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Reducing Uncertainties in Carbonate Clumped Isotope Analysis Through Consistent Carbonate-Based Standardization.

ABSTRACT: About a decade after its introduction, the field of carbonate clumped isotope thermometry is rapidly expanding because of the large number of possible applications and its potential to solve long-standing questions in Earth Sciences. Major factors limiting the application of this method are the very high analytical precision required for meaningful interpretations, the relatively complex sample preparation procedures, and the mass spectrometric corrections needed. In this paper we first briefly review the evolution of the analytical and standardization procedures and discuss the major remaining sources of uncertainty. We propose that the use of carbonate standards to project the results to the carbon dioxide equilibrium scale can improve interlaboratory data comparability and help to solve long-standing discrepancies between laboratories and temperature calibrations. The use of carbonates reduces uncertainties related to gas preparation and cleaning procedures and ensures equal treatment of samples and standards. We present a set of carbonate standards of diverse composition, discuss how they can be used to correct for mass spectrometric biases, and demonstrate that their use significantly improves the comparability among four laboratories. We propose that the use of these standards or of a similar set of carbonate standards will improve the comparability of data across laboratories.

SUBMITTER: Bernasconi SM

PROVIDER: S-EPMC6220777 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Reducing Uncertainties in Carbonate Clumped Isotope Analysis Through Consistent Carbonate-Based Standardization.

Bernasconi Stefano M SM Müller Inigo A IA Bergmann Kristin D KD Breitenbach Sebastian F M SFM Fernandez Alvaro A Hodell David A DA Jaggi Madalina M Meckler Anna Nele AN Millan Isabel I Ziegler Martin M

Geochemistry, geophysics, geosystems : G(3) 20180903 9

About a decade after its introduction, the field of carbonate clumped isotope thermometry is rapidly expanding because of the large number of possible applications and its potential to solve long-standing questions in Earth Sciences. Major factors limiting the application of this method are the very high analytical precision required for meaningful interpretations, the relatively complex sample preparation procedures, and the mass spectrometric corrections needed. In this paper we first briefly ...[more]

PMID: 30443200

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Project description:RationaleClumped isotope geochemistry examines the pairing or clumping of heavy isotopes in molecules and provides information about the thermodynamic and kinetic controls on their formation. The first clumped isotope measurements of carbonate minerals were first published 15 years ago, and since then, interlaboratory offsets have been observed, and laboratory and community practices for measurement, data analysis, and instrumentation have evolved. Here we briefly review historical and recent developments for measurements, share Tripati Lab practices for four different instrument configurations, test a recently published proposal for carbonate-based standardization on multiple instruments using multi-year data sets, and report values for 21 different carbonate standards that allow for recalculations of previously published data sets.MethodsWe examine data from 4628 standard measurements on Thermo MAT 253 and Nu Perspective IS mass spectrometers, using a common acid bath (90°C) and small-sample (70°C) individual reaction vessels. Each configuration was investigated by treating some standards as anchors (working standards) and the remainder as unknowns (consistency standards).ResultsWe show that different acid digestion systems and mass spectrometer models yield indistinguishable results when instrument drift is well characterized. For linearity correction, mixed gas-and-carbonate standardization or carbonate-only standardization yields similar results. No difference is observed in the use of three or eight working standards for the construction of transfer functions.ConclusionsWe show that all configurations yield similar results if instrument drift is robustly characterized and validate a recent proposal for carbonate-based standardization using large multiyear data sets. Δ47 values are reported for 21 carbonate standards on both the absolute reference frame (ARF; also refered to as the Carbon Dioxide Equilibrated Scale or CDES) and the new InterCarb-Carbon Dioxide Equilibrium Scale (I-CDES) reference frame, facilitating intercomparison of data from a diversity of labs and instrument configurations and restandardization of a broad range of sample sets between 2006, when the first carbonate measurements were published, and the present.

Project description:BACKGROUND:After a 1999 National Cancer Institute (NCI) clinical alert was issued, chemoradiotherapy has become widely used in treating women with cervical cancer. Two subsequent systematic reviews found that interpretation of the benefits was complicated and some important clinical questions were unanswered. OBJECTIVES:We initiated a meta-analysis seeking updated individual patient data (IPD) from all randomised controlled trials (RCTs) to assess the effect of chemoradiotherapy on all outcomes. We pre-specified analyses to investigate whether the effect of chemoradiotherapy differed by trial or patient characteristics. SEARCH STRATEGY:We supplemented MEDLINE, LILACS and CANCERLIT searches with information from trial registers, by handsearching relevant meeting proceedings and by discussion with relevant trialists and organisations. Searches were updated until October 2009. SELECTION CRITERIA:Both published and unpublished trials were eligible for inclusion provided the patients had been randomised between radiotherapy (with or without surgery) versus concomitant chemoradiotherapy (with or without surgery); that the method of randomisation precluded prior knowledge of the treatment to be assigned; and that the trial had completed patient recruitment before the date of the final analyses. DATA COLLECTION AND ANALYSIS:We carried out a quantitative meta-analysis using updated information from individual patients from all available RCTs. We sought data from all patients randomised in all eligible trials. We obtained updated information on survival, recurrence and date of last follow up. To avoid potential bias, we requested information for all randomised patients, including those who had been excluded from the investigators' original analyses. MAIN RESULTS:Eighteen trials were identified and 15 of these were eligible for inclusion in the main analysis. On the basis of 13 trials that compared chemoradiotherapy versus the same radiotherapy, there was a 6% improvement in 5-year survival with chemoradiotherapy (hazard ratio (HR) = 0.81, P < 0.001). A larger survival benefit was seen for the two further trials in which chemotherapy was administered after chemoradiotherapy. There was a significant survival benefit for both the group of trials that used platinum-based (HR = 0.83, P = 0.017) and non-platinum based (HR = 0.77, P = 0.009) chemoradiotherapy, but no evidence of a difference in the size of the benefit by radiotherapy or chemotherapy dose or scheduling was seen. Chemoradiotherapy also reduced local and distant recurrence and progression and improved disease-free survival (DFS). There was a suggestion of a difference in the size of the survival benefit with tumour stage, but not across other patient subgroups. Acute haematological and gastro-intestinal toxicity were increased with chemoradiotherapy, but data were too sparse for an analysis of late toxicity. AUTHORS' CONCLUSIONS:These results endorse the recommendations of the NCI alert, but also demonstrate their applicability to all women and a benefit of non-platinum based chemoradiotherapy. Furthermore, although these results suggest an additional benefit from adjuvant chemotherapy this requires testing in RCTs.

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Reducing Uncertainties in Carbonate Clumped Isotope Analysis Through Consistent Carbonate-Based Standardization.

Publications

Reducing Uncertainties in Carbonate Clumped Isotope Analysis Through Consistent Carbonate-Based Standardization.

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