We are looking for a method to determine the % cystine in manufactured samples of cysteine. HPLC would be fine or GC/MS.
Based on my reading, Agilent recommends the uses of either Cysteic Acid or DTDPA.
Personally, I would be more than happy to see Agilent to have details protocol described for the uses of DTDPA. I have been having some solubility issues in the lab even with the substitution of 0.1M HCl with 0.4N, pH 10.2 Borate buffer.
That's all I know and I can share. All opinion are my own and do not represent the views or endorsement from Agilent.
Best of luck.