Acceptor Phase Research Articles

Inter-nanocarrier and nanocarrier-to-cell transfer assays demonstrate the risk of an immediate unloading of dye from labeled lipid nanocapsules

Release studies constitute a fundamental part of the nanovector characterization. However, it can be difficult to correctly assess the release of lipophilic compounds from lipid nanocarriers using conventional assays. Previously, we proposed a method including an extraction with oil to measure the loading stability of lipophilic dyes in lipid nanocapsules (LNCs). The method indicated a rapid release of Nile Red from LNCs, while the loading of lipophilic carbocyanine dyes remained stable. This method, although interesting for a rapid screening of the fluorescence labeling stability of nanocarriers, is far from what happens in vivo, where lipid acceptor phases are nanostructured. Here, lipophilic dye loading stability has been assessed, by monitoring dye transfer from LNCs toward stable colloidal lipid nanocompartments, i.e. non-loaded LNCs, using new methodology based on size exclusion chromatography (SEC) and Förster Resonance Energy Transfer (FRET). Dye transfer between LNCs and THP-1 cells (as model for circulating cells) has also been studied by FACS. The assays reveal an almost instantaneous transfer of Nile Red between LNCs, from LNCs to THP-1 cells, between THP-1 cells, and a reversal transfer from THP-1 cells to LNCs. On the contrary, there was no detectable transfer of the lipophilic carbocyanine dyes. Dye release was also analyzed using dialyses, which only revealed a very slow release of Nile Red from LNCs, demonstrating the weakness of membrane based assays for investigations of the lipophilic compound loading stability in lipid nanocarriers. These results highlight the importance of using relevant release assays, and the potential risk of an immediate unloading of lipophilic fluorescent dyes from lipid nanocarriers, in the presence of a lipid acceptor nanocompartment. Some misinterpretations of cellular trafficking and in vivo biodistribution of fluorescent nanoparticles should be avoided.

A membrane introduction mass spectrometer utilizing ion-molecule reactions for the on-line speciation and quantitation of volatile organic molecules.

The ability of membrane introduction mass spectrometry to quantitatively resolve low molecular weight volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene and xylene (BTEX) using electron ionization (EI) can be compromised by isobaric interferences. This work focuses on reducing isobaric interferences with ion-molecule reactions in a portable quadrupole ion trap mass spectrometer for the analysis of VOCs. EI was used to produce reagent ions from precursors (chloroform, methyl iodide, trichloroethylene or chlorobenzene) that were continually infused into the helium acceptor phase upstream of the membrane introduction mass spectrometry (MIMS) sampling interface. The reagent ions were selectively stored in the ion trap, and then allowed to react with target VOC analytes in air samples via ion-molecule reactions within the trap storage volume. A variety of reaction times were examined (50-5000 ms), and the resulting product ions were analyzed in positive ion mode. The detection limits achieved were comparable with those obtained using EI (low ppbv), and in some cases better than for EI coupled with tandem mass spectrometry (MS/MS). For the VOCs studied, isobaric interferences were greatly reduced or eliminated using chloroform as a reagent gas. The predominant ionization mechanism was via adduct formation, although charge transfer and hydride abstractions were also observed. An internal standard was shown to be effective at correcting for signal changes due to consumption of reagent ions when complex mixtures were sampled. Ion-molecule reactions were exploited to eliminate isobaric interferences that are often encountered in direct, real-time analysis strategies for atmospheric VOC mixtures. The use of a continuously infused internal standard will improve quantitative results in field applications where analyte concentration and sample complexity may be wide ranging.

Determination of tramadol hydrochloride in water samples by directly suspended droplet three-phase liquid phase microextraction with tetrathiocyanato cobalt(II) as the complexing agent using UV-spectroscopy

Suspended droplet three-phase liquid microextraction is a relatively new sample preparation technique for analysis of drugs. In the current study, tramadol hydrochloride was determined using tetrathiocyanato cobalt(II), (NH4)2[Co(SCN)4], as the complexing agent. The maximum of absorption for the formed ternary complex between tramadol hydrochloride and tetrathiocyanato cobalt(II) was observed at 625 nm. In this method, the target compound was extracted from the aqueous phase (5 mL containing 5 μg/mL of sample, pH 11) into an organic phase and then back-extracted into a directly suspended droplet as acceptor phase (3 μL of 1.74 × 10–9 M tetrathiocyanato cobalt(II), pH 2.8). 1-Octanol was used as organic phase. Under the optimized conditions: extraction time 90 s, back-extraction time 8 min and stirring rate 750 rpm, the linear range, the relative standard deviation (RSD, n = 5) and the limit of detection for tramadol hydrochloride were found 0.5–8 μg/mL, 4.9% and 8 ng/mL (n = 5), respectively. Also, the tap water and surface water samples were successfully analyzed using the proposed method and the relative recoveries obtained from the spiked water samples were 98.2 and 97.6%, respectively.

PVDF–ErGO–GRC electrode: A single setup electrochemical system for separation, pre-concentration and detection of lead ions in complex aqueous samples

An effective electrode was developed based on electromembrane extraction (EME) and square wave voltammetry (SWV) for simultaneous separation, pre-concentration and determination of lead (II) (Pb(II)) ions in complex aqueous samples. Electrochemically reduced graphene oxide–graphite reinforced carbon (ErGO–GRC) was utilized in conjunction with the SWV. Pb(II) ions were extracted from an aqueous sample solution into an acidic acceptor phase (1M HCl) in the lumen of the polyvinylidene fluoride (PVDF) membrane bag by the application of voltage of maximum 6V across the supported liquid membrane (SLM), consisting of organic solvent and di-(2-ethylhexyl)phosphoric acid (D2EHPA). The parameters affecting the EME were optimized for Pb(II) ions. The optimum EME conditions were found to be 20% D2EHPA in 1-octanol impregnated in the wall of PVDF membrane (PVDF17) as the SLM, extraction time of 20min, pH of sample solution of 8 and a voltage of 5V. The PVDF–ErGO–GRC electrode system attained enrichment factors of 40 times and 80% of extraction with relative standard deviations (n=5) of 8.3%. Good linearity ranging from 0.25 to 2nM with coefficients correlation of 0.999 was obtained. The Pb(II) ions detection limit of PVDF–ErGO–GRC electrode was found to be 0.09nM. The newly developed single setup electrochemical system was applied to complex aqueous samples such as tap, river and sea water to evaluate the feasibility of the method for applications.

Effects of halide ions on the acceptor phase in spontaneous chemical oscillations in donor/membrane/acceptor systems

The effects of halide ions on the acceptor phase in the chemical oscillation in donor/membrane/acceptor systems were examined. The transfer of cetyltrimethylammonium (CTA+) ions from the donor phase and their adsorption and desorption at the membrane/acceptor interface led to spontaneous, nonlinear oscillations of the electric potential. Chloride ions stabilized the adsorption of CTA+ ions and gave rise to a large-amplitude, long-interval, and a long relaxation-time constant. On the contrary, iodide ions, which are more hydrophobic than chloride ions, demonstrated opposite results. This mechanism was proposed based on the simultaneous time-resolved measurements of the interfacial tensions at both the donor/membrane and membrane/acceptor interfaces and observation of the convective flow due to Marangoni instability.

Surfactant assisted pulsed two-phase electromembrane extraction followed by GC analysis for quantification of basic drugs in biological samples

In this work, a simple and efficient surfactant assisted pulsed two-phase electromembrane extraction (SA-PEME) procedure combined with gas chromatography (GC) has been developed for the determination of alfentanil, sufentanil and methadone in various samples. It has been found that the addition of anionic surfactant causes the accumulation of the cationic analytes at the SLM/solution interface resulting in an easier transfer of the analytes into the organic phase. The method was accomplished with 1-octanol as the acceptor phase and supported liquid membrane (SLM) by means of an 80V pulsed electrical driving force and the extraction time of 20min. The model analytes were extracted from 3.0mL sample solution (pH 4.0) containing 0.02% w/v surfactant (sodium dodecyl sulfate). The duty cycle of 92% and frequency of 0.357Hz gave the best performance. Extraction recoveries in the range of 70.5–95.2% and satisfactory repeatability (7.6<RSD<13.7) were obtained. The limits of detection were 1.5, 1.5 and 0.6ngmL−1 for sufentanil, alfentanil and methadone, respectively. The method offers an acceptable linearity (2.0–1000.0ngmL−1) for each analyte with coefficient of determination higher than 0.998. Furthermore, the figures of merit of SA-PEME were compared with the results from the conventional two-phase EME which confirm the advantages of the proposed technique. The method was applied for the determination and quantification of the model compounds in the wastewater, plasma, breast milk and urine samples.

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

In the present research, an effective on chip electromembrane extraction (CEME) coupled with high performance liquid chromatography was presented for analysis of nortriptyline (NOR) and amitriptyline (AMI) as basic model analytes from urine samples. The chip consists of two polymethyl methacrylate (PMMA) parts with two craved microfluidic channels in each part. These channels were used as flow path for the sample solution and a thin compartment for the acceptor phase. A porous polypropylene sheet membrane impregnated with an organic solvent was placed between two parts of chip device to separate the channels. Two platinum electrodes were mounted at the bottom of these channels that were connected to a power supply providing the electrical driving force for migration of ionized analytes from sample solution through the porous sheet membrane into the acceptor phase. This new setup provides effective and reproducible extractions with low volume of sample solution. Efficient parameters on CEME of the model analytes were optimized using one variable at a time method. Under the optimized conditions, the calibration curve was linear in the range of 10.0–500 μg L−1 with coefficient of determination (r2) more than 0.9902. The relative standard deviations (RSDs %) for extraction and determination of the analytes were less than 6.8% based on six replicate measurements. LODs less than 4.0 μg L−1 were obtained for both of the model analytes. The preconcentration factors higher than 17.0-fold were obtained. The results demonstrated that CEME would be used efficiently for extraction and determination of AMI and NOR from urine samples.

Dynamic electromembrane extraction: Automated movement of donor and acceptor phases to improve extraction efficiency

In the present research, dynamic electromembrane extraction (DEME) was introduced for the first time for extraction and determination of ionizable species from different biological matrices. The setup proposed for DEME provides an efficient, stable, and reproducible method to increase extraction efficiency. This setup consists of a piece of hollow fiber mounted inside a glass flow cell by means of two plastics connector tubes. In this dynamic system, an organic solvent is impregnated into the pores of hollow fiber as supported liquid membrane (SLM); an aqueous acceptor solution is repeatedly pumped into the lumen of hollow fiber by a syringe pump whereas a peristaltic pump is used to move sample solution around the mounted hollow fiber into the flow cell. Two platinum electrodes connected to a power supply are used during extractions which are located into the lumen of the hollow fiber and glass flow cell, respectively. The method was applied for extraction of amitriptyline (AMI) and nortriptyline (NOR) as model analytes from biological fluids. Effective parameters on DEME of the model analytes were investigated and optimized. Under optimized conditions, the calibration curves were linear in the range of 2.0–100μgL−1 with coefficient of determination (r2) more than 0.9902 for both of the analytes. The relative standard deviations (RSD %) were less than 8.4% based on four replicate measurements. LODs less than 1.0μgL−1 were obtained for both AMI and NOR. The preconcentration factors higher than 83-fold were obtained for the extraction of AMI and NOR in various biological samples.

Hollow fiber liquid–liquid–liquid microextraction followed by solid-phase microextraction and in situ derivatization for the determination of chlorophenols by gas chromatography-electron capture detection

A method based on the combination of hollow fiber liquid–liquid–liquid microextraction and solid-phase microextraction (SPME) followed by gas chromatography-electron capture detection was developed for the determination of chlorophenols in water and wastewater samples. Silica microstructures fabricated on the surface of a stainless steel wire were coated by an organic solvent and used as a SPME fiber. The analytes were extracted through a hollow fiber membrane containing n-decane from sample solution to an alkaline aqueous acceptor phase. They were then extracted and in situ derivatized on the SPME fiber using acetic anhydride. Experimental parameters such as the type of extraction solvent, acceptor phase NaOH concentration, donor phase HCl concentration, the amount of derivatizing reagent, salt concentration, stirring rate and extraction time were investigated and optimized. The precision of the method for the analytes at 0.02–30μgL−1 concentration level ranged from 7.1 to 10.2% (as intra-day relative standard deviation) and 6.4 to 9.8% (as inter-day relative standard deviation). The linear dynamic ranges were in the interval of 5–500μgL−1, 0.05–5μgL−1, 0.02–1μgL−1 and 0.001–0.5μgL−1 for 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol, respectively. The enrichment factors were between 432 and 785. The limits of detection were in the range of 0.0004–1.2μgL−1. Tap water, well water and wastewater samples were also analyzed to evaluate the method capability for real sample analysis.

Ionic-liquid-based hollow-fiber liquid-phase microextraction method combined with hybrid artificial neural network-genetic algorithm for speciation and optimized determination of ferro and ferric in environmental water samples.

A novel and environmentally friendly ionic-liquid-based hollow-fiber liquid-phase microextraction method combined with a hybrid artificial neural network (ANN)-genetic algorithm (GA) strategy was developed for ferro and ferric ions speciation as model analytes. Different parameters such as type and volume of extraction solvent, amounts of chelating agent, volume and pH of sample, ionic strength, stirring rate, and extraction time were investigated. Much more effective parameters were firstly examined based on one-variable-at-a-time design, and obtained results were used to construct an independent model for each parameter. The models were then applied to achieve the best and minimum numbers of candidate points as inputs for the ANN process. The maximum extraction efficiencies were achieved after 9 min using 22.0 μL of 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) as the acceptor phase and 10 mL of sample at pH = 7.0 containing 64.0 μg L(-1) of benzohydroxamic acid (BHA) as the complexing agent, after the GA process. Once optimized, analytical performance of the method was studied in terms of linearity (1.3-316 μg L(-1), R (2) = 0.999), accuracy (recovery = 90.1-92.3%), and precision (relative standard deviation (RSD) <3.1). Finally, the method was successfully applied to speciate the iron species in the environmental and wastewater samples.

Automated dynamic hollow fiber liquid–liquid–liquid microextraction combined with capillary electrophoresis for speciation of mercury in biological and environmental samples

A simple home-made automatic dynamic hollow fiber based liquid–liquid–liquid microextraction (AD-HF-LLLME) device was designed and constructed for the simultaneous extraction of organomercury and inorganic mercury species with the assistant of a programmable flow injection analyzer. With 18-crown-6 as the complexing reagent, mercury species including methyl-, ethyl-, phenyl- and inorganic mercury were extracted into the organic phase (chlorobenzene), and then back-extracted into the acceptor phase of 0.1% (m/v) 3-mercapto-1-propanesulfonic acid (MPS) aqueous solution. Compared with automatic static (AS)-HF-LLLME system, the extraction equilibrium of target mercury species was obtained in shorter time with higher extraction efficiency in AD-HF-LLLME system. Based on it, a new method of AD-HF-LLLME coupled with large volume sample stacking (LVSS)-capillary electrophoresis (CE)/UV detection was developed for the simultaneous analysis of methyl-, phenyl- and inorganic mercury species in biological samples and environmental water. Under the optimized conditions, AD-HF-LLLME provided high enrichment factors (EFs) of 149–253-fold within relatively short extraction equilibrium time (25min) and good precision with RSD between 3.8 and 8.1%. By combining AD-HF-LLLME with LVSS-CE/UV, EFs were magnified up to 2195-fold and the limits of detection (at S/N=3) for target mercury species were improved to be sub ppb level.

The Removal of Zn(II) Through Calix[4]Recorcinarene Derivative Based Polymer Inclusion Membrane From Aqueous Solution

In the present work, the transport of Zn(II) metal ion from an aqueous nitrate solution of different metal ions through a polymer inclusion membrane (PIM) containing calix[4]resorcinarene derivative used as a carrier were investigated. Zn(II)metal ion showing high permeability were transported through PIMs prepared from cellulose triacetate (CTA) as a polymeric support material and 2-NPOE as a plasticizer. Total Zn(II) concentration was determined with an Atomic Absorption Spectrometer (AAS) in the acceptor phase. The prepared PIM and supported liquid membrane (SLM) were characterized by using Scanning Electron Microscopy(SEM) and Atomic Force Microscopy (AFM) techniques. The effects of membrane composition, effects of type of plasticizer in the membrane, effects of carrier concentration, and the thickness of the membranes were examined in the facilitated transport experiments of Zn(II) ion through PIM. We compared the performance of SLM experiments under the optimum conditions identified by the PIM studies. Higher permeability coefficient values for Zn(II) was found for SLM, while lower values were ascertained for PIM. The kinetic parameters which have been calculated as the constant rate (k), permeability coefficient (P), flux (J) and diffusion coefficient (D).

Determination of conjugated estrogens in human urine using carrier-mediated hollow-fiber liquid phase microextraction and LC-MS/MS

The extraction conditions of the conjugated estrogens, including estrone-3-glucuronide (E1-3G), 17β-estradiol-3-glucuronide (E2-3G), and 17α-ethynylestradiol-3-glucuronide (EE2-3G), were optimized using carrier-mediated hollow-fiber liquid phase microextraction (HF-LPME) and then applied in the analysis of human urine samples. The optimal extraction conditions were as follows: organic phase composed of 20% (w/w) tri-octylamine (TOA) in 1-octanol; 2M NaCl as the acceptor phase; 800 rpm of agitation; and 50 min of extraction time. The extraction efficiency of carrier-mediated LPME was 11 times higher than that of the three-phase LPME. Estrogens and their conjugates in urine samples from pregnant and non-pregnant women were extracted and analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS). The results showed that carrier-mediated HF-LPME had good recoveries and linearity in the calibration curve. Estrogens in pregnant and non-pregnant women were mainly excreted in a conjugated form (94.85 ± 4%), whereas free estrogen was detected at a ratio of 5.15%. Both free and conjugated form of E1 were the most dominant species in all forms, which accounted for 72.7% of all the measured estrogens. Consequently, the HF-LPME in carrier-mediated mode was effectively applied to extract the estrogen conjugates in only 10 ml of human urine samples, which is the most significant advantage.

In situ emulsification microextraction using a dicationic ionic liquid followed by magnetic assisted physisorption for determination of lead prior to micro-sampling flame atomic absorption spectrometry

For the first time, a simple and efficient in situ emulsification microextraction method using a dicationic ionic liquid followed by magnetic assisted physisorption was presented to determine trace amounts of lead. In this method, 400 μL of 1.0 mol L−1 lithium bis (trifluoromethylsulfonyl) imide aqueous solution, Li[NTf2], was added into the sample solution containing 100 μL of 1.0 mol L−1 1,3-(propyl-1,3-diyl) bis (3-methylimidazolium) chloride, [pbmim]Cl2, to form a water immiscible ionic liquid, [pbmim][NTf2]2. This new in situ formed dicationic ionic liquid was applied as the acceptor phase to extract the lead-ammonium pyrrolidinedithiocarbamate (Pb-APDC) complexes from the sample solution. Subsequently, 30 mg of Fe3O4 magnetic nanoparticles (MNPs) were added into the sample solution to collect the fine droplets of [pbmim][NTf2]2, physisorptively. Finally, MNPs were eluted by acetonitrile, separated by an external magnetic field and the obtained eluent was subjected to micro-sampling flame atomic absorption spectrometry (FAAS) for further analysis. Comparing with other microextraction methods, no special devices and centrifugation step are required. Parameters influencing the extraction efficiency such as extraction time, pH, concentration of chelating agent, amount of MNPs and coexisting interferences were studied. Under the optimized conditions, this method showed high extraction recovery of 93% with low LOD of 0.7 μg L−1. Good linearity was obtained in the range of 2.5–150 μg L−1 with determination coefficient (r2) of 0.9921. Relative standard deviation (RSD%) for seven repeated measurements at the concentration of 10 μg L−1 was 4.1%. Finally, this method was successfully applied for determination of lead in some water and plant samples.

Removal of Cr(VI) through calixarene based polymer inclusion membrane from chrome plating bath water

In this study, a calixarene based polymer inclusion membrane was employed for the removal of Cr(VI) from chrome plating bath water. The prepared polymer inclusion membrane was characterized by using Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and contact angle measurements. The effects of carrier concentration, plasticizer type and temperature on the transport, the membrane’s stability and thickness were examined. The transport efficiency of Cr(VI) using the polymer inclusion membrane was approximately 97.69%. The kinetic results demonstrated that Cr(VI) can be transported from the chrome plating bath water to the acceptor phase with high selective and efficiency. The experimental results showed the prepared polymer inclusion membrane (PIM) can be used effectively for the removal of Cr(VI) from the industrial wastewater.

Calibration of a passive, in situ, integrative sampler for monitoring of microbial biotoxins in aquatic environments

In this work, an integrative passive sampler based on a silicone membrane filled with a suspension of γ-Fe2O3 at pH 3.5 was developed. The novel device was calibrated for the measurement of microcystin concentrations in water. Laboratory calibration studies of the passive sampling devises under controlled conditions of temperature, water turbulence, and analyte concentration were conducted in order to establish how variable environmental conditions affect the novel sampler's performance. The chemical uptake of microcystin (MC)-RR, -LR, and -YR into the passive sampler remained linear and integrative throughout the 28-day exposure. The relative standard deviations of mean concentrations obtained using silicone-based sampler ranged from 1.42 to 3.74% for microcystin-LR, -RR, and -YR. The values for reproducibility from triplicate samplers ranged from 3.5 to 7.1% for microcystin-LR, -RR, and -YR. The detection limits on high performance liquid chromatography (HPLC) with PDA detection for microcystins LR, RR, and YR were 24.7, 17.2, and 23.8 μg L−1 respectively, calculated as three times the signal to noise ratio. The rate of accumulation of most of the MC compounds tested was dependent on temperature and flow velocity. Furthermore, the sample matrix, e.g. humic substances, had no significant effect on the concentration of compounds trapped in the acceptor solution and once these MC compounds were trapped in the acceptor phase they did not diffuse back during the deployment period.

Two-phase/Three-phase Hollow Fibre Liquid-Phase Simultaneous Microextraction Combined with HPLC for Analysis of Phenolic Acids and Flavonoids in Traditional Chinese Medicine

A two-phase/three-phase hollow fibre liquid-phase simultaneous microextraction (2p/3p-HF-LPSME) method, coupled with high-performance liquid chromatography and ultraviolet detection, was developed and introduced for simultaneous extraction and determination of phenolic acids and flavonoids in Lonicera japonica, Herba Taraxaci and Cortex Eucommiae. Several factors affecting performance were investigated and optimized, including the type of hollow fibre liquid-phase microextraction, extraction solvent, pHs of the sample and acceptor phases, extraction time, stirring rate, salt concentration in the sample solution and volume of sample phase. Under optimised conditions, the enrichment factors of 2p/3p-HF-LPSME for analytes ranged from 9 to 171, and good linearities were obtained for all analytes with regression coefficients of between 0.9939 and 0.9996. In addition, the limits of detection were between 0.3 and 4.0 ng·mL−1, and satisfactory recoveries (90.0–106.3 %) and precisions (RSD 2.3–10.4 %) were also achieved. The simultaneous microextraction mechanism of the approach was also analysed and described. Experimental results show that the method is simple, sensitive, practical and effective, and it can be used for simultaneous preconcentration and determination of phenolic acids and flavonoids in traditional Chinese medicines.

Do “Hot” Charge-Transfer Excitons Promote Free Carrier Generation in Organic Photovoltaics?

In organic photovoltaics, the role of hot charge-transfer (CT) excitons on free carrier generation is currently under intense debate. In this paper, we carry out first-principles time-dependent density functional theory calculations to examine hot CT dissociation in polymer/fullerene heterojunctions. We reveal that whether or not hot CT states promote charge separation depends on excitation spectral range and crystallinity of the donor and acceptor phases. We find that while the crystallinity of the donor phase underlies the energy dependence of CT exciton dissociation, the crystallinity of the acceptor determines charge separation efficiency. We propose a theory that can reconcile contradictory experimental observations and provide insight into hot CT dissociation. Crucially, the timescale of hot CT dissociation is found to be comparable to the timescale of its relaxation to the lowest-lying CT state, which is localized in all interfacial models considered here.

Application of hollow fiber liquid phase microextraction for simultaneous determination of regulated and emerging iodinated trihalomethanes in drinking water

Trihalomethanes (THMs) are regulated disinfection by-products (DBPs) most commonly analyzed in quality control water supply due to their harmful effects on health. However, few data exist about the content of emerging iodo-trihalomethanes (I-THMs) which are present in drinking water at very low concentrations (in the order of ngL−1). For this reason a two-phase hollow fiber liquid phase microextraction method for the simultaneous determination of four regulated trihalomethanes and six emerging iodo-trihalomethanes using GC-μECD and GC–MS with detection limits in the range of few ngL−1 has been developed. A central composite design was used to optimize conditions for simultaneous extraction. The best extraction recovery was obtained with 19.2min at 27.1°C and 900rpm, without salt addition, using a supported hollow fiber membrane of 10.5cm (0.6mm id) and 1-octanol as acceptor phase. The limits of detection for the regulated THMs and I-THMs were 3–44ngL−1 and 1–3ngL−1, respectively. The calibration curves showed good linearity (R2>0.995) and good repeatibility (3–22%). The relative recoveries in water were between 96.5% and 105.2%. The method was applied for the simultaneous determination of trihalomethanes in supply water samples from seven water distribution systems (WDS) in the Huelva area, located at the southwest Spain, which use different water-treatment processes. The highest concentrations of I-THMs, particularly CHBrClI and CHCl2I, were detected in water treated with advanced treatment process using pre-ozonation, however these compounds were not detected or decreased along distribution system. In the samples of treated water with conventional treatment, using pre-oxidation by permanganate and distribution network, CHCl2I, CHBrClI, CHClI2, CHBrI2 and CHI3 were detected at very low concentrations (1–18ngL−1). Finally, in water samples from underground origin without oxidation treatment, in which only disinfection with sodium hypochlorite was applied, I-THMs were not detected.

Vortex-assisted liquid–liquid–liquid microextraction (VALLLME) technique: A new microextraction approach for direct liquid chromatography and capillary electrophoresis analysis

A new, rapid and sensitive microextraction technique named vortex-assisted liquid–liquid–liquid microextraction (VALLLME) is proposed. The complete extraction process involves two steps. First, a vortex-assisted liquid–liquid microextraction (VALLME) procedure was used to extract the analytes from a relatively large volume of sample (donor phase) to a small volume of organic solvent (intermediate phase). Next, a micro-vortex-assisted liquid–liquid extraction (µ-VALLE) was used to extract the target analytes from the intermediate phase to a smaller volume of aqueous solution (acceptor phase). The final extract (acceptor phase) can be directly injected into the high performance liquid chromatography or capillary electrophoresis units without any further treatments. The selection of the intermediate phase and the manipulation of pH are key parameters that ensure good extraction efficiency of the technique. The proposed technique has been successfully applied for the determination of carvedilol (used as model analyte) in biological fluid samples. The optimum extraction conditions were: toluene as intermediate phase (150μL); pH of the donor phase, 9.5; vortex time of the VALLME, 45s (maximum speed, 2500rpm); 0.1M HCl (15μL) as acceptor phase; vortexing time of the µ-VALLME, 75s (maximum stirring speed, 2500rpm) and salt concentration in the donor phase, 5% (w/v). Under these conditions, enrichment factors of 51- and 418-fold for VALLME step and VALLLME procedure, respectively, were achieved.