Polyamic acid-graphene oxide nanocomposite for electrochemical screening of antibiotic residues in water
Pollution of water sources, aquifers and wetland systems caused by industry, agriculture, and municipally treated wastewater is a worldwide problem that contributes to the scarcity of clean and potable water. Rivers, channels, lakes, oceans, and ground water are often contaminated by a variety of organic substances that can affect aquatic life and threaten human health. Organic compounds such as antibiotics that are not effectively removed by modern day water treatment technology are a growing threat to water quality and health. The emergence of antibiotics in the environment particularly aquatics have become a matter of concern as they may result in induction and spread of bacterial resistance which may be harmful to humans or animals. After administration, antibiotics for human use or their metabolites are excreted into the effluent and reach the sewage treatment plant (STP). Not all Antibiotics in sewage treatment plants are eliminated. Consequently they can pass through the sewage system and may end up in environmental and even potable water systems. Antibiotic residues have been reportedly found in places such as hospital wastewaters, wastewater treatment plants and surface waters all over the world with concentrations ranging from approximately 60-120000 ng/, 2-580 ng/L and 5-1300 ng/L respectively. The current methods that are used to detect antibiotics can be quite expensive and time consuming due to sample preparation (necessary for detection of very low concentrations of antibiotics in water) and technology used in the instruments. Electrochemical sensors and biosensors are simple systems, with high selectivity and sensitivity for individual measurements and cost effectiveness. The development of composites based on conductive phases dispersed in polymeric matrices has led to important advances in analytical electrochemistry. Polyamic acid and graphene oxide are both materials with well-defined electrochemistry and are easily processable in the design of various sensor formats. In this study we present a novel polyamic acid - graphene oxide (PAA/GO) electrode which was prepared for electrochemical screening of antibiotic residues in aqueous systems. Polyamic acid (PAA) and graphene oxide (GO) were successfully synthesized independently and characterized using SEM which was used to study the morphology of the PAA, FTIR spectroscopy to confirm chemical structures and functional groups as well as CV and SWV which were used to identify the unique electrochemical behavior of PAA and GO respectively. Polyamic acid-graphene oxide nanocomposite was prepared and characterized by CV, SWV, FTIR and SEM. The novel electrode (PAA/GO/SPCE) was prepared by electrochemically depositing PAA/GO (0.03 mg/mL) onto SPCE electrodes using 5 cycles between −1000 mV and 1000 mV at 50 mVs. The analytical performance of the electrochemical sensor towards detection of neomyxin and norlfoxacin was compared to standard Uv-vis spectroscopy method. The Uv-vis spectroscopy showed LOD of 1.61x10-5 M and 1.41x10-5 M for norfloxacin and neomycin respectively. The PAA/GO electrochemical sensor had a LOD of 3.37x10-7 M for norfloxacin and 1.066x10-6 M for neomycin. Sensitivity of the UV/vis method was comparable to electrochemical sensor sensitivity for neomycin and norfloxacin.