Flotation/ultrasound-assisted microextraction followed by HPLC for determination of fat-soluble vitamins in multivitamin pharmaceutical preparations.

Determination of Gemfibrozil in Drug Matrix and Human Biological Fluid by Dispersive Liquid-Liquid Microextraction with High Performance Liquid Chromatography

A novel low-density solvent-based vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with the solidification of floating organic droplet method coupled with high-performance liquid chromatography was developed for the determination of 3,5,6-trichloro-2-pyridinol, phoxim and chlorpyrifos-methyl in water samples. In this method, the addition of a surfactant could enhance the speed of the mass transfer from the sample solution into the extraction solvent. The extraction solvent could be dispersed into the aqueous by the vortex process. The main parameters affecting the extraction efficiency were investigated and the optimum conditions were established as follows: 80 μL 1-undecanol as extraction solvent, 0.2 mmol/L of Triton X-114 selected as the surfactant, the vortex time was fixed at 60 s with the vortex agitator set at 3000 rpm, the concentration of acetic acid in sample solution was 0.4% v/v and 1.0 g addition of NaCl. Under the optimum conditions, the enrichment factors were from 172 to 186 for the three analytes. The linear ranges were from 0.5 to 500 μg/L with a coefficient of determination (r(2) ) of between 0.9991 and 0.9995. Limits of detections were varied between 0.05 and 0.12 μg/L. The relative standard deviations (n = 6) ranged from 0.26 to 2.62%.

A novel method for the determination of four anilines (aniline, p-nitroaniline, o-nitroaniline, 2, 4-dinitroaniline) in water samples has been developed using ionic liquid-based single drop microextraction coupled with high performance liquid chromatography. The influence of experimental parameters including extraction solvent, the volume of extraction solvent, extraction time, stirring speed, pH value and NaCl concentration of sample solution, extraction temperature was investigated. The optimal experimental conditions were as follows: 9 μL 1-butyl 3-methylimidazolium hexafluorophosphate ([C 4 MIM] [PF 6 ]) as extraction drop, 10.0 mL aqueous sample with 0.33 g-mL -1 NaCl, pH 9 was extracted for 25 min, stirring at 600 r-min -1 , extraction temperature set at 50°C, then 5 μL sample was injected to HPLC, aniline and o-nitroaniline were detected at 230 nm, p-nitroaniline and 2, 4-dinitroaniline were detected at 360 nm. Under the optimal conditions, good linear relationships were obtained in the concentrations of 0.010-5.000 mg-L -1 of the anilines with the correlation coefficients of 0.9990-0.9999; the detection limits were 0.002-0.005 mg-L -1 (S/N = 3); the enrichment factors of [C 4 MIM][PF 6 ] for the four anilines were from 41.8 to 48.0. The proposed method was applied to the determination of the four anilines in tap, river, lake and waste water and recoveries of the four anilines were in the range of 90.1%-103%; RSD were 3.7%-5.9% (n = 5). The method is simple, friendly to environment, sensitive and satisfied to determine real samples.

A simple, rapid and efficient method, dispersive liquid–liquid microextraction (DLLME) in conjunction with high-performance liquid chromatography (HPLC), has been developed for the determination of three carbamate pesticides (methomyl, carbofuran and carbaryl) in water samples. In this extraction process, a mixture of 35 µL chlorobenzene (extraction solvent) and 1.0 mL acetonitrile (disperser solvent) was rapidly injected into the 5.0 mL aqueous sample containing the analytes. After centrifuging (5 min at 4000 rpm), the fine droplets of chlorobenzene were sedimented in the bottom of the conical test tube. Sedimented phase (20 µL) was injected into the HPLC for analysis. Some important parameters, such as kind and volume of extraction and disperser solvent, extraction time and salt addition were investigated and optimised. Under the optimum extraction condition, the enrichment factors and extraction recoveries ranged from 148% to 189% and 74.2% to 94.4%, respectively. The methods yielded a linear range in the concentration from 1 to 1000 µg L−1 for carbofuran and carbaryl, 5 to 1000 µg L−1 for methomyl, and the limits of detection were 0.5, 0.9 and 0.1 µg L−1, respectively. The relative standard deviations (RSD) for the extraction of 500 µg L−1 carbamate pesticides were in the range of 1.8–4.6% (n = 6). This method could be successfully applied for the determination of carbamate pesticides in tap water, river water and rain water.

The aim of the present study was to extract, preconcentrate and determine 17-β–Estradiol in water samples using a simple and efficient method; to this aim, salting-out-assisted liquid-liquid extraction and high-performance liquid chromatography with ultra violet detection at 210 nm were performed. Water-miscible acetonitrile, as the extractant and acetonitrile phase separation under high-salt conditions were applied to treat the samples. The extraction efficiency and method sensitivity were carefully monitored by controlling the effective factors and the optimum conditions were: Sodium chloride as the salting-out agent at concentration of 1.6 g, 2.40 mL of acetonitrile as extraction solvent, 5 mL of water sample, vortexing for 2 minutes and centrifuging at 4000 rpm for 5 minutes. A central composite design was applied to optimize the hydrolysis parameters. Using optimized experimental conditions, the calibration curve was found to be linear in the range of 1–120 µg L-1 in water sample and the correlation coefficient (R2); the limit of detection; limit of quantification were >0.99, 0.25 µg mL-1 and 0.83 μgL-1, respectively. The enrichment factor and extraction recoveries of the selected analyte ranged from 44.96 to 49.57 and 89.93 to 99.15% respectively. Relative standard deviations are about 5.94%. High extraction efficiency and compatibility with HPLC analysis of 17-β–Estradiol in water samples are the advantages of this method.

Vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography with UV detection was applied to determine Isocarbophos, Parathion-methyl, Triazophos, Phoxim and Chlorpyrifos-methyl in water samples. 1-Bromobutane was used as the extraction solvent, which has a higher density than water and low toxicity. Centrifugation and disperser solvent were not required in this microextraction procedure. The optimum extraction conditions for 15 mL water sample were: pH of the sample solution, 5; volume of the extraction solvent, 80 μL; vortex time, 2 min; salt addition, 0.5 g. Under the optimum conditions, enrichment factors ranging from 196 to 237 and limits of detection below 0.38 μg/L were obtained for the determination of target pesticides in water. Good linearities (r > 0.9992) were obtained within the range of 1-500 μg/L for all the compounds. The relative standard deviations were in the range of 1.62-2.86% and the recoveries of spiked samples ranged from 89.80 to 104.20%. The whole proposed methodology is simple, rapid, sensitive and environmentally friendly for determining traces of organophosphorus pesticides in the water samples.

Two-step microextraction combined with high performance liquid chromatographic analysis of pyrethroids in water and vegetable samples

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography–fluorescence detection for the determination of carbendazim and thiabendazole in environmental samples

A simple, rapid, efficient, and environmentally friendly method for the determination of five triazine herbicides in water and soil samples was developed by using dispersive liquid-liquid microextraction (DLLME), coupled with high performance liquid chromatography-diode array detection (HPLC-DAD). The water samples were directly used for DLLME extraction. For soil samples, the target analytes were first extracted by water-methanol (99:1, v/v). In the DLLME extraction method, chloroform was used as an extraction solvent, and acetonitrile as a dispersive solvent. Under the optimum conditions, the enrichment factors of DLLME were in the range between 183-221. The linearity of the method was obtained in the range of 0.5-200 ng/mL for the water sample analysis, and 1-200 ng/g for the soil samples, respectively. The correlation coefficients ranged from 0.9968 to 0.9999. The limits of detection were 0.05-0.1 ng/mL for the water samples, and 0.1-0.2 ng/g for the soil samples. The proposed method has been successfully applied to the analysis of target triazine herbicides (simazin, atrazine, prometon, ametryn, and prometryn) in water and soil samples with satisfactory results.

Using 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) ionic liquid as extraction solvent, five estrogens including estrone (E1), 17β-estradiol (E2), estriol (E3), 17α -ethynylestradiol (EE2), and diethylstilbestrol (DES) in water samples were determined by dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography with a photodiode array detector and a fluorescence detector (HPLC-DAD-FLD). The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C6MIM][PF6] dispersed entirely into the sample solution with the help of a disperser solvent (acetone). Parameters including both extraction and disperser solvents and their volumes, extraction and centrifugal time, sample pH, and salt effect were investigated and optimized. Under the optimized conditions, 110–349 fold enrichment factors of analytes were obtained. The calibration curves were linear in the concentration range of 0.2–100 µg L−1 for E2, E3, and EE2 detected with FLD, and 1–100 µg L−1 for E1 and DES detected with DAD. The correlation coefficient of the calibration curve was between 0.9990 and 0.9997. The limits of detection (LOD, S/N = 3) for the five estrogens were in the range of 0.08–0.5 µg L−1. The relative standard deviations (RSD) for six replication experiments at the concentration of 5.0 µg L−1 were ≤5.7%. The proposed method was applied to the analysis of three water samples from different sources (river water, waste water, and sea water). The relative recoveries of spiked water samples are satisfied with 89.3–102.4% and 88.7–105.2% at two different concentration levels of 5.0 and 50.0 µg L−1, respectively.

For the first time, centrifuge-less emulsification microextraction using effervescent CO2 tablet (EME-ECT) coupled with gas chromatography-mass spectrometry (GC–MS) is presented for the preconcentration and determination of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. In this method, after injection of a mixture of extraction and disperser solvents into the sample with volume of 90 mL, an effervescent tablet containing the effervescence precursors (sodium bicarbonate as carbon dioxide source and sodium dihydrogen phosphate as proton donor) was applied for phase separation. Thanks to the in situ generation of carbon dioxide, as a consequence of the effervescence reaction, the dispersed extraction solvent was collected at the surface of the aqueous sample and then was narrowed to the capillary part of a special home-made extraction cell for facile retrieval. The experimental variables, including volume of extraction and disperser solvents, ionic strength and weight of effervescent tablet, were investigated and optimized by a central composite design. Under the optimal conditions, the limits of detection were at the range of 0.01–0.1 µg L−1 and preconcentration factors were varied between 134 and 406 for different PAHs. As can be seen here, there is no need for centrifugation or a special apparatus for the proposed emulsification microextraction method and it can easily be applied for the analysis of large volumes of samples. Taking these advantages to account, EME-ECT has the most promise for becoming a quick, simple and economical approach to reduce transportation costs after water sampling in the field.

A simple and sensitive method using pre-column derivatization followed by high-performance liquid chromatography (HPLC) was developed for the determination of N,N-dimethyldithiocarbamate (DMDC) in wastewater samples. I2/KI solution was used as the pre-column derivatization reagent, and the optimum derivatization conditions were as follows: pH = 9.0, derivatization time = 15 min, I2/DMDC = 4 : 1 (molar ratio). After derivatization, DMDC was determined by HPLC–variable wavelength ultraviolet detector system at λ = 254 nm. Methanol–water (40/60, v/v) was chosen as the mobile phase. Under the above optimum conditions, good linear regression between DMDC concentration and chromatogram peak area was achieved when the DMDC concentration was in the range of 50–10 000 μg L−1. The limits of detection (LOD) and limits of quantitation (LOQ) were 12.8 μg L−1 and 42.6 μg L−1, respectively; the recovery percentages ranged from 99% to 101% for the synthetic water samples. The method was used to analyze real wastewater samples. Liquid–liquid extraction was adopted to enrich DMDC in wastewater samples, and n-hexane was used as the extraction solvent. The relative recovery for the spiked real samples ranged from 84.7% to 96.5%. This method provided high accuracy, good repeatability, simple operation and high recovery, and thus could be applied for routine analysis of DMDC in water and wastewater samples.

Application of ultrasound-assisted emulsification microextraction based on applying low-density organic solvent for the determination of organochlorine pesticides in water samples

An improved single-drop microextraction (SDME) method combined with high performance liquid chromatography has been developed for the detection of trace carbamate and organophosphorus pesticides in water samples. The most fascinating feature of the proposed method is the use of an oval-shaped polychloroprene rubber (PCR) tube to load the extraction solvent, which efficiently loads more solvent and improves the stability of extraction microdrop. Furthermore, this device provides a larger contact surface between the extraction solvent and the inner surface of the oval-shaped PCR tube than that between the extraction solvent and the tip of a microsyringe needle in the conventional SDME. It thereby avoids the problem of the drop floating upwards or dislodging from the tip of the microsyringe needle as observed in the traditional SDME. This method is significant for the great improvement it can offer in extraction efficiency. A series of extraction parameters were investigated systematically using carbamate and organophosphorus as the model analytes. Under the optimal conditions, the enrichment factors for analysis were between 117 and 177, and the limits of detection were ≦0.63 μg L(-1) (S/N = 3). The repeatability study was carried out by extracting the spiked water samples. Here the relative standard deviations varied between 4.0 and 5.8% (n = 5). Additionally, the proposed method was successfully applied to the determination of pesticides in real water samples, and good recoveries were obtained from 79% to 112%. The proposed method was demonstrated to hold advantages of low cost, simplicity of operation, and successful application to in real water samples.

Extraction and determination of estrogens in water samples were performed using alcoholic-assisted dispersive liquid–liquid microextraction (AA-DLLME) and high-performance liquid chromatography (UV/Vis detection). A Plackett–Burman design and a central composite design were applied to evaluate the AA-DLLME procedure. The effect of six parameters on extraction efficiency was investigated. The factors studied were volume of extraction and dispersive solvents, extraction time, pH, amount of salt and agitation rate. According to Plackett–Burman design results, the effective parameters were volume of extraction solvent and pH. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 220 μL 1-octanol as extraction solvent, 700 μL ethanol as dispersive solvent, pH 6 and 200 μL sample volume. Linearity was observed in the range of 1–500 μg L−1 for E2 and 0.1–100 μg L−1 for E1. Limits of detection were 0.1 μg L−1 for E2 and 0.01 μg L−1 for E1. The enrichment factors and extraction recoveries were 42.2, 46.4 and 80.4, 86.7, respectively. The relative standard deviations for determination of estrogens in water were in the range of 3.9–7.2 % (n = 3). The developed method was successfully applied for the determination of estrogens in environmental water samples.