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Limits of detection of carbon‐13 labelled drugs and their metabolites in human urine
Author(s) -
von Unruh Gerd E.,
Hauber David J.,
Schoeller Dale A.,
Hayes J. M.
Publication year - 1974
Publication title -
biomedical mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0306-042X
DOI - 10.1002/bms.1200010510
Subject(s) - fraction (chemistry) , chemistry , urine , carbon fibers , chromatography , tracer , isotopes of carbon , carbon atom , isotope , carbon 14 , carbon 13 , environmental chemistry , organic chemistry , biochemistry , total organic carbon , materials science , physics , alkyl , quantum mechanics , composite number , nuclear physics , composite material
The precise isotopic analysis of carbon by means of differential comparison of CO 2 samples is applied to neutral, acid c and basic extract fractions of human urine. It is shown that the standard deviation of the analytical procedure, including sample preparation steps, is about 1% or 0.001 atom % excess carbon‐13, but depends some what on the fraction considered. Day to day variations (expressed as standard deviations) in the isotopic composition of the urine fractions are generally less than 2.8%, 1.4% and 3.9% for the neutral, acidica and basic fractions, respectively, although the effect of unusual dietary inputs can be recognized. The ingestion of 23 μg excess carbon‐13 in the form of isotopically labelled aspirin is shown to perturb significantly the isotopic composition of the acidic urine fraction which, for a 24 hour collection period, had a mass of 570 mg C. Because only 0.01% of the fraction was consumed by isotopic analysis, further extensive analysis would be possible. It is concluded that carbon‐13 tracer experiments generally should be arranged to provide at least 5 × 10 −5 g excess 13 C/g carbon in any fraction which is to be used for lable detection.