Determination of Cd(II) and Zn(II) ions in honey samples by in-situ produced CO2-assisted dispersive micro solid phase based on covalent organic framework

An in-situ CO₂-assisted dispersive micro solid phase extraction was developed using a covalent organic framework synthesized from melamine and barbituric acid as a sorbent for the extraction of Cd(II) and Zn(II) ions from honey samples. The structural and morphological characteristics of the sorbent were evaluated using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry. The CO₂ generated by reacting tartaric acid and sodium hydrogen carbonate enabled rapid dispersion of the sorbent within the sample solution, ensuring optimal contact with the target ions. After adsorption, the dispersed sorbent particles were separated via centrifugation, followed by elution with diluted nitric acid solution to retrieve the extracted heavy metals from the sorbent surface. The analytes collected in the eluate were quantified via flame atomic absorption spectrometry. Key experimental parameters, including tartaric acid and sodium bicarbonate amounts, sorbent dosage, type and volume of elution solvent, temperature, salt addition, pH, complexing agent concentration, and centrifugation conditions were systematically optimized. The method demonstrated high sensitivity, with the limits of detection of 0.17 and 0.092 µg L^{- 1} and broad linear range spanning 0.5-100 and 0.25-100 µg L^{- 1} for Cd(II) and Zn(II) ions, respectively. Extraction recoveries of 97.2 and 95.5%, with relative standard deviations of 3.6 and 2.7% for Cd(II) and Zn(II) ions, respectively, were obtained. Validation using a certified reference material confirmed the method's accuracy, and application of the method on honey samples demonstrated its practicality.