I'll like to quantitate an amino acid derivative: 3-N-oxalyl-2,3-diaminopropionic acid, in some complex herbal mixtures, using LCMS.
Being a polar compound, it may not be well retained.
I'm now trying to optimise a method for it, but do not know how i should best approach this problem.
What LC mobile phases/conditions should I use?
What columns should I use?
Anyone can offer me some advices and guidance on this?

You might consider our approach to the retention of polar compounds. We have several methods for analysis of polar copmounds - good retention and peak shape. Here is the link for analysis of underivatized amino acids with LC/MS compatible conditions
http://www.allsep.com/makeChr.php?chr=Chr_009

Also check other methods for polar ionaziblecompounds:
http://www.allsep.com/Applications_By_Column.php

I've not tried the Allsep columns, but from the posted links, they employ TFA. You can use TFA with positive ionization, but I wouldn't recommend it with negative. If using TFA, and you don't get the sensitivity you want in positive ESI, try positive APCI. I've found that some polar compounds will retain on an ordinary C18 column, in a highly aqueous mobile phase with ~ 0.1% TFA, where retention could not be achieved without the TFA.

Another option is hydrophilic interaction chromatography (HILIC). Search this board and you'll find quite a few discussions of HILIC. It doesn't require TFA and uses > 50% acetonitrile mobile phases, usually. I've tried it and had successes and failures, depending on the compound.

Dear MG,
TFA is one of several additives you can use with our columns. You can also use ammonium formate, and ammonium acetate at pH 3-4, formic acid, acetic acid etc (different concentrations). Mobile phase can be from 0% organic to 100% organic. Our mostly common mobile phases are ACN-water 40/60 with 10-50 mmol of ammonium formate (pH=3), ACN-water-TFA=40/60/0.1 and ACN-water-HCOOH=40/60/0.1

OK, thanks for the clarification.

A compound with such a polarity can easily be separated using HILIC, especially on a HILIC silica column.

Thanks. I will try out a highly aqueous mobile phase with 0.1% TFA on ordinary RP-C18 columns first, as these are the only columns we have currently. Our lab still do not have a HILIC column to try out yet. Looks like it is useful to get one such column.