Ammonia analysis baseline problem
Posted: Tue Feb 12, 2008 4:39 pm
I'm having a bit of trouble figuring out what's going on with the baseline here. The baseline takes a dip right at the time of the ammonia peak. The same thing occurs when just water or 0.04N H2SO4 are injected.
These baselines were produced using an Agilent 1100 system, a DIONEX CS12 4x250mm column and guard column, a DIONEX cation suppressor, and an old Waters 430 conductivity detector. The solid baseline is water, the large dashes being 0.04N H2SO4, and the small dashes with the peak is a 2.3 ppm ammonia standard. The baseline dip becomes much more pronounced with the presence of ammonia.
I'm thinking that the injector is somehow involved since the baseline dips are occurring in the same places each time. But the Agilent injector is a flow-through design, so if it's contamination, the valve would be the first place to look, right?
This doesn't happen when I use our DIONEX system to perform the analysis. I think we may need both systems to get through a large set of samples, so any help is appreciated.
These baselines were produced using an Agilent 1100 system, a DIONEX CS12 4x250mm column and guard column, a DIONEX cation suppressor, and an old Waters 430 conductivity detector. The solid baseline is water, the large dashes being 0.04N H2SO4, and the small dashes with the peak is a 2.3 ppm ammonia standard. The baseline dip becomes much more pronounced with the presence of ammonia.
I'm thinking that the injector is somehow involved since the baseline dips are occurring in the same places each time. But the Agilent injector is a flow-through design, so if it's contamination, the valve would be the first place to look, right?
This doesn't happen when I use our DIONEX system to perform the analysis. I think we may need both systems to get through a large set of samples, so any help is appreciated.
), the 430 detector is designed to automatically correct for ions in the eluent, essentially acting as a built-in suppressor. I think it has something to do with this feature. When I ran a 6-cation scan, there was a dip at the beginning of each peak. I tried running the analysis unsuppressed but saw nothing. I then switched detectors to a DIONEX, keeping everything else the same. The baseline and peaks looked fine. So it has something to do with the detector.