Porous Column Research Articles

Doping amount dependence of phase formation and microstructure evolution in heavily Cu-doped Bi2Te3 films for thermoelectric applications

Heavily Cu-doped Bi2Te3 films with different Cu contents (∼47.9 at%) were prepared by co-sputtering with Cu and Bi2Te3 targets at room temperature and post-annealing at ∼500 °C. When the Cu content increased, the lattice parameters of the c-axis gradually increased with the increase of Cu intercalation into van der Waals gaps between the quintets of the Bi2Te3 layers. When a Cu content of above 43.7 at% was added, formation of a Cu2Te phase was detected along with the phase transition from Bi2Te3 to Te-deficient BixTey in the films annealed at 300 °C. The porous column structure of the pure Bi2Te3 film became gradually dense with the increase of Cu content. When the Cu content was increased, the thermoelectric power factors of heavily Cu-doped Bi2Te3 films were enhanced by the increase of carrier concentration.

Core-shell LC–MS/MS method for quantification of second generation anticoagulant rodenticides diastereoisomers in rat liver in relationship with exposure of wild rats

Second generation anticoagulant rodenticides (SGARs), pesticides used worldwide to control rodent populations, exist in two diastereoisomer chemical species because they own two stereogenic centers. A core-shell LC-MS/MS multi-residue method for comprehensive quantitative analysis of the diastereoisomers of five SGARs as well as three first generation anticoagulant rodenticide molecules has been fully validated in liver of rats according to a bioanalytical guideline. A core-shell column (superficially porous particles) has been chosen for its ability to separate the diastereomers of bromadiolone, difenacoum, brodifacoum, flocoumafen and difethialone and for its robustness to rat liver extracts. The highly selective chromatographic separation of the diastereoisomers contributes to good signal to noise ratios and then enhances the sensitivity of the method compared to the ones of fully porous columns. An elution gradient has been optimized with 10mM ammonium acetate and acetonitrile as aqueous/organic mobile phase respectively. Triple quadrupole mass detector has been used to achieve specifity and LLOQ from 0.92 to 2.2ng/g for each diastereoisomer, or first generation anticoagulant rodenticides. Then we evidenced diastereoisomeric ratios in liver of rats issued from not controlled exposure of wild rats (Rattus norvegicus) trapped in a French Parisian park through a campaign of rodent eradication. We compared them to diastereoisomeric ratios in SGARs commercial baits that contain both isomers, and showed that one of the two diastereoiomers had nearly disappeared in liver of rats. The proportions of cis-bromadiolone and trans-difenacoum were really lowered compared to the baits: 5/7 and 9/12 rats had only trans-bromadiolone and cis-difenacoum hepatic residues respectively. Liver persistence of the two diastereoisomers of bromadiolone and difenacoum was different due to differences in their pharmacokinetics in wild rats. The new core-shell LC-MS/MS method is particularly well adapted for further exploration of diastereoisomers ratios in rodent and predatory wildlife biological samples in order to evaluate ecological consequences of actual baits, to explore new formulated baits with a good balance between efficacity (ability to kill rodents) and diastereoisomers persistence, and hopefully to mitigate exposure of non-target species.

Isotopic separation of acetaldehyde and methanol from their deuterated isotopologues on a porous layer open tubular column allows quantification by stable isotope dilution without mass spectrometric detection

An isotopic separation of acetaldehyde and acetaldehyde-2,2,2-d3 was achieved in a temperature programmed run on a porous layer open tubular (PLOT) capillary column coated with particles of divinylbenzene ethylene glycol/dimethylacrylate (Rt®-U-BOND). This is the prerequisite for the development of quantitative analytical methods based on a stable isotope dilution assay (SIDA) without a mass spectrometric detection (non-MS SIDA). For routine analysis a flame ionization detector (FID) can thus be applied as a robust and low-cost alternative. In a preliminary study, static headspace extraction and gas chromatographic separation (HS-GC-FID) of acetaldehyde in aqueous solutions was shown as an application. Good linearity was obtained in a calibration range from 0.4 to 40mgL−1, with peak integration benefitting from the inverse isotope effect encountered on the specific porous polymer. Furthermore, separation of methanol and deuterated methanol (d3) could also be achieved under the same chromatographic conditions. The achieved isotopic separation of these important volatile compounds now allows non-MS SIDA-based methods that are still to be developed.

Polymer-based monolithic column with incorporated chiral metal-organic framework for enantioseparation of methyl phenyl sulfoxide using nano-liquid chromatography.

A new approach to the preparation of enantioselective porous polymer monolithic columns with incorporated chiral metal-organic framework for nano-liquid chromatography has been developed. While no enantioseparation was achieved with monolithic poly(4-vinylpyridine-co-ethylene dimethacrylate) column, excellent separations of both enantiomers of (±)-methyl phenyl sulfoxide were achieved with its counterpart prepared after admixing metal-organic framework [Zn2 (benzene dicarboxylate)(l-lactic acid)(dmf)], which is synthesized from zinc nitrate, l-lactic acid, and benzene dicarboxylic acid in the polymerization mixture. These novel monolithic columns combined selectivity of the chiral framework with the excellent hydrodynamic properties of polymer monoliths, may provide a great impact on future studies in the field of chiral analysis by liquid chromatography.

Core-shell column Tanaka characterization and additional tests using active pharmaceutical ingredients.

In the last decade, core-shell particles have gained more and more attention in fast liquid chromatography separations due to their comparable performance with fully porous sub-2μm particles and their significantly lower back pressure. Core-shell particles are made of a solid core surrounded by a shell of classic fully porous material. To embrace the developed core-shell column market and use these columns in pharmaceutical analytical applications, 17 core-shell C18 columns purchased from various vendors with various dimensions (50mm × 2.1 mm to 100 mm × 3 mm) and particle sizes (1.6-2.7 μm) were characterized using Tanaka test protocols. Furthermore, four selected active pharmaceutical ingredients were chosen as test probes to investigate the batch to batch reproducibility for core-shell columns of particle size 2.6-2.7 μm, with dimension of 100 × 3 mm and columns of particle size 1.6 μm, with dimension 100 × 2.1 mm under isocratic elution. Columns of particle size 2.6-2.7 μm were also tested under gradient elution conditions. To confirm the claimed comparable efficiency of 2.6 μm core-shell particles as sub-2 μm fully porous particles, column performances of the selected core-shell columns were compared with BEH C18 , 1.7μm, a fully porous column material as well.

Experimental Investigations of Heat Transport Dynamics in a 1d Porous Medium Column

The present study involves the experimental investigation of heat transport due to the forced convective flow through a thermally isolated porous medium column.The experiments regard the observation of thermal breakthrough curves obtained through a hot flow injection in correspondence of two thermocouples positioned along a thermally isolated column of porous medium. The experiment has been carried out for three flow rates in order to investigate the critical issues regarding heat transport phenomena such as the relationship between the thermal dispersion with the flow velocity and the validity of the local thermal equilibrium assumption between the fluid and solid phase.

Very High Efficiency Porous Silica Layer Open-Tubular Capillary Columns Produced via in-Column Sol-Gel Processing.

It is demonstrated that 5 μm i.d. capillaries can be coated with mesoporous silica layers up to 550 nm thickness. All the columns produced using in-column sol-gel synthesis with tetramethoxysilane provide plate height curves that closely follow the Golay-Aris theory. In 60 cm long columns, efficiencies as high as N = 150 000 and N = 120 000 were obtained, respectively, for a 300 and 550 nm thick porous layer. An excellent retention and plate height reproducibility was obtained when the recipes were subsequently applied to produce very long (1.9 and 2.5 m) capillaries. These columns produced efficiencies up to N = 600 000 plates for a retained and around N = 1 000 000 plates for an unretained component. Given the good reproducibility on the long capillaries, and considering that mesoporous silica is still the preferred support for LC, it is believed the present study could spur a renewed interest in open-tubular LC.

System maps for retention of small neutral compounds on a superficially porous particle column in reversed-phase liquid chromatography

The system constants of the solvation parameter model are used to prepare system maps for the retention of small neutral molecules on the ocadecylsiloxane-bonded silica superficially porous particle stationary phase (Kinetex C18) for aqueous-organic solvent mobile phases containing 10–70% (v/v) methanol or acetonitrile. A comparison of the system constants with eight commercially available octadecylsiloxane-bonded silica columns for the same separation conditions confirms that the general retention properties of Kinetex C-18 are similar to totally porous octadecylsiloxane-bonded silica stationary phases and that method transfer should be no more difficult than that usually observed when substituting one octadecylsiloxane-bonded silica column for another.

The synthesis of surface-glycosylated porous monolithic column via aqueous two-phase graft copolymerization and its application in capillary-liquid chromatography

A facile, flexible process was developed for the preparation of surface-glycosylated porous monolithic columns via aqueous two-phase graft copolymerization of polyethylene glycol diacrylate (PEGDA) and water-soluble dextran (dextran sulfate). The formation of poly(PEGDA) porous skeletons and surface glycosylation were achieved via a one-step process without pre-modification of the dextran. The synthesis conditions were thoroughly optimized. The optimal monolithic column exhibited a large dry state surface area (greater than 400m2/g), and it was evaluated as a hydrophilic liquid chromatography (HILIC) stationary phase. A typical HILIC mechanism was observed at high organic solvent content (≥65% acetonitrile). In addition, the resulting monolithic column demonstrated the potential use in analysis of complex biological sample and enviroment water.

Preparation and evaluation of 3 m open tubular capillary columns with a zwitterionic polymeric porous layer for liquid chromatography.

A 3 m zwitterionic polymeric porous layer open tubular column (3 m × 25 μm id × 375 μm od) with a polymeric porous layer thickness of 4 μm was fabricated by the copolymerization of [2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide and N,N'-methylenebis(acrylamide). The effects of the diameter of the capillary, reaction temperature, and polymerization time on the preparation of the open tubular column were investigated. Characterized by scanning electron microscopy, the zwitterionic layer was observed to be rough and throughout the fused-silica capillary homogenously, which increased the phase ratio. The separation of neutral, basic, and acidic compounds demonstrates the strong hydrophilicity of the poly[2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide coating. In addition, the poly[2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide porous layer open tubular column was applied for the analysis of flavonoids from the rootstalk of licorice, revealing the potential in separating complex samples. The relative standard deviation of retention time for run-to-run (n = 5), day-to-day (n = 3), and column-to-column (n = 3) of toluene, N,N-dimethylformamide, formamide, and thiourea were below 1.2%, exhibiting good repeatability.

Characterization of porous clay ceramics used to remove salt from the saline soils

This paper presents the characterization of porous argil ceramic columns used as a tool to remove salt from the saline soils. The characterization of the samples was performed before and after application for the salt extraction from the soil. Phase, chemical and microstructural characterizations of the whole series of samples were carried out by using X-ray diffraction technique (XRD), ICP-AES measurements and scanning electron microscope (SEM), respectively. Therefore, XRD revealed that quartz is the most important phase. Besides, sodium chloride (halite, NaCl) is the predominant compound formed during the desalination time. The presence of high-temperature phases in the ceramic columns such as diopside and anorthite showed the use of high firing temperatures, in the range 950–1050°C. In addition, SEM observation on cross-sections clearly showed a network of small dense zones, including quartz grains, interconnected by recrystallized porous phases. These images showed the importance of the pores dimensions and structures on the solution movement and salt deposal. Therefore, it revealed that the porosity heterogeneities could have a great impact on the location of efflorescence at the ceramic column surface. As a consequence, the obtained results allowed us to choose the suitable clay ceramic for the salt extraction from the soil.

A Coupled Experimental/Numerical Approach for Tuning High-Performing SOFC-Cathode

The present study concerns the influence of the micro/nano-structural properties of LSCF (La0.6Sr0.4Co0.2Fe0.8O3−δ) and 60:40 vol.% LSCF/CGO (Ce0.9Gd0.1O2-δ) composite cathode films on their electrochemical behavior. Electrostatic spray deposition technique is used to deposit 10 μm-thick functional films (Fig. 1). Contrary to expectations, pure LSCF showed a better response compared to the composite material. It exhibits Area Specific Resistance (ASR) values as low as 0.021 and 0.068 Ω.cm2 at 650 ˚C and 600 ˚C respectively. These values are, to the best of our knowledge, one of the lowest reported to date for LSCF-6428 composition in open circuit voltage (OCV) condition.1 To better comprehend the complex relationships between material properties, processing, micro/nano structure and electrode performance, a simplified geometry representing the typical 10x10x10 μm3 porous columns of the electrodes is modelled by 3D finite element (FEM).2 ASR is computed with real microstructural parameters obtained from 3D FIB/SEM technique. On the other hand, it is also calculated by a simple volume-averaged analytical model (1D-ALS model)3 within an assumed macrohomogeneous geometry. The computed ASRs with these two relatively simple models are compared to experimental results and the relevance of such models for inhomogeneous microstructures like ‘columnar’ is discussed. Figure 1: Microstructural characterization of the films a-c) LSCF, e-g) 60/40 vol.% LSCF/CGO composite films observed by SEM. 3D reconstructed images by FIB/SEM technique of (d) LSCF and (h) 60:40 LSCF/CGO composite. Celikbilek, O., Jauffres, D., Dessemond, L., Burriel, M., Martin, C.L., Djurado, E.,(2015), to be submitted to J. Mat. Chem. AHaffelin, A., Joos, J., Ender, M., Weber, A., Ivers-Tiffee, E. (2013). J. Electrochem. Soc. 160, F867–F876 Adler, S. B., Lane, J. A. & Steele, B. C. H. (1996). J. Electrochem. Soc. 143, 3554–3564 Figure 1

Simultaneous quantitative determination of 5-aza-2′-deoxycytidine genomic incorporation and DNA demethylation by liquid chromatography tandem mass spectrometry as exposure-response measures of nucleoside analog DNA methyltransferase inhibitors

The epigenetic and anti-cancer activities of the nucleoside analog DNA methyltransferase (DNMT) inhibitors decitabine (5-aza-2'-deoxycytidine, DAC), azacitidine, and guadecitabine are thought to require cellular uptake, metabolism to 5-aza-2'-deoxycytidine triphosphate, and incorporation into DNA. This genomic incorporation can then lead to trapping and degradation of DNMT enzymes, and ultimately, passive loss of DNA methylation. To facilitate measurement of critical exposure-response relationships of nucleoside analog DNMT inhibitors, a sensitive and reliable method was developed to simultaneously quantitate 5-aza-2'-deoxycytidine genomic incorporation and genomic 5-methylcytosine content using LC-MS/MS. Genomic DNA was extracted and digested into single nucleosides. Chromatographic separation was achieved with a Thermo Hyperpcarb porous graphite column (100mm×2.1mm, 5μm) and isocratic elution with a 10mM ammonium acetate:acetonitrile with 0.1% formic acid (70:30, v/v) mobile phase over a 5min total analytical run time. An AB Sciex 5500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of 5-aza-2'-deoxycytidine, 2'-deoxycytidine, and 5-methyl-2'-deoxycytidine. The assay range was 2-400ng/mL for 5-aza-2'-deoxycytidine, 50-10,000ng/mL for 2'-deoxycytidine, and was 5-1000ng/mL for 5-methyl-2'-deoxycytidine. The assay proved to be accurate (93.0-102.2%) and precise (CV≤6.3%) across all analytes. All analytes exhibited long-term frozen digest matrix stability at -70°C for at least 117 days. The method was applied for the measurement of genomic 5-aza-2'-deoxycytidine and 5-methyl-2'-deoxycytidine content following exposure of in vitro cell culture and in vivo animal models to decitabine.

A Rapid Method for the Analysis of Paralytic Shellfish Toxins Utilizing Standard Pressure HPLC: Refinement of AOAC 2005.06.

Superficially porous column technologies have previously been shown to provide faster chromatographic analysis of toxin oxidation products when analyzing shellfish for paralytic shellfish toxins. While sub 3 μm fused core columns have facilitated enhanced method performance, including significantly lower analysis times and lower LOD, they were also found to last for only a few hundred injections before pressure increases rendered them unusable with standard HPLC. Recently 5 μm superficially porous columns have become commercially available. In this study, a 5 μm fused core column was used to develop a fast chromatographic method for the analysis of paralytic shellfish toxins, with performance characteristics and column lifetime being assessed. The 5 μm column was found to be able to perform approximately 3000 injections without significant increases in back pressure or reduction in performance. Data generated using the column were found to be equivalent to that determined using current HPLC column technologies for both screening and quantitation methods. Furthermore, an increase in sensitivity for all toxins tested under the routine monitoring program for British waters was observed and the overall run time of the analysis halved. Overall, the 5 μm fused core column provided a significant increase in sample throughput, a reduction in mobile phase consumption, and an increase in method sensitivity.

Integrated on-chip mass spectrometry reaction monitoring in microfluidic devices containing porous polymer monolithic columns.

Chip-based microfluidics enable the seamless integration of different functions into single devices. Here, we present microfluidic chips containing porous polymer monolithic columns as a means to facilitate chemical transformations as well as both downstream chromatographic separation and mass spectrometric analysis. Rapid liquid phase lithography prototyping creates the multifunctional device economically.

Bearing Capacity Analysis of N90T20 Rack Column Under Eccentric Compression

The bearing capacity of cold-formed porous steel N90T20 rack column is studied, the eccentric positions, the spacing between holes, column thickness are discussed in details. The results obtained from this study demonstrate that when eccentric space is small, eccentric compression weaken column ultimate bearing capacity is small. From the results, it is clear that when eccentric space is large, eccentric compression can cause the column ultimate bearing capacity of plummeting. If the eccentricity is close proximity to the web, the ultimate bearing capacity declines to be smaller than the eccentric near the curling side of the column. The spacing of the holes on the column web do not present significant effect to the ultimate bearing capacity of the column. The wall thickness of column component greatly influence on the ultimate bearing capacity of the columns. This study makes contribution to the N90T20 rack design in the engineering practice and research areas.

Analyses of acute kidney injury biomarkers by ultra-high performance liquid chromatography with mass spectrometry.

The newly developed acute kidney injury biomarkers are very important for the early and timely detection of kidney diseases. This review contains details of the analyses of several acute kidney injury biomarkers using ultra-high performance liquid chromatography-mass spectrometry in urine and plasma samples. In this review we attempt to discuss some aspects of the types of the biomarkers, patents, sample preparation, and the analyses. Besides, efforts were also made to discuss the possible uses of superficially porous (core-shell) columns in traditional and inexpensive high-performance liquid chromatography instruments. Additionally, the challenges and the future prospects are also highlighted. The present review will be useful for the academicians, scientists, and clinicians for the early detection of acute kidney injury biomarkers.

Salt removal from soil using the argil porous ceramic

In this study, porous ceramic columns formed by argil of traditional pottery were used to remove salt from the saline soils. Experiences were conducted in a laboratory prototype to determine the salinity variation in different soil depths and locations as well as the salt germination and deposal on the porous ceramic. The obtained experimental results showed that this technique has effectively reduced the soil salt's concentration by 95%.Moreover, samples from the porous ceramic material were analyzed before and after application for the salt extraction from the soil. The analyses using the scanning electron microscopy (SEM) had showed the importance of the pore's dimensions and structures on the solution movement and salt deposal. In addition, the possible mechanisms of salt movement and deposal such as evaporation, interaction between saline solution and porous ceramic and salt ionic germination were discussed. Even a comparison with the Electrokinetic (EK) desalination method was performed to reveal the importance of using the porous ceramic column that constitutes a simple, cheap, preferment and appropriate environmental process.

Simultaneous determination of nucleoside and purine compounds in human urine based on a hydrophobic monolithic column using capillary electrochromatography.

A novel capillary electrochromatography method was developed by using a polymethacrylate ester based monolithic column for the simultaneous separation and determination of five nucleoside and purine compounds in urine. The porous monolithic column was first designed by mean of in situ copolymerizing stearyl methacrylate, trihydroxymethylpropyl trimethylacrylate, and 2-acrylamido-2-methyl-1-propanesulfonic acid in a ternary porogenic solvent including cyclohexanol, 1,4-butanediol, and water. The performance and influence factors of the monolithic columns were investigated and evaluated by a CEC method. The five compounds including guanine, adenine, adenosine, cytidine, and N6 -methyladenosine were selected as analytes. Under the optimized condition of 6.0 mM phosphate buffer at pH 5.0 without ACN, five analytes were rapidly separated in 4 min with the high separation efficiency. The recoveries of spiked samples were ranged from 89.0 to 109.0% with RSDs less than 4.83%. Therefore, the proposed method could possibly provide for rapid separation and detection of the nucleoside and purine compounds in biomedicine sample.

Direct Measurement of Trace Elemental Mercury in Hydrocarbon Matrices by Gas Chromatography with Ultraviolet Photometric Detection.

We introduce a technique for the direct measurement of elemental mercury in light hydrocarbons such as natural gas. We determined elemental mercury at the parts-per-trillion level with high precision [<3% RSD (n = 20 manual injection)] using gas chromatography with ultraviolet photometric detection (GC-UV) at 254 nm. Our approach requires a small sample volume (1 mL) and does not rely on any form of sample preconcentration. The GC-UV separation employs an inert divinylbenzene porous layer open tubular column set to separate mercury from other components in the sample matrix. We incorporated a 10-port gas-sampling valve in the GC-UV system, which enables automated sampling, as well as back flushing capability to enhance system cleanliness and sample throughput. Total analysis time is <2 min, and the procedure is linear over a range of 2-83 μg/m(3) [correlation coefficient of R(2) = 0.998] with a measured recovery of >98% over this range.