Chromatography Forum

Hello guys

I am having trouble with the combi Pal system.

It is bending plungers of my syringes during the cleaning cycle. It seems to be pulling the plunger out too far and then when it goes to remove the solvent to the waste the plunger flexes and bends. This does not happen on every clean but once every 30-50 injections. It is very frustrating as we are going through to many syringes and this should not happen. This problem has occurred over the last 2 years and we have replace the two motors that drive the combi pal system which seemed to fix it for a while (6months) but the problem has reappeared and getting worse.

One idea I have had to fix this is to reduce the amount of solvent it uses to clean the syringe. I would like to change the clean syringe macro so instead of cleaning 10ul of the syringe it only cleans 5ul (ie 50%). I have tried to change the values of the % fill but that does not seem to do anything. Is this possible? If so how?

Is this problem fixable another way? Have you seen it before?

Cheers for any help with this

Regards

Matt

What solvents are you using (in the samples and the solvent vials)?

Chloroform or hexane

Doing FAME analysis of marine oils

Cheers

Matt

When you take a syringe out of the sampler is it a bit stiff to slide - particularly after a large number of injections? One reason for having two wash solvents vials is that you can use two solvents for cleaning the syringe. In work that I do, I will use toluene - the colvent for my samples - for the first rinse solvent and ethyl acetate as a second rinse. There are some somewhat polar compunds that show up in the mix and seem to like the inside of the syringe better than the toluene rinse. But using ethyl acetate seems to get all the residue out of the syringe - and the syringe plunger will slide as easily after 500 injections as on installation.

The typical setup is before injection one rinse with toluene (to be sure there is a liquid seal present in the syringe). Sfter injection 3 or 4 rinses with toluene and then 3 or 4 rinses with ethyl acetate. If there is a condern about traces of the more polar solvent getting into the sample with only one toluene rinse before injection, go with two. But multiple rinses before injection should not be needed. The syringe should be clean wiht the post syringe rinses - or you are inviting the syringe to gather residue - stick - and wind up with a bent plunger.

Agree with Don. If you are using chloroform and hexane, the syringe plunger will eventually bind up in the barrel and the plunger will Z. If you look at the barrel, you will see a white residue inside. I have actually picked up a syringe, not realizing someone had previously cleaned it with hexane, and started to clean it with chloroform. On the second rinse, the syringe plunger froze inside the syringe barrel. I was trying to do a manual injection and never even made it to my standard. I would not do anything to the autosampler until you rule out a solvent problem. Try a new syringe using Don's solvent suggestions. I use the solvent I have in my samples for both rinses whenever possible. If you're running some samples with hexane and some with chloroform, use one syringe for the hexane samples and one syringe for the chloroform samples. Good luck.

Cheers for the replys,

I still believe that there is something wrong int he system, I use CHCl3 95% of the time and this has worked well for 5 years. in the last 2 years this has problem has started to happen. (it all started when a student put acid int he wash system and corroded a syringe) Some time it happens on after 10 injects so I do not think it is the case but can make on of my washes ethyacetate.

Has anyone got any ideas about the programming of the PAL system?

You can change how far the plunger pulls back, but the setting is not in an obvious place - have a look under syringe in objects, or maybe the wash station, I'm pretty sure that it is not part of the method. My CTC is shut down at the moment, otherwise I'd go and have a look. The operators manual is your friend - or fire off and email to the makers.

Peter

Cheers Peter,

I had a look through the whole system and and changed two parameters to 5ul (one in syringe and another somewhere else) but neither has changed the amount the injector cleans the system with.

If anyone can help me out to walk me through how to change my cleaning of the syringes to use only 5ul rather than 10ul I would be very happy

thanks in advance

Matt

Two parameters I have changes is in the "methods" under "liquid" I changed the inject volume from 10 ul to 5 ul

also in the "Utilities" in the "syringe" section I changed the fill volume to 5ul (from 10ul).

Neither of these changes have made any difference to the amount it fill at each wash

thanks

Matt

I believe this parameter is to be found in your injection methode.

I'm using an old combi-pal so I still have to use the manual controls

go to:
Menu -> methods -> "select the methode you are using when it bends the plunjers" -> just below the section were you set the pre-clean steps, you'll find "fill volume".
This is the volume the autosampler will use to rinse the syringe. Try setting it slightly lower than your injection volume. We eare using CH2Cl2 without any problems.

kind regards
Bart Mulkens
De Watergroep
Belgium