Smartphone digital image colorimetry combined with deep eutectic vs supramolecular solvents liquid-liquid microextraction for cleanup and preconcentration of zinc in fish and vegetable samples

Smartphone digital image colorimetry (SDIC) was combined with deep eutectic and supramolecular solvent liquid-liquid microextractions for the determination of zinc chelating with 1-(2-pyridylazo)-2-naphthol. A colored extract contained in a UV cuvette was placed in a locally designed colorimetric box, and the image was captured at optimum SDIC conditions. Sample cleanup and preconcentration were achieved with optimum complexation and extraction parameters. The suggested method has a limit of detection (LOD) between 3.46 and 19.43 ng mL⁻¹, an enrichment factor (EF) between 10.9 and 15.5, and a linear dynamic range between 100 and 500 ng mL⁻¹. The method shows good consistency, with a coefficient of determination (R²) between 0.9955 and 0.9998, and its precision, measured by the percentage relative standard deviation (%RSD), ranges from 1.4 to 4.2 for the same day and from 3.4 to 6.3 across different days. The accuracy of the method was also checked using a single-factor analysis of variance (ANOVA) by comparing its results with those from another independent UV–visible spectrophotometric technique, and both methods showed similar results (P > 0.05). A score of >0.62 on a scale of 0.0–1.0 for the analytical greenness when evaluated through the application of four green analytical tools indicates excellent analytical results. Additionally, promising greenness performance was also recorded with the AGREE tool when compared to other methods reported in the literature. The proposed method was employed for the determination of zinc in fish and vegetable samples, and the percentages of relative recoveries were recorded between 83.1 and 108.3 %.