A critical investigation of the separation of free noradrenaline and adrenaline from urine samples revealed serious errors
during sample pretreatment using Al2O3 as adsorbant. An exact and rapid pH adjustment of the sample, using thymol-blue as indicator, proved to be the chief prerequisite
for precise and accurate results. Increasing temperature and pH favour the oxidative decomposition of the catecholamines during
routine analysis. This was examined, using the radiotracer method and liquid scintillation counting.