Detection and determination of certain ureas with o-phthalaldehyde and N-(1-naphthyl)-N'-diethylethylenediamine.

o-Phthalaldehyde and N-(1-naphthyl)-N'-diethylethylenediamine give red or orange colours with urea and certain substituted ureas in dilute hydrochloric acid at 37 degrees . The reaction has good sensitivity and the colours are fairly stable. An individual urea can be detected at a concentration of ca. 0.05-0.2 mug/drop, and determined in the range of ca. 0.01-0.2 mumole.