Flow manifold for chemical H-point standard addition method implemented to electrochemical analysis based on the capacitance measurements

Marcin Wieczorek; Maria Madej; Karolina Starzec; Paweł Knihnicki; Anna Telk; Jolanta Kochana; Paweł Kościelniak

doi:10.1016/j.talanta.2018.03.098

Flow manifold for chemical H-point standard addition method implemented to electrochemical analysis based on the capacitance measurements

Talanta. 2018 Aug 15:186:183-191. doi: 10.1016/j.talanta.2018.03.098. Epub 2018 Apr 3.

Authors

Marcin Wieczorek¹, Maria Madej², Karolina Starzec², Paweł Knihnicki², Anna Telk², Jolanta Kochana², Paweł Kościelniak²

Affiliations

¹ Jagiellonian University in Krakow, Faculty of Chemistry, Department of Analytical Chemistry, Gronostajowa 2, 30-387 Kraków, Poland. Electronic address: marcin.wieczorek@uj.edu.pl.
² Jagiellonian University in Krakow, Faculty of Chemistry, Department of Analytical Chemistry, Gronostajowa 2, 30-387 Kraków, Poland.

PMID: 29784348
DOI: 10.1016/j.talanta.2018.03.098

Abstract

The paper presents a novel analytical method for electrochemical potassium determination using gold electrodes with self-assembled thiol monolayers (SATMs) deposited on its surface. The whole analytical procedure was carried out in a dedicated flow manifold using capacitance detection mode. The terminal functional groups on the surface of the dielectric monolayer interacts selectively with the analyte, changing the thickness of the layer depending on the amount of the analyte and the applied voltage, resulting in a change in the registered dielectric capacitance. New calibration approach based on the Chemical H-point Standard Addition Method (C-HPSAM), allowing both specific (proportional) and unspecific (constant) interference effects caused by sodium ions to be corrected, was applied. The calibration method is based on the registration of the calibration graphs by the standard addition method (SAM) three times in such different chemical conditions, which are able to differentiate the slope of each graph. The C-HPSAM was applied for the first time in electrochemical analysis. As a chemical parameter differentiating the sensitivity of the calibration graphs, the concentration of ionic strength stabilizer (ethylenediamine) was used. In order to improve the analytical procedure, to make it faster and automated, the dedicated flow system was applied. The constructed flow system was composed of several modules individually dedicated to the appropriate step of the whole analytical procedure: electrochemical cleaning of work electrode surface, adsorption of SATMs and analytical calibration. The calibration curves were obtained in the range of 0.1-0.9 mmol L^-1 with good linearity (R² = 0.996 ± 0.001) and the LOD and LOQ of 28.6 and 85.8 μmol L^-1, respectively. The proposed method was employed for potassium determination in highly mineralized water, juice and pharmaceutical samples without any special pretreatment.

Keywords: Capacitance measurements; Electrostriction; Flow technique; H-point standard addition method; Potassium determination.