Towards on-site detection of cadmium in human urine

Cadmium (Cd) is a non-essential toxic heavy metal. Human exposure to Cd occurs from multiple sources, including diet, tobacco smoke, fossil fuel combustion, and various contaminated sources. This work reports a rapid method for Cd²⁺ detection in simulated urine samples containing glucose (GLC) and human urine using the electrochemical technique of square wave anodic stripping voltammetry (ASV). Electrochemical techniques for onsite analysis and detection are preferred for their quick response time, application simplicity, inexpensive instrumentation, and potential portability. This approach is a step forward towards Cd²⁺ detection in biological fluids, despite their composition complexity due to possible interference of its constituents. Application of a simple, well controlled, and uniform carbon nanotube (CNT) thin film generated through spinnable CNT arrays enabled us to increase the surface area of traditional glassy carbon electrodes and made possible the detection of nanomolar concentration of Cd ions in urine samples. This voltammetric technique led to 1.9 nM limit of detection (LOD) in simulated urine, and 5.85 nM (female) and 324 nM (male) LOD in human urine. The developed method would facilitate high throughput screening of human urine samples for assessing Cd exposure in future studies.