New Approach for Voltammetry Near Limit of Detection: Integrated Voltammograms and Reduction of Measurements to an “Ideal” Experiment

Abstract

It is well-known that ac urrentÀvoltage curve gives information on analyte contents and low detection limits.T he main virtue of the electroanalytical technique,w here the current is registered as af unction of the applied potential (voltage), E,i sg ood metrological characteristic i.e.a ccuracy and precision, and also sensitivity and wide dynamic range for direct determination of the desired concentration. This methodology played an important role in developing of the so-called electrochemical sensing [1].I nt he special case of the stripping voltammetry,d etection limits can be decreased (or increased!) for several orders of its magnitude in comparison with the conventional ones.I n all cases,a tp resent time detection limits are evaluated with the usage of the mathematical statistics for processing of experimental data based on their Gaussian distribution. In general, in order to propose new electrochemical sensors,o ne needs to understand deeper the processes that take place near the electrode surface.I tc an help to expand sensing approach for requirements of the metrological characteristics:i .e.d etection limit, reproducibility and repeatability.T hese questions are discussed periodically in reviewers,o riginal papers and textbooks,s ee for example [1][2][3].I ts hould be noted that the Gaussian distribution is ab asic supposition and it ap riory is accepted without any proper justification. Namely,t his approach gives an impression of the relative ability of many electrochemical techniques to measure small concentrations of analytes on the level of traces in as olution. These data treatment methods are widely applied as routine programs in standard equipment (and it is included in various handbooks and textbooks) and attainable in undergraduate instructional laboratories.Among electroanalytical methods,v arious voltammetric techniques are the most attractive because of their cost and the acceptable analytic parameters,i np articular,a ssociated with limits of detection. Thel atter is evaluated with providing of the pair measurements that are repeated several times and subsequent treatment of data based on so-called 3-s rule and sensitivity coefficient. In this case,o ne can use the difference between two current values for background and extreme low concentration of analyte.T he apparatus technique helps to remove the essential part of the background current. However,a tt he same time one can lose information related to the lowest concentrations.T he details related to the conventional solution of this problem can be found in [4].T he conventional approach suffers from two unjustified basic suppositions that are instructive to repeat below:1. Thes uccessive measurements are independent from each other.2. Ther andom properties of each measurement are obeyed to the Gaussian distribution.In the recent publications [1], [ 5,6] one of the authors (RRN) based on real data proved that these suppositions should be at least reconsidered.Abstract:Ageneral approach for quantitative description of voltammograms is su...

Application of the Discrete Geometrical Invariants to the Quantitative Monitoring of the Electrochemical Background

“…Concluding this section, one can say that with the help of the rotated counterclockwise ellipse (7) we reduced 2n random points figuring in (4) to 7 statistical parameters (<x p >, <y p >, p=1,2; <xy>, A, C). If it is necessary to include the higher moments <x p y s > (p=0,1,2,..; s=0,1,2…) then other combinations of the type (4) should be considered.…”

“…When the number of the measurements are rather small there are mathematical methods that take into account the drift of the detected signal in time [6] while for the multi-cycling sensor(the number of the measurement cycles are large, M ≥ 1000) the mathematical methods related to quantitative monitoring of these sensors in time are not well developed. In this case, the electrode surface is changed significantly and can reflect the different stages of its electrochemical transformations [7,8]. It is known that in the inverse voltamperometry for the receiving of the reproducible working electrode surface, it is polarized in the cycling regime for the chosen potential range.…”