Chromatography Forum

Hello,

We run the SPME not that often in the lab. But recently we have been running it and it has beend bending the SPME fibers which is getting expensive.

Details

First (is the obious one) We bought new lids for our 20ml SPME vials.
The SPME is working fine execpt on thing.

When the SPME removes it self from the vial in the Heater/agitator before it goes to inject it, the SPME clips the edge of the lid and bends the outter casing of the spme fiber. When it goes to inject the spme fibre gets bent inside the injector and is ruined.

So, yes we are ordering some new lids and trying to get the same as before (the new ones look nearly exactly the same but possible the lids are a tiny bit smaller) but they are from a different company.

But what I would like to know has anyone else had this problem?

Is there a cure with adjustment of the combi pal settings (I have tried adjusting the Z axis on the location of the Heater/agitator by rasing it by about 1.2 mm)?

We are reluctant to keep on trialing different lids as we dont want to keep on breaking fibers.

Cheers in advance for any help out there

Matt

Here is the the broken SPME

Here is my set up


Thanks

It sounds as if your first step needs to be to re-do the alignment. If that does not work then get back to us.

Peter

The second step would be to replace the two tensions cords inside the z-axis. You will need to get your local CTC service agent to do this.

We had a Combi-Pal that repeatedly broke the autosampler syringes. The vendor couldn't resolve it and neither could we. Nothing ever was found. I suspect that it just wasn't getting to the same spot all the time. They finally replaced it.

Vial septa that are just a bit too stiff and sticky (like butyl rubber at low temp) can put just enough bend in a needle that it commits autosampler suicide on the injection port.

Peter

Cheers for the help guys.

I have re aligned the Z axis.

But back on the injection work for the next month.

Hopefully I will get to the bottom of this allthough some of your response scare me a little

Cheers for the help

Matt

If the SPME needle is touching the vial caps it is the x and y axes that need re-alignment.

Peter

Looking at your pictures again, I can almost guarantee that the shorter tension cord in the z-axis needs replacing.

The function of the short tension cord is to push the vial off the needle with the lower needle guide. If the short tension cord has been overstretched (which happens with age), there is not enough force to push the vial off the needle. Bending of the SPME needle near the tip (just like in your pics) is a sure sign of this. It normally occurs first with headspace due to the thicker septa. The thicker SPME needle probably doesn't help either. In later model CombiPALs (2007 & later), CTC slightly shortened the length on the tension cord to improve this push-off force. Your CTC service agent should fit the shorter type (make sure they do!).

I would also get the CTC service agent to change the long tension cord as well. This stops the z-axis dropping down when the power is turned off. CTC recommends both tension cords are replaced once a year.

Cheers Mcgyver,

Can i fix it with a swiss army knife, cable tie and some gum....... I am sure you could back in the 80's........joke

Cheers for the info will get onto my supplier

thanks

Cheers guys,

Bought some new Bungees and it works well. Once I had the old ones out you can feel the give inthem

But $410 kiwi dollars is a bit of a rip off for a couple bits of cord.

Matt

Sounds like you bought the preventive maintenance kit - which is a rip off for a couple of cords and a bit of grease.
You can buy the tension cords separate from the PM kit. They come as packs of 5.
If your supplier is nice they might split a pack up and sell them individually. Should be $20 - $30 if you can get them individually. Probably still pricey for a bit of bungee cord though!
CTC part numbers for the 5 packs are MZ 30-21 (280mm cord) and MZ 30-23 (90-95mm cord). Give these a go next year!