negative peaks!

[bhargavi]

why do we get negative peaks in a chromatogram?

[AA]

Could you throw in a little more information, negative peaks are caused by any number of reasons, dependant on the system (detector mostly, but not always). I guess what I am trying to say is the reason for a negative dip in UV is different that RI or ECD (and all of the other detectors too).

[bhargavi]

u mean all detectors do give negative peaks or is it spcfc to a certain kind?
i hav another question! cud u plz tell me hw are purity tests n assays in hplc different?