Agilent 1200 negative peak

[CLSgroup]

I am trying to detect three compounds which absorb at 488, 472 and 470. The original aqusition method called for acetonitrile but we are now trying to switch to methanol. With acetonitrile, there was negative abosorption before the compounds eluted and a large negative peak after (solvent peak). We have switched to methanol as our solvent B and I am having issues with getting the baseline to be nice and steady. I am also having some sample media (XAD-7 tubes) interference which I'm hoping to cure with any suggestions you may have as to how I can zero out my baseline. Our refernce spectrum is 474 and our range is from 440 to 500, negative absorption is 100.

[CLSgroup]

Correction our signals are set up for, Sample 474 Bw 4, Reference 474, Bw 100. The range is 440 to 550 not 440 to 500.

[bisnettrj2]

Turn off your reference wavelength, or set it to a region where your analytes do not absorb.

http://www.chem.agilent.com/Library/Sup ... faq184.pdf