(287f) Electrochemical Detection of Cd(II) Using Nano-Electrodes in Environmental Samples

Heavy metal toxicity is a continual global concern, which leads to deadly health disorders such as dysfunction of kidneys and livers and neurological disorders. Rapid industrialization and poor recycling methods of industrially produced metals have left humans highly vulnerable to their exposure as they bio-accumulate through the food chain. The most common route of exposure is from the water bodies where industrial effluents are dumped. The early stages of metal toxicity have common symptoms that overlap with other common diseases and thus are often misdiagnosed or not diagnosed until later. However, proper early diagnosis will largely aid in developing efficient therapeutics to treat metal toxicity, thus saving lives.

Extensive research has been done to develop various tools to detect trace amounts of metal in aqueous samples. However, these traditional techniques, such as inductive coupled plasma mass spectrometry (ICPMS), require equipment that is bulky, expensive, and difficult to operate, making them a poor choice in resource-limited settings. These techniques also need tedious sample pretreatment steps that limit real-time detection. Further, pretreatment often alters the metal speciation, a critical factor determining metal toxicity. Therefore, it is crucial to develop a robust, reliable, portable, and low-cost sensor that can provide accurate information on metal speciation of trace amounts of heavy metals in aqueous solutions.

Ion transfer between two immiscible electrolyte solutions (ITIES) is an electrochemical technique that utilizes the simple principle of ion transfer between an aqueous and organic solution. This technique is less complicated than other conventional electrochemical techniques as it does not involve any redox reactions in the system. In this study, we develop a nano-scale glass sensor that can detect Cd(II) in complicated matrices. Our electrode is a borosilicate glass electrode that is pulled using a carbon dioxide laser puller with an inner radius of ~300 nm. The nano-interface of the electrodes enables hemispherical diffusion that provides a high mass transfer rate, which is essential for fast kinetic measurements. An ionophore- 1-10 phenanthroline was used to facilitate the Cd(II) transfer across the nano-interface. The sensor was calibrated in various matrices, such as artificial seawater and tris chloride, to show its capability to withstand complicated matrices without fouling. Selectivity and stability tests were also performed to examine the sensor's performance. The sensor was also tested in the presence of different Cd(II)-ligand complexes and with a water sample collected from the Indian River Lagoon in Melbourne, FL. There's a close agreement between the concentration of Cd(II) in the lagoon determined from our sensor with previously reported values using ICPMS, thus showcasing our sensor's great potential as an environmental sensor. To the best of our knowledge, this is the first time reporting a nanometer-scale glass electrode using ITIES to detect Cd(II) in complex matrices. Further studies will be focused on detecting multiple metal ions simultaneously and developing into a portable point of care diagnostic tool to detect ingested metals in urine and blood samples.