Uncertainty in Analytical Measurements: Approaches, Evaluation Methods and Their Comparison Based on a Case Study of Arsenic Determination in Rice
Mehdi Nabi, Sayed Mehdi Ghoreishi &Mohsen Behpour
Abstract
All measurements have uncertainty and they are not absolute. Therefore, identification, determination and evaluation of critical influencing factors based on recent approaches are important and necessary. Laboratories shall identify and evaluate all components and contributions to measurement uncertainty. In this article, two different approaches for evaluation of measurement uncertainty of arsenic in rice are studied and compared. These different approaches are GUM approach and Monte Carlo approach. The results clarified, evaluated uncertainty for the measurand was the same in the GUM and MCA, statistically and it is clarified that evaluated uncertainty by these approaches have no significant difference.
Abbreviations
ρρ: Density
m: Mass
V: Volume
u : Standard uncertainty
u c : Combined standard uncertainty
U: Expanded uncertainty
Ci : Sensitivity coefficient
k: Coverage factor
ucal : Calibration uncertainty
u rep : Repeatability uncertainty
u temp : Temperature effect uncertainty
u v : Volume uncertainty
u m : Mass uncertainty
u Ccal : Calibration curve uncertainty
ΔT: Temperature deviation from 20 °C
CCcalCCcal : Sensitivity coefficient of calibration curve
Cv : Sensitivity coefficient of volume
Cm : Sensitivity coefficient of mass
Ccal : Concentration from calibration curve
CF : Final concentration
M: Number of measurements to determine c0
N: Number of measurements for the calibration
Sm : residual standard deviation
m: slope
sx¯¯¯sx¯ : standard deviation of the averages
MS: Mean square
DF: Degree of freedom
SS: Sum of square
F: F statistics
P: P value
Sr : Within-laboratory (Repeatability) standard deviation
Sl : Between-laboratory (Intermediate) standard deviation
SR : Reproducibility standard deviation
p: Number of subgroups
References:
[1] ISO/IEC GUIDE 98-1 (2009) Uncertainty of Measurement – Part 1: Introduction to the expression of uncertainty in measurement.
[2] ISO/IEC GUIDE 99 (2007) International Vocabulary of Metrology – Basic and General Concepts and Associated Terms (VIM).
[3] ISO/IEC GUIDE 98-3 (2008) Uncertainty of measurement – Part 3: Guide to the expression of uncertainty in measurement.
[4] ISO 21748 (2017) Guidance for the Use of Repeatability, Reproducibility and Trueness Estimates in Measurement Uncertainty Evaluation.
[5] EURACHEM / CITAC Guide CG 4, QUAM (2012) Quantifying Uncertainty in Analytical Measurement.
[6] EURACHEM/CITAC, Produced Jointly with EUROLAB, Nordtest and the UK RSC Analytical Methods Committee (2007) Guide Measurement Uncertainty Arising from Sampling: A Guide to Methods and Approaches.
[7] JCGM 101 (2008) Evaluation of Measurement Data – Supplement 1 to the “Guide to the Expression of Uncertainty in Measurement” – Propagation of Distributions Using a Monte Carlo Method.
Acknowledgments
The authors are grateful for financial support from the Meyar Danesh Pars Company and also the University of Kashan with Grant No. of 52798.
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Affiliations
Faculty of Chemistry, Department of Analytical Chemistry, University of Kashan, Kashan, Islamic Republic of Iran
Mehdi Nabi, Sayed Mehdi Ghoreishi & Mohsen Behpour
Corresponding author
Correspondence to Sayed Mehdi Ghoreishi.
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