Evaluation of Wet Digestion and QuEChERS-DLLME for Heavy Metal Determination in Aqueous Solutions

Abstract

The QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method, when coupled with Dispersive Liquid-Liquid Microextraction (DLLME), represents an innovative and efficient approach in analytical chemistry for the extraction and determination of contaminants in complex matrices, including environmental and aqueous samples. This study evaluates the efficiency of the QuEChERS- DLLME method in comparison to traditional wet digestion for the determination of five heavy metals— Nickel (Ni), Cobalt (Co), Chromium (Cr), Cadmium (Cd), and Lead (Pb) in aqueous solutions. A known initial concentration of 64 ppm in wet and 38.4 ppm in QuEChERS-DLLME of each metal was analyzed using Atomic Absorption Spectrophotometry (AAS). The findings indicate significant metal loss with the wet digestion method, resulting in lower recovery rates compared to QuEChERS-DLLME. Nickel exhibited a higher concentration in wet digestion (17.6 ppm ± 0.00063) compared to QuEChERS- DLLME (3.6 ppm ± 0.00075), while the latter method yielded higher recoveries for Co (13.8 ppm ± 0.0033), Cd (22.8 ppm ± 0.0018), Cr (3.6 ppm ± 0.0057), and Pb (5.8 ppm ± 0.0012). In contrast, wet digestion produced lower values for Co (9 ppm ± 0.0054), Cd (21 ppm ± 0.0021), Cr (1.2 ppm ± 0.0036), and Pb (5.4 ppm ± 0.0009). These results demonstrate that QuEChERS-DLLME is a more effective method for heavy metal analysis, offering advantages such as reduced reagent consumption, lower environmental hazards, simplified instrumentation, and improved recovery rates.