Search

• Handheld mobile app based Electrochemical sensor. • Rapid and quantitative detection of OP pesticides. • Operating over sweeping potential for on-field monitoring. • Validated with spiked vegetable extract, standard potentiostat. • Low detection limit (9.8 ng L−1), Excellent stability (85 days). A hand-held Electrochemical sensor interfaced with a smartphone has been fabricated for rapid and on-site monitoring of organophosphate (OP) in vegetable extract. The simple inexpensive architecture of Universal wireless chemical detector (UWED) tethered with a miniaturized potentiostat powered through rechargeable battery has inspired to construct sensor which, is adaptable to different types of analysis via modulation of the software. Hence, it offers new avenues for fabrication of affordable sensors and wearable devices. [ABSTRACT FROM AUTHOR]

Abstract: A novel on-line technique for stacking and sweeping of long sample plugs with simultaneous determination of charged analytes in the plant (protocatechuic aldehyde, rosmarinic acid, danshensu, salvianolic acid B, and protocatechuic acid) by the nonionic microemulsion electrokinetic chromatography (MEEKC) is presented. The preconcentration efficiency provided about 9–28-fold for stacking and 7–14-fold for sweeping in the enhancements of LOD. The effects of oil phase, Brij-35 and buffer concentrations on stacking and sweeping efficiency were examined in order to optimize the two methods. In nonionic MEEKC, the effect of the type of oil and buffer contents on preconcentration mechanism is often sophisticated. This study had demonstrated that the oil type and buffer content in nonionic microemulsion indeed markedly altered the affinity of microemulsion with analytes. Finally, in comparison to the stacking method, the most apparent disadvantages of the sweeping method were the relatively high limits of detection and poor peak shapes. [Copyright &y& Elsevier]

Abstract: This paper describes the preconcentration of three neutral steroids (testosterone, progesterone, and testosterone propionate) through a combination of off-line preconcentration using a gold nanoparticle (Au NP)-coated silica gel solid phase extraction (SPE) sorbent prior to on-line preconcentration using sweeping micellar electrokinetic chromatography (MEKC). In the initial phase of this study, the sweeping-MEKC parameters for the capillary electrophoresis (CE) separation of the steroid analytes were optimized. The sweeping-MEKC effect was greatest when the sample matrix contained ca. 18% acetonitrile and 100mM sodium dihydrogen phosphate (pH 7.0). Next, under the optimized sweeping-MEKC operating conditions, a commercial C18-bonded silica gel and a Au NP-coated silica gel were tested for their use as SPE sorbents for the SPE–sweeping-MEKC preconcentration of steroid-spiked urine samples. Of these two sorbents, the Au NP-coated SPE sorbent displayed a superior clean-up efficiency toward the sample matrix. Size exclusion chromatography (SEC) was used to characterize the interactions between urinary proteins and the Au NPs. The results indicated that the removal of the interfering signals from the urinary proteins was probably due to their interactions with residual Au metal surfaces of the Au NP-coated SPE sorbent. When combining Au NP-coated silica gel SPE with sweeping-MEKC for the CE analysis of steroid-spiked urine samples, the limits of detection (at a signal-to-noise ratio of N =3) for testosterone, progesterone, and testosterone propionate were ca. 1.59, 1.20, and 1.15μg/L, respectively; in addition, the detection sensitivities (based on peak heights) of these steroids improved by ca. 700-, 1090-, and 1100-fold, respectively, relative to those of the analytes that had not been subjected to preconcentration. [Copyright &y& Elsevier]

Abstract: A method based on magnetic separation was developed for the extraction of several estrogens (including diethylstilbestrol, estrone and estriol) in water followed by sweeping micellar electrokinetic chromatography (MEKC) analysis with UV detection. Novel magnetic octadecylsilane (ODS) particles were prepared using a silanization method with octadecyl trimethoxysilane as the surface modification reagent of magnetic Fe3O4 particles. Octadecyl trimethoxysilane was covalently immobilized on the magnetic iron oxide particles. The particles were used as the sorbents in the magnetic separation for the extraction of trace amounts of estrogens from water. The extraction condition and efficiency of the particles for the estrogens were investigated. Combining the magnetic ODS particles extraction and sweeping MEKC with UV detection, the estrogens at concentrations as low as ng/mL in water can be detected without interference from other substances in the sample matrix. [Copyright &y& Elsevier]

Abstract: Two on-line sample concentration techniques, sample stacking and sweeping under pH-suppressed electroosmotic flow, were evaluated in microemulsion electrokinetic chromatography. The concept of stacking with anion selective electrokinetic injection and a water plug in a reverse-migrating microemulsion (SASIW-RMME) was brought forward in this article. Six flavonoids were concentrated using a microemulsion consisting of 80mM sodium dodecyl sulfate, 1.2% (v/v) ethyl acetate, 0.6% (v/v) 1-butanol, 10% acetonitrile (v/v) and 50mM phosphoric acid (pH* 1.8). Significant detector response improvements were achieved. The limits of detection were in the low ng/ml level. Finally, the sample of Fructus aurantii Immaturus was analyzed using sweeping technique. [Copyright &y& Elsevier]

Abstract: On-line preconcentration is one of the aspects of analytical method development using capillary electrophoretic techniques. The choice of the sample matrix alone can significantly alter both method sensitivity and separation efficiency. The recent trend to detect samples in narrower separation vessels also necessitates the need to improve detection sensitivity. The desire to detect very low levels of analytes using limited amounts of sample from biological specimens and the high separation efficiency obtainable using very large injections compared to classical small size injections also adds to this list. Indeed, one of the rich areas of research in the capillary electrophoresis field is on on-line sample preconcentration. More than 400 published research articles gathered from the http://www.webofscience.com from the year 2000 described a form of on-line preconcentration in capillary electrophoresis. This review provides a comprehensive table listing the applications of on-line preconcentration in capillary electrophoresis. [Copyright &y& Elsevier]

Abstract: Opium samples from four different locations and poppy straw from different plant varieties have been assayed using micellar capillary electrophoresis incorporating a sweeping technique. Individual alkaloids (morphine, codeine, papaverine, noscapine, thebaine, oripavine, reticuline and narceine) were quantitatively determined in the different samples by a validated capillary electrophoresis method. Unsupervised pattern recognition of the opium samples and the poppy straw samples using hierarchical cluster analysis (HCA) and principal component analysis (PCA), showed distinct clusters. Supervised pattern recognition using soft independent modelling of class analogy (SIMCA) was performed to show individual groupings and allow unknown samples to be classified according to the models built using the CZE assay results. [Copyright &y& Elsevier]

Abstract: A method for the chiral separation of propiconazole using cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with hydroxypropyl-γ-cyclodextrin (HP-γ-CD) as chiral selector is reported. The use of a mixture of 30mM HP-γ-CD, 50mM SDS, methanol–acetonitrile 10%:5% (v/v) in 25mM phosphate buffer solution was able to separate two enantiomeric pairs of propiconazole. Stacking- and sweeping-CD-MEKC under neutral pH (pH 7) and under acidic condition (pH 3.0) were used as two on-line preconcentration methods to increase detection sensitivity of propiconazole. Good repeatabilities in the migration time, peak area and peak height were obtained in terms of relative standard deviation (RSD). A sensitivity enhancement factor of 100-fold was achieved using sweeping-CD-MEKC at acidic pH. This is the first report on the separation of two pairs of propiconazole enantiomers and all the enantiomers of fenbuconazole and tebuconazole using sweeping-CD-MEKC. The limit of detection (S/N=3) for the three triazole fungicides ranged from 0.09 to 0.1μg/mL, which is well below the maximum residue limits (MRL) set by Codex Alimentarius Commission (CAC). Combination of solid-phase extraction (SPE) pretreatment and sweeping-CD-MEKC procedure was applied to the determination of selected triazole fungicides in grapes samples spiked at concentration 10–40 times lower than the MRL established by the CAC. The average recoveries of the selected fungicides in spiked grapes samples were good, ranging from 73% to 109% with RSD of 9–12% (n =3). [Copyright &y& Elsevier]

Abstract: Flow manipulation in sweeping microchip capillary electrophoresis (CE) is complicated by the free liquid communication between channels at the intersection, especially when the electroosmotic flows are mismatched in the main channel. Sweeping in traditional CE with cationic micelles is an effective way to concentrate anionic analytes. However, it is a challenge to transfer this method onto microchip CE because the dynamic coating process on capillary walls by cationic surfactants is interrupted when the sample solution free of surfactants is introduced into the microchip channels. This situation presents a difficulty in the sample loading, injection and dispensing processes. By adding surfactant at a concentration around the critical micelle concentration and by properly designing the voltage configuration, the flows in a microchip were effectively manipulated and this sweeping method was successfully moved to microchip CE using tetradecyltrimethylammonium bromide (TTAB). The sweeping effect of cationic surfactant in the sample solution was discussed theoretically and studied experimentally in traditional CE. The flows in a microchip were monitored with fluorescence imaging, and the injection and sweeping processes were studied by locating the detection point along the separation channel. A detection enhancement of up to 500-fold was achieved for 5-carboxyfluorescein. [Copyright &y& Elsevier]

Abstract: The spent electron beam of megawatt-class CW gyrotrons requires magnetic sweeping to keep the specific heat dissipation on the collector surface within technically acceptable limits of about 500W per cm2. Conventionally this is realised with a solenoid coil placed over the collector, which sweeps the strike point of the electron beam up and down the collector-wall at low frequency (<10Hz). The low frequency is necessitated by the strong screening effects due to eddy-currents in the copper-collector-wall. This paper describes the realisation and test results obtained with a six-coil 50Hz transverse field sweep system (TFSS) on the 140GHz 1MW CW prototype gyrotron for W7-X. The advantages of this system compared to the conventional scheme are discussed and an outlook on further enhancements is given. [Copyright &y& Elsevier]

A simple, sensitive and continuous on-line stacking technique using head-column (HC)-field amplified sample injection (FASI) and sweeping was developed by combination of flow injection with micellar electrokinetic chromatography. Berberine, palmatine and jatrorrhizine were selected as model mixture to demonstrate this stacking method. Based on the characteristic of a 16-way injection valve (16-V), a sample was injected electrokinetically into a capillary after the introduction of a plug of water. Under optimum conditions, 64–86-fold improvement in the detection sensitivity was obtained for the analytes and the sample throughput can reach up to 24 h−1 using the background electrolyte containing 240 mM ammonium acetate (pH 4.7), 30% (v/v) ethanol, and 2% (v/v) polyoxyethylene sorbitan monolaurate (Tween 20). The repeatabilities ( n = 4) reached relative standard deviation values of 1.2, 2.7 and 3.1% for the peak areas and 1.6, 3.3 and 3.8% for peak heights of berberine, palmatine and jatrorrhizine, respectively. The limit of detection for the berberine, palmatine and jatrorrhizine was found to be 27, 26, 22 ng mL−1 (S/N = 3). [ABSTRACT FROM AUTHOR]

Abstract: A capillary electrophoresis Raman spectroscopy (CE-RS) method based on the stacking and sweeping modes are described. A non-fluorescent compound (malachite green, MG; crystal violet, CV) and a doubled Nd:YAG laser (532nm, 300mW) were selected as the model compound and light source, respectively. In order to carry out a quantitative and analysis of MG, a monochromator was used to collect the specific Raman line at 1616cm−1 (the N-φ and C–C stretching, corresponding to 582nm when the wavelength of the exciting source is 532nm). The limit of detection (LOD) for MG was 1.6×10−5 and 1.1×10−5 M, respectively, based on the CZE and MEKC modes. This could be improved to 3.4×10−7 and 5.3×10−9 M, respectively, when the stacking and sweeping modes were applied. The method was also extended to the determination of MG in an actual sample. [Copyright &y& Elsevier]

Abstract: A simple and rapid micellar electrokinetic chromatography (MEKC) method with UV detection was developed for the simultaneous separation and determination of all-trans- and 13-cis-retinoic acids in rabbit serum by on-line sweeping concentration technique. The serum sample was simply deproteinized and centrifuged. Various parameters affecting sample enrichment and separation were systematically investigated. Under optimal conditions, the analytes could be well separated within 17min, and the relative standard deviations (RSD) of migration times and peak areas were less than 3.4%. Compared with the conventional MEKC injection method, the 18- and 19-fold improvements in sensitivity were achieved, respectively. The proposed method has been successfully applied to the determination of all-trans- and 13-cis-retinoic acids in serum samples from rabbits and could be feasible for the further pharmacokinetics study of all-trans-retinoic acid. [Copyright &y& Elsevier]

Abstract: A new approach for the analysis of large-volume naphthalene-2,3-dicarboxaldehyde (NDA) derivatives of amino acids by micellar electrokinetic chromatography (MEKC) in conjunction with a purple light-emitting diode-induced fluorescence detection is described. In order to optimize resolution, speed, and stacking efficiency, a discontinuous condition is essential for the analysis of NDA-amino acid derivatives. The optimum conditions use 2.0M TB (pH 10.0) buffer containing 40mM sodium dodecyl sulfate (SDS) to fill the capillary, deionized water to dilute samples, and 200mM TB (pH 9.0) containing 10mM SDS to prepare 0.6% poly(ethylene oxide) (PEO). Once high voltage is applied, PEO solution enters the capillary via electroosmotic flow and SDS micelles interact and thus sweep the NDA-amino acid derivatives having smaller electrophoretic mobilities than that of SDS micelles in the sample zone. When the aggregates between SDS micelles and NDA amino acid derivatives enter PEO zone, they are stacked due to decrease in electric field and increases in viscosity. Under the optimum conditions, the concentration and separation of 0.53-μL 13 NDA-amino acid derivatives that are negatively charged has been demonstrated by using a 60-cm capillary, with the efficiencies 0.3–9.0×105 theoretical plates and the LODs at signal-to-noise ratio 3 ranging from 0.30 to 2.76nM. When compared to standard injection (30-cm height for 10s), the approach allows the sensitivity enhancements over the range of 50–800 folds for the derivatives. The new approach has been applied to the analysis of a red wine sample, with great linearity of fluorescent intensity against concentrations (R 2 >0.98) and the RSD (three repetitive runs in one day) values of the migration times for the ten identified amino acids less than 2.8%. [Copyright &y& Elsevier]

Abstract: A new method for the enrichment of Strychnos alkaloids in biological samples via liquid-phase microextraction (LPME) based on porous polypropylene hollow fibers combined with on-line sweeping in micellar electrokinetic chromatography (MEKC) was developed. Strychnos alkaloids were first extracted from urine sample which was adjusted to alkaline conditions (0.5moll−1 NaOH). The unionized analytes were subsequently extracted into 1-octanol impregnated in the pores of hollow fibers, and then into an acidic acceptor solution (100mmoll−1 H3PO4) inside the hollow fiber. The extract was analyzed directly by on-line sweeping in MEKC. In the method, the compound berberine was used as the internal standard (I.S.) for the improvement of the experimental reproducibility. The calibration curve was linear over a range of 20–200ngml−1 for both strychnine and brucine in human urine sample, with a correlation coefficient of 0.996 and 0.997, respectively. The detection limits (S/N=3:1) for strychnine and brucine were 1 and 2ngml−1, respectively. The LPME-sweeping method has been successfully applied to the analysis of strychnine and brucine in real urine sample, indicating that LPME-sweeping-MEKC is a promising combination for analysis of basic drugs present at low levels in some biological matrices. [Copyright &y& Elsevier]

Abstract: On-line sample preconcentration of oligonucleotides with a new sweeping carrier was developed by using dodecyltrimethylammonium bromide (DTAB) below the critical micelle concentration (CMC). The sweeping results with DTAB below and above the CMC were compared. The use of DTAB below the CMC benefits the preconcentration of the oligonucleotides, while the use of DTAB above the CMC is good for hydrophobic small molecules. The factors affecting the sweeping results were optimized and this method was evaluated by constructing calibration curves for thrombin aptamers. The sweeping scheme produced a 112-fold sensitivity enhancement for the oligonucleotides relative to that run in a running buffer without DTAB. The sweeping method developed here can be a good reinforcement of the preconcentration scheme by sweeping when less-hydrophobic analytes or large negatively-charged molecules need to be preconcentrated. [Copyright &y& Elsevier]

A sensitive and simple micellar electrokinetic chromatography (MEKC) method was developed for the determination of the antiepileptic drug carbamazepine (CBZ) using a sweeping on-line concentration method with photodiode array detection. The effect of pH, concentration of the running buffer solution, organic modifier, applied voltage and injection time on the concentration efficiency and separation was investigated. An untreated fused-silica capillary was used (50 cm; effective length, 40 cm, 75 μm i.d.) for the analysis. The background solution (BGS) was 50 mmol·L-1 NaH2PO4 (pH 3.0) containing 100 mmol·L-1 SDS and 20% acetonitrile (5.82 ms·cm-1) with an applied voltage of -20 kV at 25 °C. Sample introduction was performed at 0.5 psi for 90s with diode array detection at 214nm. For the method, the calibration curve was linear over a range of 0.5-40 μg · mL-1 for CBZ with a correlation coefficient of 0.998. The detection limit (S/N = 3: 1) of CBZ was 0.10 μg · mL-1. About 100-fold improvement in concentration sensitivity was achieved in terms of peak height by the sweeping method compared to conventional injection method. The sweeping-MEKC method has been successfully applied to the analysis of CBZ in tablet and human serum. [ABSTRACT FROM AUTHOR]

Abstract: The application of an on-line sweeping preconcentration method in micellar electrokinetic chromatography (MEKC) for the determination of Strychnos alkaloids, namely strychnine and brucine, has been investigated in this work. After experimental optimizations, the best separation was achieved in 50mmoll−1 H3PO4 (pH 2.0) containing 100mmoll−1 SDS and acetonitrile in a ratio of 4:1 (v/v), with an applied voltage of −20kV at 20°C. The sample matrix consisted of 100mmoll−1 H3PO4 (pH 2.0), and sample introduction was performed at 0.5psi for 270s, with photodiode array detection at 203nm. Compared with the conventional MEKC injection method, up to 100-fold improvement in concentration sensitivity was achieved in terms of peak height by using this sweeping injection technique. In the method, the compound berberine was used as the internal standard for the improvement of the experimental reproducibility. The calibration curve was linear over a range of 0.5–15μgml−1 for both strychnine and brucine, with a correlation coefficient of 0.998 and 0.997, respectively. The detection limits (S/N=3:1) for strychnine and brucine were 0.05 and 0.07μgml−1, respectively. The sweeping-MEKC method has been successfully applied to the analysis of strychnine and brucine in Strychnos nux-vomica L. and its Chinese medicinal preparations. [Copyright &y& Elsevier]

Abstract: We have investigated a rapid, simple, and highly efficient on-line preconcentration method using in micellar electrokinetic chromatography (MEKC) for the analysis of abused drugs. Ketamine is an anesthetic that has been abused as a hallucinogen. We applied the sample sweeping technique first to ketamine and its major metabolite, norketamine, and separated the analytes with MEKC. Several of the sweeping MEKC parameters to effect successful separations, such as the concentration of sodium dodecyl sulfate (SDS), the injection time, and the applied voltage were optimized. The improvements in the number of theoretical plates under the different separation conditions are presented clearly in a three-dimensional representation. The limits of detection were 2.8, 3.4, and 3.3ng/mL for ketamine, norketamine, and ketamine-D4, respectively. The enrichment factor for each compound was within the range of 540–800. Experimental results are in agreement with those of analysis conducted by gas chromatography/mass spectroscopy (GC/MS). Therefore, we believe that sweeping, combined with MEKC, represents a suitable complementary method to GC/MS for use in clinical and forensic analyses of ketamine and norketamine. [Copyright &y& Elsevier]

Abstract: A sweeping technique, in conjunction with micellar electrokinetic chromatography, for the simultaneous determination of flunitrazepam and its major metabolites, 7-aminoflunitrazepam and N-desmethylflunitrazepam, is described. The optimized conditions for the sweeping and separation were a pH 9.5 buffer, 25mM borate, 50mM cetyltrimethylammonium bromide, 30% MeOH (v/v), and a 151-mm injection length. The calibration functions were all linear with the coefficient of determination (r 2) exceeding 0.996 for the three target compounds. Using the sweeping procedure, the limits of detection were determined to be 13.4, 5.6, and 12.0ng/mL for flunitrazepam, 7-aminoflunitrazepam, and N-desmethylflunitrazepam, respectively, and the sensitivity enhancement for each compound was within the range of 110–200 fold. The RSDs for the retention time and the peak area were less than 4.10%. The optimized sweeping method was also used to examine a spiked urine sample. We conclude that sweeping with micellar electrokinetic chromatography has considerable potential use in clinical and forensic analyses of flunitrazepam and its metabolites. [Copyright &y& Elsevier]

Abstract: This paper reports a thermal lens microscope (TLM) detection coupled with capillary electrophoresis (CE) by using an interface chip (IFChip) to achieve highly sensitive detection with high reproducibility. Fused silica capillaries with an inner diameter of 50μm were directly connected to a microchannel on the IFChip. In comparison with an on-capillary detection method in CE-TLM, ca. 10-fold improvements in the reproducibility for peak height were obtained by using IFChips. The detection limit of an azo dye was estimated to be 3.6×10−7 M (100ppb), which was above 100-times lower than that of conventional absorbance detection. Toward further improvement of the detectability for nonfluorescent compounds, on-line sample preconcentration by sweeping was applied to the CE-TLM using the IFChip. Due to the sweeping effect, 3900000-fold increase in the sensitivity was successfully achieved. [Copyright &y& Elsevier]

Abstract: Determination of melatonin (MT) (N-acetyl-5-methoxytryptamine) and related indole compounds using standard capillary electrophoresis (CE) system with UV detection was investigated. Satisfactory separations of six analytes i.e. l-tryptophan (l-TRP), 5-methoxyindoleacetic acid (5-MIAA), 6-hydroxymelatonin (6-HMT), MT, serotonin (SER) and 5-methoxytryptamine (5-MTRA) were performed employing micellar electrokinetic chromatography (MEKC). The optimal background electrolytes (BGE) used for separations were 20mM tetraborate buffer (pH 9.2) and 20mM phosphate buffer (pH 3.3) when employing techniques with normal and reverse migration of micelles, respectively. Fifty millimolar sodium dodecyl sulfate (SDS) was employed as the pseudostationary phase and voltage of ±20kV was used throughout the investigation. On-line preconcentration techniques, stacking and sweeping, were applied in order to overcome high detection limits that are a serious drawback of CE with UV detection. A comparison of used techniques, concerning enhancement factors and limits of detection (LOD), is presented. Obtained results show that the use of stacking with reverse migrating micelles (SRMM) as one of preconcentration techniques allows obtaining the lowest estimated LODs for MT at the level of 30ng/mL with injection time of 99s at 0.5psi. Estimated LODs for other analytes in these conditions were, 21, 26 and 100ng/mL for l-TRP, 5-MIAA and 6-HMT, respectively. Signals of 5-MTRA and SER obtainable only with 10s injection allowed reaching estimated LODs of 62.5 and 130ng/mL, respectively. Analysis of spiked, diluted human serum was carried out as a preliminary application illustration of developed procedure. [Copyright &y& Elsevier]

Abstract: A simple and rapid sweeping method for the online improvement of detection sensitivity of the main alkaloids of Coptidis Rhizoma has been developed in this work. Optimum separation conditions were found as follows: electrophoretic running solution comprising 100mM phosphoric acid, 15mM sodium dodecyl sulfate (SDS) and 10% (v/v) tetrahydrofurane with pH 1.82; running voltage of -25kV; sample matrix composed of 50mM phosphoric acid and sample injection at 1000mbar for 60s (sample injection volume ca. 2.75μl). With this sweeping method, the concentration limits of detection of berberine, coptisine and palmatine were found to be 2.5ppb (ng/ml), which was about 500 times lower than those from conventional sample injections. Baseline separation was achieved for the main alkaloids within 15min. After validation, the developed method was applied to determine the quantity of berberine, coptisine and palmatine in a Coptidis Rhizoma sample. The method should be able to be used in identification and quantitative evaluation of the crude drugs requiring only a minor amount of sample. [Copyright &y& Elsevier]

When a gaseous phase takes place at the downstream side of a membrane separation process, two distinct options can be schematically operated in order to induce a driving force from that side: apply a lower pressure than the upstream one (thanks to a vacuum pump for instance), or exert a diluting effect by an inert gas sweep (under higher total downstream pressure conditions). The pros and cons of these two alternatives, particularly in terms of overall energy consumption, are often questioned, for instance for pervaporation applications where the first one (vacuum) is most often chosen but has never been systematically compared to the second one (sweeping gas). A simplified analysis of the above question is presented in this work. Based on a theoretical framework, which has been recently proposed, an easy to handle analytical solution to this problem is obtained. This expression enables the energy consumption under similar separation performances to be computed, providing that the permeabilities of the two compounds of the feed mixture remain constant. More specifically, it is shown that the energy consumption versus total downstream pressure curve shows invariably an asymmetrical bell shape with a maximum located at a fixed position. Operating conditions leading to minimal work of pumping will always be located at one of the two limits of the curve, that is to say either for low vacuum or high flowrate gas sweeping conditions. Nevertheless, taking into account the overall work of separation (i.e. the work needed for pure compounds recovery) clearly plays in favor of the vacuum operation. [Copyright &y& Elsevier]

High-salt stacking in electrokinetic chromatography (EKC) is defined and contrasted to the sweeping method. A recent paper argued the two methods are identical, where high concentrations of micelle in the sample were intended to mimic the effect of high-salt stacking. However, high micelle concentration in the sample matrix in EKC is analogous to using a high-conductivity sample instead of a low-conductivity sample in field amplified stacking. High-salt stacking does not require a sample free of pseuostationary phase, only a sample with a high-mobility co-ion compared to the separation buffer electrokinetic vector. High-salt stacking uses a discontinuous buffer system and should not be confused with continuous buffer stacking systems such as sweeping. [Copyright &y& Elsevier]

A series of subcooled boiling experiments was conducted on very small platinum wires having diameters of 0.1 and 0.025 mm. Vapor bubbles were visually observed to sweep back and forth along the wires in the experiments. The dynamic characteristics of bubble-sweeping phenomenon are described, and the induced bubble interaction and nonlinear growth are investigated to understand the boiling heat transfer mechanisms. An unsymmetrical temperature model is proposed to explain the physical mechanism. [ABSTRACT FROM AUTHOR]

Enantioselective separation of triadimenol, a component of systemic agricultural fungicide, by electrokinetic chromatography (EKC) using cyclodextrins (CDs) as chiral selectors was investigated. Both a neutral CD derivative, hydroxypropyl-γ-CD (HP-γ-CD), and an ionic one, heptakis-6-sulfato-β-CD (HS-β-CD), were employed as an additive in cyclodextrin–modified micellar electrokinetic chromatography (CD–MEKC) and as a chiral pseudostationary phase in CDEKC, respectively. In each system, four stereoisomeric peaks were completely or partially separated from each other. To enhance the detectability or the concentration sensitivity, on-line preconcentration techniques were applied to both EKC systems. Sweeping was used in the CD–MEKC system under an acidic condition, whereas stacking with a reverse migrating pseudostationary phase (SRMP) in the CDEKC system. Around 10-fold increase in the detection sensitivity for each peak was attained with both sweeping and SRMP systems. Good repeatabilities in the migration time, corrected peak area, and peak height were recognized in terms of the relative standard deviation. The limit of detection for each peak in the SRMP-CDEKC system, calculated from the calibration curve, was found to be 0.8–3.8 ppm. [Copyright &y& Elsevier]

This review provides an overview as well as a practical understanding of on-line sample concentration techniques in micellar electrokinetic chromatography (MEKC). MEKC as well as other capillary electrophoretic modes suffer from low concentration sensitivity due to minute sample volume and limited optical pathlength for on-capillary photometric detection. Two on-line sample preconcentration techniques, sample stacking and sweeping are known to be effective techniques for enhancement of the concentration sensitivity in MEKC. Sample stacking occurs as ions cross a boundary that separates regions of the high electric field sample zone and the low electric field background solution zone. The difference in migration velocity of pseudostationary phases within the two zones is the key to achieving the focusing effect. Sweeping is defined as the picking and accumulating of analytes by the pseudostationary phase that penetrates the sample zone devoid of pseudostationary phase. In this review, several examples of the sample stacking and sweeping under different experimental conditions are given, besides many references to applications. [Copyright &y& Elsevier]

The principal advantage of the use of Shopl''skii effect (low temperature spectrum) is that spectral sharpening occurs both in absorption and emission. However, thus far using the technique of capillary electrophoresis/low temperature fluorescence spectroscopy (CE/LTFS) either at 77 or 4.2 K remains difficult to obtain an on-line spectrum, if the analyte is present at low concentration. This paper examines the feasibility of combining the techniques of online concentration and CE/LTFS to identify LSD and related compounds in urine at 77 K. To improve sensitivity, sweeping-micellar electrokinetic chromatography (sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were used for on-line concentration which resulted in detection limits of ∼20 ∼60 ppt, respectively. [Copyright &y& Elsevier]

Quaternion notation lets us simplify and facilitate some transformation methods more than the usual way using 4×4 matrices. The main goal of this paper is to establish a new solid constructing method with advanced sweeping techniques in 3D space. We introduce several types of deformation functions to realize easy and versatile design techniques. [Copyright &y& Elsevier]

The objective of this paper is to provide an efficient and reliable algorithm for representing and evaluating the boundary of the interval Be´zier curve in 2- and 3-D. The boundary of the planar Be´zier curve is represented by a sequence of Be´zier curve segments with same degree and line segments in the order they are encountered when marching counter-clockwise along its boundary. The boundary can also be represented as a single B-spline curve having the same degree with the interval Be´zier curve. The boundary of the 3-D interval Be´zier curve is made up of trimmed Be´zier surface patches and rectangular patches. Some examples illustrate our algorithms. [Copyright &y& Elsevier]

Sweeping in capillary electrophoresis (CE) involves the interaction of a pseudostationary phase (PS) in the separation solution and a sample in the matrix that is free of the PS used. The PS includes not only the PSs employed in electrokinetic chromatography, but also complexation reagents such as borate. The sample matrix could have a lower, similar, or higher conductance than the separation solution. Thus, the basic condition for sweeping is a sample matrix free of the additive. The accumulation of analyte molecules during the interaction makes this interesting phenomenon very useful as an on-line preconcentration method for CE. Preconcentration occurs due to chromatographic partitioning, complexation, or any interaction between analytes and PS. Contact between analyte and PS is facilitated by the action of electrophoresis and is independent of electroosmosis. The analyte, PS, or both should have electrophoretic velocities when an electric field is applied. The extent of preconcentration is dictated by the strength of the interaction involved. From tens to several thousand-fold improvements in detector response for many neutral and charged analytes have been achieved with this technique, suggesting sweeping as a general approach to on-line preconcentration in CE. The mechanism and applications of the sweeping phenomenon under different experimental conditions are discussed in this review, with particular emphasis on a better understanding of the sweeping mechanism under reduced electric field (high conductivity) in the sample zone. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling of G1 bifurcation. A branch-blending strategy is applied to model the bifurcation such that the coherence among the individual branching segments is characterized. To achieve this, bi-cubic Be´zier patches are first used to generate three half-tubular surfaces by sweeping operations. The bifurcation modeling is then converted to a problem of filling two triangular holes surrounded by the swept half-tubular surfaces. In order for the bifurcation model to be G1, the candidate surfaces for hole filling are required to have (i) an inter-patch tangential continuity along the so-called star-lines; and (ii) a cross-boundary tangential continuity with the surrounding half-tubular surfaces. For inter-patch tangential continuity, we use the method proposed by Gregory and Zhou (1994) to determine the center-point, the star-lines, and the associated vector-valued cross-boundary derivatives. The problem of ensuring the cross-boundary tangential continuity with the surrounding surfaces is more difficult. We first derive the conditions for the twist-compatibility from the requirements of cross-boundary tangential continuity. The solutions for the conditions derived are then developed. The hole boundaries, originally in cubic Be´zier form, are constructively modified to the quintic form to ensure the twist-compatibility and uniqueness of the tangent planes at the hole corners. Subsequently, the half-tubular surfaces in bi-cubic Be´zier form are degree-elevated to quintic form along the sweeping directions. This is followed by the modification of the second row control points with the half-tubular surfaces in order to retain a cubic form of the surfaces'' cross-boundary derivatives. Vector-valued cross-boundary derivatives in quintic Be´zier form are constructed for the hole patches. Using a Coons–Boolean sum approach, the derivatives are utilized to modify the three Be´zier patches into the final bi-quintic form in the triangle fill area for each hole. [Copyright &y& Elsevier]

Deformation of 3D shapes usually requires the use of a deformation tool. The freeform deformation technique requires the use of a lattice of control point for deforming an object. This may require a synchronized movement of the lattice control points in order to obtain the desired effects. The axial deformation technique allows an object to be deformed by manipulating an axial curve. However, unexpected twist of the object may be obtained. This is a result of the lack of control on the local coordinate frame of the curve. This paper presents a technique for deforming objects with a set of axial curve-pairs. The use of a curve-pair allows the local coordinate frame to be controlled intuitively. A curve-pair is composed of a primary and an orientation curve. The orientation curve is an approximate offset of the primary curve. A technique is proposed for maintaining the relation between the primary and the orientation curve when the curve-pair is adjusted. By associating a complex 3D object to a curve-pair, the object can be stretched, bended, and twisted intuitively through manipulating the curve-pair. This deformation technique is particularly suitable for manipulating complex shapes (e.g. decorative components) in industrial and aesthetic design, and is also suitable for modelling characters and animals with flexible bodies. Adjusting the curve-pair according to some motion constraints produces different postures of a character or animal model. This in turn can be used as decorative components for aesthetic design. [Copyright &y& Elsevier]

Let L be a second order elliptic differential operator in R[SUPd] and let E be a bounded domain in R[SUPd] with smooth boundary ∂E. A pair (T,v) is associated with every positive solution of a semilinear differential equation Lu = &sgr;(u) in E, where T is a closed subset of ∂E and v is a Radon measure on O = ∂E \T. We call this pair the rough trace of u on ∂E. (In [E. B. Dynkin and S. E. Kuznetsov, Comm. Pure Appl. Math., 51 (1998), pp. 897-936], we introduced a fine trace allowing us to distinguish solutions with identical rough traces.) The case of &sgr;(u) = u[SUPδ with α > 1 was investigated using various methods by Le Gall, Dynkin, and Kuznetsov and by Marcus and Véron. In this paper we cover a wide class of functions and simplify substantially the proofs contained in our earlier papers. [ABSTRACT FROM AUTHOR]

Mitotane is a cytotoxic drug used in the treatment of inoperable adrenocortical carcinoma, it inhibits steroidogenesis as well, and therefore monitoring the level of steroid hormones in patients treated with mitotane is a crucial point of therapy. Hence, we have developed a simple, fast, and efficient electrophoretic method combined with reverse polarity sweeping as online preconcentration technique and dispersive liquid-liquid microextraction for the simultaneous determination of mitotane, its main metabolite DDA, and five steroid hormones (progesterone, testosterone, epitestosterone, cortisol, and corticosterone) in urine samples. In addition, a new sample matrix consisting of β-CD 2 SDS 1 complexes for a high hydrophobic compounds solubilization was developed. Approach based on the application of β-cyclodextrin and SDS complex of a ratio 2:1 allowed for hydrodynamic injection into the capillary of a solution containing both mitotane and other analytes. The detection limits of the analytes for the reverse polarity sweeping-dispersive liquid-liquid microextraction method were found to be in the range of 1.5-3 ng/mL, which were approximately 1000 times lower than in the conventional hydrodynamic injection (5 s, 0.5 psi) without any preconcentration procedure. All analytes were completely resolved in less than 13 min by uncoated silica capillary with an inner diameter of 75 μm (ID) × 60 cm. Electrophoretic separation was performed in reverse polarity with a voltage of -25 kV with a background electrolyte (BGE) consisting of 100 mM SDS, 25% ACN, 25 mM phosphate buffer (pH 2.5), and 7 mM β-cyclodextrin., (© 2021 Wiley-VCH GmbH.)

[Display omitted] • The first application of sweeping-MEKC-ICP-MS to improve detection limits. • Ultra-trace determination of oxaliplatin and its impurities B and C. • Within the optimal conditions, LODs of 1 to 3 ng mL-1 were achieved. • LOD represents the detection of 227 attomol of Pt per injection. • Compared to MEKC-UV, up to 3500-fold lower detection limits were reached. • A wide dynamic range up to six orders of magnitude (R2 ≥0.9989) was achieved. Oxaliplatin represents a platinum-based cancerostatic drug that is widely used for the treatment of various types of cancer. There are two main platinum-containing impurities, impurity B and C, that can be formed as side products at very low concentrations. Their effect on biological systems can be like the oxaliplatin itself; however, this has not been fully investigated since there is a lack of methods for their determination in ultralow concentrations. In our work, we present a method for ultra-trace determination of oxaliplatin impurities B and C, and oxaliplatin itself, using online sweeping preconcentration micellar electrokinetic chromatography coupled with inductively coupled plasma mass spectrometry (MEKC-ICP-MS). This is the first application of online preconcentration with MEKC-ICP-MS to improve the detection limits of analytes. Under the optimal conditions, 25 mM sodium phosphate buffer at pH 2.15 with 175 mM SDS, and an injection time of 90 s at 50 mbar, baseline separation of all components within 6 min was achieved. The sweeping-MEKC-ICP-MS method was fully validated in terms of linearity, limits of detection and quantification, trueness, precision, and reproducibility of migration times. Limits of detection of 2, 1, and 3 ng mL−1 for impurity B, impurity C, and oxaliplatin, respectively, were obtained, which are 3,500-, 1,700-, and 2,100-fold lower than those for a MEKC-UV method also developed and validated as a part of this work. It also represents the detection of 98 femtograms of the impurity C (or 227 attomol of Pt) per injection. The sweeping-MEKC-ICP-MS method further benefits from a wide dynamic range up to six orders of magnitude (0.01–1,000 µg mL−1 for oxaliplatin) with coefficients of determination greater than 0.9989. ICP-MS provides characteristic element/isotope-specific and structure-independent detection. ICP-MS helped identify the co-separated impurity B counter-ion that can be wrongly assigned as the platinum-based impurity B using standard UV detection. Finally, the validated sweeping-MEKC-ICP-MS method was applied to the analysis of oxaliplatin samples with variable impurities concentrations (0.06–1.0%). The trueness and precision ranged between 76 and 115% and 2–19%, respectively. This method allows the accurate determination of oxaliplatin impurities from 0.0003% levels; therefore, it could be used in routine pharmaceutical laboratories for quality control purposes. [ABSTRACT FROM AUTHOR]

Pseudophase microextraction (PPME) as a simple in-line sample concentration technique in micellar electrokinetic chromatography (MEKC) is presented. In contrast to popular electric-field driven stacking techniques in MEKC such as sweeping, PPME is pressure-driven. The technique afforded up to 403-2968x improvements in peak heights for fenoprop, dichlorprop, 1- and 2-naphthol compared to typical injection. Under the same MEKC conditions, the improvements in PPME were up to 23-59x better compared to sweeping. Briefly in PPME, the entire capillary was loaded (up to 20 capillary volumes) with the sample prepared in a dilute solution of cetyltrimethylammonium bromide ([CTAB] > critical surface aggregation concentration). The CTAB formed aggregates at the inner capillary walls and these aggregates acted as a stationary chromatographic pseudophase. After clean-up via flushing the capillary with purified water, the MEKC background solution (BGS) with sodium dodecyl sulfate was then introduced by pressure from the outlet end to elute the retained analytes. The analytes concentrate at front of the BGS and the front was moved to the inlet end of the capillary prior to MEKC. Optimization strategies and current limitations in PPME-MEKC are described. The linear ranges using a 4 capillary volume sample load obtained for fenoprop, dichlorprop, 1- and 2-naphthol were between 1 and 160 ng/mL (r 2s ≥ 0.996), LOQs = 1–2.5 ng/mL and repeatability %RSDs (n = 6) were ≤5% (intra-day) and ≤7% (inter-day) (using low analyte concentrations 1-5x LOQ). PPME-MEKC with simple dilution of fortified real samples (no off-line sample concentration) was also able to detect low levels of dichlorprop (10 ng/mL, limit set in Australia) and 1- and 2−naphthol (7.5–15 ng/mL) in a drinking water and natural water sample, respectively (% recovery = 84–108%). The concept of PPME may find use in other modes of capillary electrophoresis and other nano-microscale separations. [Display omitted] • Surfactant aggregates for in-line sample concentration in capillary electrophoresis. • Up to almost ∼3000x improvements in peak heights compared to typical injection. • Concentration performance was up to 59 times better compared with sweeping. • Analysis of low levels (7.5–15 ng/mL) of toxic analytes in fortified real samples. [ABSTRACT FROM AUTHOR]

This paper proposes a method of generating multisided patches from a curve network that has arbitrary topology. The method generates N sweep surfaces from the curves surrounding ans N-sided domain. A sweep surface is defined for each boundary of the domain by using a local parameter space that is composed of variables defined on generalized barycentric coordinates; N-sided patches are generated by blending the sweep surfaces with interpolants that preserve geometric continuity on each boundary. The geometric continuity of the curves crossing the boundaries. Moreover, curves can be represented by arbitrary degrees and nodes. [ABSTRACT FROM AUTHOR]

A class of free-form solids called profiled sweep objects is defined by four parametric curves: a 2D contour (cross-section), a 3D trajectory (spine), and two profile curves, which control the scaling of the contour as it moves along the trajectory. Subclasses of this are profiled prisms, which have a linear trajectory, and profiled generalized cylinders, which have an arbitrary 3D trajectory. First an exact definition of profiled sweep object, is presented and their relation with common sweep objects is described. Then a method is given for the construction of planar approximations of these objects that can be used for fast display generation. Finally, ray-tracing algorithms are given that directly use the exact definition for high-quality display. [ABSTRACT FROM AUTHOR]

The Asian longhorned tick, Haemaphysalis longicornis Neumann, is an invasive species in the United States. Since its earliest recorded presence in West Virginia in 2010, H. longicornis has been reported from 15 states. While its public health significance in the United States is unclear, globally it transmits pathogens that infect livestock and humans, causing economic losses and substantial morbidity. Management and control of H. longicornis requires knowledge of its biology, ecology, and distribution. Here, we address the need for effective collection methods for host-seeking H. longicornis as an important step for accurately assessing tick abundance and potential disease risk. The number of H. longicornis collected were compared across three collection methods (dragging, sweeping, CO2 traps) and three tick check distances (5 m, 10 m, and 20 m) were compared for dragging and sweeping. Field collections were conducted from June through August 2019 in Westchester County, New York, and ticks were grouped by life stage to assess collection method efficiency. Results indicated that implementing shorter (5 m) tick check distance was ideal for adult and nymphal collections. The dragging method proved better than sweeping for adult collections; however, there was no significant difference between the methods for nymphal collections, at any tick check distance evaluated. CO2 traps attracted H. longicornis, but additional research is necessary to devise an effective tick retaining method before the traps can be implemented in the field. The results are presented to inform and support H. longicornis surveillance and control programs across the nation., (© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)