Chromatography Forum

We're planning to buy a triple quad. Does anyone know something else than Varian and micromass for that? And if someone uses one of these, what can you say about that?

Hi Fred,
I think the best thing you can do is sending your sample of interest to both of the suppliers and get them analyse for you the sample, then you can choose the best among them.
Thanks

Applied Biosystems / Sciex is a popular brand where I work. As it is the only brand that I have used, I can't compare it to other brands.

The use of GC in MS MS modes is rare compared to LC because Electron impact is the most commonly used ionisation technique. EI gives structural details that are library searchable and MS MS is really only useful for cleaning up the background, this can be done by Ion traps. You do not say why you think you want an MS/MS system ? As the market for this type of application is small there are only three manufacturers of GC Triples, Varian low cost, and Micromass and possibly Thermo. You solution may however lie with traps, TOFs or even humble single quads. My advice is speak to the manufacturers of GC/MS ask about your application and buy the best solution, it may not be a triple quad.

Sorry Fred, I only read the "triple-quad" part. I have not used GC triple-quad systems.

Thank you all for your answers, it'll surely help me. About the reason I'd like a triple quad, it's because the authorities want more and more really low levels of genotoxics in API. Since now, I'm using a single quad. Thanks again

Don't know if this is totally off the mark or not, but have you considered a magnetic sector instrument? Detection limits for GC-type compounds can be extremely low using these machines. They are quite a bit more complicated to operate than quad instruments, though. Water/Micromass makes a very good one.

Mike

Dear Fred
Please clarify, "genotoxics in API". API is an LC/MS ionisation technique and you will definately benefit from looking at Triples/traps. Check you application and separation technique. GC or LC, makes a big difference.
Regards Richard

Hi Richard,
Sorry for the API stuff...actually, I'm working on Active Pharmaceutical Ingredients. About genotoxic impurities, I mean stuffs like methyl methanesulfonate which can cause cancer for exemple. We have to demonstrate that the quantity( if there is in the API) is under very low levels (usually, we must be able to get a LOQ around 500ppb (w/w API). Is that clearer?

Dear Fred
If you are looking at small toxic materials MS/MS may not be the way to go with GC. Sensitivity improvements with triples in GC EI require a strong preferably large MW ion to isolate and use to provide additional breakdown to identify the exact compound. This mode works for clean up of matrix effects as you trap a characteristic ion of your target compound and hope that any interference has a different breakdown in the second MS stage.
You might be better off looking at different solutions. You do not state the type of GC/MS quad you are using however sensitivity of standard quads has improved more than 100 fold over the last ten years. A new system might be better. Ion Traps are usually more sensitive in full scan mode than quads, get a sample run on one to see if this works for your compounds.
Possibly the best GC solution is a TOF. GC TOF is usually ten times more sensitive than a quad in full scan and because the TOF does not give any change in ion concentrations due to scanning, the spectra are pure and deconvolution routines can differentiate co-eluting peaks separated by fractions of a second. I think you may get better LOD from a TOF than a triple for your application.
Let us know how your sample ran on the different system types.
Regards Richard

Fred if possible could you reply on http://www.sepsci.com/chromforum/viewtopic.php?t=2285

TNX

Hi again Richard,
I don't really know about the TOF but I think we can only scan and in my case, we need to be in SIR to quantitate, it's why we think triple quad'd better

Quantitation on GC TOF should be as good as quad and a triple quad will not allow you necessarily to get better sensitivity by looking at SIR. GC single quad gives 10-100 fold increase in sensitivity by using single ion monitoring for quantitation and several systems now back this by alternate SIR/full scan monitoring for good sensitivity and identification. If you run a triple your sensitivity gain comes because SIR in single quad is obscured by interfering ions. Hence sensitivity in matrix is better however sensitivity overall is likely to be less than a single quad. TOF does not need SIR because it constantly collects all ions hence gives almost SIR sensitivity with full spectral information. Matrix effects can be countered by target search analysis and removal of interfering co-eluting compounds using AMDIS. I sold the first GC/TOF in the UK (a Thermo one now discontinued) and know that a major UK enviromental analysis expert also feels that TOF to be the way forward in this analysis field. I left the MS field three years ago so may not be fully up to date. INMHO not to consider all your options is a mistake