Problems in the determination of the specific radioactivity of uniformly 14C-labelled amino-acids after their reaction with ninhydrin

Modifications to the standard Technicon amino-acid analyser are described, which permit a reliable determination of the specific radioactivity of [U-14C]-amino-acids to be made after their reaction with ninhydrin. The loss of the volatile aldehyde products of the ninhydrin reaction can be prevented by trapping them with semicarbazide. Glutamate was shown to lose two carbon atoms when oxidised at pH 5·0 but only one at pH 2·5.