Covalent organic framework and montomorillonite nanocomposite as advanced adsorbent: synthesis, characterization, and application in simultaneous adsorption of cationic and anionic dyes.

In this work, Schiff base network-1 (SNW-1), as a new generation of covalent organic frameworks (COFs), was synthesized and modified by fabrication of a composite with clay mineral montomorillonite (Mt). It was used for simultaneous removal of anionic and cationic dyes from aqueous solutions. The fabricated composite was characterized successfully with various techniques. Tartrazine (TT) and methylene blue (MB) were selected as model anionic and cationic dyes, respectively. The effects of the percentage of each component in the composite, initial pH, and initial dye concentration were evaluated on the adsorption capacity. Adsorption reaction models and adsorption diffusion models were used to study the kinetic process of adsorption. Adsorption of both dyes reached equilibrium after 40 min. The obtained results were fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) models to predict the isotherms of adsorption. Under optimum conditions for removal of each dye with the composite, the maximum adsorption capacity of 519.2 and 602.7 mg g-1 were obtained for TT and MB, respectively. The used SNW-1/Mt composite could be regenerated by salty methanol. The high adsorption capacity and excellent reusability make SNW-1/Mt composite attractive for the simultaneous removal of anionic and cationic dyes from aqueous solutions.

Developing a novel packed in-tube solid-phase extraction method for determination ∆ 9-tetrahydrocannabinol in biological samples and cannabis leaves.

A novel plate-like nano-sorbent based on copper/cobalt/chromium layered double hydroxide was synthesized by a simple coprecipitation method. The synthesized nanoparticels were introduced into a stainless steel cartridge using a dry packing method. Then, the packed cartridge was introduced as a novel on-line "packed in-tube" configuration and followed by high performance liquid chromatography for the determination of trace amounts of ∆ 9-tetrahydrocannabinol from biological samples and cannabis leaves. The as-prepared sorbent exhibited long lifetime, good chemical stability, and high anion-exchange capacity. Several important factors affecting the extraction efficiency, such as extraction and desorption times, pH of the sample solution and flow rates of the sample and eluent solutions, were investigated and optimized. Under optimized conditions, this method showed good linearity for ∆ 9-tetrahydrocannabinol in the ranges of 0.09-500, 0.3-500, and 0.4-500 µg/L with coefficients of determination of 0.9999, 0.9991, and 0.9994 in water, serum and plasma samples, respectively. The inter- and intra-assay precisions (n = 3) were respectively in the ranges of 1.8-4.6% and 1.9-4.0% at three concentration levels of 10, 50, and 100 µg/L. The limits of detection were also in the range of 0.02-0.1 µg/L.

Chitosan-based sorbent for efficient removal and extraction of ciprofloxacin and norfloxacin from aqueous solutions.

Nanosheets prepared from magnesium oxide, chitosan and graphene oxide (MgO/Chit/GO) were hydrothermally synthesized and used as a sorbent for removal of ciprofloxacin and norfloxacin from aqueous solutions. Residual antibiotics in sample were determined by HPLC/UV instrument. The sorbent was characterized by FTIR, XRD, BET, SEM, and TEM. Its high adsorption capacity is attributed to the high surface area (294 m2.g-1) as compared to bare MgO/chit or bare GO. The pore size of the mesoporous sorbent typically is 15 Å. The adsorption isotherms for the two model antibiotics studied (norfloxacin, ciprofloxacin) can be described with the Langmuir model, and the maximum adsorption capacities are 1111 and 1000 mg.g-1 for ciprofloxacin and norfloxacin, respectively. The analysis of the kinetic data revealed that the synthesized sorbent followed pseudo-second-order kinetics and the maximum equilibrium was at over 120 and 150 min for ciprofloxacin and norfloxacin, respectively. Therefore, it is introduced as an economical, eco- friendly, and high-performance sorbent for removal of antibiotics from aqueous solutions. Graphical abstract Schematic presentation of dispersion of magnesium oxide/chitosan/graphene oxide (MgO/chit/GO) nanosheets in waste water for removal of ciprofloxacin and norfloxacin as water pollutants.

Synthesis and characterization of a novel biocompatible pseudo-hexagonal NaCa-layered double metal hydroxides for smart pH-responsive drug release of dacarbazine and enhanced anticancer activity in malignant melanoma.

Layered metal hydroxides have exhibited remarkable benefits in drug delivery, days or even weeks of continuous drug release with improved bioavailability and minimized adverse effects. Here, we report synthesis of a new M+ (Na+) and M2+ (Ca2+) layered double metal hydroxide-based phases with the general formula of [Na0.2Ca0.8(OH)1.4] (NO3)0.4, and 3D pseudo-hexagonal morphology. NaCa layered double metal hydroxide (NaCa-LDH), which is biodegradable, biocompatible, and pH-sensitive, could have broad applicability in drug release and other biomedical applications. Dacarbazine (DAC) is one of the most commonly used chemotherapy drugs for treating various cancers. However, its poor water solubility, short half-life in blood circulation, low response rate and high side effects limit its application. This study aimed to increase its half-life and anticancer activity; minimize its side effects; and prolong its drug release by intercalating of DAC in biodegradable NaCa-LDH (DAC-LDH). Results from the intercalation process show that NaCa-LDH is able to intercalate DAC with a simple procedure and with a good drug loading (38% w/w) through a one pot reaction. The DAC shows a sustained and pH-sensitive release, and the release rate of DAC from DAC-LDH at pH 7.4 is remarkably lower than that at pH 6.0 due to its different release mechanisms. In the latter case, the release was not complete at 24 h. We show that DAC-LDH anticancer efficacy on malignant (A-375) melanoma and breast cancer (MCF-7) cell lines is higher than that of free DAC. These nanoparticles may open a significant way toward the development of a pH-sensitive drug release system that minimizes drug side effect for a wide range of applications.

A metal organic framework prepared from benzene-1,3,5-tricarboxylic acid and copper(II), and functionalized with various polysulfides as a sorbent for selective sorption of trace amounts of heavy metal ions.

Novel composites were obtained via direct assembly of polysulfides (Sx2-, X = 3, 4, 6) on the surface of a metal organic framework (MOF; type benzene-1,3,5-tricarboxylic/Cu(II). They are referred to as Sx-MOFs and were used for highly selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions. The structure of the Sx-MOFs was characterized by Raman spectroscopy, FT-IR, X-ray diffraction, and scanning electron microscopy. The Raman spectra of Sx-MOF is similar to the bare MOF and shows the MOFs structure to be well retained after Sx functionalization. The selective interaction of Sx with soft metal ions and the high surface area of MOFs resulted in excellent affinity and selectivity for ions such as Hg(II). The Sx-MOFs of type S4-MOF had the highest distribution coefficient Kd value (~107) and best extraction recovery (~100%) for Hg(II). The S4-MOF also has high selectivity in the following order: Hg(II) > > Pb(II) > Zn(II) > Ni(II) > Co(II). The binding process of the metals occurs via M-S bonding. The ions were quantified by inductively coupled plasma optical emission spectrometry (ICP-OES). The detection limit for Hg(II) is 0.13 µg L-1. The S4-MOF was applied to the extraction of trace metal ions from natural and contaminated waters and data were compared with other sorbets. The results revealed that S4-MOF is an excellent adsorbent for sorption of heavy metal ions even in the presence of the relatively high concentration of other ions. Graphical abstract A composite was synthesized via direct assembly of polysulfides (Sx2-, X = 3, 4, 6) on surface of the metal organic framework (Sx-MOF) and was used for selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions.

One-step synthesis of Fe3PtPd(OH)2[Picolinic acid]8(H2O)4 hybrid nanorods: efficient and stable electrocatalyst for oxygen reduction reaction in alkaline solution.

Design and synthesis of effective electrocatalysts for oxygen reduction reaction in alkaline environments is critical to reduce energy losses in alkaline fuel cells. We have systematically evaluated new approaches for reducing the Pt content while retaining the activity of a Pt-based catalyst with hydrolytic phases containing hydroxide moieties in addition to metal ions and ligands. We report for the first time architectured organic-inorganic hybrid nanorod catalyst, which is fabricated by solvothermal reaction of K2MCl4 (M = Pd, Pt) with picolinic acid (PA) (chelating agent) in the presence of FeCl2. Excess base produces isostructural coordination M-PA complex to Fe-OH chains. A generic formula can be written as Fe3PtPd(OH)2[PA]8(H2O)4. The electrocatalytic activities of the hybrid nanorods are explored for oxygen reduction reaction (ORR) in alkaline medium. The onset potential of ORR is significantly reduced with a positive shift of about 109 mV and twice the reduction current density is observed in comparison with Pt/C with the same mass loading. We believe that this work may lead towards the development of heterodoped organic- inorganic hybrid materials with greatly enhanced activity and durability for applications in catalysis and energy conversion.

Electrochemically controlled fiber-in-tube solid-phase microextraction method for the determination of trace amounts of antipsychotic drugs in biological samples.

In this study, a novel 'fiber-in-tube' configuration was applied to electrochemically controlled fiber-in-tube solid-phase microextraction of antipsychotic drugs (perphenazine and chlorpromazine) from biological samples. To prepare an electrochemically controlled fiber-in-tube solid-phase microextraction column, first eight stainless-steel wires were placed into the stainless-steel column. Then, a nanostructured Cu-Cr-Al ternary layered double hydroxide/polythiophene coating was prepared on the inner surface of the stainless-steel tube and on the surfaces of the stainless-steel wires by a facile in situ electrodeposition method. The nanostructured coating exhibited enhanced long lifetime, good mechanical stability, high porosity, and large specific surface area compared with polythiophene and Cu-Cr-Al layered double hydroxide coatings. Under the optimal conditions, the limits of detection were in the range of 0.07-0.8 µg/L. This method showed good linearity for perphenazine and chlorpromazine in the ranges of 0.3-300 and 0.2-300 µg/L, respectively, with coefficients of determination more than 0.9982. The inter- and intra-assay precisions (RSD%, n = 3) were in the ranges of 3.0-5.1 and 2.5-4.5% at three concentration levels of 5, 25 and 50 µg/L, respectively. Finally, the method was applied for the analysis of the drugs in human urine and plasma samples.

Evaluation of highly efficient on-line yarn-in-tube solid phase extraction method for ultra-trace determination of chlorophenols in honey samples.

In this study a novel "yarn-in-tube" configuration was introduced by packing cotton yarn inside stainless steel cartridge named packed yarn-in-tube solid phase extraction (yarn-IT-SPE) followed by high performance liquid chromatography. For the first time, cotton yarns were coated with a new polypyrrole@copper-chromium-iron ternary layered double hydroxide nanocomposite (Yarn@PPy@Cu-Cr-Fe LDH). The yarn@PPy@Cu-Cr-Fe LDH sorbent exhibited flexible substrate, high porosity, a three-dimensional, high sorbent loading, long lifetime, good mechanical stability, high anion-exchange capacity and large specific surface area as a result it is a good choice for the separation and preconcentration of acidic cholorophenols in honey samples. Several important factors affecting extraction efficiency such as extraction and desorption times, pH of solution and flow rates of the sample solution and eluent were investigated and optimized. Under the optimal conditions, the limits of detection were in the range of 0.05-0.07 µg L-1. This method showed good linearity for chlorophenols in the range of 0.10-500 µg L-1, with coefficients of determination better than 0.9989. The inter- and intra-assay precisions (RSD%, n = 5) were in the range of 3.2-4.9% and 2.1-3.6% at three concentration levels of 2, 10 and 20 µg L-1, respectively. The validated method was successfully applied for analysis of 4-chloro-, 2,4-dichloro-, and 2,4,6-trichloro phenols in honey samples.

Functionalized layered double hydroxide with nitrogen and sulfur co-decorated carbondots for highly selective and efficient removal of soft Hg2+ and Ag+ ions.

A facile composite was fabricated via direct assembly of nitrogen and sulfur co-decorated carbon dots with abundant oxygen-containing functional groups on the surface of the positively charged layered double hydroxide (N,S-CDs-LDH). The novel N,S-CDs-LDH demonstrates highly selective bindings (M-S) and an extremely efficient removal capacity for soft metal ions such as Ag+ and Hg2+ ions. N,S-CDs-LDH displayed a selectivity order of Ag+> Hg2+ >> Cu2+ >>> Pb2+ > Zn2+ > Cd2+ for their adsorption. The enormous capacities for Hg2+ (625.0 mg g-1) and Ag+ (714.3 mg g-1) and very high distribution coefficients (Kd) of 9.9 × 106 mL g-1 (C0 = 20 mg L-1) and 2.0 × 107 mL g-1 (C0 = 20 mg L-1) for Hg2+ and Ag+, respectively, place the N,S-CDs-LDH at the top of LDH based materials known for such removal. The adsorption kinetic curves for Hg2+ and Ag+ fitted well with the pseudo-second order model. For Hg2+ and Ag+, an exceptionally rapid capture with removal ∼100% within 80 min was observed (Cions = 30 mg L-1 and V/m ratio of 1000). The adsorption isotherms were well described using Langmuir isotherm. The N,S-CDs-LDH was successfully applied to highly efficient removal of Hg2+ and Ag+ from aqueous solutions.

Fabrication of zwitterionic histidine/layered double hydroxide hybrid nanosheets for highly efficient and fast removal of anionic dyes.

In this work, the bio-nanohybrids of magnesium-aluminum layered double hydroxide intercalated with zwitterionic histidine (His-LDH) was synthesized. The crystal phase, morphology, and nanostructure of the as-prepared His-LDH were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption-desorption methods. The His-LDHs were used to remove anionic dyes, including Congo red (CR), indigo carmine (IC) and sunset yellow FCF (SY) from aqueous solutions. The detailed investigation of the kinetics and the adsorption isotherms of CR, IC and SY from aqueous solutions showed that the dyes adsorb rapidly, in accordance with a pseudo-second-order kinetics and a Freundlich adsorption isotherm model. The remarkably high adsorption capacity of the dyes on the His-LDH (efficiency of CR removal, 99.98%; maximum specific removal qmax, 1112 mg g-1; efficiency of IC removal, 98.98%; qmax, 625 mg g-1; and efficiency of SY removal, 99.78%; qmax, 400 mg g-1) is rationalized on the basis of electrostatic interactions as well as π-π and H-bonding interactions between the His-LDH adsorbent and the acidic dyes. Adsorption experiments indicate that the resulting His-LDH has great potential applications as an environmentally friendly material for the swift removal of acidic dyes from aqueous solutions.

Development of electrochemically controlled packed-in-tube solid phase microextraction method for sensitive analysis of acidic drugs in biological samples.

In the present research, for the first time, a novel "packed-in-tube" configuration has been applied to electrochemically controlled in-tube solid phase microextraction, followed by high performance liquid chromatography. In order to prepare a mini packed column, small beads of stainless steel were first placed into the stainless steel column. Then, a nanostructured polypyrrole film was prepared on the internal surface of a stainless steel tube and the surface of stainless steel particles through a facile in-situ electrodeposition method. Filling the column with tiny particles of stainless steel effectively reduces the dead volume of the extraction tube and increases the extraction phase volume. The column was used for separation and preconcentration of diclofenac and mefenamic acid as model analytes from biological samples. Several important factors affecting extraction efficiency, such as extraction and desorption times, flow rates of the sample solution and eluent, and extraction and desorption voltages were investigated and optimized. This method showed good linearity for the drugs in the range of 0.3-200.0 µg L-1, 1.1-200.0 µg L-1, and 1.8-200.0 µg L-1 with coefficients of determination better than 0.9986, 0.9973, and 0.9973 in water, urine, and plasma samples, respectively. Intra- and inter-assay precisions (RSD%, n = 3) were in the range of 2.6-4.8% and 2.9-5.1, respectively, at three concentration levels of 10, 25, and 75 µg L-1. In addition, the limits of detection were in the range of 0.02-0.04 µg L-1. The validated method was successfully applied to the analysis of diclofenac and mefenamic acid in some biological samples. Finally, it is concluded that this method can be a general and reliable alternative to the analysis of ionic compounds in biological matrices.

Multiwall carbon nanotube- zirconium oxide nanocomposite hollow fiber solid phase microextraction for determination of polyaromatic hydrocarbons in water, coffee and tea samples.

The purpose of this study was to evaluate the application of hollow fiber solid-phase microextraction (HF-SPME) followed by HPLC-UV to determine the ultra-trace amounts of polycyclic aromatic hydrocarbons (PAHs) as model analytes in complex coffee and tea samples. HF-SPME can be effectively used as an alternative to the direct immersion SPME (DI-SPME) method in complex matrices. The DI-SPME method suffers from serious limitation in dirty and complicated matrices with low sample clean-up, while the HF-SPME method has high clean-up and selectivity due to the high porosity of hollow fiber that can pick out analyte from complicated matrices. As a hollow fiber sorbent, a novel multiwall carbon nanotube/zirconium oxide nanocomposite (MWCNT/ZrO2) was fabricated. The excellent adsorption of PAHs on the sorbent was attributed to the dominant roles of π-π stacking interaction and hydrophobic interaction. Under the optimized extraction conditions, the wide linear range of 0.1-200 µg L-1 with coefficients of determination better than 0.998 and low detection limits of 0.033-0.16 µg L-1 with satisfactory precision (RSD < 6.6%) were obtained. The relative recoveries obtained by spiking the PAHs in water, coffee and tea samples were in the range of 92.0-106.0%. Compared to other methods, MWCNT/ZrO2 hollow fiber solid phase microextraction demonstrated a good capability for determination of PAHs in complex coffee and tea samples.

A nanocomposite prepared from a polypyrrole deep eutectic solvent and coated onto the inner surface of a steel capillary for electrochemically controlled microextraction of acidic drugs such as losartan.

The authors describe a new coating for use in electrochemically controlled in-tube solid phase microextraction (EC-IT-SPME). It consists of a nanocomposite that was prepared from polypyrrole and deep eutectic solvent (DES) by electrochemical deposition on the inner walls of a stainless steel capillary that serves as a working electrode. The hypertension drug losartan acts as an acidic model analyte. The extraction efficiency, mechanical stability, chemical stability and lifetime of the coating were investigated. It is found to be quite stable in relatively acidic and basic media and to be re-usable >450 times without decrease in extraction efficiency. Its extraction capability in comparison to the commercial polypyrrole coating is better by a factor of 1.5. The coated steel capillary was used as the anode (anion-exchanger), and a platinum electrode was used as the cathode. By passing a sample solution through the electrode, losartan can be extracted by applying a positive potential to the flow. In the next step, losartan is electrochemically desorbed and subjected to HPLC analysis with UV detection. Under optimal conditions, losartan can be quantified with limits of detection that range from 50 to 500 ng L-1 depending on the sample matrix. Response is linear in the 0.1-500 µg L-1 concentration range. The inter- and intra-assay precisions (RSDs; in %, for n = 3) are in the range from 2.4-4.6% and from 1.9-3.9%, respectively. Graphical abstract Schematic of the preparation of a nano-structured polypyrrole-deep eutectic solvent nanocomposite coating placed on the inner surface of a stainless steel capillary and used for electrochemically controlled in-tube solid phase microextraction of losartan from biological samples.

On-line packed magnetic in-tube solid phase microextraction of acidic drugs such as naproxen and indomethacin by using Fe3O4@SiO2@layered double hydroxide nanoparticles with high anion exchange capacity.

The authors describe a 3-component nanoparticle system composed of a silica-coated magnetite (Fe3O4) core and a layered double (Cu-Cr) hydroxide nanoplatelet shell. The sorbent has a high anion exchange capacity for extraction anionic species. A simple online system, referred to as "on-line packed magnetic-in-tube solid phase microextraction" was designed. The nanoparticles were placed in a stainless steel cartridge via dry packing. The cartridge was then applied to the preconcentration acidic drugs including naproxen and indomethacin from urine and plasma. Extraction and desorption times, pH values of the sample solution and flow rates of sample solution and eluent were optimized. Analytes were then quantified by HPLC with UV detection. Under optimal conditions, the limits of detection range from 70 to 800 ng L-1, with linear responses from 0.1-500 µg L-1 (water samples), 0.6-500 µg L-1 (spiked urine), and 0.9-500 µg L-1 (spiked plasma). The inter- and intra-assay precisions (RSDs, for n = 5) are in the range of 2.2-5.4%, 2.8-4.9%, and 2.0-5.2% at concentration levels of 5, 25 and 50 µg L-1, respectively. The method was applied to the analysis of the drugs in spiked human urine and plasma, and good results were achieved. Graphical abstract Fe3O4@SiO2@CuCr-LDH magnetic nanoparticles were synthesized and packed in to a stainless steel column. The column was applied to solid phase microextraction of acidic drugs from biological samples.

Highly selective and efficient removal of arsenic(V), chromium(VI) and selenium(VI) oxyanions by layered double hydroxide intercalated with zwitterionic glycine.

In this study, a new strategy for highly selective and extremely efficient removal of toxic oxyanions (Cr(VI), Se(VI), and As(V)) from aqueous solutions using zwitterionic glycine intercalated layered double hydroxide (Gly-LDH) was reported. Hence, to investigate the effect of zwitterionic glycine on the adsorption capacity, selectivity factor and adsorption mechanism of LDHs, two NiAl LDHs intercalated with different inter-layer anions, including NO3- and glycine, were synthesized. The obtained results show that the adsorption capacity and selectivity factor of oxyanions through ion exchange mechanism in NO3-LDH is lower than Gly-LDH. Gly-LDH displayed a selectivity order of Se(VI)

Polythiophene/graphene oxide nanostructured electrodeposited coating for on-line electrochemically controlled in-tube solid-phase microextraction.

In this work, a novel polythiophene/graphene oxide (PTh/GO) nanostructured coating was introduced for on-line electrochemically-controlled in-tube solid phase microextraction of amitriptyline (AMI) and doxepin (DOX) as antidepressant drugs. The PTh/GO coating was prepared on the inner surface of a stainless steel tube by a facile in-situ electro-deposition method and it was used as a working electrode for electrochemically control in-tube solid phase microextraction. In the PTh/GO coating, GO acts as an anion dopant and sorbent. The PTh/GO coating, compared to PTh and GO coatings, exhibited enhanced long lifetime, good mechanical stability and a large specific surface area. Regarding the in-tube SPME, some important factors such as the extraction and desorption voltage, extraction and desorption times and flow rates of the sample solution and eluent, which could affect the extraction and separation efficiency of the analytes, were optimized. Total analysis time of this method including the online extraction and desorption time was about 21min for each sample. AMI and DOX were extracted, separated and determined with limits of detection as small as 0.3µgL-1 and 0.5µgL-1, respectively. This method showed good linearity in the range of 0.7-200µgL-1, 2.3-200µgL-1 and 2.9-200µgL-1 for AMI, and in the range 0.9-200µgL-1, 2.5-200µgL-1 and 3.0-200µgL-1 for DOX in water, urine and plasma samples, respectively; the coefficients of determination were also equal to or higher than 0.9976. The inter- and intra-assay precisions (RSD%, n=3) were in the range of 2.8-3.4% and 2.9-3.9% at the three concentration levels of 5, 25 and 50µgL-1, respectively. Finally, under the optimal conditions, the method was applied for the analysis of the drugs in human urine and plasma pretreated samples and good results were obtained.

On-line electrochemically controlled in-tube solid phase microextraction of inorganic selenium followed by hydride generation atomic absorption spectrometry.

In this work, for the first time, a rapid, simple and sensitive microextraction procedure is demonstrated for the matrix separation, preconcentration and determination of inorganic selenium species in water samples using an electrochemically controlled in-tube solid phase microextraction (EC-in-tube SPME) followed by hydride generation atomic absorption spectrometry (HG-AAS). In this approach, in which EC-in-tube SPME and HG-AAS system were combined, the total analysis time, was decreased and the accuracy, repeatability and sensitivity were increased. In addition, to increases extraction efficiency, a novel nanostructured composite coating consisting of polypyrrole (PPy) doped with ethyleneglycol dimethacrylate (EGDMA) was prepared on the inner surface of a stainless-steel tube by a facile electrodeposition method. To evaluate the offered setup and the new PPy-EGDMA coating, it was used to extract inorganic selenium species in water samples. Extraction of inorganic selenium species was carried out by applying a positive potential through the inner surface of coated in-tube under flow conditions. Under the optimized conditions, selenium was detected in amounts as small as 4.0 parts per trillion. The method showed good linearity in the range of 0.012-200 ng mL(-1), with coefficients of determination better than 0.9996. The intra- and inter-assay precisions (RSD%, n = 5) were in the range of 2.0-2.5% and 2.7-3.2%, respectively. The validated method was successfully applied for the analysis of inorganic selenium species in some water samples and satisfactory results were obtained.

Preparation and evaluation of a novel molecularly imprinted polymer coating for selective extraction of indomethacin from biological samples by electrochemically controlled in-tube solid phase microextraction.

In the present work, an automated on-line electrochemically controlled in-tube solid-phase microextraction (EC-in-tube SPME) coupled with HPLC-UV was developed for the selective extraction and preconcentration of indomethacin as a model analyte in biological samples. Applying an electrical potential can improve the extraction efficiency and provide more convenient manipulation of different properties of the extraction system including selectivity, clean-up, rate, and efficiency. For more enhancement of the selectivity and applicability of this method, a novel molecularly imprinted polymer coated tube was prepared and applied for extraction of indomethacin. For this purpose, nanostructured copolymer coating consisting of polypyrrole doped with ethylene glycol dimethacrylate was prepared on the inner surface of a stainless-steel tube by electrochemical synthesis. The characteristics and application of the tubes were investigated. Electron microscopy provided a cross linked porous surface and the average thickness of the MIP coating was 45 µm. Compared with the non-imprinted polymer coated tubes, the special selectivity for indomethacin was discovered with the molecularly imprinted coated tube. Moreover, stable and reproducible responses were obtained without being considerably influenced by interferences commonly existing in biological samples. Under the optimal conditions, the limits of detection were in the range of 0.07-2.0 µg L(-1) in different matrices. This method showed good linearity for indomethacin in the range of 0.1-200 µg L(-1), with coefficients of determination better than 0.996. The inter- and intra-assay precisions (RSD%, n = 3) were respectively in the range of 3.5-8.4% and 2.3-7.6% at three concentration levels of 7, 70 and 150 µg L(-1). The results showed that the proposed method can be successfully applied for selective analysis of indomethacin in biological samples.

Electroplating of nanostructured polyaniline-polypyrrole composite coating in a stainless-steel tube for on-line in-tube solid phase microextraction.

In this work, a novel and efficient on-line in-tube solid phase microextraction method followed by high performance liquid chromatography was developed for preconcentration and determination of trace amounts of parabens. A nanostructured polyaniline-polypyrrole composite was electrochemically deposited on the inner surface of a stainless steel tube and used as the extraction phase. Several important factors that influence the extraction efficiency, including type of solid-phase coating, extraction and desorption times, flow rates of the sample solution and eluent, pH, and ionic strength of the sample solution were investigated and optimized. Under the optimal conditions, the limits of detection were in the range of 0.02-0.04 µg L(-1). This method showed good linearity for parabens in the range of 0.07-50 µg L(-1), with coefficients of determination better than 0.998. The intra- and inter-assay precisions (RSD%, n=3) were in the range of 5.9-7.0% and 4.4-5.7% at three concentration levels of 2, 10, and 20 µg L(-1), respectively. The extraction recovery values for the spiked samples were in the acceptable range of 80.3-90.2%. The validated method was successfully applied for analysis of methyl-, ethyl-, and propyl parabens in some water, milk, and juice samples.

Ultrasound-assisted liquid-phase microextraction based on a nanostructured supramolecular solvent.

Novel ultrasonically enhanced supramolecular solvent microextraction (USESSM) then high-performance liquid chromatography with ultraviolet detection have been used for extraction and determination of phthalates in water and cosmetics. Coacervates consisting of decanoic acid-based nano-structured aggregates, specifically reverse micelles, have been used the first time as solvents for ultrasound-assisted emulsification microextraction (USAEME). Sonication accelerated mass transfer of the target analytes into the nano-structured solvent from the aqueous sample, thus reducing extraction time. Several conditions affecting extraction efficiency, for example the concentrations of major components of the supramolecular solvent (tetrahydrofuran and decanoic acid), sample solution pH, salt addition, and ultrasonication time, were investigated and optimized. Under the optimum conditions, preconcentration of the analytes ranged from 176 to 412-fold and the linear range was 0.5-100 µg L(-1), with correlation coefficients (R(2)) ≥ 0.9984. The detection sensitivity of the method was excellent, with limits of detection (LOD, S/N = 3) in the range 0.10-0.70 µg L(-1) and precision in the range 4.1-11.7 % (RSD, n = 5). This method was successfully used for analysis of phthalates in water and cosmetics, with good recovery of spiked phthalates (91.0-108.5 %).