Column In Conjunction Research Articles

Low-flow-resistance Methacrylate-based Polymer Monolithic Column Prepared by Low-conversion Ultraviolet Photopolymerization at Low Temperature

A low-conversion poly(butyl methacrylate-co-ethylene dimethacrylate)-based polymer monolithic column was prepared by ultraviolet (UV) irradiation for a short time at a low temperature (-15°C). By UV irradiation for 2 min, the monolithic column exhibited a high permeability of 5.6 × 10(-13) m(2) and a high column efficiency of over 100000 plates m(-1). At this polymerization time, the conversions of butyl methacrylate and ethylene dimethacrylate were only 10 and 21%, respectively, as determined by pyrolysis gas chromatography. The low conversion led to high porosity, which in turn resulted in high permeability. The reduction in conversion also contributed to improve the compositional homogeneity of the prepared polymer monolith, which would promote high column efficiency. Using the prepared low-conversion column in conjunction with a vacuum-driven low-pressure HPLC without a conventional high-pressure pump, the separation of alkylbenzenes was successfully achieved using a low pressure of only -0.045 MPa to generate the mobile phase stream.

Greener liquid chromatography using a guard column with micellar mobile phase for separation of some pharmaceuticals and determination ofparabens

In this research, a greener chromatography employing a short column, Zorbax SB C18 cartridge (12.5×4.6mm, 5μm) commonly used as a guard column in a reverse phase high performance liquid chromatography (RP-HPLC), was utilized as the analytical column in conjunction with a more eco-friendly micellar mobile phase of sodium dodecyl sulfate (SDS) for separation tertiary mixtures of local anesthetics and antihistamines; and binary mixture of colds drugs; and quaternary mixture of some parabens with different separation conditions. The chromatographic behavior of these analytes was studied to demonstrate separation efficiency of this guard column in a micellar mobile phase. Moreover, this column and SDS mobile phase was exploited for determination of parabens in 64 samples of cosmetic product, both those that were produced locally in the community and those that were commercially manufactured. Linear calibration graphs of the parabens as detected at 254nm were obtained in the range of 1–100μmolL−1 with R2>0.9990. Percentage recoveries were 92.4–109.2 with %RSD<3, and the limit of detection and quantitation were 0.04–0.10 and 0.20–0.80μmolL−1, respectively. This analytical system is not only greener but also faster and employing simpler sample preparation than a conventional liquid chromatographic system.

Analysis of satellite-derived Arctic tropospheric BrO columns in conjunction with aircraft measurements during ARCTAS and ARCPAC

Abstract. We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo &gt;0.7), for solar zenith angle &lt;80° and clear sky conditions. The rapid activation of BrO due to surface processes (the bromine explosion) is apparent in both the OMI and GOME-2 based tropospheric columns. The wide orbital swath of OMI allows examination of the evolution of tropospheric BrO on about hourly time intervals near the pole. Low surface pressure, strong wind, and high PBL height are associated with an observed BrO activation event, supporting the notion of bromine activation by high winds over snow.

Arsenic Removal from Natural Gas Condensate using a Pulsed Sieve Plate Column and Mass Transfer Efficiency

This work applied a pulsed sieve plate column in conjunction with liquid-liquid extraction technique to remove arsenic from natural gas condensate. The relevant parameters, that is the type and concentration of the extractant, pulse velocity, volumetric-flow rate ratio of the condensate to the extractant, operating time, and extraction cycle were investigated. Mass transfer efficiency in terms of the overall height of transfer unit (HTU oy , cm) and the interfacial area (m2/m3) were calculated. The highest percentage of arsenic removal in this study was 94% corresponding to the calculated HTU oy of 26 cm and the calculated interfacial area of 118 m2/m3 at the optimum conditions: the mixture of the extractant (1 M hydrochloric acid and 20% (v/v) methanol), pulse velocity of 20 mm/s, and volumetric-flow rate ratio of the condensate to the extractant of 1:4. By using continuous operation in the cycle mode, the percentages of arsenic removal were observed at 94, 85, and 80 from the respective 1st, 2nd, and 3rd cycles. The operation was based on the condition that fresh feed was introduced in each cycle while the extractant was reused.

Preparation and characterization of porous poly(vinyl ester) resin monoliths as separation media

AbstractPorous poly(vinyl ester) resin monolithic supports were first prepared by radical polymerization of the continuous phase of oil in water high‐internal‐phase emulsions. Vinyl ester (VE) resin was used as the monomer, ethylene glycol dimethacrylate was used as a crosslinker, and poloxamer 127 was used as the emulsifier in the emulsion polymerization. The prepared columns were evaluated by scanning electron microscopy, mercury intrusion porosimetry, and Fourier transform infrared spectroscopy to observe the morphological characteristics and confirm the absorbance based on the VE resin polymer. The obtained monolith showed not only higher column permeability but also lower back pressure and higher column efficiency. To investigate the absorption performance of the monolithic column, a maximum loading capacity experiment was also applied with lysozyme (Lys), and the results show that the maximum adsorption of the poly(vinyl ester) resin monolith was 1.579 mg/g. Moreover, the capabilities of separation on this column in conjunction with high‐performance liquid chromatography were investigated. Immunoglobulin could be separated from human plasma and chicken egg yolk with high resolution within 4 min. Additionally, fast separation of two mode proteins (interleukin‐18 and Lys) was achieved on the monolith within 2 min at the rate of 1445 cm/h, which demonstrated the potential of the poly(vinyl ester) resin monolith for the fast separation of proteins. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Extraction of Nitraria tangutorum seed lipid using different extraction methods and analysis of its fatty acids by HPLC fluorescence detection and on‐line MS identification

AbstractThe seed lipid of Nitraria tangutorum was extracted by supercritical carbon dioxide extraction, microwave‐assisted reflux extraction, ultrasound‐assisted extraction, or solvent reflux extraction. The experimental parameters of supercritical carbon dioxide extraction including pressure, temperature, particle size, and extraction time were investigated. A facile and sensitive method for the simultaneous determination of 30 saturated and 9 unsaturated fatty acids by HPLC with fluorescence detection after pre‐column derivatization was developed. Fatty acid derivatives were separated on a reversed‐phase Eclipse XDB‐C8 column in conjunction with gradient elution. Identification of fatty acid derivatives was carried out by on‐line APCI/MS in positive‐ion mode. Excellent quantitative linear responses of the 39 fatty acids were observed in the range of 0.014 to 14 μmol/L with correlation coefficients higher than 0.9992. Limits of detection were in the range of 0.32–3.7 nmol/L (S/N = 3). The fatty acids in Nitraria tangutorum seed lipid with or without saponification extracted by the four different methods were determined and compared. The results indicated that the mass percentage of unsaturated fatty acids (mainly oleic acid, linoleic acid and linolenic acid) in Nitraria tangutorum seed lipid was up to 79%, and the best method was supercritical carbon dioxide extraction.

Alteration of selective neurotransmitters in fetal brains of prenatally alcohol-treated C57BL/6 mice: quantitative analysis using liquid chromatography/tandem mass spectrometry

We previously demonstrated that prenatal alcohol exposure results in brain defects at different embryonic stages. This study is aimed at characterizing the influence of prenatal alcohol exposure on the levels of several neurotransmitters at early embryonic stage 13 (E13). Pregnant C57BL/6 mice were exposed to either a 25% ethanol derived calorie diet (ALC) or pair-fed (PF) liquid diet from E7 to E13. At E13, fetal brains were collected from dams of the ALC and PF groups. Liquid chromatography/tandem mass spectrometry (LC–MS) was then used to evaluate neurotransmitter levels. This approach involved the use of an LC column in conjunction with multiple-reaction monitoring mass spectrometry. Quantitative analyses of catecholamines, idolamine, and amino acid neurotransmitters revealed significant reductions in the levels of dopamine (p=0.004), norepinephrine (p=0.0009), epinephrine (p=0.0002), serotonin (p=0.004), and GABA (p=0.002) in the ALC group compared to the PF group. However, there was no significant change in the levels of glutamate in E13 fetal brains. These findings demonstrate that prenatal alcohol exposure reduces the concentrations of some catecholamines, idolamine, and amino acid neurotransmitters in E13 fetal brains. This study suggests that alterations of selective neurotransmitters may be the cause of abnormalities in brain function and behavior found in fetal alcohol spectrum disorders.

Novel Porous Monolithic Column Using Poly(high internal phase emulsion) Methacrylate as Materials for Immunoglobulin Separation Performance on HPLC

AbstractA novel porous polymeric monolithic column based on poly(high internal phase emulsion) methacrylate monolith was prepared and applied to fast separation of proteins. The block copolymer chemistry of high internal phase emulsions was used in the experiment. These unique properties, together with high porosity, good mechanical property, chemical modification of the surface make themselves superior in monolithic medium applications. Morphology of the monolithic material was studied by scanning electron microscopy. The stability of the emulsion and the load of hydroxyl groups–the active group of the monolithic column were investigated. Additionally, the capabilities of separation of this column in conjunction with high performance liquid chromatography (HPLC) were investigated. Immunoglobulin was separated from human plasma and chicken egg yolk with high resolution on the hydrophobic interaction chromatographic column in a short time. The effects of pH and concentration of mobile phase (buffer) on the elution of immunoglobulin were investigated. Moreover, fast separation of a two mode protein mixture (α‐amylase and lysozyme) on the monolith was achieved within 1.5 min at a velocity of 1445 cm·h−1. As a result, good separation was achieved, and stable low back pressure drop was ensured at high throughput elution with an even longer column.

Extraction of Microula sikkimensis seed oil and simultaneous analysis of saturated and unsaturated fatty acids by fluorescence detection with reversed-phase HPLC

The seed oil of Microula sikkimensis Hemsl. was extracted by supercritical carbon dioxide extraction, microwave-assisted reflux extraction, ultrasound-assisted extraction and solvent reflux extraction. The experimental parameters of supercritical carbon dioxide extraction which is classic in these extraction techniques including pressure, temperature, particle size and extraction time were optimized. A simple and sensitive method for the simultaneous determination of 39 kinds of saturated and unsaturated fatty acids in seed oil using high performance liquid chromatography (HPLC) with fluorescence detection following pre-column derivatization with 1-[2-( p-toluenesulfonate)-ethyl]-2-phenylimidazole-[4,5-f]-9,10-phenanthrene (TSPP) has been developed. Fatty acid derivatives were separated on a reversed-phase Eclipse XDB-C 8 column in conjunction with a gradient elution. Quantitative linear range of 39 fatty acids was 0.014–14.29 μmol/L, and excellent linear responses were observed with correlation coefficients more than 0.9992. Detection limits were in the range of 3.24–36.97 fmol (10 μL, S/N 3:1). Stability of derivatives, method repeatability and recovery were evaluated and the results were excellent for efficient HPLC analysis. Fatty acids in M. sikkimensis Hemsl. seed oil with or without saponification by different extraction methods were analyzed and compared. The facile TSPP derivatization coupled with HPLC fluorescence detection allowed for the quantitation of short- and long-chain fatty acids from biological and natural environmental samples.

Comprehensive two-dimensional high-performance liquid chromatography system with immobilized liposome chromatography column and reversed-phase column for separation of complex traditional Chinese medicine Longdan Xiegan Decoction

A comprehensive two-dimensional HPLC system with an immobilized liposome chromatography (ILC) column in conjunction with an RP column (in tandem) was developed for the screening and analysis of the membrane-permeable compounds in a traditional Chinese medicine prescription Longdan Xiegan Decoction (LXD). More than 50 components in LXD were resolved using the developed separation system. Eight flavonoids and two iridoids were identified interacting with the ILC column; a system that mimics biomembranes. The results show that the developed comprehensive two-dimensional chromatography system can be used for identifying membrane permeable natural products in complex matrixes such as extracts of traditional Chinese medicine prescriptions.

Supercritical Fluid Chromatography and High-Performance Liquid Chromatography/Tandem Mass Spectrometric Methods for the Determination of Cytarabine in Mouse Plasma

The separation of cytarabine (ara-C) from the endogenous compounds in mouse plasma by packed-column supercritical fluid chromatography (pSFC) was achieved on bare silica stationary phase with an isocratic mobile phase composed of CO2/methanol solvent with addition of ammonium acetate. SFC is commonly assumed to be only applicable to nonpolar and relatively low-polarity compounds. In this work, a broader range of compound polarities amenable to pSFC with appropriate mobile-phase modifiers and additives under normal-phase retention mechanism was demonstrated. The pSFC was integrated with an atmospheric pressure chemical ionization source and a tandem mass spectrometer (MS/MS) to enhance the sensitivity, selectivity, and speed of the assay. The influence of mobile-phase components on chromatographic performance and ionization efficiency of the test compounds was investigated for improving the sensitivity and separation for the analyte and the internal standard. The pSFC-MS/MS approach requiring approximately 2.5 min/sample for the determination of ara-C at nanograms per milliliter in mouse plasma was partially validated with respect to stability, linearity, and reproducibility. The mouse plasma levels of ara-C obtained by the pSFC-MS/MS method were found to be consistent with those determined by various reversed-phase, high-performance liquid chromatography methods using a porous graphite carbon column, a mixed-mode column, or a C18 column in conjunction with an ion-pairing agent coupled to a tandem mass spectrometer.

Rapid Method for Quantitative Analysis of the Aroma Impact Compound, 2-Acetyl-1-pyrroline, in Fragrant Rice Using Automated Headspace Gas Chromatography

A rapid method employing static headspace gas chromatography (HS-GC) has been developed and validated for quantitative analysis of the impact aroma compound, 2-acetyl-1-pyrroline (2AP), in grains of fragrant rice. This developed method excludes wet extraction, and the rice headspace volatiles are brought directly and automatically to GC analysis. The conditions of the static HS autosampler were optimized to achieve high recovery and sensitivity. The most effective amount of rice sample used was 1 g, which provided 51% recovery and a linear multiple headspace extraction (MHE) plot of the peak area of 2AP. The sensitivity of the method was enhanced by utilizing a megabore fused silica capillary column in conjunction with a nitrogen-phosphorus detector (NPD). Method validations performed for both static HS-GC-FID and HS-GC-NPD demonstrated linear calibration ranges of 20-10 000 (r(2) = 0.9997) and 5-8000 (r(2) = 0.9998) ng of 2AP/g of rice sample, respectively. The limits of detection for both systems were 20 and 5 ng of 2AP, and the limits of quantitation were 0.30 and 0.01 g of brown rice sample, respectively. Reproducibility calculated as intraday and interday coefficients of variation were 3.25% RSD (n = 15) and 3.92% RSD (n = 35), respectively, for SHS-GC-FID and 1.87% RSD (n = 15) and 2.85% RSD (n = 35), respectively, for SHS-GC-NPD. The method was found to be effective when applied to the evaluation of aroma quality, based on 2AP concentrations, of some fragrant rice samples.

Surfing the net for software engineering notes

I mention many different free open source software (FOSS) products in this column in conjunction with the topics I select each month. This month, instead of focusing on a single topic, I thought I'd present a collection of some of the most popular free and open source software products currently in production in order to give you an impression on the size and scope of FOSS packages available.

Spectrophotometric determination of 4,6-dinitro- o-cresol (DNOC) in soil and lemon juice

Although the use of once widely applied selective herbicide, 4,6-dinitro- o-cresol (DNOC), was cancelled by US-EPA in 1987, it is still found in soil and water due to its slow degradation in the environment. Since solid phase extraction-spectrophotometry combinations are much simpler and cheaper than chromatography/MS based methods and most routine laboratories lack such sophisticated instrumentation, it is desirable to establish novel sensitive, well-established, and field-applicable spectrophotometric methods for the rapid assay of DNOC in water and soil. For this purpose, two distinct spectrophotometric methods utilizing the periodate and copper(II)-neocuproine (Nc) reagents have been developed following Zn/HCl reduction of the pesticide in a microwave oven for 15 s, and validated for DNOC determination at mg L −1 level. The LOD values were 1.6 and 0.2 mg L −1 for periodate and Cu(II)-Nc methods, respectively. Statistical comparison of the developed methods was made with the aid of high performance liquid chromatography (HPLC) equipped with a C 18 (5 μm), 250 mm× 4.6 mm ID reversed phase column in conjunction with a UV (264 nm) detector, and a methanol (HPLC grade) +0.1% glacial acetic acid mixture mobile phase. Both spectrophotometric methods were directly applicable to soil since they were not interfered with common soil cations and anions, together with some pesticides. These methods were applied to real samples such as synthetically contaminated montmorillonite and lemon juice, and overall recovery efficiencies at the order of 95% or greater were achieved in the devised adsorption/elution procedures. An 8-hydroxyquinoline (oxine)-impregnated XAD copolymer resin stabilized with Fe(III) salt was used to preconcentrate DNOC at a concentration factor of 20 from lemon juice contaminated with 1 mg L −1 DNOC, and the analyte retained at pH 2.5 was eluted with 0.025 M methanolic NaOH. Both the devised spectrophotometric methods and the proposed preconcentration column with optimized sorption and desorption conditions are novel for DNOC assay in the natural environment.

Fiber element modeling for seismic performance of bridge columns made of concrete-filled FRP tubes

Concrete-filled fiber reinforced polymer (FRP) tubes (CFFT) are an alternative to reinforced concrete, providing for rapid construction with comparable strengths and higher ductility. Despite encouraging test data, it is not clear as to whether traditional analytical tools may be used for prediction of structural performance of CFFT, especially in seismic applications. This paper reports on modeling of CFFT either as cast-in-place reinforced or precast post-tensioned column in conjunction with a reinforced concrete (RC) footing. The model is verified against two earlier experimental programs at the member-level and subassembly-level. The model was then used to conduct a parametric study of different column configurations under a constant axial load and a reversed cyclic lateral load. Moreover, seismic performance of a typical CFFT column is compared with its RC counterpart under three different ground acceleration records. The study shows that seismic analysis of CFFT columns is possible using available analytical tools for conventional RC columns. Also, CFFT columns demonstrate superior performance over their RC counterparts in response to wide-ranging ground acceleration records. Fiber architecture of the FRP tube could be optimized for strength and ductility. Internal steel reinforcement and a minimum thickness of FRP tube are deemed necessary to provide adequate ductility and system integrity in seismic applications.

Increased productivity in quantitative bioanalysis using a monolithic column coupled with high‐flow direct‐injection liquid chromatography/tandem mass spectrometry

The feasibility of using a monolithic column as the analytical column in conjunction with high-flow direct-injection liquid chromatography/tandem mass spectrometry (LC/MS/MS) to increase productivity for quantitative bioanalysis has been investigated using plasma samples containing a drug and its epimer metabolite. Since the chosen drug and its epimer metabolite have the same selected reaction monitoring (SRM) transitions, chromatographic baseline separation of these two compounds was required. The results obtained from this monolithic column system were directly compared with the results obtained from a previously validated assay using a conventional C18 column as the analytical column. Both systems have the same sample preparation, mobile phases and MS conditions. The eluting flow rate for the monolithic column system was 3.2 mL/min (with 4:1 splitting) and for the C18 column system was 1.2 mL/min (with 3:1 splitting). The monolithic column system had a run time of 5 min and the conventional C18 column system had a run time of 10 min. The methods on the two systems were found to be equivalent in terms of accuracy, precision, sensitivity and chromatographic separation. Without sacrificing the chromatographic separation, sensitivity, accuracy and precision of the method, the reduced run time of the monolithic column method increased the sample throughput by a factor of two.

Effect of a severe form of initial gas maldistribution on pressure drop of a structured packing bed

The results of an experimental study devoted to establishing the relation between a severe form of initial gas distribution, as created by a chordal blockage set-up used in a recent FRI study, and the hydraulics of a structured packing bed are presented. Both dry and wet bed experiments were conducted with air/water system under ambient conditions, using a 1.4 m i.d. Plexiglas column in conjunction with Montz-pak B1-250 packing bed of the approximately same length, employing liquid loads corresponding to that from the FRI study. From dry and wet experiments it appeared that chordal blanking of 30% of cross-sectional area at gas inlet can influence the pressure drop significantly, particularly that in the lower part of the bed.

Determination of Amino Acids from Hydrolyzed Bovine Serum Albumin by High Performance Liquid Chromatography and Identification with Electrospray Ionization Mass Spectrometry

Abstract A precolumn derivatization method for the determination of 20 amino acids using the tagging reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) as precolumn derivatization reagent was developed. Amino acid derivatives were successfully separated on a reversed-phase Hypersil BDS C 18 (4.6 mm×200 mm, 5 μm) column in conjunction with a gradient elution. Studies on derivatization conditions indicated that amino acids could rapidly and mildly react with BCEOC reagent at room temperature in the presence of sodium borate catalyst in acetonitrile solvent to give the corresponding sensitive fluorescent derivatives. Maximal derivatization yields close to 100% were observed with a 4-fold molar reagent excess. The fluorescence excitation and emission wavelengths were 333 nm and 390 nm, respectively. The identification of amino acid derivatives from hydrolyzed bovine serum albumin was carried out by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS/MS) in a positive-ion mode. Excellent linear responses were obtained with the coefficients over 0.9990. Detection limits (at a signal-to-noise of 3:1) were 6.3–117.6 fmol for the labeled amino acids.

Disturbance compensation with a torque controllable steering system

Via a conventional steering system the driver perceives desired and disturbing effects such as road feedback and resonance effects, respectively. They appear with overlapping frequency spectra within the driver's steering torque. This paper introduces a control algorithm that is suppressing periodic disturbances without affecting useful steering road feedback attributes as well as regular power assistance characteristic. This is realised by an integrated torque actuator within the steering column in conjunction with a conventional Hydraulic-assisted Power Steering (HPS) system.

The GTP-binding Protein YlqF Participates in the Late Step of 50 S Ribosomal Subunit Assembly in Bacillus subtilis

Bacillus subtilis YlqF belongs to the Era/Obg subfamily of small GTP-binding proteins and is essential for bacterial growth. Here we report that YlqF participates in the late step of 50 S ribosomal subunit assembly. YlqF was co-fractionated with the 50 S subunit, depending on the presence of noncleavable GTP analog. Moreover, the GTPase activity of YlqF was stimulated specifically by the 50 S subunit in vitro. Dimethyl sulfate footprinting analysis disclosed that YlqF binds to a unique position in 23 S rRNA. Yeast two-hybrid data revealed interactions between YlqF and the B. subtilis L25 protein (Ctc). The interaction was confirmed by the pull-down assay of the purified proteins. Specifically, YlqF is positioned around the A-site and P-site on the 50 S subunit. Proteome analysis of the abnormal 50 S subunits that accumulated in YlqF-depleted cells showed that L16 and L27 proteins, located near the YlqF-binding domain, are missing. Our results collectively indicate that YlqF will organize the late step of 50 S ribosomal subunit assembly.