Chromatography Forum

We are currently going through syringes at an unsustainable rate and have not been able to troubleshoot the issue. The syringes work fine for 2 of our methods, but the third method we are lucky to get 10 injections out of before the syringe clogs. The samples in this method are prepared in a mixture of Pyridine, HMDS, and TCMS and injected into the GC using an autosampler and an agilent syringe (ALS Syringe, PTFE-tip plunger AG5181-3354) and subsequently rinsed 5 times with DI H2O and 5 times with chromatography grade Methanol. In the past we have tried other rinse patterns involving pyridine and IPA but have not seen any signification improvement with our problem.

Shown below is an injection for a sample that it appears the syringe clogged on. After changing the syringe a second injection was taken on the sample with no problem.






Is there something that I am missing that may cause the syringe to clog as often as it does? Perhaps a wash solvent that is recommended? Anything I can do to recover syringes that clog?

You may try acetone or THF , before the water rinse , those are good wash solvents.

Since you are using pyridine as your solvent, I would try 100% pyridine as the rinse solvent.

We used trimethylsilyl derivation regularly, and I've published procedures with that technique. We most often used N,N-dimethylformamide (DMF) as our solvent for standards and samples and for our rinse solution, and used Agilent 5890 and 6890 series autosamplers/GC.

We did use pyridine as solvent for certain assays though, and did use pyridine as wash solvent for those.

Obviously, both water and methanol in rinse/wash will react with carryover derivatizing agent, which we wanted to avoid.