Hi Eva,
It sounds like you have a problem with the CO2 capillary in the conflo. First, I would check to see if the capillary is actually going into the open split correctly when you turn on the CO2 ref gas. The capillary should go up to about 5 cm above the mass spec capillary. There is a diagram in your Conflo manual to help you, if needed. If that looks ok, then you may either have a clog in the end of the capillary or it may be broken somewhere. If you find that the capillary is bulging out of the end of the open split instead of going in, just gently nudge the capillary back into the open split. I hope this helps.

Sent via the Samsung Galaxy S9, an AT&T 5G Evolution capable smartphone

-------- Original message --------
From: Eva Stueeken <[log in to unmask]>
Date: 9/11/19 7:13 AM (GMT-05:00)
To: [log in to unmask]
Subject: [ISOGEOCHEM] CO2 dilution too strong

Dear all,

Since last week we're having trouble with a too high CO2 dilution in our system. We're running an EA Isolink coupled to a MAT253 with a Conflo IV. We usually set the CO2 dilution to 80% (sometimes 70 or 90), which produces a good peak size relative to N2 and SO2 in most samples. However, we're suddenly having the problem that the CO2 peak is completely gone with this dilution level. If we dial it down to 50%, we start seeing a peak, but the sensitivity is still low. Dilutions for N2 and SO2 behave normally and the peaks look very good. We have already exchanged the water trap (magnesium perchlorate) a couple of times, but it makes no difference. The He valves in the Conflo appear to open and close normally, according to the screen.   

Has anyone experienced this before and has some advice?