Analytical Prices for Water Samples

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Four meridional sections versus depth of excess (volcanic) 3He in the South Pacific taken during the WOCE global survey.



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The time-evolving penetration of bomb-tritium into the subtropical North Atlantic, as seen along 52W. The sections span more than two decades (1981-2003).


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A two year time series of noble gas saturation anomalies at Bermuda, data-model comparison. This research was done by Rachel Stanley.



Price Schedule

The primary goal of this facility is to make helium isotope, tritium, and noble gas measurements available to the academic research community. Analytical charges are made on a per sample basis and reflect the cost of doing the measurements. Commercial analyses are also offered, but a higher rate. Please contact us at dlott@whoi.edu (with a cc to wjenkins@whoi.edu ) regarding scheduling, sample submission and sampling protocols/requirements.

Sample prices are quoted for calendar year 2013 and for planning purposes, prospective clients should anticipate a 3% per year increase.

 
 Analysis Type  Non-Commercial     Commercial 
 Tritium  $361  $541
 3He/4He, He Abundance  $361  $541
 3He/4He, He-Ne-Ar-Kr-Xe Abundances      $520  $891


Notes: An additional 5 to 15% surcharge may be applied for non-WHOI, non-NSF funded research projects. (Sorry, it's related to our overhead cost recovery structure, please contact us for details dlott@whoi.edu with a cc to wjenkins@whoi.edu ). We define "Non-Commercial" as being government-funded, academic, or non-profit entity research. Sample acquisition, containers, and shipping costs are borne by the client. Larger research projects may achieve cost savings by employing our ASEX (At Sea EXtraction system), please contact Dempsey Lott (dlott@whoi.edu) for further details. Note that samples containing elevated levels of non-atmospheric He, for example from hydrothermal or volcanic sources, will require special handling and analysis due to their variable sizing and non-atmospheric 3He/4He isotope ratio. Please contact us to discuss your options.

Tritium Measurements: Please understand that because of contamination considerations, we only measure "natural level" tritium samples, not samples expected to have elevated concentrations due to, for example, radioactive waste disposal or nuclear reactor leaks. Tritium determinations are made by 3He-regrowth mass spectrometry on water samples ranging from 100 cc to 1000 cc in volume. Samples must be in clean (tritium-free) glass bottles with polyseal caps, and preferably with an argon head-space. Analytical detection limit is related to sample size: the larger samples are required to obtain a lower detection limit. A 1 liter sample would permit a detection limit of 0.005 TU while a 0.1 liter sample provides only 0.02 TU. Measurement accuracy approaches 1% at higher tritium concentrations, but is limited by ion counting statistics as the concentration approaches detection limit. Turnaround times (the time between sample submission and result reporting) are controlled by a combination of incubation times (minimum 6 months), sample scheduling and mass spectrometer "down-time". Please consult with IGF staff (dlott@whoi.edu) regarding your needs.

Helium Isotope and Concentration Measurements: Helium isotope and concentration measurements are made on gas extracted from water samples. Samples are typically taken in copper tubing samplers, which consist of lengths of copper tubing clamped at either end with specially designed clamps. These are extracted in the laboratory into aluminosilicate glass ampoules that are subsequently mounted on the mass spectrometer for analysis. The achievable measurement precision depends on sample size. For example, 45g "normal" water samples, typical measurement precisions are 0.15% for the 3He/4He isotope ratio, and 0.5% by peak-height manometry for total dissolved He. For smaller samples (e.g., 12 g), the accuracy is degraded due to less favorable counting statistics. The table below gives an approximate idea of what to expect. Ancillary measurement of Ne concentrations are usually also made by QMS peak-height manometry to approximately 0.5% accuracy. Our primary standardization is atmospheric He and Ne, and the the 3He/4He isotope ratio is reported in percent deviation from the atmospheric standard. The results are corrected for a slight dependence of the apparent 3He/4He isotope ratio on sample size. Samples with elevated levels of non-atmospheric He (with different 3He/4He isotope ratios and abundances) will require special handling and must be dealt with on a case-by-case basis.

 Sample Water Size (g)     Expected 3He/4He Precision
 45  0.15%
 12  0.3%
 1  1%



Noble Gas Measurements: The quoted noble gas and helium isotope measurement price assumes analysis of 45g or 90g samples. Samples are processed on our new noble gas mass spectrometer system (MS3) for both noble gas abundances and the 3He/4He isotope ratio. Extracted gas samples are purified by cryogenically removing water, and by exposure to Pd catalyst (to remove methane) and SAES getters (to remove reactive gases, including hydrogen). The noble gases are subsequently separated by programmed temperature sorption/desorption on two cryogenic traps (one "nude" and one with activated charcoal). The noble gas abundances are determined by peak-height manometry using an ion counting triple mass filter QMS to a precision of 0.1 to 0.2%. Small "matrix effects" associated with the effect of variable noble gas abundance patterns on cryotrap sorption/desorption characteristics are corrected for. Noble gas accuracy for water samples, as indicated by replicate analysis is significantly worse (see table below), and may be related to sampling issuesL: specifically trapped bubbles in the sampler valves leads to variable air entrainment. We are currently exploring this and will report improved numbers in the future. Helium isotopes are measured using a magnetic sector mass spectrometer to 0.1 to 0.15%.

Noble Gas  Gas Reproducibility   Water Reproducibility
 He  0.10%  1.0%
 Ne  0.14%  0.9%
 Ar  0.10%  0.3%
 Kr  0.14%  0.3%
 Xe  0.17%  0.2%


 

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Last updated June 24, 2013
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