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Dear Mr. Kitchen,


} What is the process for silanization of injector inlet glassware inside
} of injector sleeves. We currently use split inlets and buy new ones
} although we would like to start cleaning our own. Thanks.

Answer: (c)Alltech

All untreated glass surfaces contain –OH or silanol groups. These groups
interact with most compounds that are injected into your GC. The
interaction usually takes the form of tailing peaks (reversible adsorption)
or irreversible adsorption of the compound, both of which make quantitation
difficult. However, you have several options to counteract this problem.
You can either buy deactivated liners or deactivate the liners yourself.


To deactivate the liner, you must first prepare it for silylation. Rinse
the new liner with your sample solvent to remove any manufacturing residues
that might interfere with this process.


The liner must then be dehydrated. Silylation reagents preferentially react
with small polar compounds such as water, alcohols, and amines, so these
compounds must be removed before beginning the silylation process. To
dehydrate the liner place it in an oven and heat it at 180°C for 1 hour.


Cool the oven to approximately 50°C and immediately place the liner in a 5%
solution of dimethyldichlorosilane (DMDCS) preferably in toluene, but
methylene chloride and pentane will also work. Place a piece of laboratory
stretch film such as Saran Wrap™ or Dura Seal™ over the reaction vessel.
Soak the liner in the 5% DMDCS solution for 10 minutes. Use caution when
removing the liner from the reaction vessel because anhydrous hydrochloric
acid is formed during this reaction as demonstrated by Figure 1. Due to
their volatile and flammable nature, silylating reagents (and their
solvents in some cases) should be kept away from open flames and sources of
heat and should be handled only in a hood.


The liner should be rinsed with the same solvent used in the DMDCS solution
and then soaked in methanol for 10 minutes. Once again cover the reaction
vessel with laboratory stretch film. This step takes the reaction to
completion and Residual reagent, if left on the liner, will often mimic
column bleed which could require several hours to stabilize. The liner
should then be removed from the methanol and allowed to air dry. Once dry,
the liner is thoroughly deactivated and ready for use. Do not store opened
solutions or leave covered for long periods of time.


Alltech has created a new deactivation kit specifically designed for
deactivating
injection port liners. The kit comes with 4 x10mL ampules of 5% dimethyl-
dichlorosilane (DMDCS) solution, a pair of tweezers for easy liner
handling, four test
tubes which act as the reaction vessel, and detailed instructions. This kit
includes
enough DMDCS to deactivate four injection port liners.


This is was taken from Alltech catalog: “Specialists in Chromatography”
Deactivation Kit 18107 $33.00
http://www.alltechweb.com/literature/brochure/363p7.pdf
or
http://www.alltechweb.com/searchmain.asp
(search for DMDCS - use Adobe Acrobat reader for reading PDF files)

With kind regards
Tobias Kind


PS: OK - here comes the bargain basement:

Additionally to my previous post: Finding unknown substances
(stuff,junk,everything)
I add another useful service: The "Search Adobe PDF Online"
In most cases you can instantly read "PDF-files" and you will
find exclusive documents which are not covered by other
search services!

http://searchpdf.adobe.com/


Enter:  silylation liner dmdcs
If the links contain no usefull information - try "more like this document"

(...theres a gap - I walked manually to alltechweb...)


PPS: Sorry - J. Throck Watson :-)