Sensing electrode, electrochemical sensing system comprising the same, and methods thereof

A method of determining a concentration of an analyte in a sample solution, comprising:

• (A1) forming an initial layer embedded with molecules of the analyte on a conductive surface of a glassy carbon sensor, wherein the step (A1) comprises electrochemical polymerization of a mixture containing monomers and the analyte, wherein the analyte does not participate in the electrochemical polymerization but is imprinted into the polymerization product;
• and wherein the step (A1) comprises depositing per- and polyfluoroalkyl substance (PFAS)-imprinted polymer layer on the conductive surface of the glassy carbon sensor by cyclic voltammetry in precursor solution containing the monomers of 4-(trifluoromethyl)benzene-1,2-diamine and 4-vinylaniline, and PFAS as the analyte in de-ionized (DI) water and using a ramping voltage for the electrochemical polymerization;
• (A2) conducting a crosslinking reaction on the product from the step (A1), wherein the crosslinking reaction is conducted in heptane containing azobisisobutyronitrile (AIBN), and wherein the crosslinking reaction is initiated by UV irradiation on vinyl groups in the product from the step (A1);
• and terminated with a radical inhibitor 1,4-benzoquinone in heptane;
• (A3) removing said molecules of the analyte from the initial layer from the step (A2), and leaving cavities or holes behind, the step (A3) comprises removing the imprinted PFAS molecules with pure methanol solvent, followed by thorough DI water treatment to eliminate the methanol solvent;
• wherein a sensing electrode is prepared from the steps (A1), (A2) and (A3), wherein the sensing electrode includes the glassy carbon sensor having the conductive surface, and the initial layer formed on said conductive surface;
• wherein the sensing electrode is configured for detecting the analyte, wherein the initial layer has the cavities or the holes, each of which can be filled with, bound to, or occupied by, the molecule of the analyte, and wherein a decrease of conductivity of the sensing electrode is correlated to an amount of the cavities or the holes that are filled with, bound to, or occupied by, the molecules of the analyte;
• (B) preparing an electrochemical sensing system configured for differential pulse voltammetry (DPV);
• wherein the electrochemical sensing system comprises (i) a working electrode which is the sensing electrode prepared from the steps (A1), (A2) and (A3), (ii) a reference electrode, and (iii) a counter electrode;
• (C1) providing a DPV setting with a mediator which is ferrocyne carboxyl acid (FCA) in phosphate buffered saline (PBS) buffer solution,
• (C2) inserting the electrochemical sensing system into the mediator,
• (C3) acquiring stable DPV signals through tuning scanning parameters comprising starting potential and quiet time,
• (C4) using a peak current of stabilized DPV curves as a baseline for detecting the analyte,
• (C5) incubating the electrochemical sensing system in the sample solution for a period of time,
• (C6) taking the electrochemical sensing system out of the sample solution and thoroughly rinsing the electrochemical sensing system with the mediator,
• (C7) inserting the incubated electrochemical sensing system into the mediator and measuring DPV curve of the sample solution, and
• (C8) correlating peak current reduction to the analyte's concentration in the sample solution.