Nano-structured gemini-based supramolecular solvent for the microextraction of cyhalothrin and fenvalerate.

A novel supramolecular solvent-based microextraction followed by high-performance liquid chromatography with ultraviolet detection method has been developed for the extraction and determination of two pyrethroid analytes, cyhalothrin and fenvalerate, in water and soil samples. The liquid-liquid-phase separation of surfactants has been used in analytical extraction. The surfactant-rich phase is a nano-structured liquid, recently named as a supramolecular solvent, generated from the amphiphiles. The alkyl carboxylic acid based supramolecular solvents were introduced before. Coacervates made up of gemini surfactant, consisting of two amphiphilic moieties, were first used as solvent. The effective parameters on extraction (i.e., type of organic solvent, the amount of surfactant and volume of tetrahydrofuran, sample solution pH, salt addition, ultrasonic and centrifugation time) were investigated and optimized. Under the optimum conditions, preconcentration factors of 110 and 145 were obtained for the analytes. The linearity was 0.5-200.0 µg/L with the correlation of determination of (R(2) ) ≥ 0.9984. The limit of detection of the method was (S/N = 3) 0.2 µg/L, and precisions in the range of 6.3-10.3% (RSDs, n = 5) were obtained. This method has been successfully applied to analyze real samples, and good recoveries in the range of 101.2-108.8% were obtained.

Automated hollow-fiber liquid-phase microextraction followed by liquid chromatography with mass spectrometry for the determination of benzodiazepine drugs in biological samples.

In this study, two-phase hollow-fiber liquid-phase microextraction and three-phase hollow-fiber liquid-phase microextraction based on two immiscible organic solvents were compared for extraction of oxazepam and Lorazepam. Separations were performed on a liquid chromatography with mass spectrometry instrument. Under optimal conditions, three-phase hollow-fiber liquid-phase microextraction based on two immiscible organic solvents has a better extraction efficiency. In a urine sample, for three-phase hollow fiber liquid-phase microextraction based on two immiscible organic solvents, the calibration curves were found to be linear in the range of 0.6-200 and 0.9-200 µg L(-1) and the limits of detection were 0.2 and 0.3 µg L(-1) for oxazepam and lorazepam, respectively. For two-phase hollow fiber liquid-phase microextraction, the calibration curves were found to be linear in the range of 1-200 and 1.5-200 µg L(-1) and the limits of detection were 0.3 and 0.5 µg L(-1) for oxazepam and lorazepam, respectively. In a urine sample, for three-phase hollow-fiber-based liquid-phase microextraction based on two immiscible organic solvents, relative standard deviations in the range of 4.2-4.5% and preconcentration factors in the range of 70-180 were obtained for oxazepam and lorazepam, respectively. Also for the two-phase hollow-fiber liquid-phase microextraction, preconcentration factors in the range of 101-257 were obtained for oxazepam and lorazepam, respectively.

A new effective on chip electromembrane extraction coupled with high performance liquid chromatography for enhancement of extraction efficiency.

In the present research, an effective on chip electromembrane extraction (CEME) coupled with high performance liquid chromatography was presented for analysis of nortriptyline (NOR) and amitriptyline (AMI) as basic model analytes from urine samples. The chip consists of two polymethyl methacrylate (PMMA) parts with two craved microfluidic channels in each part. These channels were used as flow path for the sample solution and a thin compartment for the acceptor phase. A porous polypropylene sheet membrane impregnated with an organic solvent was placed between two parts of chip device to separate the channels. Two platinum electrodes were mounted at the bottom of these channels that were connected to a power supply providing the electrical driving force for migration of ionized analytes from sample solution through the porous sheet membrane into the acceptor phase. This new setup provides effective and reproducible extractions with low volume of sample solution. Efficient parameters on CEME of the model analytes were optimized using one variable at a time method. Under the optimized conditions, the calibration curve was linear in the range of 10.0-500 µg L(-1) with coefficient of determination (r(2)) more than 0.9902. The relative standard deviations (RSDs %) for extraction and determination of the analytes were less than 6.8% based on six replicate measurements. LODs less than 4.0 µg L(-1) were obtained for both of the model analytes. The preconcentration factors higher than 17.0-fold were obtained. The results demonstrated that CEME would be used efficiently for extraction and determination of AMI and NOR from urine samples.

Nano polypyrrole-coated magnetic solid phase extraction followed by dispersive liquid phase microextraction for trace determination of megestrol acetate and levonorgestrel.

The aim of the present work is combination of the advantages of magnetic solid phase extraction (MSPE) and dispersive liquid phase microextraction (DLLME) followed by filtration-based phase separation. A new pretreatment method was developed for trace determination of megestrol acetate and levonorgestrel by liquid chromatography/ultraviolet detection in biological and wastewater samples. After magnetic solid phase extraction, the eluent of MSPE was used as the disperser solvent for DLLME. Emulsion resulted from DLLME procedure was passed through the in-line filter for phase separation. Finally the retained analytes in the filter was washed with mobile phase of liquid chromatography and transferred to the column for separation. This approach offers the preconcentration factors of 3680 and 3750 for megestrol acetate and levonorgestrel, respectively. This guarantees determination of the organic compounds at trace levels. The important parameters influencing the extraction efficiency were studied and optimized. Under the optimal extraction conditions, a linear range of 0.05-50ngmL(-1) (R(2)>0.998) and limit of detection of 0.03ngmL(-1) were obtained for megestrol acetate and levonorgestrel. Under optimal conditions, the method was successfully applied for determination of target analytes in urine and wastewater samples and satisfactory results were obtained (RSDs<6.8%).

Automated hollow fiber microextraction based on two immiscible organic solvents for the extraction of two hormonal drugs.

In this research, a rapid efficient and automated instrument based on hollow fiber liquid-phase microextraction (HF-LPME) followed by high performance liquid chromatography (HPLC) with UV-vis detection was applied for the preconcentration and determination of two hormonal drugs (megestrol acetate and levonorgestrel) in water and urinary samples. n-Dodecane was used as the supported liquid membrane (SLM) and methanol was used as the acceptor phase in the hollow fiber lumen. The effects of different parameters such as fiber length, extraction time, stirring rate, and ionic strength on the extraction efficiency were investigated using modified simplex and central composite design as the screening and optimization methods, respectively. The composition effect of SLM and type of acceptor phase were optimized separately. For adjustment of the SLM composition, trioctylphosphine oxide (TOPO) was chosen. Under optimized condition, the calibration curves were linear (r(2)>0.997) in the range of 0.5-200 µg L(-1). LOD for both of the drugs were 0.25 µg L(-1). The applicability of this technique was examined by analyzing drugs in water and urine samples. The relative recoveries of the drugs were in the range of 86.2-102.3% that show the capability of the method for the determination of the drugs in various matrices.

A sensitive emulsification liquid phase microextraction coupled with on-line phase separation followed by HPLC for trace determination of sulfonamides in water samples.

For the first time, ion-pair based emulsification liquid phase microextraction coupled with a novel approach for phase separation followed by high performace liquid chromatgraphy (HPLC) was utilized for trace determination of sulfonamides in water samples. After the formation of ion-pair complex with a cationic surfactant, sulfonamides were extracted into the drops of dispersed organic extracting solvent. Then, the cloudy solution was passed through an in-line filter located in a suitable holder and was separated based on emulsion filtration. By changing the HPLC valve position, the filter was laid in the mobile phase path, and the extraction phase was eluted by the mobile phase and introduced into the separation column for analysis. The effects of important parameters, such as type of extraction solvent, type of ion-pair agent and its concentration, pH of sample solution, ionic strength, and volume of extraction phase, on the extraction efficiency, were investigated and optimized. Under optimal conditions, the linear range, limits of detection, and precision (relative standard deviations) were 0.3-100, 0.1-0.3 µg L(-1), and 4.7-5.8%, respectively. Preconcentration factors (PFs) for the compounds studied were obtained in the range of 268-664. These PFs correspond to extraction recoveries in the range of 41-97%. The sample throughput of the method was 3 samples per hour, regarding 20 min analysis time for a single procedure. Finally, the method was successfully applied to determine the selected sulfonamides in some water samples.

Extraction and determination of sulfonylurea herbicides in water and soil samples by using ultrasound-assisted surfactant-enhanced emulsification microextraction and analysis by high-performance liquid chromatography.

An ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) with low-density extraction solvents was developed for the extraction of sulfonylurea herbicides from water and soil samples prior to high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV). In this technique, a surfactant was used as emulsifier which could enhance the dispersion of water-immiscible extraction solvent into aqueous phase and was favorable for the mass-transfer of the analytes from aqueous phase to organic phase. The target analytes were extracted into an extraction phase (Aliquat-336 in 1-octanol) and dispersed in an aqueous solution. After extraction and phase separation, the organic solvent on top of the solution was withdrawn into a syringe and 20 µL of it was injected into a HPLC instrument for analysis. Influential factors in extraction were investigated and optimized. Under optimum experimental conditions, calibration curve was linear in the concentration range from 1 to 100 µg/L, with coefficients of estimation (R(2) values) varying from 0.9928 to 0.9952, and satisfactory repeatabilities (4.7

On-line extraction and determination of two herbicides: comparison between two modes of three-phase hollow fiber microextraction.

Two different modes of three-phase hollow fiber liquid-phase microextraction were studied for the extraction of two herbicides, bensulfuron-methyl and linuron. In these two modes, the acceptor phases in the lumen of the hollow fiber were aqueous and organic solvents. The extraction and determination were performed using an automated hollow fiber microextraction instrument followed by high-performance liquid chromatography. For both three-phase hollow fiber liquid-phase microextraction modes, the effect of the main parameters on the extraction efficiency were investigated and optimized by central composite design. Under optimal conditions, both modes showed good linearity and repeatability, but the three-phase hollow fiber liquid-phase microextraction based on two immiscible organic solvents has a better extraction efficiency and figures of merit. The calibration curves for three-phase hollow fiber liquid-phase microextraction with an organic acceptor phase were linear in the range of 0.3-200 and 0.1-150 µg/L and the limits of detection were 0.1 and 0.06 µg/L for bensulfuron-methyl and linuron, respectively. For the conventional three-phase hollow fiber liquid-phase microextraction, the calibration curves were linear in the range of 3.0-250 and 15-400 µg/L and LODs were 1.0 and 5.0 µg/L for bensulfuron-methyl and linuron, respectively. The real sample analysis was carried out by three-phase hollow fiber liquid phase microextraction based on two immiscible organic solvents because of its more favorable characteristics.

Homogeneous liquid-phase microextraction followed by filtration-based phase separation coupled to high-performance liquid chromatography.

A simple homogenous liquid-phase microextraction methodology applying octanoic acid as the extraction phase was introduced for determination of chlorobenzenes. In this approach, phase separation phenomenon occurred by changing pH of the solution. The extraction phase was isolated based on filtration of emulsion instead of centrifugation and it was introduced to the high-performance liquid chromatography instrument as an on-line procedure. This method was used for extraction and determination of five chlorobenzenes in different samples. Experimental design and response surface methodology were used for the optimization of various parameters influencing the extraction efficiency of the method. Under optimal conditions, chlorobenzenes were effectively extracted, and preconcentration factors of 255-294 were obtained. The calibration curves were investigated in the concentration range of 1-200 µg/L and good linearity was achieved with coefficient of determinations better than 0.997. Limits of detection of 0.1 and 0.3 µg/L and suitable precision with relative standard deviations better than 5.1% (n = 5) were attained. Finally, the proposed method was applied to determine the concentration of chlorobenzenes in different samples and acceptable recoveries were gained.

SPE coupled with dispersive liquid-liquid microextraction followed by GC with flame ionization detection for the determination of ultra-trace amounts of benzodiazepines.

SPE combined with dispersive liquid-liquid microextration was used for the extraction of ultra-trace amounts of benzodiazepines (BZPs) including, diazepam, midazolam, and alprazolam, from ultra-pure water, tap water, fruit juices, and urine samples. The analytes were adsorbed from large volume samples (60 mL) onto octadecyl silica SPE columns. After the elution of the desired compounds from sorbents with 2.0 mL acetone, 0.5 mL of eluent containing 40.0 µL chloroform was injected rapidly into 4.5 mL pure water. After extraction and centrifugation, 2 µL of the sedimented phase was injected into a GC equipped with a flame ionization detector. Several parameters affecting this process were investigated and optimized. Under the optimal conditions, LODs ranged from 0.02 to 0.05 µg/L, a linear dynamic range of 0.1-100 µg/L and relative SDs in the range of 4.4-10.7% were attained. Very high preconcentration factors ranging from 3895-7222 were achieved. The applicability of the method for the extraction of BZPs from different types of complicated matrices, such as tap water, fruit juices, and urine samples, was studied. The obtained results reveal that the proposed method is a good technique for the extraction and determination of BZPs in complex matrices.

Solid phase extraction as a cleanup step before microextraction of diclofenac and mefenamic acid using nanostructured solvent.

A new pretreatment method, solid-phase extraction combined with supramolecular solvents, was proposed for the first time for extraction of diclofenac (DIC) and mefenamic acid (MEF) from urine and water samples. Supramolecular solvent (SUPRAS) is a nano-structured liquid, generated from the amphiphiles through a sequential self-assembly process occurring on two scales, molecular and nano. SUPRAS tested were generated from solutions of reverse micelles of decanoic acid (DeA) in tetrahydrofuran (THF) by addition of water, which acted as the coacervating agent. In the present study, due to matrix effect, drugs were first extracted from the samples by SPE. The extracted analytes were then eluted from the sorbent with THF, and the eluate was subjected to SUPRAS formation (SUPRASF) process. Finally, the analytes in the SUPRAS were separated and determined by HPLC-UV. Several parameters affecting the SPE-SUPRASF process were investigated and optimized. The new method provides enrichment factors in the range of 431-489 for MEF and DIC, respectively. Calibration plots are linear in the range of 2-200 µg L(-1) for MEF and 1-200 µg L(-1) for DIC, with correlation of determination (r(2)) ranging from 0.996 to 0.999. The method was successfully applied for extraction and determination of analytes in urine and water samples and relative recoveries of the studied compounds were obtained in the range of 90.4-103.8%.

Acid-induced homogenous liquid-phase microextraction: application of medium-chain carboxylic acid as extraction phase.

In this research, a novel homogeneous liquid-phase microextraction method was successfully developed based on applying octanoic acid as low-density extraction solvent. The method was applied for extraction and determination of chlorophenols (CPs) as model compounds. Twelve milliliter of the sample solution was poured into a home-designed glass vial. Sixty microliter of octanoic acid was solved in water sample by adjusting pH and ionic strength. By rapid addition of 75 µL of concentrated HCl (6 M), a cloudy solution was obtained. Phase separation occurred at 5000 rpm for 5 min. After that, 20 µL of the collected phase (approximately 26 µL) was injected into the HPLC-UV instrument for analysis. The effect of some parameters such as the volume of concentrated HCl (phase separation reagent), ionic strength, extraction time, centrifugation time, and the volume of extracting phase on the extraction efficiency of the CPs were investigated and optimized. The preconcentration factors in a range of 159-218 were obtained under the optimal conditions. The linear range, detection limits (S/N = 3), and precision (n = 3) were 1- 200, 0.3-0.5 µg/L, and 4.6-5.1%, respectively. Tap water, seawater, and river water samples were successfully analyzed for the existence of CPs using the proposed method and satisfactory results were obtained.

Electromembrane surrounded solid phase microextraction: a novel approach for efficient extraction from complicated matrices.

In the present work, electromembrane surrounded solid phase microextraction (EM-SPME) is introduced for the first time. The organic liquid membrane, which consists of 2-nitrophenyl octyl ether (NPOE), was immobilized in the pores of a hollow fiber (HF) and the basic analytes migrated in an electrical field from aqueous sample solution through the liquid membrane and into aqueous acceptor phase and then they were adsorbed on the solid sorbent, which acts as the cathode. Effective parameters such as composition of organic liquid membrane, pH of donor and acceptor phases, applied voltage and extraction time were optimized for extraction of amitriptyline (AMI) and doxepin (DOX) as model analytes and figures of merit of the method were investigated in pure water, human plasma, and urine samples. To extract the model analytes from 24 mL neutral sample solution across organic liquid membrane and into aqueous acceptor phase, 120 V electrical potential was applied for 20 min and finally the drugs were adsorbed on a carbonaceous cathode. Regardless of high sample cleanup, which make the proposed method suitable for the analysis of drugs from complicated matrices, extraction efficiencies in the range of 3.1-11.5% and good detection limits (less than 5 ngmL(-1)) with admissible repeatability and reproducibility (intra- and inter-assay precisions ranged between 4.0-8.5% and 7.5-12.2%, respectively) were obtained from different extraction media. Linearity of the method was studied in the range of 2.0-500.0 ngmL(-1) and 5.0-500.0 ngmL(-1) for AMI and DOX, respectively and coefficient of determination higher than 0.9947 were achieved. Finally, the proposed method was applied for the analysis of AMI and DOX in real samples.

Emulsification liquid phase microextraction followed by on-line phase separation coupled to high performance liquid chromatography.

An emulsification liquid phase microextraction followed by on-line phase separation coupled to high performance liquid chromatography (HPLC) is introduced based on a novel idea for the separation of dispersed organic phase from aqueous phase. In this method, the dispersed organic extraction phase was filtered using an in-line filter and it was separated from the water sample. The new approach is simple and, in addition to improving some limitations of the conventional emulsification liquid phase microextraction, eliminates the need for centrifugation in the phase separation step. To demonstrate the applicability of the method, it was applied for the extraction and determination of trace amounts of selected parabens as model analytes. In this procedure, 30 µL of 1-octanol was injected slowly into 10 mL of the aqueous sample inside the ultrasonic water bath. Then, the emulsion formed was passed through the in-line filter located in the loop of the HPLC valve and the organic extraction phase was separated and it was retained in the filter. By changing the position of the valve, the filter was located in the mobile phase pass and the retained organic phase was eluted and transferred to the separation column. The effects of some important parameters such as types of extraction solvent and its volume, ionic strength, and ultrasonication time on extraction efficiency were investigated and optimized. Under optimal conditions, preconcentration factors and limits of detection for the compounds studied were obtained in the ranges of 289-595 and 0.05-0.2 µg L(-1), respectively. Finally, the method was successfully applied to determine selected parabens in some water and cosmetic samples.

Automated preconcentration and analysis of organic compounds by on-line hollow fiber liquid-phase microextraction-high performance liquid chromatography.

The present work describes the first automated instrument, based on on-line hollow fiber liquid-phase microextraction (HF-LPME)-high performance liquid chromatography (HPLC), for the preconcentration and determination of organic compounds in various matrices. Using an automated syringe pump for loading the supported liquid membrane and acceptor solvents, a platform lift for moving the sample vial, a sampling loop for on-line injection of the extract to HPLC, along with an electronic board with an AVR microcontroller for storage of data and instrument programs, a sample preparation-HPLC method was developed that allowed sample extraction and extract injection to be carried out completely automatically. Pyridine and pyridine derivatives were chosen for the development and for testing the applicability of the automated instrument. The limits of detection (3 times the S/N) ranged from 0.5 to 1.0 µgL(-1). Effective preconcentration of the analytes was also achieved (preconcentration factors of between 40 and 220). The main advantages of the method developed are minimum sample manipulation, full automation, suitable extraction time, low solvent consumption, and ease of use. The applicability of the on-line automated HF-LPME/HPLC-UV instrument was validated for quantitative extraction and determination of pyridines in cigarette smoke.

Application of ionic surfactant as a carrier and emulsifier agent for the microextraction of fluoroquinolones.

A simple microextraction method based on emulsification of organic extraction solvent in aqueous sample using an ionic surfactant was evaluated for extraction and preconcentration of trace amounts of ofloxacin and ciprofloxacin as polar model drugs. In this method, the surfactant was used as carrier and disperser agent simultaneously. The target analytes were converted into their ion-pair complexes with Aliquat-336 and then extracted into an organic solvent (1-octanol) dispersed in aqueous solution. After extraction and phase separation, the organic solvent on top of the solution was withdrawn into the syringe and 20 µL of it was injected into a HPLC instrument for analysis. The factors influential to extraction were investigated and optimized. Under optimum extraction conditions, the limits of detection (LODs) as small as 0.06 and 0.02 ng mL(-1) and linear dynamic range of 0.1-100 and 0.06-100 ng mL(-1) were obtained for ofloxacin and ciprofloxacin, respectively. For analysis of real samples such as waste water, river water and urine samples, solid-phase extraction (SPE) was applied prior to liquid phase microextraction in order to avoid/remove matrix effect. The obtained results indicate that the proposed method is efficient, fast and inexpensive for extraction and determination of fluoroquinolones in environmental aqueous and urine samples.