Volume 3, Issue 1, March 2018, Page: 10-16
Dealing with Outlier in Linear Calibration Curves: A Case Study of Graphite Furnace Atomic Absorption Spectrometry
Njaka Namelantsoa Andriamahenina, Department of X-Ray Fluorescence and Environment, Institut National des Sciences et Techniques Nucléaires, Antananarivo, Madagascar
Elise Octavie Rasoazanany, Department of X-Ray Fluorescence and Environment, Institut National des Sciences et Techniques Nucléaires, Antananarivo, Madagascar
Herinirina Nomenjanahary Ravoson, Department of X-Ray Fluorescence and Environment, Institut National des Sciences et Techniques Nucléaires, Antananarivo, Madagascar
Lucienne Voahangilalao Rakotozafy, Department of X-Ray Fluorescence and Environment, Institut National des Sciences et Techniques Nucléaires, Antananarivo, Madagascar
Manovantsoatsiferana Harinoely, Department of X-Ray Fluorescence and Environment, Institut National des Sciences et Techniques Nucléaires, Antananarivo, Madagascar
Raoelina Andraimbololona, Department of Theoretical Physics, Institut National des Sciences et Techniques Nucléaires, Antananarivo, Madagascar
Randrianarivony Edmond, Department of Physics, Faculty of Sciences, University of Antananarivo, Antananarivo, Madagascar
Received: Nov. 16, 2017;       Accepted: Nov. 24, 2017;       Published: Jan. 2, 2018
DOI: 10.11648/j.wjac.20180301.12      View  1085      Downloads  60
Abstract
Outlier in the calibration of lead by graphite furnace atomic absorption spectrometry (GF-AAS) has been studied with help of the statistical tool F-test and T-test. The process consisted on measuring five standard solutions with three replicate to prepare the calibration curve. Ordinary least squares method (OLSM) was used to get the equation of the linear calibration curve; the correlation coefficient R² and analysis of variance (ANOVA) was used to validate the linearity of this calibration curve. Proceeding to the graphic representation and the residual plot of the calibration, a suspected outlier was found. The statistical tool F-test and T-test were used to examine the suspected outlier, they yield the same result and confirm the outlier data. The calibration curve with and without the outlier data were taken care to investigate the effect of this outlier in the limit of detection (LOD), limit of quantification (LOQ), the concentration of lead in the fourteen samples and the uncertainty related to calibration curve. It has been observed that the linearity of the calibration curve is accepted for both cases. For the case of the calibration with the outlier, the estimated LOD and LOQ were 1.76 µg L-1 and 5.18 µg L-1, respectively. The concentrations of lead in the sample are between 2.85 µg L-1 and 22.61µg L-1 and the uncertainty related to calibration curve vary between 1.17µg L-1 and 1.41 µg L-1. On the other hand, for the calibration without the outlier data, the value of LOD and LOQ were improved compared to the previous value, the value of these two parameters were 1.32 µg L-1 and 3.96 µg L-1, respectively. The concentration of lead in the sample vary between 2.75 µg L-1 and 22.52 µg L-1, compared to the previous concentration these value decrease from 0.40% and 3.29%. The uncertainties related to calibration curve vary between 0.90 µg L-1 and 1.09 µg L-1 for the second case, compared to the uncertainty in the first case, the uncertainty decreases from 22.48% to 23.53%. In conclusion, dealing with outlier improves the quality of the measurement and allow producing a reliable analytical data.
Keywords
Outlier, Calibration Curve, Lead, Graphite Furnace Atomic Absorption Spectrometry, Limit of Detection, Limit of Quantification, Uncertainty
To cite this article
Njaka Namelantsoa Andriamahenina, Elise Octavie Rasoazanany, Herinirina Nomenjanahary Ravoson, Lucienne Voahangilalao Rakotozafy, Manovantsoatsiferana Harinoely, Raoelina Andraimbololona, Randrianarivony Edmond, Dealing with Outlier in Linear Calibration Curves: A Case Study of Graphite Furnace Atomic Absorption Spectrometry, World Journal of Applied Chemistry. Vol. 3, No. 1, 2018, pp. 10-16. doi: 10.11648/j.wjac.20180301.12
Copyright
Copyright © 2018 Authors retain the copyright of this article.
This article is an open access article distributed under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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