I have HP-5890 and HP6890 in the lab. The instruments are equipped with slpit/splitless injectors. I normally use the split/splitless liner, packed with glass wool. I have noticed that HP liner contain a rather loose plug of glaswool, positioned in the middle, while equivalent liners from Alltech contain a rather tight plug, position at about 2/3 of the liner. Recently SGE is advertising FocusLiners(TM). My question is: where should the glaswool be positioned to achieve reproducible injections.
I am looking forward to reading your answer.
3M Specialty Materials Markets Group
Zwijndrecht - Belgium
By lisa on Friday, August 6, 1999 - 02:23 pm:
We have several different users of 5890s in our lab and they all do something different:
for GC/MS, we generally position the glass wool ~2/3 of the way down into the liner.
for NPD, we put it in the middle.
I think that your sample type would have a lot to do with the placement of the wool. If you have particularly dirty samples, you would probably want to move the wool down the liner. JMHO!
By John Hinshaw on Saturday, August 7, 1999 - 07:43 am:
In my experience, the glass wool should be positioned so that the syringe needle tip enters the top of the wool plug during injection. Especially for autosampler injections, this ensures that the occasional droplet of sample left hanging on the needle stays inside the inlet and doesn't get wiped off on the septum where it could cause ghost peaks, carryover, or unusual baseline problems.
The bottom of the plug should be at least 1-2 cm above the top of the column, but long enough that the syringe needle comes down to a position at least 2 cm (more is better) above the bottom of the plug. The needle cannot be allowed to exit the bottom of the plug!
The plug itself should be packed medium-tight. If too loose, the syringe needle or carrier-gas pulsations from split/splitless vent on/off transients will push the wool down onto the colum tip. If too tight, channels may form through the wool which will defeat its purpose.
Use silanized glass wool or quartz wool (better for mass spec if siloxane-fragment background is a problem). If you have a problem with trace-sample adsorption (peak tailing, lost peaks, ghost peaks) in splitless injection, try using no wool or try on-column injection.
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