Sulfanilamide Electrochemical Sensor Using Phenolic Substrates and CO₂ Laser Pyrolysis

The concentration of environmental pollutants needs to be monitored constantly by reliable analytical methods since they pose a public health risk. Developing simple and affordable sensors for such pollutants can allow for large-scale monitoring economically. Here, we develop a simple electrochemical sensor for sulfanilamide (SFD) quantification using a phenolic resin substrate and a CO₂ laser to pyrolyze the sensor geometry over the substrate. The sensors are modified with carbon nanotubes via a simple drop-casting procedure. The carbon nanotube loading effect the electrochemical performance toward a redox probe and analytical performance for SFD detection is investigated, showing no net benefit beyond 1 mg L^-1 of carbon nanotubes. The effects of the modification on the SFD oxidation are shown to be more than just an electrode area effect and possibly attributed to the fast electron transfer kinetics of the carbon nanotubes. SFD detection is performed at small solution volumes under static (800 μL) and hydrodynamic conditions (3 mL) in a fully integrated, miniaturized batch-injection analyses cell. Both methods have a similar linear range from 10.0 to 115.0 μmol L^-1 and high selectivity for SFD determination. Both systems are used to quantify SFD in real samples as a proof of concept, showcasing the proposed device's applicability as a sensor for environmental and public health monitoring of SFD.