Ricardo
At my previous place of employment we had a new Procise 494 installed. The
engineer performing the installation had real difficulties getting the
instrument up to spec. Everything appeared to be working fine, as with
your instrument, but for some reason the repetitive yields were down 2 or
3%. It appeared to be due to TFA carryover but he couldn't find where it
was coming from. Out of desparation he stripped down the TFA delivery
valve and upon examination (10x magnifier) the membrane of the vacuum
assist valve had a pitted surface. Replacing the valve block cured the
problem immediately and he postulated that sufficent TFA was being trapped
under the valve which subsequently leached out reducing the repetitive
yield. As this was a new instrument it clearly demonstrates that minor
defects can sometimes make it through QC. I would suggest you contact the
valve block supplier (PE Biosystems presummably) and ask if you can try a
replacement block.
Kevin
______________________________________
Kevin Howland
Protein Science Facility Manager
Research School of Biosciences
University of Kent
Canterbury CT2 7NJ
Tel: +44-1227-764000 ext 7987
Fax: +44-1227-763912
email: k.howland@ukc.ac.uk
At 18:39 19/04/00 -0300, you wrote:
>We have an old sequencer model PE-ABD 477A and we are experiencing low
>repetitive yields but normal low leg and normal artifact peaks. All
>deliveries are properly optimized and the reagents are all under the
>expiration date. We already check the internal diameter of the reaction
>cartridge input and output lines, the temperature of the cartridge, the
>argon pressure and the vent lines. We flushed all the chemical delivery
>system with R3 (TFA) and S4B (acetonitrile 20%). Apparently there is a leak
>in the TFA delivery valve. We saw this moistening a pH-sensitive paper,
>placing it beside the open end of the cartridge inlet line, and delivering
>argon through the E block onto the paper. The observed pH was lesser than 3,
>which indicates leakage in the TFA valve. However, two details are bothering
>us: first, the E block is new and is being used for the first time. Second,
>pressurizing the block with the TFA bottle out, using the regulator to make
>the test, one does not verify a leak. I now have some questions to experts
>in 477A. Can a new valve block leak? If argon dry is dragging TFA, or
>either, if there is a leak from the TFA bottle to the block, how can the
>block not leak in the contrary direction, I mean, from the block to outside,
>when the bottle is removed? Do somebody have any suggestion to solve the
>problem of the low yield?
>
>I am anticipatedly thankful.
>
>
>-------------------------------------------------------
>Prof. Ricardo B. Cunha
>Brazilian Center for Protein Research and Services - CBSP
>Laboratory of Protein Chemistry and Biochemistry
>Institute of Chemistry
>University of Brasilia
>Brasilia - DF Brazil
>ZIP: 70910-900
>
>Tel: 55-21-61-307-2142
>Fax: 55-21-61-272-4548
>mailto:rbcunha@unb.br
>http://www.geocities.com/Athens/Acropolis/5221
>http://www.unb.br/cbsp
>------------------------------------------------------
>
>
>
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