Desenvolvimento de um método voltamétrico automatizado em sistema fluxo batelada para a determinação de naftaleno

Abstract

Polycyclic aromatic hydrocarbons (PAHs) represent an environmental and public health problem, as these compounds are recognized for their high toxic, mutagenic, and carcinogenic potential. Among them, naphthalene (NAF) stands out due to its high frequency of occurrence in water bodies and its association with adverse health effects. Therefore, this work aimed to develop an automated voltammetric method in a flow-batch analysis (FBA) system for the determination of NAF, seeking greater precision, reproducibility, and sensitivity compared to traditional methods, which consist of manual addition of solutions via pipetting. The proposed automated system has a mixing chamber made of polytetrafluoroethylene (PTFE), a peristaltic pump, solenoid valves, and a program written in LabView® was developed for its management, allowing the automation of steps such as electrochemical treatment of the working electrode, addition, and disposal of solutions. A boron-doped diamond electrode (BDDE) was used as the working electrode, and square wave voltammetry (SWV) was chosen as the analytical technique due to its high sensitivity and speed of analysis. Preliminary studies showed that pH influences the electrochemical response of the analyte, with pH 10 of the Britton-Robinson (BR) buffer being the optimal condition for analysis. NAF exhibited irreversible redox behavior, with the mass transfer process governed by diffusion. Optimization of the experimental parameters resulted in the following ideal conditions: frequency of 50 Hz, amplitude of 5 mV, and increment of 7 mV. Under these conditions, no memory effect was observed in the electrode, ensuring good reproducibility of the results. After optimization of the voltammetric parameters, analytical curves of the traditional method and the proposed system were obtained for comparison of the two methods. The analytical curves showed adequate linearity (R2 = 0.9886 for the traditional method and R2 = 0.9954 for the FBA system). The detection and quantification limits obtained were 4.17 × 10−8 mol·L−1 and 1.26 × 10−7 mol·L−1, respectively, for the benchtop method, and 1.52 × 10−8 mol·L−1 and 4.60 × 10−8 mol·L−1 for the FBA, indicating a significant improvement in terms of sensitivity, reproducibility, and data acquisition speed when applying voltammetric FBA. The proposed method shows great potential for application in environmental analyses as a future prospect, providing an efficient and automated alternative for monitoring contaminants in drinking water.