A simple and portable vacuum assisted headspace solid phase microextraction device coupled to gas chromatography based on covalent organic framework/metal organic framework hybrid for simultaneous analysis of volatile and semi-volatile compounds in soil.

Various microextraction methods have demonstrated a positive effect when assisted by vacuum. However, working with such systems is often laborious, they often require expensive and non-portable vacuum pumps, and may even suck off some sample vapor or solid particles during the evacuation process. To address these issues, a simple, and affordable vacuum-assisted headspace solid-phase microextraction (HS-SPME) device was developed in this study. The device, named In Syringe Vacuum-assisted HS-SPME (ISV-HS-SPME), utilizes an adjustable 40 mL glass syringe as a vacuum provider and sampling vessel. A new fiber coating, made from a hybrid of covalent triazine-based frameworks and metal-organic frameworks (COF/MOF), was prepared and characterized by Fourier transform infrared spectrometry, field emission scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis, and Brunauer-Emmett-Teller techniques for use in the ISV-HS-SPME. By optimizing parameters such as extraction temperature, extraction time, desorption temperature, desorption time, and, humidity using a simplex method, the ISV system was found to increase the extraction efficiency of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in solid samples by up to 175%. The determinations were followed by GC-FID measurements. Compared to three commercially available fibers, the ISV-HS-SPME device with the COF/MOF (2DTP/MIL-101-Cr) fiber exhibited significantly higher peak areas for PAHs and BTEX. The linear dynamic ranges for BTEX and PAHs were 7.1-9000 ng g-1 and 0.23-9000 ng g-1, respectively, with limits of detection ranging from 2.1-5 ng g-1 for BTEX and 0.07-1.6 ng g-1 for PAHs. The relative standard deviation of the method was 2.6-7.8% for BTEX and 1.6-6.7% for PAHs. The ISV-HS-SPME was successfully used to simultaneously determine PAHs and BTEX in polluted soil samples with recoveries ranging from 80.4 to 108%.

Ionic Liquid-Based Magnetic Needle Headspace Single-Drop Microextraction Combined with HPLC/UV for the Determination of Chlorophenols in Wastewater.

A magnetic needle headspace single-drop microextraction (MN-HS-SDME) method coupled to HPLC/UV has been developed. Trihexyl(tetradecyl)phosphonium chloride was employed as an ionic liquid (IL) solvent for the headspace extraction of some chlorophenol (CP) compounds from wastewater samples. Despite of the nonmagnetic character of the IL, a significant improvement in the extraction efficiency was obtained by the magnetization of the single-drop microextraction needle using a pair of permanent disk magnets. A simplex method for the fast optimization of the experimental conditions (e.g., stirring speed, ionic strength, pH, extraction time and temperature) was used. The coefficients of determination (R2) varied between 0.9932 and 0.9989, the limits of detection were from 0.004 to 0.007 µg mL-1 and the relative recoveries were in the range of 88-120% for the studied analytes. The developed MN-HS-SDME HPLC/UV method was successfully applied to the determination of CPs in industrial wastewater.

Superparamagnetic Tragacanth Coated Fe3O4@SiO2 Nanoparticles for the Loading and Delivery of Metformin.

A novel superparamagnetic nano-composite of Fe3O4@SiO2 coated by tragacanth gum (TG) as a natural product has been prepared. The obtained SiO2@Fe3O4@TG nanoparticles were characterized by Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, scanning electron microscopy and dynamic light scattering analyzer. The magnetic nano-composite was applied for the loading and delivery of metformin, an oral diabetes medicine. The conditions for the loading of the drug were optimized by a central composite design optimization method. The maximum loading efficiency of the sorbent for metformin was obtained at pH 7 and its maximum in-vitro release was achieved at pH 1.6, using a phosphate-buffered saline medium. The loading capacity of the sorbent was dependent on the initial metformin concentration and exceeded to 19.6 mg/g in a 200 mg/L solution. A study of the adsorption isotherms for the drug indicated the best fitting into the Langmuir and Freundlich isotherms at the low and high metformin concentrations, respectively. The results indicated that the prepared Fe3O4@SiO2@TG adsorbent, as a non-toxic and low-cost sorbent, was quite appropriate for drug delivery applications.

Magnetic fiber headspace solid-phase microextraction of Ferulago angulata volatile components using Preyssler-type polyoxometalate/metal-organic framework/silica aerogel sorbent.

A new hybrid of silica aerogel with a Preyssler-type polyoxometalate and MIL-101(Cr) metal-organic framework was prepared and used as a highly porous fiber coating for headspace solid-phase microextraction of Ferulago angulata volatile components. Applying a permanent magnetic field to the sorbent increased the extraction efficiency for most of the plant's components, up to 5.53 times. Optimization of the extraction parameters was carried out using a GC-MS instrument and by a simplex method. The extraction efficiency of the P5W30/MIL-101(Cr)/silica aerogel fiber exceeded 3.5 times of a mesoporous SBA-15 fiber. The prepared fiber was stable in multiple injections with relative standard deviations of 5.3 to 10.9% for 5 replicates. The proposed method was successfully applied to the extraction and identification of volatile components of some F. angulata samples. According to the results obtained by GC-FID, ß-bourbonene, ß-gurjunene, ß-elemene and cedrenol were the main components of the plant.

Removal of histamine from biological samples by functionalized Fe3O4@Agarose@Silica nanoparticles and its fast determination by ion mobility spectrometry.

A three-step process was developed for the synthesis of magnetic iron oxide nanoparticles coated with agarose, their functionalization with iminodiacetic acid (IDA) and layering of the particles with a silica shell. The prepared Fe3O4@Agarose/IDA@Silica nanoparticles were characterized by scanning electron microscopy, energy dispersive X-ray analysis and Fourier transform infrared spectroscopy. Ion mobility spectrometry (IMS) was successfully used for the ultrafast and interference free determination of histamine in serum samples in this work. Effect of different parameters on histamine adsorption by the nanoparticles such as pH, ionic strength, contact time and adsorbent amount were investigated. Under the optimized conditions, adsorption capacities up to 178 mg g-1 of the adsorbent were obtained. For interpreting histamine adsorption on the nanoparticles, the adsorption isotherms were studied and the Freundlich model was found to be more applicable than the Langmuir model. It was found that the prepared nanoparticles could remove up to 92 % of histamine from human serum samples.

A fast and simple method for determination of ß-carotene in commercial fruit juice by cloud point extraction-cold column trapping combined with UV-Vis spectrophotometry.

Cloud point extraction with cold column trapping (CPE-CCT) was used for the rapid preconcentration and UV-Vis spectroscopy of beta-carotene in fruit juice samples. A central composite design was employed to optimize parameters such as pH, incubation time, cloud point temperature and surfactant concentration. A detection limit of 0.01 mg/L of beta-carotene (3SB/m), a coefficient of determination of 0.998 and a linear range of 0.04-10 mg/L were obtained. The CPE-CCT method was confirmed in comparison with the corresponding direct HPLC standard method. A simple, portable and cost-effective device was also utilized. Owing to eliminating centrifugation, the conditions of CPE-CCT were more moderate and its sample handling easier compared to conventional CPE.

Cooling assisted headspace microextraction by packed sorbent coupled to HPLC for the determination of volatile polycyclic aromatic hydrocarbons in soil.

A headspace microextraction by packed sorbent technique (HS-MEPS) was developed that is assisted by cooling the extraction phase and, in the same time, heating the sample matrix. The innovated cooling assisted HS-MEPS system was optimized for the extraction and HPLC determination of volatile polycyclic aromatic hydrocarbons (PAHs) in solid samples. Amino ethyl-functionalized SBA-15 was used as a nanoporous sorbent for packing the conical hub of the MEPS syringe. For efficient extraction of PAHs, several parameters such as the nature and mass of sorbent, eluent type, elution volume, extraction temperature and number of draw-eject cycles of the syringe were studied and optimized. Under the optimal experimental conditions, only 2 mg of the sorbent was sufficient by applying a temperature of 0 °C to the sorbent while the sample was heated up to 150 °C. Linear calibration curves (R2 > 0.95) were obtained for all the studied PAHs and their quantitation limits were in the range of 0.042-0.25 ng g-1. The method was successfully applied to the extraction and HPLC analysis of PAHs in some polluted soil samples.

Magnetic fiber headspace solid-phase microextraction coupled to GC-MS for the extraction and quantitation of polycyclic aromatic hydrocarbons.

A technique was developed for magnetic fiber headspace-solid phase microextraction (MF-HS-SPME) of polycyclic aromatic hydrocarbons (PAHs). The efficiency of the extraction of a steel SPME fiber coated with an aminoethyl-functionalized SBA-15 (Santa Barbara Amorphous 15; a nanoporous sorbent) is substantially improved after its magnetization during HS-SPME. The effects of magnetic field strength, extraction temperature, extraction time, moisture content of the sample, desorption time and desorption temperature were optimized using a simplex method. The application of a moderately strong magnetic field to the fiber results in up to 135% increase in the extraction efficiency and wider linear dynamic ranges. The PAHs (specifically naphthalene, acenaphthene, fluorene, anthracene, phenanthrene, fluoranthene and pyrene) were then quantified by GC-MS analysis. Comparison of an electromagnet and a permanent magnet indicated the superior effect of the permanent magnet for the target analytes due to the Ohmic heating of the magnetic coil and its negative effect on the extraction of some of the PAHs. The limits of detections of the PAHs are between 0.17 to 0.57 ng g-1 by using the electromagnet, and between 0.10 and 0.32 ng g-1 for the permanent magnet. Relative standard deviations of 2.9 to 7.6% were obtained for six replicated analyses of the analytes. The method was applied to some polluted soil samples, and satisfactory results were obtained. Graphical abstract Schematic representation of the designed magnetic fiber headspace solid-phase microextraction (MF-HS-SPME) system using (a) an electromagnet, (b) a pair of permanent disc magnets.

A Needle Trap Device Packed with Nanoporous Silica Sorbents for Separation and Gas Chromatographic Determination of Polycyclic Aromatic Hydrocarbons in Contaminated Soils.

SBA-15 and MCM-41 nanoporous silica sorbents were synthesized and functionalized by amine groups and used, for the first time, for packing a needle trap device (NTD). The characteristics of the synthesized SBA-15 and MCM-41 sorbents were investigated by X-ray diffraction, scanning electron microscopy and Fourier transfer infrared spectroscopy. The NTD coupling to gas chromatography with a flame ionization detector (GC-FID) was carried out to extract and determine polycyclic aromatic hydrocarbons (PAHs) in contaminated soil samples. The performances of the sorbents for the extraction of PAHs were compared under identical conditions and the NH2-SBA-15 sorbent showed superior results. Extraction temperature, extraction time, recycling gas flow rate, sample moisture, desorption time and desorption temperature were evaluated and optimized for the system. Under the optimum conditions, detection limits of 0.0004-0.0035 µg g-1, quantitation limits of 0.001-0.01 µg g-1 and relative standard deviations of 7.4-14.9% were obtained for the PAHs. The results showed the more effectiveness of this sorbent for the extraction of the PAHs compared to that of a commercial sorbent. The method was successfully applied for the extraction and determination of PAHs in polluted soil samples collected from gas stations, with recoveries ranging from 64 to 112%.

Preconcentration and GC-MS determination of caffeine in tea and coffee using homogeneous liquid-liquid microextraction based on solvents volume ratio alteration.

A simple, fast and green homogeneous liquid-liquid microextraction (HLLME) method based on solvents volume ratio alteration (SVRA) combined with gas chromatography-mass spectrometry (GC-MS) was developed for the preconcentration and determination of caffeine in tea and coffee samples. In the proposed HLLME-SVRA method, the primary extraction from solid samples was achieved by a 2:1 ethanol-water mixture. A micro-volume of dichloromethane (DCM) formed a homogeneous solvent with this mixture after choosing an appropriate volume ratio between the three solvents. After vigorous shaking, an extra volume of water was added that resulted in phase separation due to the solvents volume ratio alteration. As a result, complete extraction of caffeine was achieved after centrifugation. The sedimented dichloromethane phase was then injected into GC-MS for the analysis. The influence of a number of parameters influencing the efficiency of the extraction was investigated and optimized. Under the optimal conditions, an enrichment factor of 11, a limit of detection of 0.05 µg mL-1 and a limit of quantification of 0.16 µg mL-1 were obtained for caffeine. A linear dynamic range of 0.16 to 50 µg mL-1 and a determination coefficient (R2) of 0.9980 were achieved. The precision of the method, expressed as relative standard deviation, was 4.8% for six replicated measurements. The method was successfully applied to the determination of caffeine in tea and coffee samples.

Synthesis of Silver Nanoparticles-Agarose Composite and Its Application to the Optical Detection of Cyanide Ion.

A highly sensitive and selective colorimetric method was developed for the detection of CN- ion based on the surface plasmon resonance of silver nanoparticles (AgNPs) embedded in a transparent agarose matrix. The AgNPs were prepared by chemical reduction of Ag+ in the presence of sodium borohydride as the reducing agent and agarose as the stabilizing agent. Characterization of the nanoparticles was performed with UV/Vis spectrometry and scanning electron microscopy. A calibration curve was derived for the absorbance of the sensor at 410 nm, that was linear over a range from 1.5 to 120 µmol L-1 with an R2 value of 0.998 (n = 8). A detection limit of 0.69 µmol L-1 and a relative standard deviation of 3.8% were obtained for CN- for 8 replicates. A reproducibility of about 6.1% was also obtained for four batches of the sensor. The sensor showed excellent selectivity for CN- ion at the presence of a number of interfering ions with concentrations exceeding 50 times of that of the analyte. The results showed successful application of the AgNPs-agarose as a colorimetric sensor for easy and selective monitoring of CN- ion in aqueous solutions.

Comparison of Ultrasound-Assisted Headspace Solid-Phase Microextraction and Hydrodistillation for the Identification of Major Constituents in Two Species of Hypericum.

Ultrasound-assisted headspace solid-phase microextraction (UA-HS-SPME) and hydrodistillation (HD) methods, coupled to gas chromatography-mass spectrometry (GC-MS), were used for the extraction and analysis of volatile compounds from Hypericum perforatum and Hypericum scabrum collected from two different sites in Iran. In the UA-HS-SPME method, various experimental parameters such as the type of fiber coating, sonication time, extraction time, extraction temperature and desorption time were investigated. The highest extraction efficiency was achieved by a 100-µm polydimethylsiloxane (PDMS) fiber. Consequently, 36 compounds were identified in H. perforatum and H. scabrum samples, using the UA-HS-SPME-GC-MS method, of which 14 were the same in both species. On the other hand, 57 compounds of these species were identified by the HD-GC-MS method, of which 21 were the same. The predominant constituents identified using the UA-HS-SPME method in H. perforatum included ß-caryophyllene, α-pinene, γ-cadinene, α-selinene, germacrene-D, limonene and myrcene, and in H. scabrum were α-pinene, nonane, ß-pinene and limonene. The common constituents identified by the HD-GC-MS method for H. perforatum involved germacrene-D, limonene, ß-caryophyllene, α-pinene, ß-pinene and germacrene-B, and for H. scabrum were α-pinene, ß-pinene, germacrene-D, nonane, limonene and γ-cadinene. The results about the main constituents of the examined species correspond to the findings of other researchers. Additionally, comparing UA-HS-SPME-GC-MS and HD-GC-MS methods showed that the UA-HS-SPME-GC-MS method is much faster and simpler, and it requires much less sample size and lower temperature.

A novel dispersive liquid-liquid microextraction method based on solidification of floating organic drop for preconcentration of Pd(II) by graphite furnace atomic absorption spectrometry after complexation by a thienyl substituted 1,2-ethanediamine.

A novel dispersive liquid-liquid microextraction method based on solidification of floating organic drop (DLLME-SFO) was developed for the preconcentration of ultratrace amounts of palladium (Pd)(II) before its determination by electrothermal atomic absorption spectrometry. Diphenyl ether (m.p. 26°C) was used for the first time as a heavier than water organic solvent in the developed method. Pd was complexed by N,N'-bis(thiophen-2-ylmethylene)ethane-1,2-diamine to be extracted into the dispersed diphenyl ether phase using acetonitril as the disperser solvent. Upon cooling and centrifugation, the organic solvent was sedimented at the bottomn and the aqueous phase was easily decantated. Some factors influencing the extraction efficiency of Pd(II) and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent and salting out effect, were studied and optimized both with univariate and multivariate methods. Under the optimized conditions, the calibration graph exhibited linearity over a range of 10 - 120 µg L(-1). The enrichment factor was 83.3, the detection limit for Pd (3σ) was 47 ng L(-1) and the relative standard deviation was 3.2% (n = 10, 1 ng mL(-1)). The method was successfully applied to the determination of trace amounts of Pd(II) in water samples.

Rapid monitoring of carvacrol in plants and herbal medicines using matrix solid-phase dispersion and gas chromatography flame ionisation detector.

Matrix solid-phase dispersion (MSPD) method coupled with gas chromatography flame ionisation detector as a quick and easy extraction technique has been developed to extract carvacrol from plants and herbal medicines. Influence of important parameters on the MSPD method efficiency, such as the sorbent material, the ratio of sample to sorbent material, elution solvent and volume of the elution solvent has been evaluated and optimised. Carvacrol was successfully extracted by diatomaceous earth as sorbent with 350 µL of dichloromethane as elution solvent. The calibration curve showed good linearity (r(2) = 0.9965) and precision (RSD < 8.16%) in the concentration range of 0.5-100 µg mL(-1) for carvacrol. The limit of detection and limit of quantification were 0.1 and 0.5 µg mL(-1), respectively. The recoveries were in the range of 74.4-80.5% with relative standard deviation (RSD) values ranging from 8.4% to 9.8%. The reported MSPD extraction method revealed to be simpler and faster than conventional methods used to quantify carvacrol from plants and herbal medicines.

Rapid screening of oleuropein from olive leaves using matrix solid-phase dispersion and high-performance liquid chromatography.

Matrix solid-phase dispersion (MSPD) methodology as a quick and easy extraction method has been developed to extract oleuropein from Olea europaea leaves. This method has been compared with conventional maceration and Soxhlet extraction (SOXE) methods. Variables affecting MSPD, such as the sorbent material, the ratio of sample to sorbent material, elution solvent, and volume of the elution solvent, have been fully evaluated and optimized. Oleuropein was successfully extracted by silica sorbent with 350 microL of dichloromethane-methanol (70 + 30, v/v) as the elution solvent. The calibration curve showed good linearity (r2 = 0.9985) and precision (RSD <4.5%) in the concentration range of 0.5-100 microg/mL for oleuropein. The LOD and LOQ were 0.14 and 0.5 microg/mL, respectively. The recoveries were in the range of 88.0-94.0% with RSD values ranging from 6.0 to 9.8%. The extraction yields obtained by the MSPD method were comparable with those obtained by the maceration and SOXE methods. The reported MSPD extraction method was revealed to be eco-friendly, simpler, and faster than conventional methods used to quantify oleuropein in O. europaea leaves.

Cold column trapping-cloud point extraction coupled to high performance liquid chromatography for preconcentration and determination of curcumin in human urine.

A cold column trapping-cloud point extraction (CCT-CPE) method coupled to high performance liquid chromatography (HPLC) was developed for preconcentration and determination of curcumin in human urine. A nonionic surfactant, Triton X-100, was used as the extraction medium. In the proposed method, a low surfactant concentration of 0.4% v/v and a short heating time of only 2min at 70°C were sufficient for quantitative extraction of the analyte. For the separation of the extraction phase, the resulted cloudy solution was passed through a packed trapping column that was cooled to 0 °C. The temperature of the CCT column was then increased to 25°C and the surfactant rich phase was desorbed with 400µL ethanol to be directly injected into HPLC for the analysis. The effects of different variables such as pH, surfactant concentration, cloud point temperature and time were investigated and optimum conditions were established by a central composite design (response surface) method. A limit of detection of 0.066mgL(-1) curcumin and a linear range of 0.22-100mgL(-1) with a determination coefficient of 0.9998 were obtained for the method. The average recovery and relative standard deviation for six replicated analysis were 101.0% and 2.77%, respectively. The CCT-CPE technique was faster than a conventional CPE method requiring a lower concentration of the surfactant and lower temperatures with no need for the centrifugation. The proposed method was successfully applied to the analysis of curcumin in human urine samples.

Microextraction in a packed syringe for the analysis of olive biophenols in rat plasma using CMK-3 nanoporous sorbent.

A carbon-based nanoporous sorbent was first used for microextraction in a packed syringe (MEPS) before HPLC/UV analysis of some biophenols in rat plasma. A laboratory-made programmable apparatus was designed and used for automation of the extraction procedure. The MEPS syringe was packed with 2 mg of CMK-3 sorbent, between the barrel and the injection needle, and mounted on an apparatus for programming of the conditioning, sampling, washing, elution and cleaning steps. All steps of the microextraction procedure were carefully optimized on the system. For optimization of important factors, such as the number of adsorption and elution cycles, elution volume and pH, a multivariate central composite design method was used. The highest recoveries were obtained for 24 and 10 times of adsorption and elution cycles, respectively, using 100 µL of acetonitrile as the eluent and a sample pH of 2. Good results were obtained in terms of the precision (RSD 1.6, 2.5 and 2.3%) and detection limit (0.7, 4.7 and 0.25 µM) for caffeic acid, tyrsol and oleuropein, respectively. The method was simple, efficient and appropriate for sample clean up before analysis by HPLC, and was successfully applied to the determination of biophenols in the plasma of several rats that received an olive leaves extract either by a gavage or an intraperitoneal injection method. A positive correlation was found between the amount of olive extract's feeding of the rats and the level of their plasma biophenols.

One-step synthesis of agarose coated magnetic nanoparticles and their application in the solid phase extraction of Pd(II) using a new magnetic field agitation device.

A magnetic solid phase extraction method based on agarose coated magnetic nanoparticles)ACMNPs(coupled to a new magnetic field agitation (MFA) device was developed and investigated for the separation, preconcentration and determination of Pd(II) in aqueous solutions. For the first time, the formation of the nanoparticles and their encapsulation in agarose micro-flakes was conducted in a single step. For this purpose, preparation of the magnetic iron oxide nanoparticles was performed in an alkaline agarose solution. The sizes of Fe3O4 nanoparticles and agarose micro-flakes were 10-14 nm and 90-130 µm, respectively. The nanomagnetic agarose particles were functionalized by iminodiacetic acid and subjected to magnetic field agitation in the MFA device. The influence of different analytical parameters such as pH, ionic strength, type and volume of desorption solvent and amount of the adsorbent on the preconcentration of Pd(II) were investigated. Eight replicated analysis at the optimized conditions, resulted in a recovery of 94.1% with an RSD of 5.2% for Pd(II). The detection limit of the method (3σ) was 47 ng L(-1) for the analyte. The method was successfully applied to the determination of Pd(II) in natural water samples.

Synthesis and characterization of an azo dibenzoic acid Schiff base and its Ni(II), Pb(II), Zn(II) and Cd(II) complexes.

The new Schiff base 4,4'-(1E,1'E)-(3,3'-(1E,1'E)-(pyridine-2,6-diylbis(azan-1-yl-1-ylid ene))bis(methan-1-yl-1-ylidene)bis(4-hydroxy-3,1-phenylene))bis(diazene-2,1-diyl)dibenzoic acid (1) was prepared from the condensation reaction of 2,6-diaminopyridine with 4-((3-formyl-4-hydroxyphenyl)diazenyl)benzoic acid in methanol. The compound 1 is potentially an N, O multidentate chelating ligand which could form stable complexes with metal ions in 1:1 up to 1:3mol ratio of metal to ligand. The 1:1 complexes of Schiff base 1 with Ni(II), Pb(II), Zn(II) and Cd(II) have been synthesized by its condensation reaction with appropriate salts of metal ions. Structures of Schiff base (1) as well as its complexes with abovementioned metal ions were characterized by elemental analysis, mass, IR, UV-vis., (1)H and (13)С NMR spectroscopy.

Selective dispersive liquid-liquid microextraction and preconcentration of Ni(II) into a micro droplet followed by ETAAS determination using a yellow Schiff's base bisazanyl derivative.

A simple, rapid and sensitive method was developed for the selective separation and preconcentration of Ni(II) using dispersive liquid-liquid microextraction, by a yellow Schiff's base bisazanyl derivative, as a selective complexing agent. In this method, a mixture of 45 µL chloroform (extraction solvent) and 450 µL tetrahydrofuran (dispersive solvent) is rapidly injected by syringe into a 5 mL aqueous sample containing 3% (w/v) sodium chloride and an appropriate amount of the Schiff's base. As a result, a cloudy solution is formed by entire dispersion of the extraction solvent into the aqueous phase. After centrifuging for 5 min at 5000 rpm, the sedimented phase is directly injected into the electrothermal atomic absorption spectrometry for Ni(II) determination. Some important parameters, such as kind and volume of extraction and dispersive solvents, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor for the presented method is 138. The calibration curve was linear over a nickel concentration range of 10-50 ng mL(-1). The detection limit and relative standard deviation were 0.04 ng mL(-1) and 2.1%, respectively. The method was successfully applied to the extraction and determination of Ni(II) in different water samples.