I need the help because I break 6 syringes in one month. I use hexane, ethyl acetate and ethanol for cleaning, but they don't resolve my problem. The plunger of the syringe gets stuck when I analyze many samples.
I usually use dichloromethane which seems to work fairly well. I wash 10 times before and 10 times immediately after an injection - before to make sure the syringe doesn't contain any contaminants and after to make sure all the sample is removed before you store the syringe. Unfortunately it is the nature of this type of syringe that they do block up or stick on a fairly regular basis.
It's going back a long time, but I recall successfully using pyridine, which was part of the reagent mix for organic acids. When you've finished a sequence, remove the plunger and clean it. Stick the needle through a septum or piece of closed silicone tubing connected to vacuum and aspirate a solvent such as methanol. Make sure to dry off any protic solvent before you re-use the syringe.
As pyridin is often used as a solvent during silylation, I've got best results using Pyridine for cleaning the "normal" Hamilton 701 series syringe together with vacuum - similar to Christopher R. Lee.
You get nearly rid of this cleanung problem when using the automatic Hamilton syringe for constant rate
"1-20µl x 0.05µl Constant Rate Syringe, CR700-20"
There is no steel plunger, the silylation reagent comes in contact with glas and PTFE.
And the needle is -of course- replaceable.
... a fairly reliable alternative
It's a little bit off-topic, but Satoshi's answer provides, indirectly, a reminder that ordinary soft tissues are a disaster in all kinds of laboratories. Kimwipes have been around for a long time, and as there seems to be no satisfactory alternative I regret not having shares in their manufacturer; institutional procurement services sometimes need persuading that the choice of such apparantly trivial items can be critical.
Thank you all,
was a good discussion, but I would not have followed more closely I will test a few options. I really did not know the KIMWIPE and I'll buy it to clean the piston.
Dichloromethane it's not recommended by the Hamilton for wash solvent because it can dissolve the "glue" of syringe. Anyway, thank you Valerie.
For now, i have resolved with Toluene and Acetone as wash solvents 1 and 2.
@Breno Paulo
Hope you have found a solution to your problem. This problem happens in our lab also on a regular basis. We use nHexane as the pre-injection and post injection solvent. Which solvents you are using right now in your lab? Toluene as pre-injection solvent and Acetone as post injection solvent ?
BTW I would like to know about the solvent used for column conditioning. Is methanol is sufficient ?
Pre-injection, you need a solvent that won't react with the silylating reagents, but is miscible with them.
Post-injection, it would be best to use a miscible solvent that *does* react, so preventing reaction with the glass. You also need to remove HCl from the TMCS. Perhaps that's why pyridine worked for me (it was also part of the silylating mixture; also, neat pyridine will contain a trace of water). Methanol may be a good alternative, but bear in mind that as you want to rinse with a reactive solvent, you must purge it or let it evaporate beforre using the syringe again. NB methanol and hexane don't mix, and hexane is neurotoxic.
Finally, dichloromethane is not compatible with steel, except for brief contact.
Ratheesh Chandran we program the software of automatic injection for wash one time in pre-injection with Toluene. In post-injection we are using Toluene and Acetone P.A. We programmed to wash 10x with each solvente in post-injection for minimize the carry-over. We are using too pyridine in derivatization solution, around 10%.
Best regards
Acetone should react with residual reagent, as the enol; TMS enols are not stable enough to be useful. I suppose the jamming could be due to some reaction with the glass that generates a polymer or changes its specific volume, though I havn't read anything about that.
We have been using dichloromethane for may years without any problems so was not aware that it isn't compatible with steel. We run many of our GC-MS samples in dichloromethane and it does not seem to cause a problem. It evaporates very quickly so is never in contact with the syringe parts for long. We rarely take our syringes apart to clean them as we have an autosampler on our current machine which does if for us. The syringes will usually run hundreds of injections without jamming. We had more problems with the syringes for our GC when it was manual injection, although not as badly as you describe. I have also used syringes in the lab for measureing small amounts of liquid and washing out as soon as you have used the syringe as well as before you use it seems to help, although they do jam more often than those on the GC-MS, particularly if your samples are sticky/thick.
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