Receptors, Sensors and Related Topics

 

Publication

Compounds

Matrixes/
solvents

Methods

Results

Available files

J. Org. Chem. 2013, 78, 7796−7808. Accurate Method To Quantify Binding in Supramolecular Chemistry

Synthetic molecular receptors (derivatives of indolocarbazole, urea, thiourea, etc)

Acetonitrile with 0.5% of water

UV-Vis spectrophotometry

An accurate measurement method of host−guest binding affinities (binding constants) is introduced whereby differences in binding strength (ΔlogKass values) are measured between two host molecules toward a particular guest under identical solvent conditions. This method was applied to the measurement of the binding strength of 28 synthetic anion receptors (indolocarbazoles, ureas, thioureas) toward acetate in acetonitrile containing 0.5% water. A self-consistent (consistency standard deviation 0.04 log units) binding affinity scale ranging for around 2.7 log units was constructed from the results. This new approach of ligand receptor binding measurement is expected to find use in accurate quantification of a wide range of binding processes relevant to supramolecular chemistry.

Ligand-receptor Binding constant measurement data, structures of the receptor molecules, absolute association constants pKa values of the more acidic receptor molecules (PDF)

Chem. Comm. 2012, 48, 10490-10492. Unusual para-substituent effects on the intramolecular hydrogen-bond in hydrazone-based switches

Hydrazone-based molecular switches

Acetonitrile

UV-Vis spectrophotometry, NMR,

The switching of the described molecular switches is sensitive towards acidity of the medium. The two H-bond fragments HNNQCCQN and HNNQCCQO in a series of hydrazone-based switches adopt two distinct H-bonding motifs. The HNNQCCQN fragment cannot take advantage of RAHB enhancement, because that will diminish the aromatic character of the pyridyl group. On the other hand, the HNNQCCQO fragment follows RAHB theory. By measuring the pKa values of the pyridyl ring and dissecting its components, we were able to show that both electron donating and withdrawing p-substituents strengthen the H-bond in the HNNQCCQN fragment by inversely modulating the acidity and basicity of the NH and pyridyl nitrogens, respectively.

 

Sensors 2010, 10, 4430-4455 Measurement Uncertainty Estimation in Amperometric Sensors: A Tutorial Review

No limits

No limits

Electrochemical amperometric sensors

This tutorial focuses on measurement uncertainty estimation in amperometric sensors. The main uncertainty sources are reviewed and their contributions are discussed with relation to the principles of operation of the sensors, measurement conditions and properties of the measured samples. The discussion is illustrated by dissolved oxygen (DO) measurement case studies based on the two major approaches for uncertainty evaluation: the ISO GUM modeling approach and the Nordtest approach.

Graphical representation of the paper

 

Figure 2. Expanded uncertainties for all conditions using two estimation approaches

Meas. Sci. Technol 2007, 18, 1877. Model-based measurement uncertainty estimation in amperometric dissolved oxygen concentration measurement

Dissolved oxygen, DO, (O2)

Water (H2O)

Electrochemical amperometric sensors

Uncertainty sources in amperometric dissolved oxygen (DO) concentration measurement are explored and an ISO GUM uncertainty estimation procedure based on a detailed measurement model is presented. The procedure is applied to two different commercial amperometric DO measurement instruments of galvanic type differing in cathode and membrane area and membrane thickness. The complete uncertainty budgets of several typical measurement processes of the two instruments are discussed. From this comparison evidence is provided that the deciding influential factors may be different for the investigated instruments under otherwise comparable measurement conditions, even though the instruments follow the same working principles. Variations in the relative expanded uncertainty between U = 0.8% and U = 9% (k = 2) were observed for the same instrument under different conditions. At DO concentrations lower than around or below 4 mg l−1 (depending on other conditions), the background current of the sensor becomes the dominating uncertainty source. At DO concentrations above that range, a variety of influence factors become relevant depending on the specific conditions, for instance stirring speed and membrane properties. The high importance of the cathode and membrane area, membrane material and membrane thickness on the uncertainty is demonstrated. Based on these results, a set of recommendations for the DO sensor design is formulated.

Table 1. Measurement conditions and uncertainty budgets of the results obtained by instruments I and II corresponding to the cases 15

using calibration in water

 

Figure 3. The relative uncertainties of DO concentrations measured with instruments I and II calibrated in air and in water. The points have

been connected for better readability

 

Excel spreadsheet of uncertainty calculation examples for Instrument I

Accreditation and Quality Assurance 2004, 9, 340-348. Estimation of uncertainty in electrochemical amperometric measurement of dissolved oxygen concentration

Dissolved oxygen, DO, (O2)

Water (H2O)

Electrochemical amperometric sensors

A procedure for the estimation of measurement uncertainty of dissolved oxygen (DO) concentration measurement based on the ISO approach is presented. It is based on a mathematical model that involves 14 input parameters. The uncertainty of DO concentration strongly depends on changes in experimental details (temperature difference between calibration and measurement, the time interval between calibration and measurement, etc.). The relative measurement uncertainty is, however, practically independent of the DO concentration itself. The uncertainty is the lowest if the calibration and the measurement are done at the same temperature and on the same day. A calculation tool is provided (in the form of a GUM Workbench file) for practitioners that can be used for uncertainty calculation of DO concentrations at very different experimental conditions.

Fig. 1 Schematic presentation of a galvanic dissolved oxygen (DO)

sensor

 

Table 1 The uncertainty budgets at DO concentration 7.0 mg/l various measurement conditions

 

 

 

Comments

Should you have any questions regarding the data, the used experimental, data treatment or computational methods, etc, please do not hesitate to contact Ivo Leito (e-mail: ivo.leitobwut.ee)!     Proposals for collaboration are also most welcome!

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See also other research topics at UT Chair of Analytical chemistry

  

University of Tartu

 

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Last edited:  Friday, 27-Sep-2013 19:42:26 EEST