PMID- 20718408
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20110104
LR  - 20100914
IS  - 1520-6882 (Electronic)
IS  - 0003-2700 (Linking)
VI  - 82
IP  - 18
DP  - 2010 Sep 15
TI  - Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass 
      spectrometry.
PG  - 7849-51
LID - 10.1021/ac101570f [doi]
AB  - An anomalous stable hydrogen isotopic fractionation of 4  per thousand in gaseous hydrogen 
      has been correlated with the process of adding liquid nitrogen (LN(2)) to top off 
      the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum 
      equilibration system. Although the cause of this isotopic fractionation is 
      unknown, its effect can be mitigated by (1) increasing the capacity of any dewars 
      so that they do not need to be filled during a daily analytic run, (2) 
      interspersing isotopic reference waters among unknowns, and (3) applying a linear 
      drift correction and linear normalization to isotopic results with a program such 
      as Laboratory Information Management System (LIMS) for Light Stable Isotopes. 
      With adoption of the above guidelines, measurement uncertainty can be 
      substantially improved. For example, the long-term (months to years) delta(2)H 
      reproducibility (1sigma standard deviation) of nine local isotopic reference waters 
      analyzed daily improved substantially from about 1  per thousand to 0.58  per thousand. This isotopically 
      fractionating mechanism might affect other isotope-ratio mass spectrometers in 
      which LN(2) is used as a moisture trap for gaseous hydrogen.
FAU - Coplen, Tyler B
AU  - Coplen TB
AD  - U.S. Geological Survey, 431 National Center, Reston, Virginia 20192, USA. 
      tbcoplen@usgs.gov
FAU - Qi, Haiping
AU  - Qi H
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Anal Chem
JT  - Analytical chemistry
JID - 0370536
EDAT- 2010/08/20 06:00
MHDA- 2010/08/20 06:01
CRDT- 2010/08/20 06:00
PHST- 2010/08/20 06:00 [entrez]
PHST- 2010/08/20 06:00 [pubmed]
PHST- 2010/08/20 06:01 [medline]
AID - 10.1021/ac101570f [doi]
PST - ppublish
SO  - Anal Chem. 2010 Sep 15;82(18):7849-51. doi: 10.1021/ac101570f.