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Start Over Author "Wachter U" Journal isotopes in environmental and health studies
8 results on '"Wachter U"'

4. Simultaneous Determination of Plasma Enrichments of 1-13C- and 15N-Labelled Phenylalanine and Tyrosine

Author

Wachter, U., Tugtekin, I., Georgieff, M., Radermacher, P., and Vogt, J.

Abstract

A methylchloroformate derivative was used for the simultaneous determination of plasma enrichments of 1-13C-phenylalanine, 1-13C-tyrosine, 15N-phenylalanine and 15N-tyrosine by gas chromatography/mass spectrometry. All four tracer enrichments could be measured in a single GC run. A specific ion fragment was obtained for each tracer. This approach allowed an easy determination of the "tracer to tracee ratios". Each ion fragment could be measured with an appropriate single-to-noise ratio and precision in samples obtained from 100 μl plasma. The derivatization consists of a fast one-step reaction. Therefore it is well suited for studies involving a large number of samples, such as non-steady state bolus studies.

Published
1998
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5. Determination of 13CO2/12CO2Ratio by IRMS and NDIRS

Author

Barth, E., Tugtekin, I., Weidenbach, H., Wachter, U., Vogt, J., Radermacher, P., Adler, G., and Georgieff, M.

Abstract

AbstractBreath tests using 13C-labelled substrates require the measurement of 13CO2/12CO2ratio in breath gas samples. Next to isotope ratio mass spectrometry (IRMS), which is very sensitive but also complex and expensive, alternatively isotope selective nondispersive infrared spectrometry (NDIRS) can be used to determine the 13CO2/12CO2ratio in expired breath. In this study we compared NDIRS- with IRMS-results to investigate whether the less expensive and very simply to operate NDIRS works as reliable as IRMS. For this purpose we applicated 1-13C-Phenylalanine to patients with advanced liver cirrhosis and healthy volunteers and took duplicated breath samples for IRMS and NDIRS at selected time points. Our data show a good correlation between these two methods for a small number of samples as required for simple breath tests. Longer series, where repeated measurements are required on the NDIRS instrument lead to a decreasing correlation. This indicates the superiority of IRMS concerning 13CO2-kinetics over longer time periods.

Published
1998
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7. Determination of 13CO2/12CO2 ratio by IRMS and NDIRS.

Author

Barth E, Tugtekin I, Weidenbach H, Wachter U, Vogt J, Radermacher P, Adler G, and Georgieff M

Subjects
Carbon Isotopes, Case-Control Studies, Evaluation Studies as Topic, Humans, Kinetics, Liver Cirrhosis diagnosis, Liver Cirrhosis metabolism, Phenylalanine, Breath Tests methods, Carbon Dioxide analysis, Mass Spectrometry methods, Spectrophotometry, Infrared methods
Abstract

Breath tests using 13C-labelled substrates require the measurement of 13CO2/12CO2 ratio in breath gas samples. Next to isotope ratio mass spectrometry (IRMS), which is very sensitive but also complex and expensive, alternatively isotope selective nondispersive infrared spectrometry (NDIRS) can be used to determine the 13CO2/12CO2 ratio in expired breath. In this study we compared NDIRS- with IRMS-results to investigate whether the less expensive and very simply to operate NDIRS works as reliable as IRMS. For this purpose we applicated 1- 13C-Phenylalanine to patients with advanced liver cirrhosis and healthy volunteers and took duplicated breath samples for IRMS and NDIRS at selected time points. Our data show a good correlation between these two methods for a small number of samples as required for simple breath tests. Longer series, where repeated measurements are required on the NDIRS instrument lead to a decreasing correlation. This indicates the superiority of IRMS concerning 13CO2-kinetics over longer time periods.

Published
1998

8. Determination of (13)CO(2)/(12)CO(2) Ratio by IRMS and NDIRS.

Author

Barth E, Tugtekin I, Weidenbach H, Wachter U, Vogt J, Radermacher P, Adler G, and Georgieff M

Abstract

Abstract Breath tests using (13)C-labelled substrates require the measurement of (13)CO(2)/(12)CO(2) ratio in breath gas samples. Next to isotope ratio mass spectrometry (IRMS), which is very sensitive but also complex and expensive, alternatively isotope selective nondispersive infrared spectrometry (NDIRS) can be used to determine the (13)CO(2)/(12)CO(2) ratio in expired breath. In this study we compared NDIRS- with IRMS-results to investigate whether the less expensive and very simply to operate NDIRS works as reliable as IRMS. For this purpose we applicated 1-(13)C-Phenylalanine to patients with advanced liver cirrhosis and healthy volunteers and took duplicated breath samples for IRMS and NDIRS at selected time points. Our data show a good correlation between these two methods for a small number of samples as required for simple breath tests. Longer series, where repeated measurements are required on the NDIRS instrument lead to a decreasing correlation. This indicates the superiority of IRMS concerning (13)CO(2)-kinetics over longer time periods.

Published
1997
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