A method of electrochemical sensing includes providing an electrochemical sensor comprising a glassy carbon substrate and gold nanoparticles located on a surface of the glassy carbon substrate; and sensing electrochemically a compound selected from the group consisting of polyfluoroalkyl compounds or perfluoroalkyl compounds using the electrochemical sensor. PFOA quantification was performed by Square Wave Adsorptive Cathodic Stripping Voltammetry (SW-AdCSV) in test solutions with a 100-5,000 ppt concentration. The concentration has a linear relationship with the stripping current within this range. Analysis of tap and groundwater samples performed by additions method demonstrated precision and accuracy above 95%. These electrodes show stability throughout 200 cycles, and reproducibility across similarly prepared but different electrodes above 97.5%. Providing the electrochemical sensor can include providing at least one member selected from the group consisting of perfluoro-1-octanethiol (PFTO), 2,2,2-trifluoroethanethiol (TFET) or perfluorodecanethiol (PFDT) on the surface of the glassy carbon substrate.