Units of Gass chromatorgraphy using TCD detector.

[mianamjad]

I am using a newly acquired GC with TCD detector, where the Y Axis units are uV, what are these units and how can you calculate concentrations from this. I am new to chromatography. thanks in advance

[dblux_]

I am using a newly acquired GC with TCD detector, where the Y Axis units are uV, what are these units and how can you calculate concentrations from this. I am new to chromatography. thanks in advance

Units in question is detector response expressed as voltage of electric signal.
Before you make use of it you must calibrate your instrument ie. find dependence of peak areas (µV*time) as a function of concentration of your analyte.

[mianamjad]

thanks for the help buddy. but as i told u i am very new to gc, so is it possible you can give me some more details?

[dblux_]

thanks for the help buddy. but as i told u i am very new to gc, so is it possible you can give me some more details?

Prepare a series of calibration standards covering your expected analyte concentration.

Measure peak areas for each calibration standard and graph it on Y axis, on X axis graph corresponding concentration values.
This will be your calibration curve.

Then run your sample and for achieved peak area find corresponding concentration from the curve.

That's it. BTW - your chromatograpy software will make graphs for you.

And read about calibration. It's essential for quantity analyses.

[DAVID ROBERTS]

I am new enough to make lots of mistakes. A semi developed method I am working with gives an Ref Gas as 3x the carrier gas flow for my TCD. 5980. Method was set up with He as carrier. I am now using N2 a the carrier. Does a signal level of ~170 mv. seem ok with 3 air to 1 nitrogen?

[AICMM]

David,

It's not really about base signal, it's about noise and signal to noise. An HP can often have that kind of base signal (at least the ones I work on) but it should have pretty low fluctuation around that number. Also, what concentrations are you running and have you shot anything yet? Reason being, if you are looking at high concentrations then the background signal is not crucial (nor, for that matter, is the noise really) but if you are looking at low levels then it becomes pretty important.

Typically, the more details you provide the more help you get.

Best regards,

AICMM