I would expect it is ok. As the flow path is less restricted on the "dillution on" side you may get a bit of change in the back pressure on the line, Should not make much of an effect on chromatography, just be wary of the jump timing from N2 to CO2.
On Sat, Mar 29, 2008 at 7:36 PM, Melissa Bautista <[log in to unmask]
Thanks William and Brian for your suggestions and advice. A check for flow
from the stainless purge line indicated that this was blocked. I replaced
this and also disassembled and cleaned the three-way valve, as described. I
replaced the glass capillary from the EA to the open split, but the split
itself is still quite clean. Brian, you may remember that we cleaned it
while you were here. I also baked and blew out the stainless transfer line
from the EA to the conflo. After all was reassembled and the carrier flow
turned back on (set at 100ml/min), the flow rate increases slightly from 100
ml/min with dilution off to 107 ml/min with dilution on. Is this normal?
-------- Original Message --------
Subject: Re: [ISOGEOCHEM] EA carrier flow
Date: Fri, 28 Mar 2008 10:44:18 -0400
From: B Jones <[log in to unmask]>
Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
To: [log in to unmask]
There is most likely a problem with the pneumatic valve inside the
Conflo interface. I would assume a blockage in the "dilution on" split
section. If you remove the cover from the Conflo you will see a small
pneumatic valve on the right. The Ea flow from the back of the interface
connects to this valve. This valve switches from a split of the EA flow
from 72ml/min with dilution off to 79.5ml/min with dilution on (flow
rates based on 80ml/min EA flow; as in conflo manual pg 2-3). It does
this by switching flow paths, one path being more restricted than the
It would appear that the "dilution on" flow path is clogged and creates
a back pressure on the EA slowing flow. I would suggest disassembly of
the valve and both flow paths and cleaning both thoroughly with acetone
followed by MeOH. Dry parts well in a oven at ~30C. I would also suggest
replacement (or at very least cleaning as above) of the glass capillary
associated with the EA flow to the open split. While it is open, you may
want to clean the open split glass as well, but it can be a pain to
remove and reset all capillaries. Noticeable brown stains in the open
split would suggest a need to perform this extra work.
On Fri, Mar 28, 2008 at 12:10 AM, Melissa Bautista
<[log in to unmask] <mailto:[log in to unmask]>> wrote:
This is in regards to a change in carrier flow rate from our Flash
to a Conflo III.
The carrier flow is set at 100ml/min. However, when the He dilution
capillary is dropped in, the flow rate drops to c. 58ml/min. I have
the heights of the capillaries in the open split and they are positioned
correctly according to the manual. Can anyone tell me why this happens?
Southern Cross University
Lismore NSW Australia
"It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it."
US President, George W. Bush