Metrological Traceability of Measurement Results in Chemistry: Concepts and Implementation

Bièvre, Paul De; Dybkær, René; Fajgelj, A.; Hibbert, D. Brynn

doi:10.1515/iupac.83.0516

Cited by 15 publications

(26 citation statements)

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“…Gravimetric U and Pb reference materials do not contain synthetic isotopes (e.g., 205 Pb, 233 U) and, therefore, the concentration of such tracer isotopes can be determined relative to the 'gravimetric' isotopes (i.e., 206 Pb, 238 U) via mass spectrometry. Following the gravimetric calibration scheme outlined above the accuracy of the U-Pb system can be directly traceable to the SI system of units (De Bièvre et al, 2011) (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Metrology and Traceability of U-Pb Isotope Dilution Geochronology (EARTHTIME Tracer Calibration Part I)

Condon¹,

Schoene²,

McLean³

et al. 2017

Preprint

116

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Mixed 235 U-233 U-205 Pb (-202 Pb) tracers for U-Pb isotope-dilution isotope ratio mass spectrometry have been prepared under the auspices of the EARTHTIME Initiative. The methods and results for the preparation and calibration of the U/Pb ratio and isotopic abundances are given, and the various sources of uncertainty are discussed and quantified. The accuracy of the EARTHTIME U-Pb tracer isotopic composition can be traced back to SI units via a series of assay and isotopic composition reference materials combined with the experiments described herein. The parameters used in calculating U/Pb ratios (and inferentially U-Pb dates) have correlated uncertainties that result in a total uncertainty contribution to 206 Pb/ 238 U dates of ± < 0.03% (95% confidence). For suitable terrestrial materials such as zircon, when other sources of uncertainty have been minimised (e.g., open-system behaviour, 238 U/ 235 U variation, intermediate daughter product disequilibrium, common Pb, etc.) the U-Pb tracer calibration uncertainty is a limiting factor in the accuracy of U-Pb geochronology -but less so than the uncertainty in the 238 U and 235 U decay constants (±0.11 and 0.14% 2r). The calibration approach of the mixed EARTHTIME 235 U-233 U-205 Pb (-202 Pb) tracers, in addition to updated values for reference materials (e.g., mixed gravimetric reference solutions), and parameters (e.g., Pb reference material assay), can be applied to other laboratory-specific U-Pb tracers and will facilitate the generation of accurate and directly inter-comparable U-Pb data.

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Section: Introductionmentioning

confidence: 99%

Metrology and Traceability of U-Pb Isotope Dilution Geochronology (EARTHTIME Tracer Calibration Part I)

Condon¹,

Schoene²,

McLean³

et al. 2017

Preprint

116

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“…We are evaluating the suitability of digital PCR (dPCR) limiting dilution end-point technologies [2] for measuring the mass concentration of human genomic DNA in aqueous buffer. If dPCR can be successfully established as a potentially primary method [3], we anticipate using commercially available implementations to value assign a suite of calibration materials designed for use by the forensic community that will be stable over time and provide results that are traceable [4] to the International System of Units (SI).…”

Section: Introductionmentioning

confidence: 99%

Real-time cdPCR opens a window into events occurring in the first few PCR amplification cycles

2015

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Polymerase chain reaction (PCR) end-point limiting dilution techniques, collectively termed "digital PCR (dPCR)", have been proposed as providing a potentially primary method for DNA quantification. We are evaluating several commercially available dPCR systems for use in certifying mass concentration in human genomic DNA reference materials. To better understand observed anomalies among results from chamber- and droplet-dPCR (cdPCR and ddPCR) systems, we have developed a graphical tool for evaluating and documenting the performance of PCR assays in real-time cdPCR systems: the ogive plot, the cumulative distribution of crossing threshold values. The ogive structure appears to embed information about early amplification events. We have successfully simulated ogives observed with different assays and reaction conditions using a four-stage amplification model parameterized by the probability of creating an intact 1) first generation "long" amplicon of indeterminate length from an original DNA target, 2) second generation defined-length amplicon from a long amplicon, and 3) defined-length amplicon from another defined-length amplicon. We are using insights from this model to optimize dPCR assay design and reaction conditions and to help validate assays proposed for use in value-assigning DNA reference materials.

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“…To a metrologist the problem is easy: data that can be demonstrated to be metrologically traceable to a reference of some standing (such as a realization of a unit in the SI), with an appropriate estimate of measurement uncertainty, are evaluated as fit for some intended use if the measurement uncertainty is within a target range. Even now, when we have a better understanding of the requirements for metrological traceability, [2] published data do not always have clear-cut evidence of traceability or measurement uncertainty estimated by a method compatible with the Guide to the Evaluation of Uncertainty of Measurement (GUM). [3] Real-world evaluation is complex and very dependent on both the field of interest and the data themselves.…”

Section: Approaches To Data Evaluationmentioning

confidence: 99%

Managing Standards and Critical Evaluation in a World of Big Data

Hibbert¹,

Shaw²,

Magalhães³

2017

Chemistry International

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IUPAC is very interested in data, big or small. Its web site opens with the statement, “The International Union of Pure and Applied Chemistry (IUPAC) is the world authority on … many other critically-evaluated data.” While the ‘…’ covers compelling and widely popular topics, such as naming new elements, the mission of IUPAC to give its imprimatur for chemical data is of great importance to health, security, and trade in the world. In this article, after a review of present activities, we will contemplate how a comprehensive approach might be structured under IUPAC project rules and then look to the future in a world of ‘big data’ and ‘smart instruments’.

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Metrological Traceability of Measurement Results in Chemistry: Concepts and Implementation

Cited by 15 publications

References 0 publications

Metrology and Traceability of U-Pb Isotope Dilution Geochronology (EARTHTIME Tracer Calibration Part I)

Metrology and Traceability of U-Pb Isotope Dilution Geochronology (EARTHTIME Tracer Calibration Part I)

Real-time cdPCR opens a window into events occurring in the first few PCR amplification cycles

Managing Standards and Critical Evaluation in a World of Big Data

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