By Anonymous on Tuesday, October 22, 2002 - 06:08 am:
There is a strange peak coming out at 265 nm in all the spectrum I have created.The spectra is created by Turbochrome and Perkin Elmer DAD 235C detector. My mobile phase is 50% methanol and 50% sodium acetate buffer 50 millimolar pH 4.7. If I create the Spectra in a UV spectrophotometer non of the peak at 265 nm appear. How do I determine where this strange peak protruding out of the spectra comes from? It appears in all the spectra I make with the above equipment.
By lcguy1 on Tuesday, October 22, 2002 - 11:58 am:
Sounds like you may have a bad diode in the Diode array. Try taking a spectra across a region of your chromatogram where there are no peaks. Is the spike at 265nm still there. If so, it may be the array.
By Anonymous on Tuesday, October 22, 2002 - 12:20 pm:
Adding to lcguy1:
Run a set of known analytes such as parabens, where you know the lamda max is at 254, if you see the peak at 265 then the problem is in the detector.
By Anonymous on Wednesday, October 23, 2002 - 08:57 am:
Hi. Thanks for the tip. Just for clarification. The peak I am seeing has a narrower bandwidth which is superimposed on the spectra of the compund of interest. So I am seeing the normal spectra of a compound plus this unknown peak protruding either in the up slope, down slope or the top of the wider bandwidth Spectra depending on the chemical being evaluated. Again thanks for the tips.
By Alex Buske on Wednesday, October 23, 2002 - 11:03 pm:
Anon 021022 - try to get baseline spectra or go to real 3D-data (in the method editor choose Spectral Aqusition - Mode: Time).
If the Band appears also in the baseline region then a Diode from the array is out of function. On the 235C there is 1 diode per 4 or 5 nm, everthing else is interpolated. So a bad diode should not produce a band broader than 20 mnm.
Alex