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Abstract In this work, CdTe/CdS quantum dots were incorporated in a capillary electrophoresis system for the determination of glyphosate in soil samples. Fluorescence spectroscopic evaluation indicates there is an interaction between CdTe/CdS quantum dots and glyphosate, which produces an enhancement of the emission signal as a result of the formation of quantum dots-glyphosate complex. A capillary electrophoresis system for the separation of the complex from the remaining CdTe/CdS quantum dots is described herein. The variables involved in the separation were evaluated and optimized using a central composite design. Signals are elucidated under optimal conditions by calculating the difference in their electrophoretic mobility. The methodology selectivity allows the determination of glyphosate in complex matrices such as soil samples. The proposed method exhibits a linear range from 77.1 to 700 mg kg−1 with a limit of detection of 25.7 mg kg−1 and adequate repeatability and reproducibility (%RSD <5.0%). The described methodology was applied to 7 soil samples collected from crop fields in Hidalgo, Mexico, found concentrations varied from 320.6 to 607.7 mg kg−1. Highlights • CdTe/CdS quantum dots were characterized in presence of glyphosate. • CdTe/CdS quantum dots were incorporated in a CZE-LIF system for the determination of glyphosate. • The method was applied to soil samples. [ABSTRACT FROM AUTHOR]

A spectrophotometric method based on the use of silver nanoparticles is presented for the determination of lipoxygenase activity in cereal grains. The method involves the synthesis of prism silver nanoparticles with a maximum absorption at 752 nm, followed by the abatement of the signal as a consequence of the oxidation produced by hydroperoxides generated in the enzymatic reaction. The quantification of the hydroperoxides produced by reaction of lipoxygenase with linoleic acid allows the determination of the enzyme activity in cereal grains. Under optimal conditions, the linear range of the calibration curve ranges from 1.0 to 5.0 μM, with a limit of detection of 0.34 μM. The method was validated comparing the results with those obtained by ferrous-xylenol orange method. A relative standard deviation < 5.0% was obtained in all cases and no significant differences were observed (p<0.05). [ABSTRACT FROM AUTHOR]

Ternary quantum dots (QDs) are novel nanomaterials that can be used in chemical analysis due their unique physicochemical and spectroscopic properties. These properties are size-dependent and can be adjusted in the synthetic protocol modifying the reaction medium, time, source of heat, and the ligand used for stabilization. In the last decade, several spectroscopic methods have been developed for the analysis of organic and inorganic analytes in biological, drug, environmental, and food samples, in which different sensing schemes have been applied using ternary quantum dots. This review addresses the different synthetic approaches of ternary quantum dots, the sensing mechanisms involved in the analyte detection, and the predominant areas in which these nanomaterials are used. [ABSTRACT FROM AUTHOR]