Using an Agilent HPLC along with an ACN/Formic (Mobile) and Water/Formic (Stationary) method with a Restek column … my method does not give enough resolution when it comes to D8/D9 seperation. Does anyone have a method using the same solvents or column that will solve this issue or even have a suggestion on a different method?
Thanks
KingRat
@MagisterChemist might be able to help
I know he has methods for seperation of cbc and d10, I bet he has a good method for d8/d9
Might use a different column though
SRI GC-FID separate them very well. Not helpful I know.
Yes i have methods that get at least baseline resolution between them. Mine uses methanol instead of acn.
I had a horrible experience using a GCFID but I think it was the instrument, that said, obviously I don’t want to have to go out and buy new equipment if I can use my own but thank you. Someone sent me a method file to try.
Yes, thank you… that was where I was going to go… as I used Methanol for separations on a larger scale prep system and it worked much better. However I no longer have that method. Someone else sent me a method file with the same column and solvent system so I am going to give that a try. I will PM you.
I can shoot you my method as well. It separates the d8 and d9 but i dont really do any d8 work so im not sure how it does when there is 98%d8 and <3% d9 but you are welcome to try it. its a 35 minute method and uses an agilent column.
OK. What column exactly are you using? “restek column” is not specific enough.
I knew you were going to ask that… LOL… god it is the one everyone is using 2.7um 150mm, Raptor ARC I think…
For the Raptor ARC 18, there’s a method straight from Restek that can baseline resolve 16 cannabinoids.
I was about to say this, GC-FID (or GC- anything) will work better here because of the difference in boiling points relative to the difference in polarities is much greater.
Maybe MeOH/water on a gradient as your mobile phase? How are you using a liquid as a stationary phase in an HPLC? If it’s supposed to be stationary and your mobile phase is miscible with it then I’m not familiar with what you’re doing there. Usually the column contains the stationary phase unless there’s a method I’m not familiar with.
You can probably get reasonable separation with an isocratic method somewhere around 70% ACN.
A bit of HPLC terminology: Your aqueous mobile phase (Mobile Phase A by convention) is water with formic acid. Your organic mobile phase (Mobile Phase B by convention) is acetonitrile with formic acid. Your mobile phase is the combination of your water and your acetonitrile. Your stationary phase is your column, Restek Raptor ARC-18.
Here are some applications, there are at least a dozen more out there:
https://www.restek.com/chromatogram/view/LC_GN0578
https://www.restek.com/Technical-Resources/Technical-Library/Foods-Flavors-Fragrances/fff_FFFA3123-UNV
sonication is your friend
Ok… can you send me a link to that method?
Yeah… I knew I misspoke on that one, I am used to running a CPC (counter current chromo) unit which has it’s phases in liquids…
Thank you for that… but it appears that I am running that exact method you linked to… which was 25%/75% and flowrate of 1.5 … but as you said, maybe go with 70/30 … I am running the pump isocratic, are you saying to not go from 70/30 to 100/0 and back?
Can you post a chromatogram of your d8 and d9 on your current method?
Yeah, I’m suggesting keeping it at 70% Acetonitrile. After d8 and d9 elute you can ramp quickly up to 100% acetonitrile to flush anything else from the column and then back down to 70% ACN to re-equilibrate for the next run.
82% meoh 18% water, each 0.1% formic acid. 1250 ul per minute, 15 min run time. I got decent resolution with this.
https://www.restek.com/chromatogram/view/LC_GN0578
Been using this restek method for a while now and so far it’s the best I’ve seen for D8/D9 separation as well as the CBD/A-CBG/A cluster at the 2.5-3.5 retention time mark - that area can get messy with other methods. Was able to add in CBLA as well with no interference. The Ammonium formate in the mobile phase is a game changer.
When sample prepping, sonicate for at least 20 minutes. IME this helps retain the separation in light of matrix effects.
Not sure what your experience level is, so forgive me if this is elementary, but make sure you filter your sample prior to injection and use a guard column if you can afford it. It’ll make life a lot easier in the long run
With a column of that price category like the ARC-18, using guard columns and filtering at 0.45 micron should be a given.