Chromatography Forum

Now i am developing for chloroquine determination by UPLC-MS
i get problem that after inject standard mix to UPLC, i can not wash it from column. it remain contaminate in the next injection. i try to used 5% formic in MeOH as strong wash and 50% MeOH as weak wash but it did not work. and i try to used propanol, ethanol, dichromethan replace MeOH but it did work too.

Can you help me for this problem?

Best regard

If you inject your standard mix and then a series of blanks, what happens?
Presumably you are seeing some carryover, but does the amount decrease exponentially or linearly.

If it's exponential, you are probably seeing "physical" carryover of the standard in the injection system (maybe in the needle, connecting tubing, valve, loop, etc.). In that case changing the wash will do no good, you have to improve the plumbing.

If it's a more gradual decrease (close to linear), then it is probably adsorption of some kind, in which case an appropriate wash should get rid of it. The catch here is that it is not necessarily sticking to the column, so make sure you flush the rest of the system as well (including the injector).

Thank you for your answer

If a series of blank decrease and then increase.. what about it?
and I startup system or prime solvent alway when change type of wash solvent but did not flush. Is it necessary?


Best regard

hello you can make passivation of you system hplc without column and deconnected from ms with, acid acetic at 8% rince your valve at different position load and inject, and after rince with lot of water.