Signal interpretation in ChemStation: 5890 vs. 6890

[bjackson@microbe.com]

I am trying to use older software to increase productivity while keeping cost down.

I currently use an hp 5890 w/ HP GC ChemStation Rev. A. 04. 01. 1990-1996 w/ customized macros to crunch my data
this works fine.

I also have a hp 6890 w/ HP GC Chemstation Rev. A. 06. 01 [403] 1990-1998, the customized macros are having an issue with the signal interpretation.

The 5890 signal, interpreted thru ChemStation gives area counts in the thousands, while the 6890 signal interpreted thru its ChemStation gives me picoamperes (pA) with values ranging 0-100, the custom macros does not like this. I get error message in the data file.

Is there a way to fix? Can I change the way the signal is interpretted on either GC?

Thanks

[bjackson@microbe.com]

Good Morning, ALL!

Well, I just got off the phone with Aglient support. There is NOT a way to change the signal interpretation, according to the Aglient support rep, this was one of the major changes between the 5890 (area counts) and the 6890 (picoamps).

So this doesn't help!

Shouldn't there already exist a macro which would account for this change? I'm not a programmer and I have limited knowledge on how these macros are organized and how they work together, so any help or advice would be appreciated!

Thanks!

[edwsynergy]

Is there a way you could multiply all the picoamp values by 1000 when you read them from a file?

[Consumer Products Guy]

Well, I just got off the phone with Aglient support. There is NOT a way to change the signal interpretation, according to the Aglient support rep, this was one of the major changes between the 5890 (area counts) and the 6890 (picoamps).

Well, I'm agreein' with Agilent on this one. I just went over and checked, and our 5890 (which runs on newer software than yours) does also read as "Area Counts". So not a "software revision thing".

[bjackson@microbe.com]

I also had the same idea as using a "multiplication factor", but I can't locate the signal parameters in the macros. Ugh! This is frustrating!

Thanks!

[CharapitsaS]

I also had the same idea as using a "multiplication factor", but I can't locate the signal parameters in the macros. Ugh! This is frustrating!

Thanks!

There is the following way to solve your task.
Any arithmetic manipulations (*C;%C;+C;-C; summation and subtraction of chromatograms) may be done in Unichrom ( free downloud is here http://www.unichrom.com/dle.php ).Users Guide and Installation manual for dounload is here http://www.unichrom.com/docse.shtml . After installation of Unichrom you may read your chromatograms (files with extention *.ch) and perform any arithmetc manipulations.
You may send me file of your chromatogram with description what you want to manipulate and I will help.

Regards,
Siarhei

[Peter Apps]

A peak area has to be in units of signal intensity multiplied by time.

Any measurement result that is in pA is a signal intensity, not a peak area. Without a time factor, signal and peak area are not comparable (in the strict sense of the term).

Peter

[bjackson@microbe.com]

A peak area has to be in units of signal intensity multiplied by time.

Any measurement result that is in pA is a signal intensity, not a peak area. Without a time factor, signal and peak area are not comparable (in the strict sense of the term).

Peter

You are correct Peter. My apology for not being more specific. I am assuming during the computers automatic integration the separate variables, i.e. the signal strength and time are in the same units as you say. However, there is some unknown factor which increases the signal by a factor of ~1000 on the 5890. So when I try to use our custom macro operation on the 6890 (which does not have this unknown factor?) it does not see any of the peaks, they just come up as noise in the baseline. I hope this explains my dilemma. Sorry for the confusion.

[Peter Apps]

Best guess is that there are pA on one and nA on the other, or some other SI unit multiplier (maybe even seconds to milliseconds). You might be able to select output units somewhere in the instrument or software set up.

That it is not exactly 1000 for an SI multiplier is because each instrument, even of the same type, gives a slightly different signal for the same mass of substance in a peak.

Peter

[Yama001]

Hmm I do not have anything to compare anymore, but I thought the opposite occured- the 6890 would produce much greater peak counts than the 5890.

My understanding of this is poor, but I believe the Chemstation software was not designed to handle the potential dynamic range of a 6890 detector, particular from the micro-ECD. When a 6890 method is first created, you will be asked if you want to focus on small peaks (trace analysis) or large ones. The software will scale the signal produced depending on what you pick. The method.ini file in the method directory will have an entry for "gc6890scale". It possible this scaling is part of the confusion.

[GasMan]

If you go onto the Agilent web site and type in 5965-8901E in the search box, you will get a technical note explaining a little on how the 6890 handles data. There is also reference to another note, 5965-1640E, which deals with the differences between the 5890 and 6890, but this is not avialble on the web site. I am trying to get a copy of this and will post if I can make it available.

Gasman

[bjackson@microbe.com]

If you go onto the Agilent web site and type in 5965-8901E in the search box, you will get a technical note explaining a little on how the 6890 handles data. There is also reference to another note, 5965-1640E, which deals with the differences between the 5890 and 6890, but this is not avialble on the web site. I am trying to get a copy of this and will post if I can make it available.

Gasman

Thanks, that might help! Currently, I have a programmer trying to remedy it with another macro.