Dispersion Of Extraction Solvent Research Articles

Stir flat sheet membrane liquid phase microextraction for the selective chemiluminescence determination of ofloxacin and fleroxacin in human urine

Stir flat sheet membrane liquid phase microextraction procedure for the chemiluminescence determination of polar antibiotics (ofloxacin and fleroxacin) in human urine samples was developed. The microextraction procedure assumed simultaneous ion-pair complex formation between antibiotic and anionic dye in acidic medium, dispersion of extraction solvent by rotation of a stir flat sheet microporous membrane unit, mass-transfer of complexes from sample into microdroplets of extraction solvent followed by extract collection into the unit. After preconcentration the unit was immersed in alkaline aqueous solution for analytes re-extraction based on ion-pair complex decomposition followed by the chemiluminescence analysis of obtained aqueous phase. The developed microextraction procedure allowed to exclude matrix effects for the selective, simple, and rapid chemiluminescence determination of ofloxacin and fleroxacin in urine samples. The calibration graphs were linear over the concentration ranges of 0.1–25 mg L−1 for ofloxacin and fleroxacin. The LOD values, calculated from the blank tests based on 3σ, were 30 µg L−1 for ofloxacin and fleroxacin. The procedure was conveniently applied to the determination of fluoroquinolones in urine samples.

In-syringe dispersive liquid-liquid microextraction using deep eutectic solvent as disperser: Determination of chromium (VI) in beverages

A novel approach for dispersive liquid-liquid microextraction based on the use of deep eutectic solvent as a disperser was presented for the first time. The procedure was automated based on an in-syringe flow system coupled with UV–Vis detection and demonstrated by the determination of chromium (VI) in beverages. This analytical task was used as a proof-of-concept example. The automated extraction procedure involved the aspiration of aqueous sample into a syringe pump with homogeneous mixture of extraction solvent (1-oсtanol) and deep eutectic solvent (tetrabutylammonium bromide – formic acid) containing color-forming reagent (1,5-diphenylcarbazide). This led to decomposition of deep eutectic solvent in aqueous phase resulting in dispersion of extraction solvent, oxidation of 1,5-diphenylcarbazide to 1,5- diphenylcarbazone in the presence of chromium (VI), and formation of colored chromium (III) complex with 1,5-diphenylcarbazone and its fast extraction. In this case composition of deep eutectic solvent played a key role for analyte extraction. Tetrabutylammonium bromide promoted mass transfer between aqueous phase and the extraction solvent droplets as a salting out agent, bromide ion acted as an ion-pare agent for analyte complex extraction, formic acid provided required pH value for analyte complex formation. Under the optimal conditions the limit of detection, calculated from a blank test based on 3s, was 0.2 μg L−1. The automated dispersive liquid-liquid microextraction using deep eutectic solvent as disperser can be considered as an available, efficient, rapid and environmentally friendly sample pretreatment approach.

Effervescence assisted dispersive liquid–liquid microextraction followed by microvolume UV-Vis spectrophotometric determination of surfactants in water

ABSTRACTThe novel and simple methods for the sensitive determination of cationic and anionic surfactants in water based on effervescence assisted dispersive liquid–liquid microextraction and microvolume UV-Vis spectrophotometry have been developed. The method involves ion-pair extraction of cationic and anionic surfactants with organic dyes (methyl orange and azure A, respectively) during the dispersion of extraction solvent (CHCl3) by CO2 bubbles which are formed by the injection of a mixture of the extraction solvent and proton donor solvent into the sample solution which contains carbonate-ions as effervescency agent. The analytical performance of the proposed procedure was compared with the conventional dispersive liquid–liquid microextraction. Appropriate experimental conditions for both methods were investigated. The absorbances of the colored extracts at wavelengths of 440 and 625 nm obey Beer's law within the range of 0.1–5.0 mg/L for both cationic and anionic surfactants. The limit of detection (LOD) obtained using the effervescence assisted extraction method was 30 µg/L for cationic and anionic surfactants. The proposed methods were successfully applied to determination of surfactants in water samples.

Progress of Extraction Solvent Dispersion Strategies for Dispersive Liquid-liquid Microextraction

Abstract Dispersive liquid-liquid microextraction (DLLME) is a new sample preparation technique emerging recently. The dispersion of organic extraction solvent at micro-liter level in aqueous samples is the key step in DLLME. The published strategies of dispersion for DLLME are roughly classified into three types in terms of the instruments used and dispersion principles, namely physical dispersion method, in-situ chemical reaction-based dispersion method and new dispersion medium-based dispersion method. The physical dispersion method includes mechanical shaking method, ultrasound/microwave-assisted method and solubility-adjustment method. The in-situ chemical reaction method is referred to the two modes, in which either the dispersed extraction solvent is formed by in-situ chemical reaction or the dispersion of extraction solvent is achieved by the gas generated from chemical reactions. The new dispersion medium-based dispersion method uses some non-volatile substances, such as medium-chain saturated fatty acids, ionic liquid, surfactant and kapok fiber fragments, to substitute the dispersive solvent used in conventional DLLME. A total of 96 relevant literatures are cited in this review and the prospects of DLLME are highlighted.