa 1978)
I think your customer knows less than you and just used a term they had heard
Your application may run fine on standard capillary GC coupled to a "unit" resolution MS such as an Ion Trap or Quadrupole.

As it is pesticides you might find a benefit looking at MS/MS that can be used to target componds and remove interference using either a trap or a multiple stage system based on quads and or TOF.

Accurate Mass. Unit mass MS systems give data that reads the mass of a fragment/compound only to a single mass unit. TOF and Sector based instruments can be capable of accurate mass, resolving co-eluting compounds based on the accurate measurement of the elemental masses e.g. Oxygen 15.9994, Hydrogen 1.0079


Note that Gas Chromatography has not stood still either . You now have GC x GC systems and Fast Gas chromatography (Thermo Ultra fast) all of which can be attached to an MS system for resolving and identifying the most complex mixtures.

[MarkRob]

thanks for the feedback.

From a client, I had a question about dioxins and furans and I knew that they had to be done by HR GC-MS.

So, I did some investigation on the topic and found the information lacking. Furthermore, I contacted a sales rep (whose company shall remain nameless) who was really confused about the instrumentation (and she was selling some of it--I know, she should know her product before trying to sell it)

My main question, which I should have stated better, is: Is HR GC-MS the next big thing that I should know about? My GC-MS systems are running fine for now or at least until they lower action levels again.

Thanks for the info!

I appreciate any comments

[CE Instruments]

Accurate Mass GC/MS has been around for years in Sector MS systems and are essential to specifically identify the actual Dioxin as different ones have different required detection levels. You can run the samples on standard Quads no problem, fine until you get a positive
Accurate Mass will not be the latest thing until someone makes a benchtop low cost system. (IMO)

[Ron]

The customer wanted to know about GC with high resolution mass spectrometers. Most labs that did this analysis for dioxins and furans have stopped doing this analysis due to cost and complexity of the instruments. People are now talking about this for flame retardants, but most have decided it is not woth the additional expense.

Is this the next big thing in GCMS? Probably not, higher resolution instruments are becoming more common, but they are still about twice as expensive as a single quad. Triple quad GCMS is probably the next big thing, several are available now, and new models are on the way.

[AICMM]

All,

I would like a clarification here. I thought that TOF was good for high mass (ie 30,000 dalton) but not necessarily high resolution (ie. 15.99.) For high resolution you went to either a sector (expensive and difficult but used to be common for dioxins) or to an FT-MS (which I know very little about.)

An aside, MS/MS is supposed to be possible on ion trap (MSn) but I have never done it myself having grown up on quadrapoles. Not high resolution but then again neither is a triple quad, right?

A different aside, PBB's (fire retardents) should be very do-able by ECD.

Best regards.

[Stryder08]

All,

I would like a clarification here. I thought that TOF was good for high mass (ie 30,000 dalton) but not necessarily high resolution (ie. 15.99.) For high resolution you went to either a sector (expensive and difficult but used to be common for dioxins) or to an FT-MS (which I know very little about.)

An aside, MS/MS is supposed to be possible on ion trap (MSn) but I have never done it myself having grown up on quadrapoles. Not high resolution but then again neither is a triple quad, right?

A different aside, PBB's (fire retardents) should be very do-able by ECD.

Best regards.

TOF is a great high resolution instrument. Benchtop single stage oa-TOFs using ESI are available with LC systems for around $200K - 300K. We have two Waters Acquity UPLC with LCT Premier XEs in our lab and I love them. Exact mass to 4 decimal places along with mass accuracy in the range of 1 - 5 ppm error routinely.

Yes, Sectors and FT-MS are the ultimate mass accuracy tools, but TOFs provide high resolution (~ 10,000 on my instruments). As you said sectors and FTMS are difficult to use and VERY expensive, even compared to the available benchtop oa-TOFs. Also, high mass range analysis can be done on ESI-TOFMS instruments by using the multiply charged ions that form.

We also have a couple of QTraps from Applied Biosystems on which we have never used the trapping function, but instead have used them as MS/MS. Very doable. And reliable.

[CE Instruments]

With all systems there is always a compromise. Sectors only scan slowly so they can give high resolution but over a narrower mass range. TOF instruments can give high resolution but this is traded against the number of scans per second. Not much of a problem for LC but with Fast gc and peaks only a couple of seconds wide it was not possible to do high resolution work on Capillary with Fast GC with suffuicient data points for good quantitation six years ago

[Ron]

GC TOFs are somewhat uncommon at the present time, and as pointed out in a previous post you can have very high speed on a TOF, or very high resolution, but not both. Some GC TOFs are biased toward speed of data acquisition, but the mass accuracy suffers as a result. The newer GC TOFs seem to be more focused on higher resolution. TOF resolutions of >20,000 are common, with mass accuracy in the low ppm range.

TOFs can be and often are used for high mass applications, especially in MALDI for life science work. There are currently detectors that allow detection in the megadalton mass range.

Ion traps can be used for MS/MS, and this is commonly done in LCMS, and occassionally in GCMS. As you stated, this is a low resolution analysis.

ECDs can be used for flame retardants, but for positive compound identification mass spectrometry is the preferred detection method.