Simple determination of some antidementia drugs in wastewater and human plasma samples by tandem dispersive liquid-liquid microextraction followed by high-performance liquid chromatography.

In this work, a simple method, namely, tandem dispersive liquid-liquid microextraction, with a high sample clean-up is applied for the rapid determination of the antidementia drugs rivastigmine and donepezil in wastewater and human plasma samples. This method, which is based on two consecutive dispersive microextractions, is performed in 7 min. In the method, using a fast back-extraction step, the applicability of the dispersive microextraction methods in complicated matrixes is conveniently improved. This step can be performed in less than 2 min, and very simple tools are required for this purpose. To achieve the best extraction efficiency, optimization of the variables affecting the method was carried out. Under the optimized experimental conditions, the relative standard deviations for the method were in the range of 6.9-8.7%. The calibration curves were obtained in the range of 2-1100 ng/mL with good correlation coefficients, higher than 0.995, and the limits of detection ranged between 0.5 and 1.0 ng/mL.

Centrifugeless ultrasound-assisted emulsification microextraction based on salting-out phenomenon followed by high-performance liquid chromatography for the simple determination of phthalate esters in aqueous samples.

A fast, sensitive, and centrifugeless ultrasound-assisted emulsification microextraction followed by a high-performance liquid chromatography method is developed for the determination of some phthalate esters in aqueous samples. In this method, a simple approach is followed to eliminate the centrifugation step in dispersive liquid-liquid microextraction using an organic solvent whose melting point is near the ambient temperature, consumption of the extracting solvent is efficiently reduced, and the overall extraction time was found to be only 7 min. The variables affecting the method are optimized. Under the optimal experimental conditions (75 µL of 1-undecanol, a flow rate of 2.0 mL/min, and an ultrasound irradiation of 1 min), the proposed method exhibits good preconcentration factors (52-97), low limits of detection (1.0-5.0 ng/mL), and linearities in the range of 5-1500 ng/mL (r2 ≥ 0.995). Finally, the method is successfully applied to the analysis of phthalate esters in the drinking and river water samples. To study the probable release of the phthalate esters from a polyethylene container into boiling water, the boiling water exposed to the polyethylene container was analyzed by the proposed method.

Centrifugeless dispersive liquid-liquid microextraction based on salting-out phenomenon as an efficient method for determination of phenolic compounds in environmental samples.

A new centrifugeless dispersive liquid-liquid microextraction (DLLME) method was applied for the convenient extraction of some phenolic compounds from environmental samples. After dispersing the extracting solvent into the sample solution (10.0 mL), the mixture was passed through a small column filled with 5 g sodium chloride. As a result, phase separation was achieved via the salting-out phenomenon, and the extracting solvent was suspended on top of the sample solution. Using a low-toxic and solidifiable extracting solvent (1-dodecanol), after immersing the column into an ice bath, the extracting solvent was solidified, collected easily, and injected into an HPLC-UV instrument. The overall extraction time was 7 min, consumption of the extracting solvent was efficiently reduced to 50 µL, and the centrifugation step was simply eliminated, which made the automation of the procedure easier than the normal DLLME technique. A series of parameters influencing the extraction were investigated systematically. The optimal experimental conditions were found to be 50 µL of 1-dodecanol as the extracting solvent, a flow rate of 2.0 mL min-1, and a pH value of 4.0 for the sample solution. Under these conditions, the method provided a good linearity in the range of 0.5-800 ng mL-1, low limits of detection (0.1-0.3 ng mL-1), good extraction repeatabilities (RSDs below 9.1%, n = 5), and enrichment factors of 100-160. Graphical Abstract Schematic diagram of the centrifugeless dispersive liquid-liquid microextraction.