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Solid-phase extraction combined with dispersive liquid–liquid microextraction has been developed as a new approach for the extraction of enrofloxacin in chicken meat prior to high performance liquid chromatography with UV detection. In the SPE-DLLME, enrofloxacin was first extracted from chicken meat into the mixture of 10 mL acetonitrile acidified with formic acid buffer (pH=4) and 10 mL EDTEA-McIlvaine buffer (0.1 M) and 20 mL n-hexane as an extracting phase by using ultrasound-assisted extraction. Then, the extract by ultrasound-assisted extraction was used for solid-phase extraction. After clean-up, enrofloxacin was preconcentrated by using DLLME technique. Thus, 1.5 mL methanol extract (disperser solvent) and 200 µL chloroform (extraction solvent) were added to 5.0 mL ultrapure water and a DLLME technique was applied. Under the optimum conditions, the linearity of the method was in the range from 10 to 500 µg kg-1 with the correlation coefficient (r2) of 0.9972. The method detection limit was 5.0 µg kg-1. The proposed method has been successfully applied to the analysis of the enrofloxacin in chicken meat, and a satisfactory result was obtained.

In this study, dispersive liquid-liquid microextraction based on the solidification of floating organic droplets was used for the preconcentration and determination of thorium in the water samples. In this method, acetone and 1-undecanol were used as disperser and extraction solvents, respectively, and the ligand 1-(2-thenoyl)-3,3,3-trifluoracetone reagent (TTA) and Aliquat 336 was used as a chelating agent and an ion-paring reagent, for the extraction of thorium, respectively. Inductively coupled plasma-optical emission spectrometry was applied for the quantitation of the analyte after preconcentration. The effect of various factors, such as the extraction and disperser solvent, sample pH, concentration of TTA and concentration of aliquat336 were investigated. Under the optimum conditions, the calibration graph was linear within the thorium content range of 1.0-250 µg L-1 with a detection limit of 0.2 µg L-1. The method was also successfully applied for the determination of thorium in the different water samples.

A new liquid phase microextraction method based on the dispersion of an extraction solvent into aqueous phase coupled with solid-phase extraction was investigated for the extraction, preconcentration and determination of uranium in water samples. 1-(2-Pyridylazo)-2-naphthol reagent (PAN) at pH 6.0 was used as a chelating agent prior to extraction. After concentration and purification of the samples in SPE C18 sorbent, 1.5 mL elution sample containing 40.0 µL chlorobenzene was injected into the 5.0 mL pure water. After extraction and centrifuging, the sedimented phase was evaporated and the residue was dissolved in nitric acid (0.5 M) and was injected by injection valve into the ICP-OES. Some important extraction parameters, such as sample solution flow rate, sample pH, type and volume of extraction and disperser solvents as well as the salt addition were studied and optimized. Under the optimum conditions, the calibration graph was linear in the range of 0.5-500 µg L-1. The detection limit was 0.1 µg L-1. The relative standard deviation (RSD) at 5.0 µg L-1 concentration level was 6.6%. Finally, the developed method was successfully applied to the extraction and determination of uranium in the well, river, mineral, waste and tap water samples and satisfactory results were obtained.DOI: http://dx.doi.org/10.4314/bcse.v29i3.4

A novel approach for the determination of ecstasy and amphetamines (3,4-methylenedioxymethylamphetamine (MDMA, Ecstasy), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxyethylamphetamine (MDEA) and 3,4-methylenedioxypropylamphetamine (MDPA)) in biological samples is presented. The analytes were extracted from the matrix and transferred to a small volume of a high density, water insoluble solvent using solid-phase extraction (SPE) followed by dispersive liquid-liquid microextraction (DLLME). This combination not only resulted in a high enrichment factor, but also it could be used in complex matrices (biological samples). Some important extraction parameters, such as sample solution flow rate, sample pH, type and volume of extraction and disperser solvents as well as the salt addition, were studied and optimized. Under the optimized conditions, the calibration graphs were linear in the range of 0.5-500 µg L-1 and 1.0-500 µg L-1 with detection limits in the range of 0.1-0.3 µg L-1 and 0.2-0.7 µg L-1 in urine and plasma samples, respectively. The results showed that SPE-DLLME is a suitable method for the determination of ecstasy components and amphetamines in biological and water samples. DOI: http://dx.doi.org/10.4314/bcse.v28i3.3