Colorimetric sensor for detection of trace level Al(III) in aqueous medium based on organic-inorganic nanohybrid

Fluorescence-based method for fast quantification of active aluminums in natural and treated water

Fast quantitative determination of active aluminum (Al_a) in natural and treated water is extremely desirable. The fluorescence method based on complexation by 8-hydroxyquinoline (8-HQ) is highly promising, but the measurement could be severely interfered by hardness ions and natural organic matter (NOM). This study was devoted to refining the 8-HQ complexation-fluorescence method for measurement of Al_a by eliminating the interferences. Results showed that magnesium ions at a typical concentration in natural water could have a substantial positive interference, due to the formation of Mg-8-HQ complexes which have fluorescence regions similar to Al-8-HQ. NOM, represented by fulvic acid (FA), could not interfere the aluminum measurement considerably. It was primarily because 8-HQ has much stronger complexing ability than NOM with aluminum. Theoretical calculations showed that reducing the buffering pH (from 7.5) to 6.5 or using a masking ligand such as edetate (EDTA) could effectively alleviate the interference mainly caused by magnesium. Experimental results confirmed the theoretical predictions. Refined procedures were suggested for more accurate while fast determination of Al_a in natural or treated water. The refined method has a quantification limit of ~4 μg/L, a linear range of measurement up to 700 μg/L, and a relative standard deviation of ~0.8%.

Development of a fluorescent probe for detecting Al3+ in cooked wheaten food based on phosphonic acid group functionalized polythiophene derivatives

As an unnecessary trace element, the content of aluminium in biological systems should be strictly controlled. Therefore, it was necessary to develop a convenient method for detection of aluminium ions. In this study, a fluorescent probe based on polythiophene derivatives was developed and used to detect Al³⁺ in Chinese traditional pasta. The fluorescence of this probe showed a significant decrease in hexamethylenetetramine-HCl buffer solution (pH 5) when Al³⁺ was present. In addition, the probe exhibited good sensitivity and selectivity to Al³⁺ over other metal ions when EDTA was used as the masking agent. Fluorescence intensity had a good linear relationship with the Al³⁺ concentration in the range 0.1-10 μM and the limit of detection for Al³⁺ was 39 nM. Furthermore, the probe was successfully applied to detect Al³⁺ in food samples and the results were consistent with ICP-AES.

Anthocyanin immobilization in carboxymethylcellulose/starch films: A sustainable sensor for the detection of Al(III) ions in aqueous matrices

A robust and sustainable sensor for the detection of Al(III) ions in water was developed by immobilization of anthocyanin (AN) from black rice in a film formed by carboxymethylcellulose (CMC) and starch. Characterization of the films was performed using solubility, thickness, FTIR, and mechanical analysis. The film exhibited an irreversible color change from red to purple in response to the presence of Al(III). The best colorimetric response of the sensor was observed at pH 4.5 and a time of 60 min, achieving the detection of 3 mg L^-1 of Al(III). For concentrations higher than 5 mg L^-1, the sensor response time decreased to 20 min. The minimum Al(III) concentration detected with the naked eye was lower than the maximum permissible concentrations in aqueous effluents according to different legislations, indicating the potential of this study to develop sensors for the detection of Al(III).