Is there is a "smoothing" function on Chemstation?

[lynzjm]

Hi all,

we have a "smoothing" function on Chromeleon we use for other systems but we have an Agilent 1100 which is all connected up to Chemstation (we don't have Chemstore we just have to use Chemstation offline for manipulations and peak areas etc). Does anyone know if its possible to smooth using Chemstation?

Cheers,
Lynsay

[tlahren]

I have MSD Chemstation not the LC Chemstation. But a lot of commands are interchangeable. I'm pretty sure that smoothing is available as a macro in newer versions of MSD Chemstation but I'm not sure. When I search the help menu for "SMOOTH" i get back two commands that give examples of how to produce a "smoothed" chromatogram using the command prompt. I tried it and it does work. I'd have to play around with the filter variables to get it to work "right" but it should be able to do what you want.

Once you get it down to a sequence you can place all the commands as a sequence into one of the "Custom Tool Macros" (assuming that LC Chemstation has these little Hammer Icons at the top menu bar). All you would have to do then is click the button to run the new "Smoothing" macro.

Again you will have to play with the filter options listed in the help menu or if you are a more advanced macro writer you can just have an input box where you enter that info each time.

Hope this helps a little. Let me know if you have more specific questions.

Ty

[tlahren]

I forgot another option. In MSD Chemstation there is an option to switch to the RTE integrator. This integrator has a "Smoothing" check box in it. This might be what you're looking for. The RTE is not usually the default integrator so you would have to change it under "Chromatogram - Select Integrator" and then edit it under "Chromatogram - Edit Integration Parameters." Again, I'm not sure if the menu options are the same in LC chemstation (as I'm assuming you have) but they may be similar.

Ty

[lmh]

LC chemstation is totally different to GC chemstation, but smoothing is easy.

In the signal details box, if you are carrying out off-line data-processing, you will probably have some signals specified in your method. If not, when opening a file, tick the box marked "load using signal details". Now go to signal details, and transfer anything you want into the table of signals used in the method, which is towards the bottom of the signal details page. The available signals are in a drop-down box at the top.
Now move to the extreme right hand end of this table. You will find a column in the table for smoothing, where you can specify the algorithm, and another column where you can specify the number of points over which smoothing is carried out.

I STRONGLY recommend Savitsky-Golay smoothing rather than Gaussian. If you want to know why, try both... with S-G you can use a huge number of points to smooth over (11, 13...) without increasing peak-width.

There are a few hitches of which you should be aware:
(1) When you start a new calibration table, for some reason Chemstation will forget any smoothing information in the signal details box, so you'll have to restore this on opening your first calibration point.
(2) If you are using LC-MS and have SIM signals, they won't appear in the drop-down list to add to the method until you've extracted them using File - Extract ion chromatogram.

[lynzjm]

Thanks Ty and Imh,

Thats brilliant, I'll pass this on to my colleague, he says to thank you both very much for your help!

Cheers,
Lynsay

[lmh]

always glad to help. The signal details you've put in your method, provided you leave "open using signal details" ticked, will apply to chromatograms in files you open to examine manually, and also to any batch processing you carry out. Do ask if your colleague gets stuck.