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

Marcin Urbanowicz,Maria Bocheńska,Dorota Pijanowska,Radosław Pomećko,Kamila Sadowska

doi:10.3390/s20102817

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.

Highlights

Human saliva is one of the body fluids, produced by the salivary glands
The type of plasticizer may constant of the membrane and ion-ionophore complex binding constant
The comparison of metrological parameters for three constructions (LE-ion-selective electrodes (ISEs), GC-ISE, Au-ISE) showed that the most advantageous parameters were obtained for glassy carbon sensors as the electrode material (S = 59.9 mV/dec, LOD =1.6 × 10−6 M)

Summary

Introduction

Human saliva is one of the body fluids, produced by the salivary glands. The whole saliva is a complex fluid consisting of saliva—an exocrine secretion, gingival fluid and serous exudate [1].The main role of saliva is to maintain oral homeostasis and to facilitate the initial digestion and swallowing of food [2]. Human saliva is one of the body fluids, produced by the salivary glands. The whole saliva is a complex fluid consisting of saliva—an exocrine secretion, gingival fluid and serous exudate [1]. The main role of saliva is to maintain oral homeostasis and to facilitate the initial digestion and swallowing of food [2]. There are three main pairs of salivary glands: parotid, sublingual and submandibular, which produce 95% of saliva volume. Healthy salivary glands produce 1–1.5 L of saliva per day [3]. Saliva production is controlled by two mechanisms: blood filtrate into the glands cavity and the proteins’ and proteoglycans’ secretion by secretory part cells [4]. Saliva is isotonic, Sensors 2020, 20, 2817; doi:10.3390/s20102817 www.mdpi.com/journal/sensors

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