Developing New Colorimetric Methods for Trace Metal Analysis: Evaluating Bicinchoninic Acid and Alizarin Red S for Copper and Lead Detection

Abstract

The contemporary environmental threat stemming from heavy metal contamination in Earth's ecosystems underscores the importance of early detection. Given the significant potential health risks associated with excessive copper and lead concentrations, the quest for efficient, reliable, and cost-effective detection techniques is vital. This dissertation aims to probe into alternative detection methods, namely colorimetric techniques, to overcome the economic and operational challenges of traditional methods like AAS and ICP-MS/OES. Central to this research is the evaluation of the Bicinchoninic Acid (BCA) method for detecting copper and Alizarin Red S for tracing lead. The BCA method demonstrated a substantial sensitivity, revealing a Limit of Detection (LoD) of 0.0636 mg/L for copper within mere minutes, positioning it favorably against global health standards. However, while Alizarin Red S offers a consistent colorimetric detection method for lead, its sensitivity (LoD of 0.998 mg/l) fails to align with the stringent standards set by the USEPA for drinking water. Moreover, in testing the reliability of these methods, the study incorporated absorbance measurements at optimal wavelengths and utilised a computerised analytical model. This computational approach not only eliminated human biases but also elevated the sensitivity and precision of detection. As an example, for copper, the model fitting brought about a remarkable improvement in both LoD and LoQ values. A significant portion of the research extended to practical applications, where water samples from various Sheffield locations were tested using the BCA method and compared with ICP-OES and ICP-MS. Additionally, the efficacy of the BCA technique was trialed on soil samples, outlining a detailed procedure from sample preparation to copper extraction. In conclusion, while the BCA method offers a promising alternative for copper detection in both water and soil samples, the Alizarin Red S method requires further refinement for broader applications, especially concerning drinking water. This research underscores the potential and challenges of colorimetric detection techniques in the fight against environmental contamination.