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Blank correction for isotope ratio measurement on small amounts of substances is often limited by presence of a blank, with an apparent isotopic composition different from that of the sample. For isotope ratios, blank correction is commonly performed either by the regression method, which works without the need for estimation of the blank, or by the subtraction method. With the subtraction method, estimation of the amount and isotope delta of the blank is required, and these estimates could be obtained either by direct, semi-indirect, or indirect measurement. Previously given expressions for the standard uncertainties of indirectly measured blank amounts and blank isotope deltas did not account for covariance between input quantities. In the present work, a previously published data set was re-evaluated, with covariance terms properly included in the calculation of uncertainties. It was shown that covariance effects may yield a significant reduction in uncertainty estimates, both for blank quantities and for blank corrected results. For series measurements on a standard material, it was also shown that the distribution of individual corrected isotope delta values around the average value was approximately normal, with its standard deviation equal to the estimated standard uncertainty of the corrected values. In most cases, it was observed that the regression and subtraction methods yield approximately the same blank corrected average values and uncertainties, regardless of method selected for estimation of blank quantities.
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences , SE-90183 Umeå, Sweden.
This article was published in the following journal.
Name: Analytical chemistry
Past computer solutions for confidence intervals, both in paired counting and when the sample is counted an integer number of times more than the blank, are extended to computing the precision of the ...
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The uncertainty principle being a cornerstone of quantum mechanics, it is surprising that, in nearly 90 years, there have been no direct tests of measurement uncertainty relations. This lacuna was due...
Ramped pyrolysis (RP) targets distinct components of soil and sedimentary organic carbon based on their thermochemical stabilities and allows the determination of the full spectrum of radiocarbon (14C...
Stable isotopes are extensively used as tracers for the study of plant-water sources. Isotope-ratio infrared spectroscopy (IRIS) offers a cheaper alternative to isotope-ratio mass spectroscopy (IRMS),...
In this short-term study a method for the evaluation of the metabolic competency of the urea cycle in vivo will be assessed. In order to monitor the efficacy of new treatment options for p...
The goal of this study will be to determine whether PCC confers any benefits over FFP in the traumatic intracranial hemorrhage with respect to multiple factors including time to correction...
The study is designed to determine whether a dual isotope protocol is equivalent to a single isotope in the diagnosis of myocardial ischemia and infarction using MYOVIEW SPECT imaging.
This study evaluates the intrastromal correction of ametropia with a femtosecond laser made by 20/10 PERFECT VISION. This laser generates a beam of ultrashort, infrared pulses which enable...
The purpose of this study is to test a correction factor which would allow ankle brachial indexes taken in the seated position to accurately predict an ankle brachial index taken in the su...
The waist circumference measurement divided by the hip circumference measurement. For both men and women, a waist-to-hip ratio (WHR) of 1.0 or higher is considered "at risk" for undesirable health consequences, such as heart disease and ailments associated with OVERWEIGHT. A healthy WHR is 0.90 or less for men, and 0.80 or less for women. (National Center for Chronic Disease Prevention and Health Promotion, 2004)
The ratio of two odds. The exposure-odds ratio for case control data is the ratio of the odds in favor of exposure among cases to the odds in favor of exposure among noncases. The disease-odds ratio for a cohort or cross section is the ratio of the odds in favor of disease among the exposed to the odds in favor of disease among the unexposed. The prevalence-odds ratio refers to an odds ratio derived cross-sectionally from studies of prevalent cases.
The professional practice of primary eye and vision care that includes the measurement of visual refractive power and the correction of visual defects with lenses or glasses.
Measurement of the index of refraction (the ratio of the velocity of light or other radiation in the first of two media to its velocity in the second as it passes from one into the other).
Hydrogen. The first chemical element in the periodic table. It has the atomic symbol H, atomic number 1, and atomic weight 1. It exists, under normal conditions, as a colorless, odorless, tasteless, diatomic gas. Hydrogen ions are PROTONS. Besides the common H1 isotope, hydrogen exists as the stable isotope DEUTERIUM and the unstable, radioactive isotope TRITIUM.