By Young on Wednesday, February 11, 2004 - 11:31 am:
I wonder what is the practical difference wether mV or mAU is used as signal axis unit for a UV chromatogram.
By Chris Pohl on Thursday, February 12, 2004 - 04:23 pm:
None, unless you're trying to compare data from two different systems expressed in differing units. But for things like efficiency and asymmetry and retention time, it has no bearing. It only materially affects the units of the area and peak high.
By Young on Friday, February 13, 2004 - 06:46 am:
Does it affect linearity? I heard that by using mV , you will lose in linearity. How is it possible?
By mbg on Friday, February 13, 2004 - 06:53 am:
I prefer mAU, especially when reviewing other's data. I can better gauge when the analyte could be saturating the system. Generally, I like to work at 800mAU or lower.
With mV, it gets more complicated to determine such a thing. Is their system on a 1V or 10V output? Does 1V = 1AU or 3?
By Chris Pohl on Friday, February 13, 2004 - 05:31 pm:
Young,
There is no reason to expect using millivolts to have any influence on the linearity of your response. The only possible caveats being that you may not as readily know when you're in a nonlinear range of the detector as mentioned above or if there's something wrong with the way the detector electronics have been designed in order to provide such an output. But in general, there should be no negative consequence in terms of linearity in switching to a millivolt output.
By Young on Sunday, February 15, 2004 - 01:46 pm:
mbg,
If I understand u, it is possible to set 1V=1AU; isnt'it? In this case, what difference does it make?
By mbg on Tuesday, February 17, 2004 - 07:05 am:
So long as it's communicated to all those observing the data that 1V=1AU then no difference.
The only way I think mV detection would have a linearity problem is if mV signal was a function of % transmittance instead of absorbance. Then some math before plotting a curve would correct this.