Low cost field GC for quick and dirty Potency

I am strongly considering picking up an SRI Instrumnets 420 Mini gas chromatograph for quick and dirty but close enough analysis of both plant material and crude extracts. This GC is a very small form factor and does not require gas cylinders as it has an on-board hydrogen generator and air compressor, and is configured exclusively for major cannabinoid quantification using FID. The price point is 5K. The benefits are cost, size (portability), and onboard A/D converter and free analysis software. SRI is a very small company with basically no more than 3 techs, one of which is the Owner, Hugh. The downside to this little GC is that there is really no flexibility; you can change the column, but it is set up for the one small coil 15 meter column supplied and there is little to nothing in the way of method or instrument modification. So any future thoughts of upgrading this GC for terps residuals etc is straight up no go. If I can I will post a link to the SRI Youtube video showing this little dedicated GC. Here is the product page: Gas Chromatographs - PeakSimple - SRI Instruments - Cannabis Testing Equipment. Here is a Youtube video: - YouTube.

Note that GC does not have native cannabinoid acid detection abilities and thus requires derivitization, but that can be done easily enough for rough quantification of the acids. They do have more flexible models at around 10K and up. I was just wondering if anyone had any experience with this model, or any other SRI GCs for our analytes of concern.

Also, to save the obvious coming replies, I am fully aware of the superiority and advantages of HPLC and GS/MS.
Thanks all!


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I haven’t used one, but I have called and talked with their sales rep.

it’s 3x the price of the 420 GC. but for that price I think it does a better job of the tasks you actually need done. ie it can tell you % decarbed. which might not be a problem today, but will eventually be a problem you want to solve.

you can solve it with the 420…but you’ll have to use some chemistry and a derivitizing agent I’d rather not use in my current lab.

I’ve got an early 8610c. currently back-flushing the column with acetone. probably going to flush it again with something else tomorrow. once I figure out what to throw at it.

I don’t have a heated injector port, and I really should give Hugh $1000 to upgrade my machine. He’s a great guy, and talked with me for hours to get me up to speed once upon a time, even though I purchased my unit used from a dispensary owner!

You can get qualitative terpene data out of it, but manually injected heat-space analysis is never going to get you quantitative solvent or terpene numbers. SRI does now have a head-space rig that looks more up for the task. I’m not sure how well it would add on to their current 8610c. I suspect two machines would be a more reasonable setup.

The required derivatization of the carboxyl group to allow quantification of the acid cannabinoids is one I would rather avoid. The same agent will stop you joining amino-acids into proteins ie kill you. I find co-worker’ coffee cups on my lab bench way too often to allow that stuff in the lab.


Can you tell me about your experience with the 8610c and why you are back flushing your coulmn? I imagine to are trying to clean up and reactive the column. I have an old 9300 SRI but those old models can not support the higher oven temp required for cannabinoid analysis. Also, they have the small oven like the 310 models so you have to use the 4" metal columns like the Restek MXTs. The 9300 I have would be good for terpenes with the right column due to the higher vapor pressure of terpenes. I may end up selling it. I also have a late model 8610c but I picked it up from a school auction but it was set up with an external detector, and I was told it was never used, but without an FID, and given the need for a heated injection port, it isn’t worth much. Greg at SRI said the AD board is worth 5 times what I paid for it, but SRI does not really have a trade in program as far as I know. I would like to stay with SRI because Hugh is so helpful and I feel they will remain that way.

As far as the Lightlab unit, it is out of my current budget, and I really do not feel great about the lack of detailed information on the site. They do not really say much about - well, much of anything really- the detection method, other that spectroscopy. They also do not say much about the chromatography side, ie the columns, mobile phases, reservoirs, injectors. etc, and a lot of other things I would be curious about. I did write them for more info.

Finally, I do actually have 4, yeas 4 Agilent 5890 Series II GCs that I am bringing out of storage; All total I have 5 FIDs, one NPD and 2 TCDs. The problem with the 5890s is the HPIB communication commundrum. The GCs were running on long gone integrators for the most part, and one was running on Chemstation but the old Win XP workstation is gone, so I am pulling together the HPIP to PCI cards for an old computer and managed to get a copy of Chemstation from the late 90s or early 2000s. The 5890s are really good GCs, with heated injection ports, split/splitless,EPC opions, & sold build; injector liners, detector parts, and spares are cheap and easy to find because there were (and still are) so many in service. Agilent support is weak to nill, but the forums are great (ie: https://www.chromforum.org/viewtopic.php?f=2&t=85034). My biggest hurdle with the 5890s is the data communications issue.

Thanks for your feedback cyclopath, I appreciate it, it is nice to know that I am not the only one who loves the courteous nature of Hugh and the gang at SRI.

Any other chromatographers please feel free to chime in, but remember, I am on a tight budget and am just working with GC/FID without GC/MS or HPLC for now. I have certainly been scolded by many for even mentioning using GC without GC/MS or better yet HPLC, but I have to stay in budget for the next few months and have to work with what I have or can get before I can move forward!


I’m back flushing the column because the peak shapes suggest there are rocks in it.

last time that happened, it was kief. I suspect it’s sugar or chunks of cookie this time. responsible minion was poached by another team, so I can’t press them for details.

got any suggestions on an appropriate solvent for the second wash?!?

Its an invaluable tool. even without the heated injector. been running it for 4 years.

as far as the details on the Orange Photonics, it’s just HPLC a prepacked column, and a diode array. custom methanol based mobile phase.

tell them it’s a religious decision. Jah requests that we set cannabis on fire. You’ve chosen to perform that task in an itty bitty tube. with hydrogen. :slight_smile:

…and throwing away tools that give you perfectly good data is abhorrent



What column stationary phase are you running? I am sure you have already chopped the first meter or so off the dirty column, but that would be first. I have never personally tried to rinse a gc column but would love to hear how this goes for you. If you are using a Restek column, they can recommend the best series of column washes specific to the stationary phase, but I see some chromatographers recommend going from MeOH to Acetone to Hexane. Of course always rinsing from the detector end to the inlet end.

Restek has a chart of acceptable solvents for rinsing (http://www.restek.com/Restek-Capillary-Column-Installation-Guide-Section-III-Operational-Information) and they appear to really like a mixture of 20% DI H2O, 60% MeOH, 20% DCM that they call “Magic Mix.” Interestingly, the DCM apparently swells the stationary phase to allow the polar solvents to better penetrate and rinse. They do mention that this may not be recommended on thick film stationary phases >3um as this could over swell the polymer and clog the column.

Obviously proper column conditioning would be essential after the rinsing procedure…in some cases they recommend a vacuum pull from both ends for 24 hours followed by dry carrier gas flow for 6 hours at low temp then slowly ramp (4degC/min) temp to max column operating temperature for final bake out.

Hope this helps; keep us posted, I’m always very interested in others cannabinoid friendly GC experiences!


thanks for the links. should have gone looking on Restek’s site. or called them. Pretty sure I’m running a 3um 0.53mm MXT-35 MXT-35 Columns (Siltek-treated stainless steel)

Greg @ SRI said water was ok, or water/MeOH, he mentioned magic mix, but didn’t mention what the extra ingredient was. I obviously read that stuff last time around, because I had DI water, MeOH, and had the distinct inclination to add DCM (if I had a local source). I also had the bit about “thick” (>3um) films.

we’ll see how it goes. I did acetone, reinstalled the column, deinstalled the column, ran hexane. might run hexane a second time. didn’t give it near enough time to get the solvent out gently. restek says that will likely damage the bonding. so I may just have finished it off.

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