A sensitive and selective amperometric determination of perfluorooctanesulfonic acid on Mo₂Ti₂AlC₃ MXene precursor-modified electrode

Various commercial and industrial products widely use highly toxic eight-carbon-chain perfluorooctanesulfonate (PFOS), posing a significant threat to the health of living organisms. In this study, the electrochemical detection of PFOS was achieved by developing a carbon paste electrode (CPE) using the Mo₂Ti₂AlC₃ MAX phase. Mo₂Ti₂AlC₃ was synthesized and directly used to construct the CPE. The electrochemical performance of the prepared sensor was tested using various electrochemical techniques, such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and amperometric titration. The developed electrochemical sensor exhibited two linear ranges from 0.001 to 0.09 μM and from 1.1 to 62.6 μM, with a detection limit of 0.04 nM. The sensor demonstrated high sensitivity, measuring 145.1 μA μM⁻¹ cm⁻², and a response time of 5 s for PFOS quantification at a working potential of 0.3 V. Additionally, the sensor demonstrated outstanding resistance to typical interfering chemicals. The applicability and reliability of the developed sensor for PFOS determination were further tested in real samples, yielding recoveries in the range of 92.6–108.2%, with relative standard deviation (RSD) values between 1.8% and 3.7%. The Mo₂Ti₂AlC₃ MAX phase-based electrochemical sensor is simple, rapid, sensitive, and cost-effective, making it a promising approach for the quantification of PFOS in environmental water and soil samples.