Buying old GC/MS

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

3 posts Page 1 of 1
Hello,

I'm pretty new in chromatography world. I have worked more on DSC,TGA,FT-IR analysis for polymers but never on gc machines. So I have zero experience on gc analizers but I know a few teachers from academy that have worked on which i could ask for help.

I need a GC for CBD oils in which I will be looking for solvent residues and potency. I know that with GC high temperatures some cannabiods degradate and can give false measurement but curently im looking only for GC and MS.

I was looking at Varian 3800/2000 and Perkin Elmer Clarus 500. I searched for support and i could find for agilent not particulary for varian and perkin elmer, shimadzu could also be an option but im looking more at lower budget.

I would really appreciate every opinion.
Thanks in advance.
trkoo wrote:
Hello,

I'm pretty new in chromatography world. I have worked more on DSC,TGA,FT-IR analysis for polymers but never on gc machines. So I have zero experience on gc analizers but I know a few teachers from academy that have worked on which i could ask for help.

I need a GC for CBD oils in which I will be looking for solvent residues and potency. I know that with GC high temperatures some cannabiods degradate and can give false measurement but curently im looking only for GC and MS.

I was looking at Varian 3800/2000 and Perkin Elmer Clarus 500. I searched for support and i could find for agilent not particulary for varian and perkin elmer, shimadzu could also be an option but im looking more at lower budget.

I would really appreciate every opinion.
Thanks in advance.


The Varian company was broken up and most was purchased by Agilent and some by Brueker, but support for those is not very good now, mostly by independent service people.

There are a lot of sources for Agilent parts even for older instruments now. An Agilent 6890/5973 or 6890/5975 could be a good instrument for what you are wanting to do. The 5973 is past service life but shares most parts in common with the 5975 so they are still easy to find parts for repairs.

When we were doing CBD analysis we found it easier to use HPLC with UV detection than with the GC/FID because of the breakdown problem you mentioned, but many labs do use GC for this analysis.
The past is there to guide us into the future, not to dwell in.
The Varian Saturn instruments were inexpensive when new, and are inexpensive now, for a reason.

They CAN give good results, but among other things Finnigan treated the construction of ion traps as something of a trade secret, and the Varian design is a bit of a reverse engineering attempt at them. They work well in good shape with a competent operator, but need you to be a bit more hands-on than a novice GC-MS user would probably want to be.

Ion traps have pretty much fallen out of favor in GC-MS applications(they are still common for LC-MS). I talked to Thermo a year or so back about a Q-Exactive GC-MS, and they said it hadn't been made in a couple of years.

Ion Traps have some upsides and downside. Unlike a quadrupole where the quads just scan continuously, there are several "stages" in acquiring an ion trap spectrum. Even so, surprisingly enough, they can be more sensitive in full scan mode than a quadrupole, but the quad rules for selective ion monitoring(something that to me is a bit counter-intuitive).

One big issue is that traps give non-classical mass spectra. If you know what you're looking for, this isn't an issue, but it can be if you're matching up to a library.

The Varians are super easy to maintain-I can breakdown, clean, and reassemble the complete trap a lot faster than I can an Agilent source. Still, though, as mentioned, you're on your own for service.

On the other hand, in operation they are somewhat more hands-on. When tuning, with an Agilent you just open the cal gas valve and it's all correct. On the Varian traps, there's a needle valve on the front and you have to adjust it slowly while watching the screen to make sure you're getting the right amount of cal gas. Most mass specs have RF coils that can be adjusted(called "dipping" the coils). On Agilents, I've dusted off 30 year old ones, dipped the coils as part of the set up, and found that often times they didn't need to be touch, or sometimes needed a tiny tweak. On the Varian traps, I dipped the coils EVERY SINGLE TIME I tuned them, and usually they needed some adjustment.

Something worth mentioning-the Varian traps specifically, and as far as I know all traps-MUST have helium present in the trap to work correctly. Forget using hydrogen or some other less expensive carrier gas in them-they just won't work.

I find the 3800 a bit of a cantankerous GC. The EPCs are a bit buggy, especially compared even to a generation older Agilent instruments. 3800s are very capable instruments, but need to be a bit more hands on(and hope to goodness you don't want to run a small split ratio). I fought wars with the CP8400 autosampler and finally quit using it. Even my old 7673 HP/Agilent samplers can run for years without an adjustment and only an occasional syringe change. The 8400 ate syringes for breakfast, and calibration was a constant battle.

I sporadically kept our 2100 running at my last job, but at the end of the day it just wasn't worth it.

The 1200 and 300 triple quads are superb instruments, and despite the lack of service availability, I'd still recommend them. The ion traps are a different story.
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