Hi Thomas,

The few times this has happened to us was simply the fact that the TCD carbon peak had migrated enough that it did not call the peak as ‘carbon’.

Did you check the TCD tab? Does it definitely have ‘carbon’ labeled or is it instead 'peak 2'. Simply changing the range of where to look for carbon worked and we were able to get our dilutions back. Our peaks shifted occasionally as we had leak issues in our autosampler. This confused us to no end as the problem was apparently random calling a dilution sometimes, but not other times or starting fine, and finishing with no dilution. Also large carbon peaks would often shift outside the window and it would no longer call the carbon peak.

Hope that’s it as its an easy fix!

Cheers,

Chris
—
Chris Wurster, Ph.D.
Lecturer, Environmental Earth Science
College of Science & Engineering
James Cook University
Cairns 4870
Australia

https://research.jcu.edu.au/portfolio/christopher.wurster/

Office: D3-114
Phone” +61 4232 1338
Fax: +61 7 4232 1583



> On 7 Jun 2021, at 23:54, Thomas J. Boyd <[log in to unmask]> wrote:
> 
> Hi all, 
> 
> I “inherited” a Flash 2000 HT and have begun analyzing materials for CN isotopes. Among the inheritance was the SmartEA option which I installed. The system interfaces through a Conflo IV to a Delta V Advantage IRMS. The unit works well and I have no trouble obtaining N and C peaks – both with the TCD and the IRMS, all with appropriate delay through the SmartEA additional tubing. Because my anticipated sample stream will contain unknowns, I’d like to use the SmartEA autodilution (I will likely not know the CN ratio for samples coming in, so pre-defining dilution will be challenging). I followed the Conflo IV manual to set up the reference regression – but I cannot get the autodilution to work during run(s). I took the opportunity to replace the aging computer, so I have a clean IsodatNT install (latest service pack - .94). That did not help. I still cannot get any dilution using reference automatic. 
> 
> Here are the details: 
> 
> Set up a sequence with ~0.050 to 1.000 mg standard (urea). Used “Start Reference Regression” for the first standard, then “Add Reference Regression” for each subsequent (0.050, 0.100, 0.250, 0.500, 0.750 and 1.00 mg – roughly). Subsequent samples produced “infos” similar to the below after running: 
> 
> Set Reference Dilution to 49 [%]
> Peak Center found at [57209]
> Sample Dilution found at 0 []
> Detector Signal added: Ret:110.562[sec]  Ampl:64757 [mV] : 13:11:21 
> N2 Expected MS Signal is: 0.000 [mV] 
> Set Sample Dilution to 0 [%] 
> Sample dilution: 000 0 
> Detector Signal added: Ret:219.562[sec]  Ampl:42148 [mV] : 13:13:12 
> CO2 Set Reference Dilution to 27 [%] 
> Expected MS Signal is: 0.000 [mV] 
> Set Sample Dilution to 0 [%] 
> Sample dilution: 000 0
> 
> The TCD had varying amplitudes (mV intensity), yet no matter what, the sample dilution was set to 0 (because the Expected MS Signal was always 0.000 [mV]?). The Conflo IV manual does not mention using these sequence line(s), but I also tried the same series of standards using “TCD MS Calibration Start” and “TCD MS Calibration Add” for the first and remaining standards. Results for subsequent samples were the same as above, always “Expected MS Signal is: 0.000 [mV].”
> 
> In the Databases directory, the following have been created, so it’s doing something: 
> Flash TCD CO2 BlankData.iso
> Flash TCD CO2 Reference.iso
> Flash TCD N2 Reference.iso
> 
> I’m at a loss for anything else to try… I must be missing something. Could be the way I’m searching, but I cannot find any posts in the IsoGeoChem archive addressing this issue? Any ideas?