By Anonymous on Tuesday, April 27, 2004 - 08:59 am:
hi, could anyone tell me the linear dynamic range of Agilent 1100 with UV detection. I heard from some people when the signal height with relative fair peak width is more than 1000 with the unit mAU, it is out of the linearity range. Could any expert tell me some information about that? Thanks s lot!
By Consumer Products Guy on Tuesday, April 27, 2004 - 12:16 pm:
You should establish your linearity range yourself for your analyte. We've established Agilent 1100 diode-array detector UV linearity up to 3000 ng injected (2.1mm x 130mm column) for certain sunscreen components; cGMP details at least five points to determine the line for pharmaceuticals. The 1000 mAU is a useful rule of thumb, but if you're that high, why not dilute your standard and samples, or inject less? Keep it simple.
By Tom Mizuakmi on Tuesday, April 27, 2004 - 04:58 pm:
http://www.chem.agilent.com/temp/radE9A51/00046148.pdf
Agilent claims >2AU, I routeinly go to signal heights of 1.2 to 1.5 AU with no linearity problems. That is constant specific response based on area. This is for both the VWD and the DAD detectors.
By Anonymous on Wednesday, April 28, 2004 - 04:19 am:
Surely this depends on the path length of the detector cell you are using. The concentration necessary to generate an absorbance of 1.5A.U. will depend on the path length of the cell.
By Consumer Products Guy on Wednesday, April 28, 2004 - 07:36 am:
You could also use a wavelength not at the apex, to decrease the absorbance. Nobody says you need to use the apex, most do to obtain most sensitivity, but that doesn't seem to be your issue.
By Anonymous on Sunday, May 2, 2004 - 04:30 pm:
However, be aware that if you are off lambda max (the apex of the spectrum), then you increase the possibility of robustness problems resulting from spectral shifts secondary to variations in conditions (temperature, pH, etc.).
By Tim on Saturday, May 8, 2004 - 05:53 am:
We have experienced issues with 1100s where we used the analogue output attached to an A/D convertor connected to our previous data system. Peaks which got close to or above 1000 mAU were distorted at the top of the peak.
This is caused by a limitation on the output range from the analogue port (max 1000 mV). To get over this, you can increase the attenuation (from 1000 to 2000 or even 4000 in some newer 1100s).
Alternately you can connect direct digital signal out to ChemStation/Cerity/Millennium and won't get this issue, till you reach the >2AU range as Tom pointed out.