Chromatography Forum

..for smaller than expected analyte peaks there could be a bunch of reasons; for higher? We're using a DX500 for major anions, org. anions and cations analysis. We're currently running anions using AS-9 by Dionex (low-level concentrations), and we've been very pleased with the performance of the system.

The only thing changed before this rise in the peaks height/area was observed ,was the stock solution from which we make our eluent. However the new stock was prepared in a decent way, with 18,2 MΩ-cm water, and the background conductivity we see for our eluent when running it, is the same as before. Retention times of the compounds are also the same as before. However, the peaks have increased we have been checking it with our standards which one day before yesterday were giving extremely good results (accuracy <=3% from theoretical values) (and nothing has been touched in the data acquisition software in the pc, regarding attenuation of the signal and so).

Any ideas/suggestions would be more than welcomed.

How big is your sample loop size, or is your system using a concentrator?

Have you tried to re-prepare your standards, or did you run all your different levels of standard? Did all levels of standard increase in peak area?

How do you inject your standard? Maybe the pump, autosampler is injecting more than you expected into the concentrator.

many thanks for the reply, we've managed to find the cause of the phenomenon though. It had to do with the suppressor, another user of the system had ran eluent through the suppressor without supplying current and then calibrated the instrument under these conditions. This resulted in small analyte peaks phenomena, and later on when i carried out a service procedure to the suppressor the analyte peaks seemed bigger - but they were actually the ones they should be.

Anyway, thank you for the reply.