Development of integrated electroanalytical systems using alternative platforms aiming at flow analytical applications

Author(s)

Iana Vitória Spadini Arantes

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2024-11-28

Examining board members

Thiago Regis Longo Cesar da Paixão; Bruno Campos Janegitz; Eduardo Mathias Richter

• Advisor: Thiago Regis Longo Cesar da Paixão

Abstract

This thesis presents simple and low-cost methods for manufacturing electrochemical sensors in integrated devices using alternative platforms, such as paper and 3D printed cells, to perform flow injection (FIA) and batch injection (BIA) analyzes of various electroactive species. The work was divided into three parts. First, a microfluidic paper-based electroanalytical device (µPAD) was developed using paper capillarity to explore two different configurations, aiming to perform FIA and BIA on a detection platform with fully integrated electrodes. For this purpose, graphite deposition by pencil drawing on chromatographic paper pre-treated with a CO2 laser proposed a simple method of manufacturing electrodes on paper. Laser pretreatment of paper was essential to improve electrochemical performance against redox probes and drugs, such as paracetamol (PAR). The PAR was also used to compare the FIA and BIA-µPAD systems using amperometry technique. The BIA-µPAD was able to quantify pharmaceutical samples (LD and LQ of 0.046 and 0.154 mmol L-1, respectively) with results comparable to a standard UV-Vis method. The second part shows the development of a fully integrated BIA system on a waterproofed kraft paper substrate with electrodes manufactured by laser-induced carbonization. The CO2 laser was also used to induce the synthesis of gold nanoparticles (AuNPs) on the carbonized surface by reducing a precursor agent (HAuCl4) previously added to the surface. Cyclic voltammograms in 0.5 M H2SO4 confirm the presence of Au on the surface through this metal\'s characteristic oxidation and reduction peaks. Other characterization techniques, such as SEM and EDX were also performed. It was observed that the presence of AuNPs catalyzed the reduction reaction of the chemical species sodium hypochlorite (NaClO), which was used as a proof of concept for the operation of the proposed BIA-ePAD, resulting in LD and LQ of 6.70 and 22.1 µmol L-1, respectively, and an average recovery of 97% of NaClO in water samples. Finally, in the last part, a completely 3D printed device is presented, where a new conductive filament is proposed for printing the electrodes, using carbon black, recycled PLA, and different plasticizing agents. These electrodes are used with a miniaturized BIA cell, also printed in 3D, and the entire system is coupled to a portable potentiostat, which facilitates field application. The electrodes were characterized electrochemically by surface techniques such as XPS and SEM. Finally, the system was applied to determine the drug atropine in adulterated beverage samples and showed versatility by being used both for static analyzes using a pulse technique (LD and LQ of 2.60 and 8.80 µmol L-1, respectively) and for hydrodynamic analyzes by BIA-amperometry (LD and LQ of 0.51 and 1.68 µmol L-1, respectively), both presenting recoveries from 102 to 109% atropine in real samples, despite being a miniaturized system. (AU)

• FAPESP's process: 19/15065-7 - Development of paper-based electrochemical systems aiming flow analysis of forensic samples
• Grantee: Iana Vitória Spadini Arantes
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)