Sono-assisted photocatalytic degradation of ciprofloxacin in aquatic media using g-C3N4/MOF-based nanocomposite under visible light irradiation.

This research study is centered on the sono-assisted photocatalytic degradation of a well-known antibiotic (ciprofloxacin; CIP) in aquatic media using a g-C3N4/NH2-UiO-66 (Zr) catalyst under visible light irradiation. Initially, the catalyst was prepared by a simple method, and its physiochemical features were thoroughly analyzed by XRD, FT-IR, FE-SEM, EDX, EDS-Dot-Mapping, and UV-Vis analytical techniques. After that, the impact of several influential factors affecting the performance of the applied sono-assisted photocatalytic process such as the initial concentration of CIP, solution pH, catalyst dosage, light intensity, and ultrasound power was fully assessed, and the optimal conditions were established. After 75 min of the sono-assisted photocatalytic treatment, the complete degradation of CIP (10 mg/L) was accomplished under the condition as follows: g-C3N4/NH2-UiO-66 (Zr), 0.6 g/L; pH, 5.0, and ultrasound power, light intensity 75 mw/cm2, 200 W/m2. Meanwhile, the photocatalytic degradation of CIP followed the pseudo-first-order kinetic model. In addition, the scavenger experiments demonstrated that OH˚ and O2°- radicals played a key role in the sono-assisted photocatalytic degradation process. It is also acknowledged that the applied catalyst was reused for five consecutive runs with a minor loss observed in its degradation efficiency. In a further experiment, a significant synergistic effect with regard to the degradation of CIP was observed once all three major parameters (visible light, ultrasound waves, and catalyst) were used in combination compared to each used alone. To sum up, it is thought that the integration of g-C3N4/MOF-based catalyst, ultrasound waves, and visible light irradiation could be potentially applied as a promising strategy for the degradation of various pharmaceuticals on account of high degradation performance, simple operation, excellent reusability, and eco-friendly approach.

A new MOF-based modified adsorbent for the efficient removal of Hg(ii) ions from aqueous media: isotherms and kinetics.

Herein, a new MOF-based modified adsorbent for the efficient removal of Hg(ii) ions from water media was successfully prepared. Initially, a MOF nanocomposite was synthesized and applied as an efficient adsorbent for the removal of the target heavy metal ion. Following the synthesis, the MOF-based modified adsorbent was identified and characterized by SEM, XRD and FT-IR analytical instruments. The impact of several key variables such as pH of aqueous solution, adsorbent dosage, contact time, and initial concentration of the analyte of interest on the adsorption efficiency was also investigated in detail. Under the optimal conditions established (pH, 3; dose of adsorbent, 0.4 g L-1; contact time, 40 min and the analyte's concentration of 1 mg L-1) the removal efficiency of 96.3% for Hg(ii) was obtained. The results of the studies on the isotherm and kinetics of adsorption revealed that the adsorption process of Hg(ii) matched with the Langmuir isotherm (R2 > 0.990) and the pseudo 2nd-order kinetic models (R2 > 0.998). Additionally, reuse of the applied adsorbent for five consecutive tests exhibited a small percentage of drop (about 8%) in the removal efficiency of the target ion. Finally, the results indicated that the MOF-based modified compound could be potentially applied as a highly efficacious adsorbent for the discharge of Hg(ii) from aquatic media.

Correction: Adsorptive removal of Hg2+ from environmental water samples using thioglycerol-intercalated magnetic layered double hydroxides.

Correction for 'Adsorptive removal of Hg2+ from environmental water samples using thioglycerol-intercalated magnetic layered double hydroxides' by Ali Esrafili et al., Anal. Methods, 2020, 12, 2279-2286, DOI: 10.1039/D0AY00448K.

Adsorptive removal of Hg2+ from environmental water samples using thioglycerol-intercalated magnetic layered double hydroxides.

Herein, the removal of Hg2+ from environmental water samples was carried out using a novel nanoadsorbent based on magnetite nanoparticles coated by a thioglycerol-intercalated layered double hydroxide. The prepared material was characterized using scanning electron microscopy equipped with an energy dispersive X-ray analyzer and Fourier transform infrared spectrometry. The effective parameters of the removal procedure were identified and optimized through the one-variable-at-a-time method. Under the optimal conditions, the removal characteristics of the synthesized adsorbent including selectivity, distribution coefficient, and loading capacity were calculated in the presence of some interfering ions. The removal efficiency of 94.98% together with the distribution coefficient of 5.00 × 105 mL g-1 and loading capacity of 480.69 mg g-1 showed the considerable capability of this novel adsorbent in the selective removal of Hg2+ from aqueous samples. To evaluate the performance of the synthesized adsorbent in the removal of Hg2+ from environmental water samples, the removal of the desired analyte was carried out using four different real samples. The removal procedures were conducted at the analyte concentration levels of 10.0 and 50.0 mg L-1 for each aqueous sample. The obtained results showed that the removal efficiency was in the range of 91.99-94.97%, which confirmed the high performance of the synthesized adsorbent in the removal of Hg2+ from real samples. Furthermore, the relative standard deviation of as low as 4.18-6.17% showed the acceptable repeatability of this method.

Carrier-mediated extraction: Applications in extraction and microextraction methods.

The present review is mainly focused on the overview of carrier mediated extraction (principles and applications) being reported over the last two decades and discusses the extraction process through carriers in various extraction methods such as Bulk liquid membranes, supported liquid membranes, emulsion liquid membranes and polymer inclusion membranes. Several types of carriers such as neutral, anionic, cationic, macrocyclic and supramulecular carriers are discussed. Also their application for metal, anions, drugs and environmental compounds are investigated. Carriers have been demonstrated to be useful for the selective extraction and recovery of numerous cations and anions enhancing the extraction properties of traditional solvent extraction and ion-exchange processes. Several types of carriers have different transport mechanisms. In these mechanisms, transport configurations are addressed and emphasized and the detailed information on the type of carrier are presented along with their specific separation modes. The performance of different carriers in terms of selectivity as well as efficiency are also discussed. Finally, the application of different carriers for the extraction of various compounds are compared and reviewed. To our best knowledge no reviews have been published on carrier-mediated extraction methods.

Spin-column micro-solid phase extraction of chlorophenols using MFU-4l metal-organic framework.

A novel metal-organic framework called MFU-4 l was synthesized from ZnCl2 and 1H-1,2,3-triazolo[4,5-b][4',5'-i])dibenzo[1,4]dioxin. MFU-4 l was characterized and is shown to be a viable sorbent for spin-column micro-solid phase extraction of 4-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. Following extraction and elution with methanol, the chlorophenols were quantified by a GC-MS instrument. Various parameters affecting adsorption and desorption were optimized by the one variable at-a-time method. The main feature of the utilized metal-organic framework is its outstanding performance in ultratrace extraction of the target analytes due to the different amino groups existed in the linker structure. Under optimal conditions, the calibration plots are linear in the 0.5-400 µg kg-1 concentration range for water samples, and from 1.0-400 µg kg-1 for soil samples. The respective limits of detection are 0.10 and 0.50 µg kg-1 for water and soil samples, respectively. On top of that, limits of detections are lower than 0.10 and 0.50 µg Kg-1 for water and soil samples, respectively. Inter-day and intra-day relative standard deviations were in the range of 4.4-7.8% for the selected chlorophenols. Preconcentration factors are in the range of 26.3-29.6 for aqueous samples. The method was used to analyze soil and environmental water samples. Graphical abstractSchematic representation of spin-column micro-solid phase extraction of chlorophenols using the MFU-4 l metal-organic framework.

Simultaneous extraction of 32 polychlorinated biphenyls by using magnetic carbon nanocomposite based dispersive microextraction, subsequent dispersive liquid-liquid microextraction with two miscible stripping solvents, and quantitation by GC-µECD.

A highly sensitive new method is described for performing dispersive microextractions. It is making use of a magnetic carbon nanocomposite and two miscible organic solvents. The method was applied to simultaneous extraction of 32 polychlorinated biphenyls (PCBs) prior to their quantitation by gas chromatography with electron capture detection. The effects of pH value of sample for both micro solid phase extraction and dispersive liquid-liquid microextraction, of the amount of sorbent, extraction time, type and volume of the miscible organic solvents and of salt addition were optimized. Figures of merit obtained under optimized conditions (sample solution: 500 ml, volume of disperser solvent, ACN, 1.5 mL; volume of extraction solvent, TCB, 30 µL; extraction time: 50 min, 20 mg magnetic sorbent, centrifuge, 5 min, 4000 rpm), include (a) preconcentration factors between 10,880 and 34,000; (b) repeatabilities of ≤14.9%, (c) detection limits between 0.01 and 0.2 ng kg-1, and (d) linear dynamic ranges from 0.05 to 100 ng kg - 1. The method was applied to the simultaneous analysis of residues in (spiked) real samples of fish, milk, packing sheet, and tap waters. Some of the analytes were found to be present in fish samples. The method is simple, rapid, and more sensitive than any of the previously reported ones. Graphical abstract Schematic presentation of simultaneous extraction of 32 polychlorinated biphenyls (PCBs) by using magnetic carbon nanocomposites (MCNs) based dispersive microextraction (M-SPE), subsequent dispersive liquid-liquid microextraction (DLLME) with two miscible stripping solvents, and quantitation by GC-µECD.

Dispersive solid-phase extraction of selected nitrophenols from environmental water samples using a zirconium-based amino-tagged metal-organic framework nanosorbent.

This study has centered on the establishment of an efficient, simple and reliable dispersive solid-phase extraction method followed by an accurate trace determination of selected nitrophenols as a class of compounds with high toxicity and low degradability. To achieve the above goal, a zirconium-based amino-tagged metal-organic framework nanosorbent was synthesized, characterized and eventually employed for the extraction of two nitrophenols from various environmental water samples. Once the extraction of analytes had occurred, they were desorbed from the metal-organic framework sorbent using an appropriate mixed solvent followed by high-performance liquid chromatography with ultraviolet detection. Under the optimal extraction conditions, the calibration curves for the analytes were linear over the concentration range of 1-200 µg/L. The accuracy of the method was tested by the relative recovery experiments on the fortified real samples with the results falling within the range of 91 to 106%, while the corresponding precisions varied in the span of 4.6-9.0%. Based on a signal-to-noise ratio of 3, the method detection limits were determined to be 0.5 µg/L for both analytes.

Application of a surfactant-assisted dispersive liquid-liquid microextraction method along with central composite design for micro-volume based spectrophotometric determination of low level of Cr(VI) ions in aquatic samples.

A fast, simple, low cost surfactant-assisted dispersive liquid-liquid microextraction method along with central composite design for the determination of low level of Cr(VI) ions in several aquatic samples has been developed. Initially, Cr(VI) ions present in the aqueous sample were readily reacted with 1,5­diphenylcarbazide (DPC) in acidic medium through complexation. Sodium dodecyl sulfate (SDS), as an anionic surfactant, was then employed as an ion-pair agent to convert the cationic complex into the neutral one. Following on, the whole aqueous phase underwent a dispersive liquid-liquid microextraction (DLLME) leading to the transfer of the neutral complex into the fine droplet of organic extraction phase. A micro-volume spectrophotometer was used to determine Cr(VI) concentrations. Under the optimized conditions predicted by the statistical design, the limit of quantification (LOQ) obtained was reported to be 5.0 µg/L, and the calibration curve was linear over the concentration range of 5-100 µg/L. Finally, the method was successfully implemented for the determination of low levels of Cr(VI) ions in various real aquatic samples and the accuracies fell within the range of 83-102%, while the precision varied in the span of 1.7-5.2%.

Trace quantification of selected sulfonamides in aqueous media by implementation of a new dispersive solid-phase extraction method using a nanomagnetic titanium dioxide graphene-based sorbent and HPLC-UV.

Herein, a new dispersive solid-phase extraction method using a nano magnetic titanium dioxide graphene-based sorbent in conjunction with high-performance liquid chromatography and ultraviolet detection was successfully developed. The method was proved to be simple, sensitive, and highly efficient for the trace quantification of sulfacetamide, sulfathiazole, sulfamethoxazole, and sulfadiazine in relatively large volume of aqueous media. Initially, the nano magnetic titanium dioxide graphene-based sorbent was successfully synthesized and subsequently characterized by scanning electron microscopy and X-ray diffraction. Then, the sorbent was used for the sorption and extraction of the selected sulfonamides mainly through π-π stacking hydrophobic interactions. Under the established conditions, the calibration curves were linear over the concentration range of 1-200 µg/L. The limit of quantification (precision of 20%, and accuracy of 80-120%) for the detection of each sulfonamide by the proposed method was 1.0 µg/L. To test the extraction efficiency, the method was applied to various fortified real water samples. The average relative recoveries obtained from the fortified samples varied between 90 and 108% with the relative standard deviations of 5.3-10.7%.

Application of dispersive solid phase extraction based on a surfactant-coated titanium-based nanomagnetic sorbent for preconcentration of bisphenol A in water samples.

Herein, a new extraction method employing a surfactant-coated titanium-based nanomagnetic sorbent for the effective extraction of bisphenol A (BPA) from various water samples was developed. Initially, the titanium-based nanomagnetic particles (Fe3O4/SiO2/TiO2 NPs) were successfully synthesized and subsequently characterized by Transmission Electron Microscopy and Fourier-transform infrared spectrometry. Two cationic surfactants were then incorporated into the particles to form a new sorbent for enhancing the extraction of BPA through micelle formation. Once the analyte was extracted, it was desorbed from the sorbent and quantified by high performance liquid chromatography with ultra violet detection (HPLC-UV). Various factors affecting the extraction and desorption of the analyte were investigated in detail and the optimum conditions established. Under these established conditions, the calibration curve was linear over the concentration range of 1-500ng/mL. The limit of detection was determined to be 0.5ng/mL based on a signal-to-noise ratio (S/N)=3. To test the extraction efficiency, the method was applied to various real water samples that were spiked. The average recoveries obtained from the spiked samples ranged between 92-105% with relative standard deviations of 3.2-7.8%. Finally, the approach was determined to be effective for BPA environmental analysis.

Application of a dispersive solid-phase extraction method using an amino-based silica-coated nanomagnetic sorbent for the trace quantification of chlorophenoxyacetic acids in water samples.

Herein, an amino-based silica-coated nanomagnetic sorbent was applied for the effective extraction of two chlorophenoxyacetic acids (2-methyl-4-chlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid) from various water samples. The sorbent was successfully synthesized and subsequently characterized by scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The analytes were extracted by the sorbent mainly through ionic interactions. Once the extraction of analytes was completed, they were desorbed from the sorbent and detected by high-performance liquid chromatography with ultraviolet detection. A number of factors affecting the extraction and desorption of the analytes were investigated in detail and the optimum conditions were established. Under the optimum conditions, the calibration curves were linear over the concentration range of 1-250, and based on a signal-to-noise ratio of 3, the method detection limits were determined to be 0.5 µg/L for both analytes. Additionally, a preconcentration factor of 314 was achieved for the analytes. The average relative recoveries obtained from the fortified water samples varied in the range of 91-108% with relative standard deviations of 2.9-8.3%. Finally, the method was determined to be robust and effective for environmental water analysis.

Application of modified hollow fiber liquid phase microextraction in conjunction with chromatography-electron capture detection for quantification of acrylamide in waste water samples at ultra-trace levels.

Herein, a simple and sensitive method was successfully developed for the extraction and quantification of acrylamide in water samples. Initially, acrylamide was derivatized through a bromination process. Subsequently, a modified hollow-fiber liquid-phase microextraction was applied for the extraction of the brominated acrylamide from a 10-ml portion of an aqueous sample. Briefly, in this method, the derivatized acrylamide (2,3-dibromopropionamide) was extracted from the aqueous sample into a thin layer of an organic solvent sustained in pores of a porous hollow fiber. Then, it was back-extracted using a small volume of organic acceptor solution (acetonitril, 25µl) located inside the lumen of the hollow fiber followed by gas chromatography-electron capture detection (GC-ECD). The optimal conditions were examined for the extraction of the analyte such as: the organic solvent: dihexyl ether+10% tri-n-octyl phosphine oxide; stirring rate: 750rpm; no salt addition and 30min extraction time. These optimal extraction conditions allowed excellent enrichment factor values for the method. Enrichment factor, detection limit (S/N=3) and dynamic linear range of 60, 2ngL-1 and 50-1000ngL-1 to be determined for the analyte. The relative standard deviations (RSD%) representing precision of the method were in the range of 2.2-5.8 based on the average of three measurements. Accuracy of the method was tested by the relative recovery experiments on spiked samples, with results ranging from 93 to 108%. Finally, the method proved to be simple, rapid, and cost-effective for routine screen of acrylamide-contaminated highly-complicated untreated waste water samples.

Combination of hollow fiber liquid phase microextraction followed by HPLC-DAD and multivariate curve resolution to determine antibacterial residues in foods of animal origin.

In the present research, a carrier mediated hollow fiber based liquid-phase microextraction approach (HF-LPME) prior to high performance liquid chromatography-diode array detection (HPLC-DAD) was developed for the simultaneous determination of the antibacterial residues of four tetracyclines (TCs) and five quinolones (QNs), which are commonly used as veterinary medicines. In order to obtain high extraction efficiency, the parameters affecting HF-LPME were optimized using a three-factor and three-level Box-Behnken design under response surface methodology. This method was validated according to the recommendations of the Food and Drug Administration (FDA), and, for the first time, successfully applied to a wide range of animal source food samples such as fish, milk, and honey as well as the liver and muscles of lamb and chicken. Analytical performance was determined in terms of linearity, intra- and inter-assay precision, detection and quantification limits, matrix effect, accuracy, and drug stability in real samples. Detection and quantitation limits for the different antibiotics ranged between 0.5-20ngg(-1) and 1.25-40ngg(-1), respectively. Intra and inter-day repeatability, expressed as the relative standard deviation, were in the ranges of 3.4-10.7% and 5.0-11.5%, respectively. The procedure allows good preconcentration factors of 175-700. The results of the validation process proved that the method is suitable for determining TCs and QNs residues in surveillance programs. Finally, the applicability of the proposed method was successfully confirmed by the extraction and determination of nine antibiotics in various animal source food samples. The importance of this methodology relies on the combination of HF-LPME/HPLC-DAD second-order data with multivariate curve resolution-alternative least squares (MCR-ALS) algorithm, which improves the resolution of some overlapped chromatograms and, hence, increases the accuracy and repeatability of drug determination.

Combination of solid-phase extraction with dispersive liquid-liquid microextraction followed by GC-MS for determination of pesticide residues from water, milk, honey and fruit juice.

In this work, an effective preconcentration method for the extraction and determination of traces of multi-residue pesticides was developed using solid-phase extraction (SPE) coupled with dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry (GC-MS). Variables affecting the performance of both extraction steps such as type and volume of elution and extraction solvents, breakthrough volume, salt addition, extraction time were thoroughly investigated. The proposed method resulted in good linearities (R(2)>0.9915) over the ranges of 1-10,000ngkg(-1), limits of detection (LODs) in the range of 0.5-1.0ngkg(-1) at S/N=3, and precision of RSD% of ⩽11.8. Under optimal conditions, the preconcentration factors were obtained in the range of 2362-10,593 for 100mL sample solutions. Comparison of the proposed method with other ones demonstrated that SPE-DLLME method provides higher extraction efficiency and larger preconcentration factor for determination of pesticides residues. Further, it is simple, inexpensive, highly sensitive, and can be successfully applied to separation, preconcentration and determination of the pesticides (and other noxious materials) in different real food 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.

Three-phase hollow fiber microextraction based on two immiscible organic solvents for determination of tricyclic antidepressant drugs: comparison with conventional three-phase hollow fiber microextraction.

The aim of this research was to compare the extraction efficiencies of two modes of three-phase hollow fiber microextraction (HF-LLLME) based on aqueous and organic acceptor phases for analysis of tricyclic antidepressant (TCA) drugs. High-performance liquid chromatography with photodiode array detection (HPLC-DAD) was applied for determination of the drugs. In order to examine the ability of the new concept of HF-LLLME based on organic acceptor solvent in comparison with aqueous acceptor phase to extract the analytes, four TCAs were selected. The effect of different extraction conditions (i.e., type of acceptor phase, hollow fiber length, ionic strength, stirring rate, and extraction time) on the extraction efficiency of the TCAs was investigated and optimized using central composite design (CCD) as a powerful tool. Both methods were characterized by good linearity and high repeatability, but HF-LLLME with organic acceptor provided higher extraction efficiency and thus lower limits of detection (LODs). Calibration curves were linear (r(2)>0.996) in the range of 0.2-200 µgL(-1). LODs for all the TCAs ranged from 0.08 to 0.2 µgL(-1) using HPLC-DAD. Also an improvement in sensitivity of several orders of magnitude was achieved using single-ion monitoring GC-MS analyses (0.04 µgL(-1)) due to compatibility of this technique with GC instrument. The applicability of the proposed HF-LLLME/GC-MS and HPLC-DAD methods was demonstrated by analyzing the drugs in spiked urine and plasma samples. The obtained recoveries of the drugs in the range of 87.9-109.2% indicated the excellent capability of the developed method for extraction of TCAs from complex matrices.

Three-phase hollow fiber liquid-phase microextraction based on two immiscible organic solvents for determination of tramadol in urine and plasma samples.

Recently, the new concept of three-phase liquid microextraction was introduced based on applying two immiscible organic solvents in lumen and wall pores of hollow fiber. In the present work, this novel microextraction technique combined with gas chromatography-mass spectrometry has been developed for determination of tramadol, an analgesic agent, in plasma and urine samples. A systematic investigation of the proposed method was applied to find optimal extraction conditions and evaluate the interaction effects between the factors by designing experiments according to the methodology of Box-Behnken response surface design. Analysis of variance (ANOVA) revealed that the important factors contributing to extraction efficiency are extraction time, stirring rate and hollow fiber length. Under the optimum conditions, the developed method provided a preconcentration factor of 546, good repeatability (RSD %=6.4), and good linearity (r(2)=0.995) for spiked plasma and urine real samples. The linear dynamic range from 0.1 to 400 µg L(-1) and limit of detection (LOD) of 0.08 µg L(-1) were obtained under selected ion monitoring mode. The results demonstrated that three-phase hollow fiber microextraction based on two immiscible solvents is a simple and accurate technique with very good preconcentration factor and clean-up for extraction of tramadol from biological samples.

A new strategy to simultaneous microextraction of acidic and basic compounds.

The simultaneous extraction of acidic and basic pollutants from water samples is an interesting and debatable work in sample preparation techniques. A novel and efficient method named ion pair based surfactant assisted microextraction (IP-SAME) was applied for extraction and preconcentration of five selected acidic and basic aromatic species as model compounds in water samples, followed by high performance liquid chromatography-ultraviolet detection. A mixture including 1 mL of ultra-pure water (containing ionic surfactant as emulsifier agent) and 60 µL 1-octanol (as extraction solvent) was rapidly injected using a syringe into a 10.0 mL water sample which formed an emulsified solution. IP-SAME mechanism can be interpreted by two types of molecular mass transfer into the organic solvent (partitioning and ion pairing for non-ionized and ionized compounds, respectively) during emulsification process. The effective parameters on the extraction efficiency such as the extraction solvent type and its volume, type of the surfactant and its concentration, sample pH and ionic strength of the sample were optimized. Under the optimum conditions (60 µL of 1-octanol; 1.5 mmol L(-1) cethyltrimethyl ammonium bromide (CTAB) as emulsifier agent and sample pH 10.0), the preconcentration factors (PFs), detection limits and linear dynamic ranges (LDRs) were obtained in the range of 87-348, 0.07-0.6 µg L(-1) and 0.1-200 µg L(-1) respectively. All of natural water samples were successfully analyzed by the proposed method.

A novel approach to automation of dynamic hollow fiber liquid-phase microextraction.

An automated dynamic two-phase hollow fiber microextraction apparatus combined with high-performance liquid chromatography was developed for extraction and determination of chlorophenoxy acid (CPA) herbicides from environmental samples. The extraction device, called TT-extractor, consists of a polypropylene hollow fiber mounted inside a stainless steel tube by means of two tee-connectors in flow system. An organic solvent, which fills the lumen and the pores of the hydrophobic fiber, is pumped through the fiber repeatedly and the sample is pumped along the outer side of the fiber. The factors affecting the dynamic hollow fiber liquid-phase microextraction (DHF-LPME) of target analytes were investigated and the optimal extraction conditions were established. To test the applicability of the designed instrument, CPAs were extracted from environmental aqueous samples. The limits of detection (LODs) as low as 0.5 µg/L, linear dynamic range in the range of 1-100 µg/L and the relative standard deviations of <7% were obtained. The developed method can provide perconcentration factors as large as 230. A hollow fiber membrane can be used at least 20 times with neither loss in the efficiency nor carryover of the analytes between runs. The system is cheap and convenient and requires minimal manual handling.