I’ve had this old 8610a kicking around the shop for more than a few years, and finally found the time to get it up and running. Having read a few threads here, and other places, it appears the common opinion on these units is that they do not work well for potency testing.
Well, that’s not entirely true.
Is it optimal? Probably not. Does it work well enough for my needs? Yes, yes it definitely does.
Now, I am in no sense an expert in this field. I love to tinker, and I have experience with HPLC, GCMS, both of which I also own and resurrected from the dead.
Here is what I have learned, in no particular order, but im hoping some members here will gain some useful information or maybe save some time if they have an old unit and want to make it work for them.
Firstly, the column. Mine came with an MXT-1, 15m, 0.53mm I’d, 5um film. I couldn’t find really any examples of methods using this column for my purpose, but I found one that works to resolve at least CBD, THC, CBG well, I’ll post my method below.
Secondly, this unit has the old style heater which is a ceramic light bulb looking unit with an exposed element wrapped around the outer wall. The oven does reach 235⁰c without much trouble but going from 235⁰c to 260⁰c takes some time. My cannabinoids seem to elute off the column somewhere between 225 and 235⁰c so no biggie.
Thirdly, this unit takes external gas cylinders which honestly, I’ve heard mixed opinions about the on unit H2 generator on the newer units being sometimes not the best, but I don’t know how they were maintained or used in those situations. I do know that external gas inputs are just one less thing to go wrong, so to me I appreciate this aspect of the older machines.
Now, when I bought this unit it did not come with a peaksimple 1 channel serial interface. I sourced one on Ebay, and wired it up as per the schematics on the inside of the interface chassis. It is old, so Serial connection, not USB.
Now to my actual runs. I found that the unit does produce consistent retention times with decent peak shape. The tempurature gradient I chose really kind of works with the machines limits and my tolerance for a reasonable run time.
One down side, which is also column dependant, is that it has trouble resolving D8/D9 fully. I did definitely play with gradient, and head pressure on the column to get the peaks nice, which I improved the separation somewhat to get 2 peaks, but they are sharing the base. Can you integrate it still? Yes. Will I? No. Lol. I’ve ordered another column at 30m instead.
My temp gradient is as follows:
205 start, hold 1m, then ramp @ 13⁰c /min to 225
225, hold 1 m, ramp @ 0.5⁰c/min to 235
235, hold 0, ramp 30⁰c /min to 255
255, hold 1m, ramp 0⁰c/min to 205
205 hold 1m
Carrier gas (N2) flow = 18.85ml/min
Hydrogen flow = 20ml/min
Make up FID = 250ml/min
FID signal = High
Attenuation = 1
I’ve included a picture of CBD, CBG, THC peaks separating, although I had my order of elution wrong in the photo, which I’ve since rectified in my bracketing. Also that photo was at the beginning of my method development, I’ve since spread out the peaks by adjusting the gradient and head pressure to have a bit more resolution from eachother.
If anyone else has been thinking of getting theirs going I’ll gladly offer any further advice or input from my experiences. Nothing tickles my fancy like old ass analog lab gear still putting in work.
-Ian
