Isolating Vitamin B12

[syx]

We have got difficulties with samples contain vitamin B12. The problems are occurred due to its low dose and instability in the present of other components in the product (vit C, Fe, Cu, etc) when prepared as solution. Several literature mentioned that the best way of stabilizing vit B12 solutions has proved to be the addition of cyanide ions.
Van Melle has described a simple method of isolating vitamin B12 by filtration through a column of Amberlite XE 97. Unfortunately, we cannot find this type of column packing in Rohm & Haas website.
Does anybody know alternative column packing for Amberlite XE 97?
Thanks in advance.

[oscarBAL]

I think there are Inmunoafinitty columns for these vitamins; i am currently using IA for clean up sample for micotoxins and they work very well; I think they are a expenciver than convenciotal SPE but work very well!!