Chromatographic determination of certain organic acids and spectroscopic determination of cadmium and antimony following preconcentration using deep eutectic solvent extraction

In this thesis, three different analytical methods were developed and validated for the determination of organic acids and heavy metal ions in fruit juices, water, and food samples. The first method presents an optimized approach for the analysis of ascorbic acid (AA) and oxalic acid (OA) in fruit juices using High-Performance Liquid Chromatography with Ultraviolet detection (HPLC-UV). The Limit of Detection (LOD) values for AA and OA were determined as 1.4 mg/L and 1.3 mg/L, respectively, with recovery rates of 81-103% in apple and orange juices. The second method combines Hydrophilic Dextrin-Based Liquid-Phase Microextraction (HDES-ELFME) with Flame Atomic Absorption Spectrometry (FAAS) for the determination of cadmium (Cd(II)) ions. Under optimized parameters, Cd(II) levels of 12-18 μg/L were detected in water samples, while concentrations of 0.37-0.73 μg/g were measured in food samples (spinach, celery, leek), with a recovery rate of 95.3-97.8%. The third method utilizes Hydrophilic Deep Eutectic Solvent (DES)-based Liquid-Phase Microextraction (ESFME) and Atomic Absorption Spectrometry (AAS) for the analysis of antimony (Sb(III)). Demonstrating high sensitivity with an LOD of 3.7 μg/L and an enrichment factor of 41.7, the method detected Sb(III) levels of 12-21.6 μg/L in water samples and achieved recovery rates of 90-102.5% in food samples (spinach, celery, leek, pine honey, flower honey, white rice, and black rice).