Short Separation Time Research Articles

Microfluidic fast chiral separation of baclofen and phenylalanine enantiomers based on cyclodextrin-electrokinetic chromatography

A green chiral lab-on-a-chip cyclodextrin-based microchip electrophoretic method was developed for enantioseparation of baclofen (BCN) and phenylalanine (Phe) enantiomers for the first time. All BCN and Phe enantiomers were offline labeled with 4-fluoro-7-nitrobenzofurazan (NBD-F) or fluorescein-5-isothiocyanate (FITC) fluorogenic reagents prior to microfluidic injection in a dynamically coated polymethylmethacrylate microchip. The enantioseparation was performed using borate buffer solution (50 mM; pH 9.5) containing a dynamic coating polymer (methylcellulose) and a chiral selector of cyclodextrin (CD) family as the background electrolyte. The combination of sieving properties of methylcellulose polymer and inclusion complex formation properties of the cyclodextrins rendered a novel green pseudo-stationary phase for the microfluidic chiral separation of the studied enantiomers in short separation time. Seven CD chiral selectors were investigated in our study to illustrate the proposed enantioseparation mechanism in the dynamically coated microfluidic channels. The results indicated that use of a modified cyclodextrin, heptakis-(2,6-di-O-methyl)-β-cyclodextrin (HDM-β-CD), resulted in extra interactions with the analytes of interest, leading to extra resolution with high number of theoretical plates. Therefore, HDM-β-CD was able to separate the NBD-labeled and FITC-labeled enantiomers of BCN and Phe within short analytical time. Sensitivity problem of microchip electrophoresis was overcome by application of field-enhanced injection stacking which improved sensitivity to a higher extent by online preconcentration of the labeled enantiomers in the microfluidic channels. The method was fully validated and successfully applied for the assay of BCN enantiomers and Phe enantiomers in their pure racemic mixtures. Moreover, the developed method was applied for precise analysis of BCN enantiomers in pharmaceutical formulations and in biological samples. The extraction recovery values of BCN enantiomers in biological samples were > 87.5% and %RSD < 7.0.

Synthesis of benzo[h]quinolone and benzo[c]acridinone derivatives by Fe3O4@PS‐Arginine[HSO4] as an efficient magnetic nanocatalyst

AbstractFe3O4 magnetic nanoparticles were synthesized and functionalized by propylsilan and after that arginine. The synthesized Fe3O4@PS‐Arginine magnetic nanoparticles were modified to obtain Fe3O4@PS‐Arg[HSO4]. These nanoparticles were used as environmental friendly solidacid magnetic nanocatalyst for the synthesis of 2‐amino‐4‐arylbenzo[h]quinoline‐3‐carbonitrile and 10,10‐dimethyl‐7‐aryl‐9,10,11,12‐tetrahydrobenzo[c]acridin‐8(7H)‐one derivatives via the one‐pot reaction of α‐naphthilamine and aromatic aldehydes with malononitrile or dimedone. Simple operation, high reaction yields, reusability of catalyst for several times, short reaction time and easy separation from reaction mixture are the key advantages of using this catalyst.

Advances in polydopamine surface modification for capillary electrochromatography

Capillary electrophoresis (CE) has a wide range of applications in analytical fields due to its advantages of low sample consumption, short separation time, and high separation efficiency. The cathodic electroosmotic flow (EOF) and single electrophoretic separation mechanism are not optimal for many CE applications. Hence, the use of an unmodified fused-silica capillary leads to insufficient separation performance that cannot meet the requirements for various complex sample systems, especially neutral and chiral compounds. Therefore, it is necessary to introduce various capillary modification strategies in CE so that its potential for practical application can be expanded. Mussel-inspired polydopamine (PDA) and PDA-derived coating materials have fascinating advantages such as simple surface coating procedures, strong surface adhesiveness, good chemical stability, latent reactivity with many functionalized molecules, and good biocompatibility. Thus, they have been widely utilized in different research fields, including catalysis, sensing, water treatment, sample pretreatment, biomedicine, chromatographic separation, and CE. The preparation of PDA coatings is simple as it involves physical adsorption, and the obtained surface adhesive coatings possess good stability similar to covalently bonded coatings. Therefore, PDA and PDA-derived coatings are well suited for the modification of fused-silica capillaries. More importantly, the PDA coating can be utilized as an intermediate reaction platform for diverse subsequent surface modification because of its strong surface adhesive property and strong latent reactivity with many functionalized molecules (such as polymers, proteins, and nanomaterials). Consequently, various chromatographic retention mechanisms can be introduced on the inner wall of the capillary, thereby contributing to the fabrication of multi-functional PDA-based stationary phases for CEC. Owing to these outstanding advantages, researchers are paying increasing attention to the great application potential of PDA and PDA-derived coatings in CEC. In this paper, recent advances in the methods for preparing PDA coatings, especially the recently developed fabrication strategies and various applications of PDA-modified silica capillary in open tubular-capillary electrochromatography (OT-CEC) and capillary electrochromatography monolithic columns, are summarized and discussed. Furthermore, the application prospects of PDA-based coating materials in CEC are prospected in this review. Although PDA and PDA-derived coating materials are seeing widespread utilization in field of CEC, researchers have still not reached a definite conclusion regarding the PDA formation and coating mechanisms, and further investigation is needed in this direction. The PDA coatings formed using existing methods are generally thin. In the early stage, many studies adopted the strategy of repeated coating to improve the coating effect of PDA in capillaries, but this method was found to be time-consuming and less efficient. In order to improve the preparation efficiency of PDA-modified CEC columns, many researchers have focused on fast deposition induced by a strong oxidant to obtain PDA-coated columns. However, the controllability of the PDA coating obtained by this method is poor. Thus, it is necessary to further explore new preparation strategies for PDA-coated CEC capillaries with better reproducibility and stronger operability. On the other hand, although a strategy for directly synthesizing functional PDA-coated CEC columns in the organic phase has been proposed, its application potential in CEC remains to be further explored. In addition, the PDA coating itself has poor porosity and a small specific surface area, which may be significantly improved by modifying the coating on the porous monolithic column surface. However, there has been limited research on the use of PDA coatings in monolithic columns, and their application potential remains to be expanded. With in-depth research into the formation mechanism and preparation methodologies of PDA coatings, PDA, which is a highly malleable biomimetic material, will play a more important role in advances in the fields of CE and CEC.

Determination of Volatile Fuel Oxygenates in Water by Gas Chromatography–Triple Quadrupole Mass Spectrometry: Effect of Automated Sample Preparation Techniques

Considering the adverse effects of gasoline additives and aromatic compounds on the quality of the water supply and the ecological environment of the water, a methodology, with short chromatographic separation time (22.5 min) and high separation quality, was optimized for the determination of 11 common gasoline additives and aromatic compounds using gas chromatograph coupled with triple quadrupole mass spectrometer (GC–QqQ–MS/MS) system. The extraction procedure of analytes was performed by headspace solid–phase microextraction (HS–SPME) and purge and trap (P&amp;T), respectively. Both of the two extraction methods provided excellent chromatographic resolution in subsequently GC–QqQ–MS/MS detection system, with the coefficients of linear regression of the calibration curves with HS–SPME and P&amp;T pretreatments were 0.9965~0.9998 and 0.9961~0.9999, respectively, n = 7. The limit of detections (LODs) of these selected oxygenate compounds were discovered to be 0.52~32 ng/L in the P&amp;T–GC–QqQ–MS/MS detection system and 0.11~151 ng/L in the HS–SPME–GC–QqQ–MS/MS detection system. For benzene, toluene, ethylbenzene and xylene isomers (BTEX), the HS–SPME–GC–QqQ–MS/MS system provided outstanding detection performance because of the lower LOD obtained. However, for other selected compounds, the P&amp;T–GC–QqQ–MS/MS system offered lower LODs. The proposed extraction–detection procedure is a simple and sensitive analytical approach for the detection of gasoline additives and aromatic compounds in water.

Perspective of self-assembled InGaAs quantum-dots for multi-source quantum implementations

In recent years, semiconductor quantum dots have demonstrated their potential to reach the goal of being an ideal source of single and entangled photon pairs. Exciting reports of near unity entanglement fidelity, close to unity photon indistinguishability, and high collection efficiency in nanophotonic structures have been demonstrated by several distinct groups, showing unequivocally the maturity of this technology. To achieve the required complexity and scalability in realistic quantum photonic implementations, two-photon interference of photons from multi-sources must be reached. While high indistinguishability values have been observed for photons generated from the same source within a relatively short time separation, achieving similar visibility for larger time separation or in multi-source experiments still requires intensive efforts. In fact, the coupling to the particular mesoscopic environment of charge carriers confined in the quantum dot leads to decoherence processes, which limit the quantum interference effects to a short time window. Here, we discuss the progress in studying the dynamics of this decoherence, which crucially depends on the evolution of line broadening in high-quality self-assembled InGaAs quantum dots. Characterization of line broadening mechanisms is the first fundamental step to be able to counteract them. Optimization of the growth and active and passive control of the radiative transitions are crucial for the technological readiness of non-classical light sources based on semiconductor platforms.

Multi-Δt 3D-PTV based on Reynolds decomposition

A novel approach is investigated to extend the range of measurable velocities by 3D-PTV systems. The method is specifically conceived for robotic volumetric PTV measurements, but it has applications for other similar techniques. The multi-Δt method relies upon combining the information from two or more sets of double-frame images with pulse separation of different time duration. Measurements with a short time separation yield a robust particle velocity field estimation with a higher percentage of valid vectors, yet a low measurement precision. Conversely, measurements with longer time separation potentially offer a higher measurement precision but suffer from an increased probability of spurious particle pairing. Reynolds decomposition is used to combine the two (dual-Δt) sets where a predictor for the mean particle displacement and its statistical dispersion is used to pair particle recordings from a longer time separation. For this reason, this method is aimed at the analysis of turbulent flows where the Reynolds decomposition is meaningful (e.g. turbulent flows with steady/quasi-steady boundary conditions). The extent of the search region is selected dynamically, based on the estimate of the velocity fluctuations from the short time separation evaluation. A more advanced variant of the algorithm contemplates the progressive increase of the pulse separation (multi-Δt) until the expected dispersion of data due to turbulent fluctuations eventually exceeds the distance between neighbouring particles.Flow measurements in the near wake of a truncated cylinder obstacle and of an Ahmed body are carried out to examine the performance of the proposed method. Reference data is taken from time-resolved multi-frame analysis based on the Shake-The-Box (STB) algorithm. The two experiments differ for the measurement principle used: the first one is conducted with a tomographic-like system (large aperture), whereas the latter uses coaxial volumetric velocimetry. The rate of correct pairing as well as the velocity dynamic range dependence upon the choice of the time separation are monitored and discussed. The results compare favourably with the STB analysis, indicating that the measurement of the time-average velocity field can be based on dual-Δt 3D-PTV measurements removing the constraint of time-resolved particle motion recording.

Collection and Separation of Fleroxacin and Ciprofloxacin in Ultrasound-Assisted Ionic Liquid Salting-Out Microextraction System.

An ultrasound-assisted ionic liquid (IL) salting-out microextraction system was developed and applied for the extraction of quinolone antibiotics from urine. A precipitate was formed from the salt and IL, and it acted as the sorbent for the analytes. The precipitate containing the analyte was separated by filtration, redissolved, and the solution then was evaporated. The resulting extract was redissolved for high-performance liquid chromatographic analysis. Several parameters, including type and volume of IL, the type and amount of salts, sample pH, temperature and extraction time were optimized. Under the optimal experimental conditions, the limits of detection for fleroxacin and ciprofloxacin were 3.12 and 4.97μgL-1, respectively. When the present method was applied to real urine sample analysis, the analyte recoveries ranged from 82.3 to 106.8%. This ultrasound-assisted IL salting-out microextraction system had the characteristics of high recoveries, shorter separation time and easy-to-perform collection procedure, which yielded the method to have potential for wide application.

Estimation of measurement uncertainty and validation of RP-HPLC for simultaneous determination of five antihistamines in pharmaceutical formulations

Nowadays, measurement uncertainty is considered an essential parameter for method evaluation. Measurement uncertainty estimation requires a detailed study of all possible sources of uncertainty. The aim of this work was to develop and validate an isocratic reversed-phase high-performance liquid chromatographic method for the simultaneous separation and determination of five antihistamines in pharmaceutical formulations and to establish a procedure to evaluate the measurement uncertainty of values generated by the validated method. A relatively short chromatographic separation time, less than 9 min, was achieved by means of a Waters XBridge C18 (4.6 mm×250 mm, 5 µm) analytical column under isocratic conditions using a mobile phase consisting of sodium perchlorate buffer (pH 3.5; 0.1 mol L−1)–acetonitrile (55:45, v/v) at a flow rate of 1 mL min−1 and UV detection at 235 nm. The selectivity, method linearity, accuracy, precision, limits of detection (LOD) and limits of quantification were examined as parts of the method validation. The described method shows excellent linearity over a range of 30 μg mL−1 to 70 μg mL−1 for all compounds with correlation coefficients higher than 0.995. The standard deviations of the intraday and inter-day precision were all less than 2 %. The LOD of all studied compounds ranged from 0.029 μg mL−1 to 0.03 µg mL−1. Using EURACHEM/CITAC guide and Valid Analytical Measurement (LGC/VAM) protocol, measurement uncertainty associated with precision and standard preparation were the most important contributing for the five antihistamines, accounting for 87.72 % to 91.03 % and 4.05 % to 10.24 % of total uncertainty, respectively, and overall uncertainties obtained were from 0.05 mg to 0.58 mg. Therefore, the proposed method was suitable for the routine analysis of antihistamines in pharmaceuticals formulations with the required accuracy, precision and measurement uncertainty.

Ultra-high performance supercritical fluid chromatography combined with quadrupole time-of-flight mass spectrometry for the characterization of pentaerythritol fatty acid esters.

Pentaerythritol fatty acid esters are an excellent lubricant oil additive, due to their good biodegradability, thermal ability, anti-wear, and friction properties. However, to meet the application requirements, fatty acids with different alkyl chain lengths are reacted with pentaerythritol, resulting in complex ester compositions. To reveal the relation between the functionalities and the composition of esters, it is important to develop a method for their analysis. We developed a method using ultra-high-performance supercritical fluid chromatography combined with quadrupole time-of-flight mass spectrometry (UHPSFC/QTOF-MS) to separate and characterize pentaerythritol fatty acid esters. This method has the advantages such as short analysis time and high separation efficiency for such weakly polar compounds; high-resolution mass spectrometry (HRMS) provides exact mass information, enabling the identification of the structure of the pentaerythritol fatty acid esters. Based on the exact masses and characteristic ions, the pentaerythritol fatty acid esters and their main fragmentation pathways were identified; the fatty acid composition was also deduced from characteristic product ions. A dihydrogen rearrangement reaction caused the neutral loss of fatty acid fragment; [M + Na-FA]+ product ions (a stable six-member ring structure) were produced due to the absence of a γ hydrogen in pentaerythritol fatty acid esters. A UHPSFC/QTOF-MS method was successfully employed for the separation of pentaerythritol fatty acid esters. Exact masses and product ion information were determined using HRMS. The composition of the fatty acids was effectively deduced by characteristic ions and their relative abundances. This method is an effective means for the quality control and process optimization of this type of product, serving as a positive reference for further study on pentaerythritol fatty acid esters.

DETERMINATION OF FOUR ARSENIC SPECIES IN ALGAE BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY COUPLED WITH HYDRIDE GENERATION ATOMIC FLUORESCENCE SPECTROMETRY

A rapid method has been developed for the determination of silver arsenite As(III), dimethylated arsenic DMA, monomethylated arsenic MMA, and arsenate As(V) in algae sample using liquid chromatography coupled with hydride generation atomic fluorescence spectrometry (LC-HG-AFS). Types, flow rate and pH of mobile phase were optimized. Under the optimal conditions, there were good linear relationships in the range of 0 -200 µg L-1 with correlation coefficients larger than 0.9995. The limits of detection and quantification of As(III), DMA, MMA, and As(V) were 0.005- 0.010 mg kg-1 and 0.019-0.034 mg kg-1, respectively. The recoveries at three spiked levels of 0.02, 0.5 and 1.0 mg kg-1 were in the range of 93-105 % with relative standard deviations (RSD, n=6) of 3.6%-6.2%. The proposed method was successfully applied in the determinaton of four arsenic species in algae sample. The developed method is simple, higher precision, stable data collection, and shorter separation time, and could be applied in the speciation and study of arsenic species in algae.

Chemometrically Assisted Development of Ultra-High-Performance Liquid Chromatography Method for the Simultaneous Quantification of Sofosbuvir, Daclatasvir and Ledipasvir in Pharmaceutical Dosage Forms.

A new ultra-high-performance liquid chromatography method for the simultaneous quantification of sofosbuvir, daclatasvir and ledipasvir was developed. Two combinations of these direct-acting antivirals are used in hepatitis C virus infection therapy and show high efficacy and safety. Fractional factorial design was used for screening the most influential factors on separation and time analysis. These significant factors were optimized using a central composite design. The optimum resolution was carried out by using a Waters XBridge C18 column (150mm, 4.6mm ID, 5μm) at a temperature of 35°C±2°C and acetonitrile/sodium perchlorate buffer (10mM, pH=3.2) (40: 60v/v) as mobile phase at a flow rate of 1.5mLmin-1. UV detection was set at λ=210nm. A short chromatographic separation time was achieved. The developed method was validated according to the accuracy profile approach and was found specific, precise, faithful and accurate. The detection limits were between 0.07 and 0.13μgmL-1. Hence, this novel method can be employed for the routine quality control analysis and in dissolution profile studies of generics containing these products.

Concept Development and Risk Reduction for MISTiC Winds, A Micro-Satellite Constellation Approach for Vertically Resolved Wind and IR Sounding Observations in the Troposphere

MISTiC Winds is an instrument and constellation mission approach to simultaneously observe the global thermodynamic state and the vertically resolved horizontal wind field in the troposphere from LEO SSO. The instrument is a wide-field imaging spectrometer operated in the 4.05–5.75 μm range, with the spectral resolution, sampling, radiometric sensitivity, and stability needed to provide temperature and water vapor soundings of the atmosphere, with 1 km vertical resolution in the troposphere-comparable to those of NASA’s atmospheric infrared sounder (AIRS). These instruments have much higher spatial resolution (&lt;3 km at nadir) and finer spatial sampling than current hyperspectral sounders, allowing a sequence of such observations from several micro-satellites in an orbital plane with short time separation, from which atmospheric motion vector (AMV) winds are derived. AMVs for both cloud-motion and water vapor-motion, derived from hyperspectral imagery, will have improved velocity resolution relative to AMVs obtained from multi-spectral instruments operating in GEO. MISTiC’s extraordinarily small size, low mass (&lt;15 kg), and minimal cooling requirements can be accommodated aboard an ESPA-class microsatellite. Low fabrication and launch costs enable this constellation to provide more frequent atmospheric observations than current-generation sounders provide, at much lower mission cost. Key technology and observation method risks have been reduced through recent laboratory and airborne (NASA ER2) testing funded under NASA’s Instrument Incubator Program and BAE Systems IR&amp;D, and through an observing system simulation experiment performed by NASA GMAO. This approach would provide a valuable new capability for the study of the processes driving high-impact weather events, and critical high-resolution observations needed for future numerical weather prediction.

Towards an efficient and durable superhydrophobic mesh coated by PDMS/TiO2 nanocomposites for oil/water separation

Oil spill accidents and industrial oily wastewater are threatening all living species in the ecological system. Development of materials with special wettability for oil/water separation has been the subject of many researches. Herein, superhydrophobic and superoelophilic nanocomposite coatings, based on titanium dioxide (TiO2) nanoparticles and polydimethylsiloxane (PDMS), were applied on metal meshes with different pore sizes (25 and 100 μm). Morphological analysis revealed that adding PDMS, as a binder, significantly changes the surface structure of the coatings. For 100 μm-sized meshes, PDMS causes a two-tier roughness whereas a uniform and finely packed single-scale nanostructure was formed for 25 μm-sized meshes upon PDMS addition. Exceedingly high content of nanoparticles was found to impose a detrimental influence on uniformity of morphology. All the samples exhibited superhydrophobicity; however, their mechanical durability results were significantly diverse. PDMS introduction was found to impose a substantial improvement in abrasion resistance. Oil/water separation experiments revealed that the mesh with smaller pore size exhibited a more efficient separation while a much shorter separation time and higher flux could be achieved by the mesh with larger pore size. In addition, the mesh with smaller pore size exhibited a more abrasion resistant coating which could be more beneficial in real-life applications.

The use of magnetic iron oxide based nanoparticles to improve microalgae harvesting in real wastewater

A novel approach for harvesting Scenedesmus sp. microalgae from real wastewater by using adsorbents of magnetite-based nanoparticles (Fe3O4 NPs) was tested in this study for the first time for this microalgae. Using these NPs, the harvesting efficiency was even higher than 95%. The optimal conditions (0.14 gNPs/L, a short magnetic separation time of only 8 min and 27 min of contact time) were found using the response surface methodology. The best fitting of the adsorption equilibrium results was achieved by the Langmuir isotherm model, and the maximum adsorption capacity for Scenedesmus sp. reached 3.49 g dry cell weight (DCW)/g Fe3O4 NPs. Zeta potential measurements and the Dubinin-Radushkevich isotherm model analysis pointed out that the main adsorption mechanism between Scenedesmus sp. cells and Fe3O4 NPs was electrostatic interaction. Finally, Fe3O4 NPs were six times successfully reused by combining an alkaline treatment with an ultrasonication process, which implies microalgae lysis. The results herein obtained highlight the potential for magnetic separation of microalgae from wastewater, which is capable of reaching a high harvesting efficiency in a very short time.

Multivariate optimization and validation of a procedure to direct determine acetonitrile and ethanol in radiopharmaceuticals by GC-FID

A fast and simplified analytical procedure was developed and validated for the direct determination of organic solvents (acetonitrile and ethanol) in radiopharmaceuticals samples ([18F]FMISO, [18F]FES and [18F]FLT) by gas chromatography coupled with flame ionization detection (GC-FID). Optimization studies were performed with the aid of two-level full factorial design. The optimum conditions were located using Derringer's desirability function. Procedure validation assured the compliance of the assay to Brazilian regulatory agencies standards (ANVISA and INMETRO). Values for LOD and LOQ were commensurate with the level at which the impurities must be controlled. Good linearity was achieved (R ≥ 0.990) for acetonitrile and ethanol concentrations ranging from 0.003 to 0.09% (w/v) and 2.1 to 11.0% (v/v), respectively. Accuracy and precision assessments were performed using samples fortified with standards (spiked samples). The developed procedure proved to be selective, sensitive, accurate (95.9–117.8% of nominal values) and precise (RSD ≤ 9.7%). The validated procedure was successfully used to assess organic solvents levels in a Brazilian radiopharmaceuticals samples manufactured by Radiopharmaceutical Research and Production Unit of Nuclear Technology Development Center (CDTN), in Belo Horizonte (Brazil). The analytes could be well resolved in 1.5 min and accurately determined in three different types of radiopharmaceuticals. This procedure is applicable to samples even with high ethanol content up to 11% (v/v). Other advantages include no sample preparation, short chromatographic separation time and minimum manual operation. As results, the proposed procedure can be useful in the routine analysis for the determination of acetonitrile and ethanol in radiopharmaceutical samples.

Evaluation of prenylflavonoids and hop bitter acids in surplus yeast.

This study developed a high performance liquid chromatography with diode array detection (HPLC-DAD) and tandem mass spectrometry (MS-MS) method for determination of prenylflavonoids and hop bitter acids in surplus yeast, a byproduct from beer brewing process. This method enabled the simultaneous separation of 4 prenylflavonoids and 20 hop bitter acids within 30min by employing a Hypersil-Keystone HyPURITY C18 column and a gradient mobile phase composed of phosphoric acid aqueous solution at pH 1.6 and acetonitrile. For HPLC-DAD analysis, the limits of detection and limits of quantitation ranged from 0.04 to 0.15µg/mL and from 0.12 to 0.45µg/mL, respectively, and the recoveries ranged from 82.6 to 99.7%. The intra-day variability and inter-day variability ranged from 1.37 to 8.82% and from 0.68 to 9.74%, respectively. For qualitation by MS-MS, the positive mode was discovered to possess satisfactory collision capacity and high sensitivity for prenylflavonoids, while the negative mode was more suitable for the ionization of hop bitter acids. The content of hop bitter acids in surplus yeast were higher than that of prenylflavonoids, and isomers and oxidation products of hop bitter acids were found. This study has advantages in identifying more components, short separation time, satisfactory resolution, high accuracy and high precision.

Oxygen content of high ferrotitanium prepared by thermite method with different melt separation temperatures

High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content (≥ 10 wt%) because of the short slag-metal separation time. In this study, CaO and CaF2 are added to the melt to improve the basicity of the slag and melt separation under heat preservation is performed to strengthen slag-metal separation. The thermodynamics of the step-by-step reduction process of TiO2 in the Ti–Al–Fe–Si–O system whose composition is close to the alloy after melt separation were calculated. Samples of alloys and slags before and after melt separation were systematically analyzed. The result indicates that the reaction that TiO is reduced by Al to Ti is the limited step in the reduction process of TiO2. The O content of the alloys slightly decreases with temperature from 1873 to 2023 K, which agrees with the changes in the law of deoxidation limit. It is mainly attributed to the movement of chemical reactions in the alloy melt at different temperatures and slag-metal interfacial reaction. The addition of Al2O3–CaO–CaF2 slag and high temperature promote the removal of Al2O3 and titanium suboxides. The minimum contents of O and Al in the alloy reach 1.84 wt% and 3.26 wt%, respectively.

Electrophoresis of megaDalton proteins inside colloidal silica.

With the growth of the biopharmaceutical industry, there is a need for rapid size-analysis of proteins on the megaDalton scale. The large pore sizes needed for such separations cannot be easily reached by pushing the current limits of size-exclusion chromatography or gel electrophoresis. The concept detailed here is the formation of arbitrarily wide pores by packing nonporous colloidal silica in capillaries. This method can be called packed-capillary electrophoresis, or "pCE". Electrophoresis of protein standards (11-155kDa) by pCE, using 345 nm diameter particles in 100 μm diameter capillaries, gives 2x higher resolution than a typical PAGE gel in 1/6 of the time. The electropherograms show that pCE is highly efficient, with half-micrometer plate heights for all seven standards, giving 105 plates for a 50 mm length. The large pore radius of 65 nm enables baseline resolution of proteins of 0.72, 1.048 and 1.236 MDa in less than 15 min. The short separation time of pCE is attributed to the absence of small pores that restrict protein migration in gels. The pCE separation is applied to the analysis of a stressed pharmaceutical-grade IgG4 sample, giving unprecedented baseline resolution of monomer, dimer, trimer and tetramer in less than 10 min.

Optimization and characterization of magnetite-reduced graphene oxide nanocomposites for demulsification of crude oil in water emulsion.

Oily wastewater from the oil and gas industry negatively affects the environment. Oily wastewater typically exists in the form of an oil-in-water emulsion. Conventional methods to treat oily wastewater have low separation efficiency and long separation time and use large equipment. Therefore, a simple but effective method must be developed to separate oil-in-water emulsions with high separation efficiency and short separation times. Magnetite–reduced graphene oxide (M–RGO) nanocomposites were used as a demulsifier in this work. Magnetite nanoparticles (Fe3O4) were coated on reduced graphene oxide (rGO) nanosheets via an in situ chemical synthesis method. The synthesized M–RGO nanocomposites are environmentally friendly and can be recovered after demulsification by an external magnetic field. M–RGO characterization was performed using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning microscopy, Raman spectroscopy, and vibrating sample magnetometry. Demulsification performance was evaluated in terms of M–RGO dosage, effects of pH, and brine concentration. The demulsification capability of M–RGO was determined based on the residual oil content of the emulsion, which was measured with a UV-vis spectrometer. The response surface method was used to determine the optimum conditions of the input variables. The optimum demulsification efficiency achieved at pH 4 and M–RGO dosage of 29 g L−1 was approximately 96%. This finding demonstrates that M–RGO nanocomposites are potential magnetic demulsifiers for oily wastewater that contains oil-in-water emulsions. Also, the recyclability of this nanocomposite has been tested and the results shown that it is a good recyclable demulsifier.

Catalytic activity of zeolite Hβ for the preparation of fuels’ additives: Its product distribution and scale up calculation for the biofuel formation in a microwave assisted batch reactor

Viability for oxo pentanoate, pentanoate and butanediaoate production as potential biofuel produced from carboxylic acid by acid hydrolysis of lignocellulosic biomass has been identified. Carboxylic acids like butanedioic acid (BA), 4-oxo pentanoic acid (oPA) and pentanoic acid (PA) were reacted with alcohols like primary alcohol as Methanol (MeOH), Ethanol (EtOH) and secondary alcohol as 2-Propanol (2-PrOH) using Microwave Irradiation (MWI). H2SO4 as homogeneous catalyst and Hβ as solid acid catalyst were studied to establish efficient esterification reactions with variation in the operating conditions (reaction time, feed ratio, catalyst dosage, microwave power, reaction temperature, type of catalyst, etc.). The comparison was established with conventional as well as MWI process with the use parent zeolite Hβ and desilicated Hβ (D-Hβ) to produce respective esters. Further Hβ and D-Hβ have been analysed by different characteristics for the solid catalyst. Acidity of zeolite β by Ammonia temperature program desorption (NH3-TPD), average particle size by DLS, SEM & TEM, framework confirmation by XRD & FTIR, while surface area, pore size and pore volume were measured by BET method. This study was to establish efficient selectivity and conversion analysis of the desired biofuels’ additives with use of MWI, a cleaner production technique. It has advantages of high selectivity, good conversion, short reaction time and less separation cost. Further to apply conversion & selectivities’ analysis and to scale up the reaction, batch reactor model equation is developed with MWI process based on the reaction constant and concentration of the stoichiometric reactants.