Derivitising Glyphosate

[Aviator]

Hi all,

I'm currently trying to derivitise glyphosate for an LCMS/MS method to no avail. I've managed to get it working to an extent, i.e. I can see my glyphosate and AMPA peaks but I cannot for the life of me get them to be linear when I try a calibrated range (it ends up looking more like a scatter graph). I know the instrument is capable of doing this particular range because I can get it to work using premade, bought-in standards which have already been derivitised (using the same derivitisation agent, FMOC-CL). Occassionally as well, I find that the derivitisation process doesn't work at all and instead of getting a single glyphosate peak, I might get several smaller ones. Does anyone have any suggestions?

When it comes to derivitisation we really don't know all that much at all so if you have any advice no matter how basic, I'd be glad to hear it.

Many thanks,

Aviator

[chemex]

Aviator,

The problem is your derivatisation step. What is your derivatisation procesure? I am working with Glyphosate and AMPA at the moment. I am not an expert but it seems as the pH is a very critical factor.

I have a procedure which work well so far. My borate buffer at a pH around 9 and I used a 5mM ammonium acetate solution (pH 6.5) for the mobile phase

[laco]

Aviator,

I use a borate buffer as well (PH 9.5), I add the F-moc (in excess) and let react for 30-60min. I stop the rection with HCl. If you have a lot of scatter for your calibration curve, make sure that there is a 10 to 20 fold concentration between your lowest calibration point and your highest.

My mobil phase is water and MeOH

[BMU_VMW]

After derivatisation, we use SPE to further concentrate Glyphosate en AMPA.
Do you do so to? If not, don't you have problems with borate-buffer and FMOC-Cl precipitating in the LC-MSMS system?

kind regards
BMu