A rapid, sensitive, high clean-up and economic three phase hollow fiber liquid phase microextraction method followed by HPLC-UV was applied for speciation of inorganic selenium in water and biological samples.
The speciation of chromium(VI) and chromium(III) was investigated by using hollow fiber liquid-phase microextraction based on two immiscible organic solvents followed by high performance liquid chromatography with ultraviolet detection. In this method, chromium(VI) and chromium(III) reacted with ammonium pyrrolidine dithiocarbamate to produce hydrophobic complexes. Subsequently, the complexes were first extracted into a thin layer of organic solvent (n-dodecane) present in the pores of a porous hollow fiber, and then into a μL volume of an organic acceptor (methanol) located inside the lumen of the hollow fiber. Then, the extracting organic phase was injected into the separation column of the high-performance liquid chromatograph for the analysis of both chromium species. Effective parameters on extraction were optimized using one-variable-at-a-time method and central composite design. Under optimized conditions, a linear range of 0.25-100 and 0.5-100 μg/L (R > 0.998), the limits of detection of (S/N = 3) 0.08 and 0.1 μg/L and a preconcentration factor of 625 and 556 were achieved for chromium(VI) and chromium(III), respectively. The method was successfully applied to the speciation and determination of chromium species in different water samples and satisfactory results were obtained.
This paper reports a new approach for the simultaneous extraction of individual analytes based on the simultaneous application of multiple magnetic sorbents using a simple automated system. A mixture of...
A sensitive and selective method is reported for the determination of the low amount of tetracycline in real samples. The tetracycline is extracted and preconcentrated by dispersive liquid‐liquid microextraction followed by retrieval of the extract with magnetic solid‐phase extraction. The extracted analyte is determined by a selective spectrophotometric method based on the formation of a water‐soluble violet mono azo dye between the tetracycline and diazotized p‐nitroaniline in the basic medium. The dispersive liquid‐liquid microextraction was performed using acetonitrile as the disperser solvent and 1‐octanol as the extracting solvent. The extracted tetracycline in the dispersive liquid‐liquid microextraction step was retrieved by dispersed hydrophobic oleic‐acid‐modified Fe3O4 magnetic nanoparticles. Thus, the method enjoyed the high surface area and strong magnetism properties of these nanoparticles avoiding the time‐consuming centrifugation or column‐passing processes. Finally, the tetracycline was eluted from the magnetic solid phase into 0.5 ml of ethanol, and coupled with diazotized p‐nitroaniline in the basic medium for spectrophotometric quantification. Under the optimum conditions, good linearity (in the range of 7.6–650.0 μg/L with R2 = 0.9987), low detection limit (2.3 μg/L), and preconcentration factor of 30.0 were obtained. The proposed method was successively applied to the determination of tetracycline in different samples.
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