[lgilotea]

Hi,

I am trying to setup an old Liquid Chromatograph Dionex (LC20) to perform Arsenic speciation, mainly determine As V in bacterial cultures. I am using a AS7/AG7 column from Dionex, carb (1.8mM)/bicarb.(1.7 mM) eluent and UV detection at 195 nm. Chromatograms are very noisy, and not reproducible, even changing the deuterium lamp, the absorbance detector. Any ideas ? any detailed protocol ? I know that an ICP MS detection will be better but we do not have the device, so trying the UV detection based on litterature found
thank you

[Train]

When you say it's not reproducible I assume you mean consecutive injections from the same HPLC vial?  If you inject just mobile phase can you get reproducible chromatograms?  If so, does a mobile phase injection look identical before and after a sample injection?

At such a low wavelength just about anything organic will absorb.  If your problem occurs with both samples and mobile phase, then I think your most likely culprit is some kind of contamination of your mobile phase or LC.