Hydroxylamine HCl will be better than o-methoxyamineHCl. Oxime formation involves availability of lone pair of electrons on Nitrogen which is involved in breaking and making of new bonds. In O methoxyamine oxygen being more electro-negative pulls electron towards itself and availability of lone pair on nitrogen is reduced. Hence oxime formation is less easy with Omethoxyamine

Dear Mrinal,

both chemicals are used to derivatize keto-groups in alpha-keto acids. hydroxyl amine is more reactive, so products will form faster and more easily, while the derivate is less reactive and may not form suffiicient amount of product desired. we use both chemicals to stabilize sensitive metabolites, e.g. oxaloacetate and to derivatize analytes prior to GC-MS analysis. the choice can also depend on the mass shift, one wants to introduce into the analyte by the derivatization to avoid interference with the matrix during later MS analysis.

Best,

Christoph

Thank you Dr. Bhaswati and Dr. Wittman. Indeed very helpful.....