Chromatography Forum

Hello everybody,

I'm having some problems with stability of aflatoxin solutions (B1, B2, G1, G2). My stock solutions are prepared from individual Sigma powders in toluene/acetonitrile (98:2) and dilutions from this stock solution showed minus 50% in peak areas in 1 month time!!! (normally 1 year of shelf life!)

We respect all instructions for avoiding degradation (protect from light & oxydation, pre-rinsed flasks with an acid solution in order to eliminate basic pH of glass surface...)

Has anybody already had this kind of problem with these compounds from this supplier?

Thank you in advance for your help!!

Hi

No experiance of this but a bit suprised that you store in a mix of toluene and acetonitrile, sure a weak base but still.

Have you tried storing the stock solution in different solvents, like pure Toluene or methanol?

If the substance reacts with silanol over time, a polar solvent may sheild your substance alternatively deactivate the glassware (did so with deca-BDEs).

Did my graduate work on mycotoxins many years ago, but did not encounter these kinds of problems.

1. Try normal glassware without the acid treatment, or at least make sure that you have removed all acid traces. These molecules can be hydrolyzed by either acid or base.

2. Try plastic (non-glass) containers.

Thank you for your answers.

We tested a mix supelco solution in methanol and we obtained good results.

The only difference we can see, wich could explain bad results + degradations, is that from supelco solution we don't have to evaporate at any stage, while from sigma solutions (prepared in toluene/acetonitrile) there must be an evaporation step to change solvent into methanol.

We suspect losses of aflatoxins during evaporation step and a change on quality of nitrogen used to evaporate, which changed some months ago... but maybe we won't ever know !

Finally it seems to work in another way,
that's what counts!

thank you anyway...