Measurement of specific radioactivity of tryptophan labeled with carbon-14 in plasma by high-performance liquid chromatography with a synchronized accumulating radioisotope detector.

Measurement of specific radioactivity by a high-performance liquid chromatograph with a synchronized accumulating radioisotope detector was conducted. Accuracy of measurement for an authentic sample containing 0.2 nCi of tryptophan labeled with carbon-14 exceeded 95%. In the case of a plasma sample obtained 120 min following intravenous administration of 15 muCi of labeled tryptophan to a rat, the coefficient of variation was 7.0%.