Chromatography Forum

I think I'm trying to pull of the impossible here. I'm trying to separate cysteine, methionine, and homocysteine using strong anion ex but I am encounter virtually no retention at all for pH values 11-11.5.

Anyone familiar with separating these 3 via anion ex? Doing the separation with cation ex is pretty easy but I only have an anion ex column at this time.

Thanks. Happy Holidays.

Mike

The three amino acids in question (hcy, met and cys) can be separated on Dionex AminoPac PA10 column. This is an anion exchange column with a backbone that is relatively hydrophobic. The column manual can be found on the Dionex web site.
The eluent pH has to be >12.0 with that column. This is not only to achieve the separation but also to create conditions suitable for detection by integrated amperometry (IA) on a gold working electrode. If you are using IA and not seeing any peaks it may be because the pH is not alkaline enough to support the electrode reaction.
By the way, if IA is carried out under acidic conditions (e.g. Dionex OmniPac PA500), it is highly specific for S-containing species (Met, hcy, cys, GSH, GSSG etc). Nothing else gets detected under those conditions and one obtains interference-free separations out of of complex samples.

Check out SIELC (primesep) columns. I developed a method for cysteine and cystine using their columns, and had little to no luck with other columns.

Good luck.
s