UV-VIS Spectrophotometric Determination of Selected Heavy Metals (Pb, Cr, Cd and As) in Soil, Water and Biological Samples with Acetylpyridine-2,4-Dinitrophenyl Hydrazone as the Chromogenic Reagent

Source abstract

The persistence of toxic heavy metals in the environment represents a major threat to ecological systems and human health. Among these contaminants, lead (Pb), cadmium (Cd), chromium (Cr), and arsenic (As) are particularly concerning due to their bio-accumulative potential and adverse biological effects. Conventional analytical methods such as atomic absorption spectrophotometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS), though highly sensitive, remain costly, instrument-intensive, and less accessible in resource limited regions. This study developed and validated a simple, rapid, and cost-effective UV Visible spectrophotometric method using acetylpyridine-2,4-dinitrophenyl hydrazone (APDH) as a novel chromogenic reagent for the quantification of Pb, Cd, Cr, and As in soil, water, and biological samples. The method was optimized with respect to complexation conditions, pH, reagent concentration, and interference effects. Comparative evaluation with AAS demonstrated excellent agreement, with relative errors within ±3.5% and no significant statistical differences (p > 0.05) across all matrices. The developed method successfully detected trace levels of metals, such as 0.008 µg/g Cd in well water and 0.010 µg/g As in irrigation water, confirming its sensitivity for environmental monitoring. Recovery studies conducted by spiking known concentrations (50–500 µg/mL) yielded high recoveries (99.80 99.99%) with low standard deviations (±0.1–0.4), affirming the accuracy and reproducibility of the technique. Application to real samples from the Challawa Industrial Area of Kano State, Nigeria, revealed elevated levels of Pb and Cr in wastewater and soil, highlighting significant industrial contamination and associated ecological risks. The robustness of the APDH method across diverse matrices, including animal tissues, plant samples, soils, and water, underscores its versatility and field applicability. In conclusion, the APDH-based spectrophotometric method provides a reliable, sensitive, and low-cost alternative to conventional spectrometric techniques for heavy metal determination. Its validated performance and practical adaptability make it a promising tool for routine environmental and biological monitoring, particularly in developing regions where access to advanced instrumentation is limited.