Potentiometric Solid-Contact Ion-Selective Electrode for Determination of Thiocyanate in Human Saliva

Abstract

A new solid-contact potentiometric ion-selective electrode for the determination of SCN− (SCN-ISE) has been described. Synthesized phosphonium derivative of calix[4]arene was used as a charged ionophore. The research included selection of the ion-selective membrane composition, determination of the ISEs metrological parameters and SCN-ISE application for thiocyanate determination in human saliva. Preparation of the ISEs included selection of a plasticizer for the ion-selective membrane composition and type of the electrode material. The study was carried out using ISE with liquid internal electrolyte (LE-ISE) and solid-contact electrodes made of glassy carbon (GC-ISE) and gold rods (Au-ISE). The best parameters were found for GC sensors for which the ion-selective membrane contained chloroparaffin as a plasticizer (S = 59.9 mV/dec, LOD = 1.6 × 10−6 M). The study of potentiometric selectivity coefficients has shown that the thiocyanate-selective sensor could be applied in biomedical research for determination of SCN− concentration in human saliva. The accuracy of the SCN− determination was verified by testing 59 samples of volunteers’ saliva by potentiometric sensors and UV-Vis spectrophotometry as a reference technique. Moreover, SCN− concentrations in the smokers’ and non-smokers’ saliva were compared. In order to investigate the influence of various factors (sex, health status, taken medications) on the thiocyanate level in the saliva, more extensive studies on a group of 100 volunteers were carried out. Additionally, for a group of 18 volunteers, individual profiles of SCN− concentration in saliva measured on a daily basis for over a month were collected.

Electrochemical sensors for analyte in saliva: recent update

“…Similarly, ISEs have been used for the detection of salivary thiocyanate. Urbanowicz et al (2020) demonstrated a new solid-contact potentiometric ISE for determining thiocyanate levels in human saliva. Researchers used a synthesized phosphonium derivative of calix[4] arene as a charged ionophore and found the most advantageous parameters when using glassy carbon sensors as the electrode material.…”

New Materials Used for the Development of Anion-Selective Electrodes—A Review

“…The electrode had a wid range of 0.5-12.5 and a good detection limit of 5.6 × 10 −6 M. The ISE was also characte by an average slope and linearity range. Urbanowicz et al presented three types of SCN − -ISEs, where one was a liqui two were solid contact electrodes [100]. All three electrodes in the membrane had ionophore a tetrakis-(4-diphenylmethylphosphonium-butoxy)-tetrakis-p-tert-buty [4]arene tetrathiocyanate (Figure 25).…”

“…Analogous to the electrode describ the previous paper, the concentration of SCN − ions in the saliva of non-smokers and s ers was investigated. Urbanowicz et al presented three types of SCN − -ISEs, where one was a liquid and two were solid contact electrodes [100]. All three electrodes in the membrane had as an ionophore a tetrakis-(4-diphenylmethylphosphonium-butoxy)-tetrakis-p-tert-butylcalix [4]arene tetrathiocyanate (Figure 25).…”

Highly Stable Potentiometric (Bio)Sensor for Urea and Urease Activity Determination

“…Contrarily, potentiometric sensors are commonly used for urea determination in biological and environmental samples [8][9][10]. Direct potentiometric sensing with minimal sample pre-treatment and fast and reliable data processing is the method-of-choice in medical laboratories for determination of many diagnostically important analytes, for example, Na + , K + , Ca 2+ , H + , Cl − , and SCN − [10][11][12][13][14]. Enzyme immobilization on the surface of the ion-selective membrane enables detecting and determining the non-ionic analytes, such as urea, by detecting changes in the concentration of ionic products of enzymatic reactions.…”