Faster and more precise isotopic water analysis of discrete samples by predicting the repetitions’ asymptote instead of averaging last values

Hachgenei, Nico; Vaury, Véronique; Nord, Guillaume; Spadini, Lorenzo; Duwig, Céline

doi:10.1016/j.mex.2022.101656

Cited by 3 publications

(3 citation statements)

References 7 publications

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“…and developing a memory-correction equation. 8,15,[21][22][23][24] For example, Guidotti et al 21 proposed the three-pool model, in which each measured sample is a mixture of three pools of water that have different sizes and exchange rates. They showed that the method can correct huge memory signals, without the need for "true" values.…”

Section: Estimation-the Me Is Characterized By Measuring Known Samplesmentioning

confidence: 99%

“…This is handy because numerous injections from the same vial may result in an evaporative fractionation. According to Schauer et al, 8 the most effective tools against the ME are the conditioning vials and the selective sequence of waters; however, they are cautious and state that their approach does not fully remove the ME. Estimation—the ME is characterized by measuring known samples and developing a memory‐correction equation 8,15,21–24 . For example, Guidotti et al 21 proposed the three‐pool model, in which each measured sample is a mixture of three pools of water that have different sizes and exchange rates.…”

Section: Introductionmentioning

confidence: 99%

“…Estimation—the ME is characterized by measuring known samples and developing a memory‐correction equation 8,15,21–24 . For example, Guidotti et al 21 proposed the three‐pool model, in which each measured sample is a mixture of three pools of water that have different sizes and exchange rates.…”

Section: Introductionmentioning

confidence: 99%

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A simple method for rapid removal of the memory effect in cavity ring‐down spectroscopy water isotope measurements

Keinan

Goldsmith

2023

Rapid Comm Mass Spectrometry

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RationaleThe accuracy determined in the routine analysis of water isotopes (δ17O, δ18O, δ2H) using cavity ring‐down spectroscopy is greatly affected by the memory effect (ME), a sample‐to‐sample carryover that biases measurements. This study aims to develop a simple method that rapidly removes the ME.MethodsWe developed a method, designed for the Picarro L2140‐i, that removes the ME by injecting small amounts of water with an extreme isotopic value (“kick”) in the opposite direction of the ME. We conducted 11 experiments to identify the optimal kick for pairs of isotopically enriched and depleted samples. Once quantified, the optimal kick was used to create an ME‐free, unbiased calibration curve, which was verified using international and internal lab standards.ResultsOur kick method removes the ME very efficiently in half the time it takes for experiments without a kick. The optimal number of kick injections required to minimize stabilization time between standards of different compositions is three injections of δ2H ≈ −1000‰ water per a 100‰ difference between standards. Three runs of routine measurements using the kick method resulted in uncertainties of 0.03‰, 0.2‰, and 5 permeg for δ18O, δ2H, and 17O‐excess, respectively.ConclusionsThis study demonstrates a new method for rapidly removing the ME. Our kick protocol is a readily available, cheap, and efficient approach to reduce instrumental bias and improve measurement accuracy.

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Section: Estimation-the Me Is Characterized By Measuring Known Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A simple method for rapid removal of the memory effect in cavity ring‐down spectroscopy water isotope measurements

Keinan

Goldsmith

2023

Rapid Comm Mass Spectrometry

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Transit time tracing using wetness-adaptive StorAge Selection functions—application to a Mediterranean catchment

Hachgenei,

Nord,

Spadini

et al. 2024

Journal of Hydrology

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Water vapor stable isotope memory effects of common tubing materials

Meyer,

Welp

2024

Atmos. Meas. Tech.

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Abstract. Water molecules in vapor can exchange with gaseous water molecules sticking to surfaces of sampling tubing, and exchange rates are unique for each water isotopologue and tubing material. Therefore, water molecules on tubing walls take some time to reach isotopic equilibrium with a new vapor isotopic signal. This creates a memory effect that is observed as attenuation time for signal propagation in continuous stable water vapor isotope measurement systems. Tubing memory effects in δD and δ18O measurements can limit the ability to observe fast changes, and because δD and δ18O memory are not identical, this introduces transient deuterium excess (D-excess, defined as δD-8×δ18O) artifacts in time-varying observations. To our knowledge, a comprehensive performance comparison of commonly used tubing material water exchange properties in laser-based measurement systems has not been published. We compared how a large isotopic step change propagated through five commonly used tubing materials for water isotopic studies – perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), high-density polyethylene (HDPE), and copper – at two different temperatures and an airflow rate of 0.635 L min−1 through approximately 100 ft (30.5 m) of 1/4 in. (6.4 mm) outer diameter (o.d.) tubing. All commonly used tubing materials performed similarly to each other in terms of attenuation times, reaching δ18O-location-adjusted δD and δ18O 95 % completion in less than 45 s, with slight variations based on temperature. PFA does appear to perform slightly better than the other materials, although memory metric differences are small. A tubing material commonly used in the early 2000s but reported to have memory effects on δD, Dekabon, was also tested at ambient temperature and changing humidities. The Dekabon isotopic equilibrium was not reached until nearly an hour after source transition, much later than H2O mixing ratios equilibrated. Bev-A-Line XX (used in some soil O2 and CO2 gas studies) was also tested at ambient temperature, but it did not approach isotopic equilibrium until after nearly 6 h of testing. Therefore, we cannot recommend the use of Bev-A-Line XX or Dekabon in water vapor isotope applications. Source transition from heavy to light or from light to heavy affected isotopic transition speed only in experiments where H2O ppmv was changing. While a shorter tubing lengths and smaller inner diameters shorten the delay of signal propagation through the tubing, they did not greatly change the attenuation curves under these conditions for the current commonly used tubing materials tested. However, in Dekabon, attenuation curves were greatly extended with increased tubing length. Our results show that the commonly used plastic tubing materials tested were not inferior to copper in terms of isotopic memory under these conditions, and they are easier to work with and are less expensive than copper.

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Faster and more precise isotopic water analysis of discrete samples by predicting the repetitions’ asymptote instead of averaging last values

Cited by 3 publications

References 7 publications

A simple method for rapid removal of the memory effect in cavity ring‐down spectroscopy water isotope measurements

A simple method for rapid removal of the memory effect in cavity ring‐down spectroscopy water isotope measurements

Transit time tracing using wetness-adaptive StorAge Selection functions—application to a Mediterranean catchment

Water vapor stable isotope memory effects of common tubing materials

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