Please Avoid Plotting Analytical Response against Logarithm of Concentration

Urban, Pawel L.

doi:10.1021/acs.analchem.0c02096

Cited by 29 publications

(17 citation statements)

References 19 publications

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“…Under this condition, the function does not warrant reliable fitting. 3 However, the application of mathematical methods is only to obtain an ideal functional relationship and does and will not affect the accuracy of experimental data. From a statistical point of view, a nonlinear model can be transformed into a linear model under certain conditions.…”

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confidence: 99%

“…There is, of course, also the view that a linear relationship between the response and logarithm of concentration does not prove the validity of the method. Urban expressed an opinion that it is inappropriate to relate the analytical response to the logarithm of the concentration, which can lead to a false description of performance descriptors, generating an illusion of linearity with the nonlinear calibration data set. Under this condition, the function does not warrant reliable fitting .…”

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confidence: 99%

“…Urban expressed an opinion that it is inappropriate to relate the analytical response to the logarithm of the concentration, which can lead to a false description of performance descriptors, generating an illusion of linearity with the nonlinear calibration data set. Under this condition, the function does not warrant reliable fitting . However, the application of mathematical methods is only to obtain an ideal functional relationship and does and will not affect the accuracy of experimental data.…”

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confidence: 99%

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Logarithmic Data Processing Can Be Used Justifiably in the Plotting of a Calibration Curve

et al. 2021

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The article is a response to a recent opinion piece that log concentration values should not be applied in analytical chemistry. An essential aim in the development of analytical chemistry methods is to obtain more sensitive and accurate detection values. For the application of chemical analysis methods, the obtained experiment data need to fit with the mathematical functions in the first place. As influenced by different detection principles and analytical methods, data can be displayed in a coordinate system with two linear axes for linear function fitting, or the data can first be taken through a logarithmic transformation and then for function fitting. Using raw data or data after logarithmic transformation primarily depends on analytical principles, without special rules of data formats. For example, ultraviolet− visible spectrophotometric data are more suitable for direct linear fitting. However, enzyme-catalyzed reaction or electrochemical data in logarithmic form are more appropriate for function fitting. This transformation of data form will not affect the soundness of fit statistics; rather, it simplifies the complexity of function analysis and calculation, which are the essence of analytical chemistry. In this brief article, we provide justification and legitimacy of the application of logarithmic processing in various fields of quantitative analytical chemistry.

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Logarithmic Data Processing Can Be Used Justifiably in the Plotting of a Calibration Curve

et al. 2021

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“…One can realize a linear calibration curve by taking the semilog plot of the current response vs concentration (i.e., natural log of concentration). Recently, the use of semilog plots was appropriately called into question . We chose to report both plots due to the wide reporting of such graphs with semilog plots already in the literature.…”

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confidence: 99%

Electrochemical Sensing of Perfluorooctanesulfonate (PFOS) Using Ambient Oxygen in River Water

Clark

Dick

2020

ACS Sens.

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Per-and polyfluoroalkyl substances (PFAS) are an emerging class of pervasive and harmful micropollutant. Nextgeneration sensors are necessary to detect PFAS at sub-nanomolar levels. Electrochemistry can measure analyte concentrations at sub-10 nM levels and offers a deployable platform; however, the lack of chemical reactivity of PFAS species requires electrode surface functionalization with a molecularly imprinted polymer (MIP). Previously, such sensors have required a well-characterized oneelectron mediator (i.e., ferrocene carboxylic acid or ferrocene methanol) for detection. Natural waterways do not have an abundance of ferrocenyl compounds for quantification, implying that these mediators limit sensor practicality, deployability, and cost. Here, we take advantage of ambient oxygen present in river water to quantify one of the more harmful PFAS molecules, perfluorooctanesulfonate (PFOS), from 0 to 0.5 nM on a MIP-modified carbon substrate. Differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) generated calibration curves for PFOS in river water using oxygen as the mediator. Importantly, we show that electrochemical impedance spectroscopy is superior to voltammetric techniques: like ultramicroelectrodes, this technique can be used in low-conductivity matrices like river water with high reproducibility. Further, impedance provides a PFOS limit of detection of 3.4 pM. We also demonstrate that the common interferents humic acid and chloride do not affect the sensor signal. These results are a necessary step forward in developing deployable sensors that act as a first line of defense for detecting PFAS contamination at its earliest onset.

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“…The reason for the malpractice mentioned above is presumably due to a lack of comprehensive understanding of reaction mechanisms and physicochemical processes of target-sensor-analytical response correlations (Figure ). This severe concern was raised by Prof. Urban in the previous report, and nonlinear fitting was seen as a plausible solution . Here, this perspective highlights the importance of examining the signal transformation mechanism before deciding to plot an analytical response against an appropriate form of concentration.…”

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confidence: 75%

Re-Examination of Plotting Analytical Response against Different Forms of Concentration

et al. 2021

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Please Avoid Plotting Analytical Response against Logarithm of Concentration

Cited by 29 publications

References 19 publications

Logarithmic Data Processing Can Be Used Justifiably in the Plotting of a Calibration Curve

Logarithmic Data Processing Can Be Used Justifiably in the Plotting of a Calibration Curve

Electrochemical Sensing of Perfluorooctanesulfonate (PFOS) Using Ambient Oxygen in River Water

Re-Examination of Plotting Analytical Response against Different Forms of Concentration

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