99.
Abstract The increasing application of
13C-labelled urea in medicine requires simple and reasonable methods for measuring highly enriched
13C in urea. The combination: ultimate organic analysis—mass spectrometry so far prescribed is complicated and expensive. For medical diagnosis, however, isotope selective nondispersive infrared spectrometers (NDIRS) have been available for many years. One of these tools is FAN
ci2 which is very reasonable and easily to be operated. By means of such devices also urea highly enriched in
13C can be analysed, provided that the samples are first diluted with a defined amount of urea of natural isotopic composition and then transformed into carbon dioxide by means of urease. The relative abundance of
13C in this carbon dioxide, measured by nondispersive infrared spectrometry, is then a measure of the
13C abundance in the initial urea sample. Comparison of results of such measurements with those attained by mass spectrometry proves that this procedure is feasible and yields precise results.
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