EVALUATION OF WATER REMOVAL AND MEMORY EFFECT IN (CO2)-C-13 BREATH TESTS BY ISOTOPE RATIO MASS-SPECTROMETRY

The usefulness of different ways of water removal in off-line sample p reparation of human breath samples for (CO2)-C-13 breath tests was exa mined and compared. Cryogenic water trapping and water removal with co mmon desiccants like silicagel blue, Mg(ClO4)2, and molecular sieves w ere checked for reliability and reproducibility. With silicagel blue a nd Mg(ClO4)2, memory effects for C-13 content were observed. The use o f molecular sieve 4 angstrom and 5 angstrom led to tremendous carbon i sotope fractionation. Molecular sieve 3 angstrom was found to be an ex cellent alternative to the established use of Mg(ClO4)2 and of cryogen ic water trapping.