Applications of gas-liquid chromatography in protein chemistry. II. Determination of amide residues in nanomolar amounts of proteins.

A method for the quantitative determination of amide residues in nanomolar amounts of proteins is described, based on dilute acid hydrolysis at 100 degrees, followed by isothermal gas-liquid chromatography of the ammonia released by on-column neutralisation of the hydrolysate and quantitation by means of a conductometric detector. Amide contents are given for twenty well characterised proteins, as well as for asparagine and glutamine.