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splitless injection with wool
Posted: Mon May 15, 2006 3:09 pm
by WK
I'm really just looking for opinions.
I get better peak shapes and response using wool rather than using the "recommended" empty liner. My samples contain quite a bit of less volatile material so using wool is ideal.
Is this a complete no-no? If so why?
WK
Posted: Mon May 15, 2006 3:27 pm
by mjfrayer
I would not call this a no no by any means. The added surface area in the inlet liner insures uniform evaporation of analyte substance. The mixing caused by the plug also aids in application of a uniform sample "plug" to the column. I have personally seen major differences in peak shape when measuring alcohols.
Matt
Whatever works for you
Posted: Tue May 16, 2006 9:27 am
by Peter Apps
If wool in the inlet works well then it cannot be a no-no.
Good practise is whatever gives good results.
Peter
Posted: Tue May 16, 2006 5:37 pm
by DR
It may work for a while, but this can only end in tears.
Posted: Tue May 16, 2006 8:59 pm
by Victor
I agree with mjf's reasoning on this one, and with Peter Apps.
The problem with using wool ( are you using ordinary glass wool?) is that the increased surface area this provides may cause reversible or irreversible adsorption of strongly polar solutes. Presumably, you are not using samples with such "active" consituents, otherwise you might have encountered these problems already. It is possible that such problems might be limited somewhat if you used quartz wool, but I wouldn't bet on it. For such samples I might be inclined to start with an empty liner or even an empty liner one where the sample has to perform contortions (their are many designs available from companies like Restek) to encourage the volatilization of less volatile solutes-if that is what you are talking about by saying "less volatile material".
Posted: Wed May 17, 2006 6:48 am
by Peter Apps
DR is right, insofar as you will see some deterioration in performance as gunk builds up in the inlet.
But this is true for any inlet design (except the really fancy ones that automatically change the liner !!) and for empty as well as packed liners.
When performance deteriorates it is time to change or clean the liner, no matter what design you have or whether it contains glass wool or any other packing.
Peter
Posted: Fri May 19, 2006 3:03 pm
by Douglas Moore
I agree with MJF as well. It increases the surface area to improve vaporization in the inlet. However, you need to keep tabs on how long it has been used, because it can trap high BP materials which act as active sites.
You can purchase different types of glass wool for different purposes. Silanized works well for general purpose, phosphoric acid treated for acidic compounds, pesticide grade is recommended for pesticide applications. Check out Supelco.