Friends;

I have just received a LC method for the analysis of Carbamates and to my surprise the mobile phase includes ammonium carbamate (not carbonate).This is the first time I encountered such mobile phase component.

Have you ever hear of such mobile phase additive?, can anyone inform me about its properties? (UV, pKa, etc). Another surprising fact is the small concentration employed, 0.002M. Onbviously, the method has no information as to the intended purpose of it.

I would appreciate any nformation on this very unusual situation.

Thanks;

Benjamin

Benjamin,

Ammonium carbamate is the ammonium salt of carbamic acid, made by reacting ammonia with carbon dioxide. Ammonium carbonate, also contains ammonium carbamate. Most supplies of ammonium carbonate state that the content of the reagent consists of various ratios of ammonium carbonate and ammonium carbamate, but at least one source indicates that ammonium carbonate is really the double salt: ammonium bicarbonate-ammonium carbamate. Either way, carbamic acid is not hydrolytically stable in water, yielding carbon dioxide and ammonia via hydrolysis. I'm a bit puzzled by the use of this compound as eluent, though, since ammonium carbamate hydrolyzes to mostly ammonium carbonate during the dissolution process. Perhaps the author of the method was unaware of this or at least thought that starting with pure ammonium carbamate would be better than starting with an unknown mixture as in the case of ammonium carbonate. But in reality, an equilibrium the result is the same: ammonium carbamate plus water equals ammonium carbonate. At any given concentration the ratio will vary but at 2 mM it should be virtually 100% ammonium carbonate.