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Highlights: [•] I critically evaluate the practical and theoretical status of NACE over the last five years. [•] I base my review on the sound background of solution chemistry in organic solvents. [•] I scrutinize the progress of NACE concerning the understanding of zone broadening based on the plate height concept. [ABSTRACT FROM AUTHOR]

Highlights: [•] I critically evaluate the practical and theoretical status of NACE over the last 5 years. [•] I base my review on the sound background of solution chemistry in organic solvents. [•] I scrutinize the progress of NACE concerning the understanding of electrophoretic migration and separation selectivity. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent “bar” not floating at the sample solution and exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15μL toluene, 40°C, stirring at 750rpm for 30min with 1.5g sodium chloride addition in 20.0mL donor phase), the linear ranges of anabolic steroids were 0.25–200ngmL−1 with gas chromatography–mass spectrometry. The limits of detection were lower than 0.10ngmL−1. The recoveries and precisions in spiked urine and hair samples were between 73.97–93.56% and 2.18–4.47% (n =5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method. [Copyright &y& Elsevier]

Abstract: A novel method using sample preparation method, “ultrasound-assisted emulsification microextraction” (USAEME) with manual shaking, coupled with gas chromatography using and an electron capture detector (GC–ECD) was developed for the analysis of organochlorine pesticides (OCPs) in aqueous samples. The apparatus is simple and easy to operate. After manual shaking for 10s, ultrasound was used to accelerate emulsification of the organic solvent (1-decanol) in aqueous solution. Only 10μL of the low-toxicity extraction solvent is used in this method; no dispersive solvent is required and the total extraction time is ∼4min. Manual shaking before ultrasound-assisted emulsification enhances the extraction efficiency by >100%. The effects of horizontal and vertical orientation as well as the location of the sample within the ultrasonic bath were studied. After centrifugation, we used an improved solvent collection system (ISCS) to reduce the amount of extraction solvent required. A 1μL sample of the extract was injected into the GC column. Under optimum conditions, the linear range of the method is 5–2500ngL−1 for most of the OCPs, and the limit of detection of the method ranged from 0.6 to 2.9ngL−1.The relative recoveries ranged from 75 to 107% for sea water and from 70 to 99% for field fresh water. The method, which provides good enrichment factors, low LODs and minimization of the consumption of organic solvent, provides a rapid, simple and environment-friendly procedure for determining OCPs in aqueous samples. [Copyright &y& Elsevier]

Abstract: The on-line sample concentration technique, micelle to solvent stacking (MSS), was studied for small organic cations (quaternary ammonium herbicides, β-blocker drugs, and tricyclic antidepressant drugs) in reversed migration micellar electrokinetic chromatography. Electrokinetic chromatography was carried out in fused silica capillaries with a background solution of sodium dodecyl sulfate (SDS) in a low pH phosphate buffer. MSS was performed using anionic SDS micelles in the sample solution for analyte transport and methanol or acetonitrile as organic solvent in the background solution for analyte effective electrophoretic mobility reversal. The solvent also allowed for the separation of the analyte test mixtures. A model for focusing and separation was developed and the mobility reversal that involved micelle collapse was experimentally verified. The effect of analyte retention factor was observed by changing the % organic solvent in the background solution or the concentration of SDS in the sample matrix. With an injection length of 31.9cm (77% of effective capillary length) for the 7 test drugs, the LODs (S/N=3) of 5–14ng/mL were 101–346-fold better when compared to typical injection. The linearity (R 2, range=0.025–0.8μg/mL), intraday and interday repeatability (%RSD, n =10) were ≥0.988, <6.0% and <8.5%, respectively. In addition, analysis of spiked urine samples after 10-fold dilution with the sample matrix yielded LODs=0.02–0.10μg/mL. These LODs are comparable to published electrophoretic methods that required off-line sample concentration. However, the practicality of the technique for more complex samples will rely on dedicated sample preparation schemes. [Copyright &y& Elsevier]

Abstract: To develop an efficient green extraction approach for recovery of bioactive compounds from natural plants, we examined the potential of pressurized liquid extraction (PLE) of ginger (Zingiber officinale Roscoe) with bioethanol/water as solvents. The advantages of PLE over other extraction approaches, in addition to reduced time/solvent cost, the extract of PLE showed a distinct constituent profile from that of Soxhlet extraction, with significantly improved recovery of diarylheptanoids, etc. Among the pure solvents tested for PLE, bioethanol yield the highest efficiency for recovering most constituents of gingerol-related compounds; while for a broad concentration spectrum of ethanol aqueous solutions, 70% ethanol gave the best performance in terms of yield of total extract, complete constituent profile and recovery of most gingerol-related components. PLE with 70% bioethanol operated at 1500psi and 100°C for 20min (static extraction time: 5min) is recommended as optimized extraction conditions, achieving 106.8%, 109.3% and 108.0% yield of [6]-, [8]- and [10]-gingerol relative to the yield of corresponding constituent obtained by 8h Soxhlet extraction (absolute ethanol as extraction solvent). [Copyright &y& Elsevier]

Abstract: The adsorption isotherms of phenol were acquired by frontal analysis on six different reversed phase adsorbents from five different organic solvent solutions. The end-capped octadecyl columns only differed in the bonding density of the C18 ligands. The inverse method was used to confirm the estimated isotherm parameters derived from the frontal experiments. The effect of the bonding density of the end-capped octadecyl bonded phase on the adsorption properties of phenol from different mobile phase compositions was investigated. The adsorption behavior of phenol has changed from Langmuir type to BET type with the change of the organic modifier and the bonding density of the adsorbent. [Copyright &y& Elsevier]

Abstract: Two-step stacking of organic cations by sweeping and micelle to solvent stacking (MSS) in capillary zone electrophoresis (CZE) is presented. The simple procedure involves hydrodynamic injection of a micellar sodium dodecyl sulfate solution before the sample that is prepared without the micelles. The micelles sweep and transport the cations to the boundary zone between the sample and CZE buffer. The presence of organic solvent in the CZE buffer induces the second stacking step of MSS. The LODs obtained for the four beta blocker and two tricyclic antidepressant test drugs were 20–50 times better compared to typical injection. [ABSTRACT FROM AUTHOR]

Abstract: A novel molecular complex-based dispersive liquid–liquid microextraction (DLLME) method was established via hydrogen bond interaction between the extractant and the analytes. In this approach, tri-n-butylphosphate (TBP), a Lewis base, was directly used, instead of the traditional water-immiscible organic solvents, as the extractant for DLLME. The phenols (p-benzenediol, m-benzenediol, o-benzenediol and phenol), which are typical Lewis acids, were successfully extracted from environmental aqueous samples. In addition, phase separation was achieved in a disposable polyethylene pipet with the open and narrow tip upside, for a collection of the above extractant layer, i.e. TBP. To achieve satisfactory extraction performance, several extraction parameters, such as type of extractant solvents, extractant volume, pH of sample solution, ionic strength of sample solution and extraction time, were optimized. Additionally, the proposed method was applied to environmental water samples. Under the optimized conditions, the limits of detection and limits of quantification for the phenols were 7–29 and 25–98μg/L, respectively. The calibration curves showed good linearity (r 2 ≥0.9961) over the investigated concentration range. The repeatability of the method was investigated by evaluating the intra- and inter-day precisions. The relative standard deviations (RSDs) obtained were lower than 11.2% and 13.9% at different concentration levels. The recoveries ranged from 83.2% to 117.8%, with RSDs less than 13.1%. The developed approach provides a new way to facilitate DLLME of organic polar compounds from aqueous solutions. Moreover, it enables a convenient collection of solvent less dense making use of a cheap and disposable polyethylene pipet. [ABSTRACT FROM AUTHOR]

Abstract: Micelle to solvent stacking (MSS) is a new on-line sample concentration technique for charged analytes in capillary zone electrophoresis (CZE). Sample concentration in MSS mainly relies on the reversal in the effective electrophoretic mobility of the analyte at the boundary zone between the sample solution (S) and CZE background solution (BGS) inside the capillary. The basic condition for MSS is that the S is prepared in a matrix that contains an additive (i.e., micelles) which interacts with and has an opposite charge compared to the analytes. In addition, the BGS must contain a sufficient percentage of organic solvent. MSS was first reported for organic cations using anionic dodecyl sulfate micelles as additive in the S and methanol or acetonitrile as organic solvent in the BGS. Here, theoretical and experimental studies on MSS are described for organic anions using cationic cetyltrimethyl ammonium micelles as additive in the S and methanol as organic solvent in the BGS. Up to an order of magnitude improvement in concentration sensitivity was obtained for the test hypolipidaemic drugs using MSS in CZE with UV detection. The optimized method was also evaluated to the analysis of a spiked wastewater sample that was subjected to a simple extraction step. [Copyright &y& Elsevier]

Abstract: An in-syringe ultrasound-assisted emulsification microextraction (USAEME) was developed for the extraction of organophosphorus pesticides (OPPs) from water samples. The OPPs subsequently analyzed gas chromatography (GC) using a microelectron capture detector (μECD). Ultrasound radiation was applied to accelerate the emulsification of μL-level low-density organic solvent in aqueous solutions to enhance the microextraction efficiency of OPPs in the sample preparation for GC-μECD. Parameters affecting the efficiency of USAEME, such as the extraction solvent, solvent volume, pH, salt-addition, and extraction time were thoroughly investigated. Based on experimental results, OPPs were extracted from a 5mL aqueous sample by the addition of 20μL toluene as the extraction solvent, followed by ultrasonication for 30s, and then centrifugation for 3min at 3200rpm, offered the best extraction efficiency. Detections were linear in the concentration of 0.01–1μg/L with detection limits between 1ng/L and 2ng/L for OPPs. Enrichment factors ranged from 330 to 699. Three spiked aqueous samples were analyzed, and recovery ranged from 90.1% to 104.7% for farm-field water, and 90.1% to 101.8% for industrial wastewater. The proposed method provides a simple, rapid, sensitive, inexpensive, and eco-friendly process for determining OPPs in water samples. [Copyright &y& Elsevier]

Abstract: An electro membrane extraction (EME) methodology was utilized to study the isolation of some environmentally important pollutants, such as chlorophenols, from aquatic media based upon the electrokinetic migration process. The analytes were transported by application of an electrical potential difference over a supported liquid membrane (SLM). A driving force of 10V was applied to extract the analytes through 1-octanol, used as the SLM, into a strongly alkaline solution. The alkaline acceptor solution was subsequently analyzed by high performance liquid chromatography-ultraviolet (HPLC-UV) detection. The parameters influencing electromigration, including volumes and pH of the donor and acceptor phases, the organic solvent used as the SLM, and the applied voltage and its duration, were investigated to find the most suitable extraction conditions. Since the developed method showed a rather high degree of selectivity towards pentachlorophenol (PCP), validation of the method was performed using this compound. An enrichment factor of 23 along with acceptable sample clean-up was obtained for PCP. The calibration curve showed linearity in the range of 0.5–1000ng/mL with a coefficient of estimation corresponding to 0.999. Limits of detection and quantification, based on signal-to-noise ratios of 3 and 10, were 0.1 and 0.4ng/mL, respectively. The relative standard deviation of the analysis at a PCP concentration of 0.5ng/mL was found to be 6.8% (n =6). The method was also applied to the extraction of this contaminant from seawater and an acceptable relative recovery of 74% was achieved at a concentration level of 1.0ng/mL. [Copyright &y& Elsevier]

Abstract: Liquid–liquid–liquid microextraction (LLLME) with directly suspended droplet in high-performance liquid chromatography (HPLC) has been applied as a new, rapid and easy method for the determination of 3-nitroaniline in environmental water samples. The target compound was extracted from the aqueous sample solution (donor phase, pH 13) into an organic phase and then was back-extracted into a directly suspended droplet of an acidic aqueous solution (acceptor phase, pH 0.3). In this method, without using a microsyringe as supporting device, an aqueous large droplet is freely suspended at the top-center position of an immiscible organic solvent, which is laid over the aqueous sample solution while being agitated. Then, the droplet was withdrawn into the microsyringe and directly was injected into the HPLC system with UV detection at 227nm. Up to 148-fold enrichment of the analyte could be obtained under the optimal conditions [i.e. donor phase: 0.1M sodium hydroxide solution (4.5mL); organic phase: o-xylene/1-octanol (90:10, v/v; 250μL); acceptor phase: 0.5M hydrochloric acid and 500mM 18-crown-6 ether (6μL); extraction time: 60s; back-extraction time: 6min and stirring rate: 600rpm]. The limit of detection was 1μg/L (n =7) and the relative standard deviation (RSD, n =5) was 4.9 at S/N=3. The calibration graph was linear in the range of 5–1500μg/L with r =0.9983. All experiments were carried out at room temperature (22±0.5°C). [Copyright &y& Elsevier]

Abstract: An epoxy-based monolith has been developed for use as hydrophilic support in bioseparation. This monolith is produced by self-polymerization of polyglycerol-3-glycidyl ether in organic solvents as porogens at room temperature within 1h. One receives a highly cross-linked structure that provides useful mechanical properties. The porosity and pore diameter can be controlled by varying the composition of the porogen. In this work, an epoxy-based monolith with a high porosity (79%) and large pore size (22μm) is prepared and used in affinity capturing of bacterial cells. These features allow the passage of bacterial cells through the column. As affinity ligand polymyxin B is used, which allows the binding of gram-negative bacteria. The efficiency of the monolithic affinity column is studied with Escherichia coli spiked in water. Bacterial cells are concentrated on the column at pH 4 and eluted with a recovery of 97±3% in 200μL by changing the pH value without impairing viability of bacteria. The dynamic capacity for the monolithic column is nearly independent of the flow rate (4×109 cells/column). Thereby, it is possible to separate and enrich gram-negative bacterial cells, such as E. coli, with high flow rates (10mL/min) and low back pressure (<1bar) in a volume as low as 200μL compatible for real-time polymerase chain reaction, microarray formats, and biosensors. [Copyright &y& Elsevier]

Abstract: The four nerve agent degradation products methylphosphonic acid (MPA), ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA) and cyclohexyl methylphosphonic acid (CMPA) have been successfully extracted from aqueous sample solution by ion-pair liquid–liquid–liquid microextraction. In this procedure, the target analytes in the sample solution were converted into their ion-pair complexes with tri-n-butyl amine and then extracted by an organic solvent (1-octanol) layer on top of the sample solution. Simultaneously, the analytes were back-extracted into a drop of an aqueous acceptor solution which was suspended in the organic phase at a microsyringe needle tip. The factors influential to extraction: type of organic solvent, type of ion-pair reagent and its concentration, pH values of sample solution and acceptor aqueous phase, stirring rate and extraction time were investigated in detail. After extraction, the drop of the acceptor solution was withdrawn into the syringe and injected into a capillary electrophoresis system for analysis. Using contactless conductivity detection, direct quantification of these compounds is possible. Moreover, large-volume sample injection was employed for further preconcentration. Improvements in the limits of detection between 2.5 and 4 orders of magnitude could be achieved and concentrations at the ng/mL level can be determined. This newly established approach was successfully applied to a spiked river water sample. [Copyright &y& Elsevier]