I am manually injecting samples in our HP 5890 GC. I am new to GC and related stuff. I would appreciate any suggestion on improving injection techniques or rather details of how to load a sample in a syringe and inject it.
By Maggie on Friday, June 25, 2004 - 07:05 am:
[I'm not sure I'm on the right board -- if this question pertains to electrochemical detection, read on...] This is not the whole story, but here are some refinements I've been taught:
1) Use a Kimwipe to wipe off the outside of the syringe needle before injecting, to reduce carryover. Do it fairly quickly so the Kimwipe isn't held to the opening of the syringe needle, which could suck some sample out.
2) When you've put in the needle in the Load position, and then turn to Inject, keep the syringe in the injection valve. Take it out after turning it back to Load before the next injection.
3) Make sure you feel the added resistance of the little "collar" inside of the injection valve, to ensure that you're putting the syringe all the way in.
4) I don't know if there's anything special about loading a sample into a syringe, other than do it relatively slowly so you don't generate bubbles, and if you have to suck up the whole sample, you'll eventually get the sense -- visually -- of when the last microliter has been taken up.
By ab on Saturday, June 26, 2004 - 01:28 am:
I think the Anonymous is the same undergraduete student, who is trying to do the ethanol curve.
Using an internal standard, you can inject as you wish. Result must be good anyway.
Maggi, the question relates to making an injection in GC's injector. Usually there is no valve to make an injection in.
By Anonymous on Monday, June 28, 2004 - 03:24 pm:
This is my method for injecting a 1 ul sample using a 10 ul syringe:
Insert the needle into the headspace of the vial containing your sample. Draw the plunger up to the 4 ul mark. Lower the needle down into the sample, them raise the plunger another ul. Withdraw the needle back into the headspace and pull the plunger up until you can see your sample with air on either side. Verify the accuracy of your volume and repeat the procedure if you seem to have more or less than 1 ul. If you are happy with your sampling, wipe the outside of the needle, then insert your needle through the GC septum, holding the plunger in place. Inject rapidly but gently. Good luck