peak symetry

[jonh29]

Any sugestions on how to remove a dip in a baseline which resolves right before the primary active being analyzed? My mobile consists of 60% H20, 40% Acetonitrile, buffered with Sodium Dihydrogen Phosphate and pH with Phosphoric Acid to 1.3. I'm using a Cation Column. Any suggests would be great!!

Thanks

[unmgvar]

at what RT does it happen?

[tom jupille]

And what kind of detector? And what is your sample dissolved in?

A good general rule is "to do the best chromatography, disturb the equilibrium of your system as little as possible". In practice, this means that the best sample diluent is the mobile phase.

[jonh29]

The RT is at 3.0 min using a UV detector. I QS the samples with mobile phase. One problem which doesn't help, the best absorption for the analyt is at 195nm.

[tom jupille]

At 195 nm, even a small mismatch between your diluent and the mobile phase will show up (e.g., if the acetonitrile concentration has changed a bit due to evaporation.). Your best bet may be to tweak the conditions to better resolve the dip from your analyte.

Another possibility (admittedly a long shot): if your UV detector is a DAD (diode array detector) is that some DAD's allow you to set a reference wavelength. If that's the case, try turning the reference wavelength function "off".

[unmgvar]

what are the dimension of your column? and the system you are using? i am assuming you have a flow of 1ml/min.
can you also give further detail on your cation column? vendor, type particle size