Chromatography Forum

GCs.

The software for my GC displays scale in Volts, but I want to compare a chromatogram to one that uses Pa for the scale. Does anyone know the conversion factor? thx

The pA to volts conversion would depend on the range and attenuation settings of the electrometer that converts pA from the detector to volts to the recorder (which these days is then promptly digitised for software processing). To a large extent, beyond both pA and V being proportional to compound quantity the output is arbitray - it only makes sense in terms of how much of a chemical generated the signal once you have done a calibration.

What do you need the comparison to tell you ? - that one detector is more sensitive than another ?

Peter

I'm using a GC method developed from one of our partners. It's using Pa scale. When I try to run method I get very low carryover from one of the compounds. My chromatgram's scale is Volts. The blank contained in the method appears that it has no carryover, but the scale is different and it's not very large so I don't trust it. If I knew the conversion between the two different units I could get a better idea if the problem is my fault or if it's possible that carryover from the displayed chromatogram is hidden by its scale. thx

You should search the archives before you post.

On April 30 of this year I posted:

Older versions of HP (Agilent) GCs used microVolt as the Y axis parameter. More recent versions use pA as the parameter of scale for the Y axis.

I believe if you divide the 'counts' or mV by 2048 you will approximate the output in pA.

4100 counts or microV equals approximately a 2 pA signal.

I hope this is useful as well as accurate. My memory is not as good as it used to be.

best wishes,

Rod

Hi Mike

On other data systems, poresuming that you have both chromatograms in electronic form, adjust the scales on each until a common peak is about the same size, or if there are no common peaks until the basleine noise looks the same.

Peter

Thx for the help. What archives are you referring to chromatographer1? link please.

the site is called Chromatography Forum (hee hee)

Rod

Mike, use the search function at the top of the page to search through old threads.

Kinda glad you didn't though, didn't know the actual conversion (I just roughly estimate if thats all I need, and the software I use takes care of conversions from different data systems so I don't usually have to worry about it ) good to know.