Innovative micelle-assisted extraction and digital image colorimetry for trace As(V) detection in water samples

This study presents an innovative coacervation-based extraction method for detecting and quantifying trace levels of As(V) (including AsO₄^3-, HAsO₄^2-, and H₂AsO₄^-) in aqueous samples. The method utilizes the cationic surfactant cetyltrimethylammonium bromide (CTAB) as both an ion-pairing agent and extraction medium for As(V) separation in the form of a dark blue, negatively charged β-keggin molybdoarsenate complex. A water-miscible organic solvent is introduced to promote the dispersion of the surfactant, enhance interactions with the As(V) ions, and facilitate micelle formation. The separation of the extracted phase is achieved through centrifugation. Method efficacy was assessed via UV-Vis spectrophotometry at 810 nm and a digital image colorimetry technique. The results demonstrated remarkable sensitivity, with detection limits as low as 0.17 µg L^-1 for spectrophotometric analysis and 3.4 µg L^-1 for colorimetric analysis. Both limits are significantly below the World Health Organization (WHO) recommended maximum of 10 µg L^-1 for As(V) in drinking water. This method has been successfully applied to real-world environmental water samples, proving its practicality, reliability, and potential as a robust analytical tool for monitoring As(V) contamination.