New and conventional evaporative systems in concentrating nitrogen samples prior to isotope-ratio analysis
Studies were conducted to quantify and compare the efficiencies of various evaporative systems used in evaporating /sup 15/N samples prior to mass spectrometric analysis. Two new forced-air systems were designed and compared with a conventional forced-air system and with an open-air dry bath technique for effectiveness in preventing atmospheric contamination of evaporating samples. The forced-air evaporative systems significantly reduced the time needed to evaporate samples as compared to the open-air dry bath technique; samples were evaporated to dryness in 2.5 h with the forced-air systems as compared to 8 to 10 h on the open-air dry bath. The effectiveness of a given forced-air system to prevent atmospheric contamination of evaporating samples was significantly affected by the flow rate of the air stream flowing over the samples. The average atmospheric contaminant N found in samples evaporated on the open-air dry bath was 0.3 ..mu.. N, indicating very low concentrations of atmospheric NH/sub 3/ during this study. However, in previous studies the authors have experienced significant contamination of /sup 15/N samples evaporated on an open-air dry bath because the level of contaminant N in the laboratory atmosphere varied and could not be adequately controlled. Average cross-contaminant levels of 0.28, 0.20, and 1.01 ..mu.. of N were measured between samples evaporated on the open-air dry bath, the newly-designed forced-air system, and the conventional forced-air system, respectively. The cross-contamination level is significantly higher on the conventional forced-air system than on the other two systems, and could significantly alter the atom % /sup 15/N of high-enriched, low (N) evaporating samples.
- Research Organization:
- Dept. of Agriculture-ARS, Fort Collins, CO
- OSTI ID:
- 6078771
- Journal Information:
- Soil Sci. Soc. Am. J.; (United States), Vol. 51:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
EVAPORATION
COMPARATIVE EVALUATIONS
EFFICIENCY
SYSTEMS ANALYSIS
LABELLED COMPOUNDS
SAMPLE PREPARATION
AMMONIA
DRYING
FORCED CONVECTION
ISOTOPE RATIO
MASS SPECTROSCOPY
NITROGEN 15
RELIABILITY
TRACER TECHNIQUES
CONVECTION
ENERGY TRANSFER
HEAT TRANSFER
HYDRIDES
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MASS TRANSFER
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PHASE TRANSFORMATIONS
SPECTROSCOPY
STABLE ISOTOPES
510101* - Environment
Terrestrial- Basic Studies- Radiometric Techniques- (-1989)