On-line in-syringe ultrasound-assisted cloud point-dispersive liquid-liquid microextraction for the fluorescent determination of aluminum in water and milk samples

Abstract

In this work, a simple, fast and ecological method to determine aluminum in natural and mineral water, and milk samples was developed. Aluminum is a toxic element that can be found in packaging as well as in different containers. The World Health Organization has fixed limits for the presence of aluminum in drinking water and food. Therefore, it is important to develop new reliable methods for its determination. This new procedure was performed by means of an in-syringe cloud point-dispersive liquid-liquid microextraction (Fig 1) using a mixture of an ionic liquid and a surfactant as extractant instead of organic solvents. 8-hydroxyquinoline was used as chelating agent to extract Al3+ with a subsequent online spectrofluorometric detection. Under the optimal conditions, the preconcentration factor was 200, and the recovery values were between 91.4-109.1% (n=3) with satisfactory % Relative Standard Deviation (%RSD) values, which indicate appropriate accuracy and precision. The limits of detection (LOD) were 1.7 and 5.5 μg L-1, and the limits of quantification (LOQ) were 5.7 and 18.4 μg L-1 for water and milk samples, respectively. The obtained results demonstrated the applicability of the proposed method for the determination of aluminum in real water and milk samples. The main advantage of this research was that ultrasound energy was applied to improve the extraction and preconcentration steps, which was reflected in a reduction in the total analysis time. In addition, the method also complies with some principles of green chemistry, since it uses environmentally friendly solvents, a reduced volume of reagents, and generates low amounts of waste.