Chromatography Forum

Dear All,
Is there any method to determine carbendezim and benomyl separately.Iam not getting the peak of benomyl I am injected samples in Acetonitrile.and extracted also in Acetonitrile.My mobile phase is in methanol and water.I read in some literature that benomyl is easily hydrolysis to carbendezim in presence of methanol.Is the all benomyl converted to carbendazim.Is there any method to separate this compounds please give the details.Iam using API-2000 LCMSMS for this

Most likely you are losing the benomyl in your sample extraction step. It is difficult at best to keep benomyl from hydrolyzing to MBC under HPLC conditions - as you have probably seen, all of the methods report benomyl as MBC. You might be able to acheive a separation with careful pH control using a buffer/acetonitrile eluant - I'd start with a pH of around 8 (you'll need a pH tolerant column) and use phosphate as my buffer.

A phosphate buffer is a bad idea when running LCMS. The lab I formerly worked at reported any hit as Benomyl/Carbendazim, no further qualification. If you want to try what mckrause suggested, try an ammonium bicarbonate buffer adjusted to the desired pH with ammonium hydroxide. But, you will need a pH-tolerant column, like an XBridge C18 or a ZORBAX Extend C18

viewtopic.php?f=1&t=12516&hilit=carbonate+buffer

I looked into this sometime ago myself. The only thing I found was in an old review.

"Special techniques are necessary to determine benomyl itself and in presence
of carbendazim because of the tendency of benomyl to be transformed to the
stable carbendazim (see under section Comments on the properties of benzimidazoles relevant to analysis) . To overcome this problem, the base catalysed conversion of benomyl to BBU 1-(benzimidazol-2-yl)-3—butylurea and carbendazim to 2-aminobenzimidazole has been used (White et al (92) ; Baude et al. (9) Baude et al. (10))."

Here's the link.

http://www.iupac.org/publications/pac/1 ... 1x2567.pdf

The problems begin with benomyl before you even get it on your instrument mind.

As with the previous posts, we just quantify benomyl as the sum of benomyl, carbendazim, thiophanate and thiophanate-me.

If you manage to make any progress though. Please let us all know.