Magnetic core micelles as a nanosorbent for the efficient removal and recovery of three organophosphorus pesticides from fruit juice and environmental water samples.

Sodium dodecyl sulfate coated amino-functionalized magnetic iron oxide nanoparticles were used as an efficient adsorbent for rapid removal and preconcentration of three important organophosphorus pesticides, chlorpyrifos, diazinon and phosalone, by ultrasound-assisted dispersive magnetic solid-phase microextraction. Fabrication of amino-functionalized magnetic nanoparticles was certified by characteristic analyses, including Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Affecting parameters on the removal efficiency were investigated and optimized through half-fractional factorial design and Doehlert design, respectively. The analysis of analytes was performed by high-performance liquid chromatography with ultraviolet detection. Under the optimum conditions, extraction recoveries for 20 ng/mL of organophosphorus pesticides were in the range of 84-97% with preconcentration factors in the range of 134-155. Replicating the experiment in above condition for five times gave the relative standard deviations <6%. The calibration curves showed high linearity in the range of 0.2-700 ng/mL and the limits of detection were in the range of 0.08-0.13 ng/mL. The proposed method was successfully applied for both removal and trace determination of these three organophosphorus pesticides in environmental water and fruit juice samples.

Optimization of multiwalled carbon nanotubes reinforced hollow-fiber solid-liquid-phase microextraction for the determination of polycyclic aromatic hydrocarbons in environmental water samples using experimental design.

A novel design of hollow-fiber liquid-phase microextraction containing multiwalled carbon nanotubes as a solid sorbent, which is immobilized in the pore and lumen of hollow fiber by the sol-gel technique, was developed for the pre-concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples. The proposed method utilized both solid- and liquid-phase microextraction media. Parameters that affect the extraction of polycyclic aromatic hydrocarbons were optimized in two successive steps as follows. Firstly, a methodology based on a quarter factorial design was used to choose the significant variables. Then, these significant factors were optimized utilizing central composite design. Under the optimized condition (extraction time = 25 min, amount of multiwalled carbon nanotubes = 78 mg, sample volume = 8 mL, and desorption time = 5 min), the calibration curves showed high linearity (R2  = 0.99) in the range of 0.01-500 ng/mL and the limits of detection were in the range of 0.007-1.47 ng/mL. The obtained extraction recoveries for 10 ng/mL of polycyclic aromatic hydrocarbons standard solution were in the range of 85-92%. Replicating the experiment under these conditions five times gave relative standard deviations lower than 6%. Finally, the method was successfully applied for pre-concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples.

Optimization of alcohol-assisted dispersive liquid-liquid microextraction by experimental design for the rapid determination of fluoxetine in biological samples.

A sensitive and rapid method based on alcohol-assisted dispersive liquid-liquid microextraction followed by high-performance liquid chromatography for the determination of fluoxetine in human plasma and urine samples was developed. The effects of six parameters on the extraction recovery were investigated and optimized utilizing Plackett-Burman design and Box-Benken design, respectively. According to the Plackett-Burman design results, the volume of disperser solvent, extraction time, and stirring speed had no effect on the recovery of fluoxetine. The optimized conditions included a mixture of 172 µL of 1-octanol as extraction solvent and 400 µL of methanol as disperser solvent, pH of 11.3 and 0% w/v of salt in the sample solution. Replicating the experiment in optimized condition for five times, gave the average extraction recoveries equal to 90.15%. The detection limit of fluoxetine in human plasma was obtained 3 ng/mL, and the linearity was in the range of 10-1200 ng/mL. The corresponding values for human urine were 4.2 ng/mL with the linearity range from 10 to 2000 ng/mL. Relative standard deviations for intra and inter day extraction of fluoxetine were less than 7% in five measurements. The developed method was successfully applied for the determination of fluoxetine in human plasma and urine samples.