Stationary Phases For Separation Research Articles

Synthesis and Chromatographic Evaluation of Perfluorooctyl Stationary Phase for Separation of Basic Compounds

Synthesis and Chromatographic Evaluation of Perfluorooctyl Stationary Phase for Separation of Basic Compounds

Трехпараметрическая модель межмолекулярных взаимодействий как основа для классификации и выбора неподвижных фаз для газовой хроматографии

Описан метод трехпараметрической характеристики селективности газохроматографических неподвижных фаз, который базируется на представлении энергии межмолекулярного взаимодействия вкладами неполярных, полярных сил и водородных связей. Все параметры, используемые в математических выражениях, имеют физический смысл, переносимы и не требуют проведения дополнительных экспериментов. Характеристики неподвижных фаз могут быть рассчитаны как из экспериментальных данных по хроматографическому удерживанию, так и a priori, по известной структурной формуле фазы. Описаны оба способа и проведен расчет параметров для ряда веществ. Полученные разными способами характеристики селективности неподвижных фаз согласуются между собой. Рассматривается также основанная на трехпараметрической модели концепция выбора неподвижной фазы для разделения близких веществ.

Front Cover: Comparative study of different chemistries and particle properties, high‐performance liquid chromatography stationary phases in separation of escitalopram oxalate and its impurities in different pharmaceutical dosage forms

Front Cover: Comparative study of different chemistries and particle properties, high‐performance liquid chromatography stationary phases in separation of escitalopram oxalate and its impurities in different pharmaceutical dosage forms

Comparative study of different chemistries and particle properties, high‐performance liquid chromatography stationary phases in separation of escitalopram oxalate and its impurities in different pharmaceutical dosage forms

AbstractThe liquid chromatographic separation performance of 12 different columns was evaluated for the estimation of the escitalopram oxalate and six of its impurities in different pharmaceutical formulations. All columns exhibited a reasonable separation power. Six columns with three different chemistries and two different particle morphology (i.e. core‐shell and fully porous particle) were nominated for further evaluation. The objectives of the current study were to develop a simple method for detection of escitalopram oxalate and its impurities and to compare the separation power of the stationary phase of different chemistry and particle properties. The separation was carried out under isocratic elution by using acetonitrile/methanol/water/phosphate buffer solution (pH = 3.5, 50 mM) (25:5:20:50, v/v/v/v) mixture as mobile phase, with a flow rate of 1.2 mL min−1. The core‐shell phenyl‐hexyl column showed the best separation performance over the traditional octadecyl and pentafluorophenyl phases. The developed method was applied for detection of escitalopram oxalate and its impurities in valid and expired dosage forms.

Ionic liquid-modified mesoporous silica stationary phase for separation of polysaccharides with size exclusion chromatography

Abstract Size exclusion chromatography (SEC) was developed for the separation of large molecules, such as proteins, polymer, peptides, nucleic acid, and polysaccharides. In this study, ionic liquid-modified silica was synthesized to examine the retention behavior of polysaccharides, such as dextran, fucoidan, alginic acid, and laminarin. Commercial SEC column separated large molecules according to their molecular size. However, Ionic liquid-modified silica is expected to retention behavior by the functional group between ionic liquid-modified silica surface with polysaccharides. The SilprBimCl column has larger retention than the other ionic liquid-modified silica columns owing to the large pore size and specific physical and chemical properties of the ionic liquids. 2.93 was the largest retention factor in SilprBimCl column from 5 kDa dextran. Under the SilprBimCl column, the molecular weights of fucoidan, alginic acid and laminarin were 205, 245, and 7–650 kDa respectively.

Determination of formaldehyde and acetaldehyde in packaging paper by dansylhydrazine derivatization-high performance liquid chromatography-fluorescence detection

A high performance liquid chromatography with fluorescence detection (HPLC-FLD) method was developed for the simultaneous determination of formaldehyde and acetaldehyde in packaging paper by dansylhydrazine (DNSH) derivatization. The samples were extracted by derivatization reagent for 30 min, and derived for 24 h. After purifying treatment with a PSA/C18 cartridge, a Diamonsil® C18 column (150 mm×4.6 mm, 5 μ m) was used as stationary phase for separation, the mixtures of acetic acid aqueous solution (pH 2.55)-acetonitrile were used as mobile phases by gradient elution, and the excitation and emission wavelengths were 330 nm and 484 nm, respectively. The results showed that the recoveries of formaldehyde and acetaldehyde spiked in the samples were 81.64%-106.78%, and the relative standard deviations (RSDs) were 2.02%-5.53% (n=5). The limits of detection of formaldehyde and acetaldehyde were 19.2 μ g/kg and 20.7 μ g/kg, respectively. The limits of quantification of formaldehyde and acetaldehyde were 63.9 μ g/kg and 69.1 μ g/kg, respectively. The method is simple, sensitive and reproducible. It provides a basic approach for the determination of trace formaldehyde and acetaldehyde.

Gold nanoparticles assisted laser desorption/ionization mass spectrometry and applications: from simple molecules to intact cells.

Gold nanoparticles (AuNPs) assisted laser desorption/ionization mass spectrometry (GALDI-MS) provided new horizons and offered many functions for various applications. This review summarized AuNPs applications for analytical, biotechnology and proteomics. AuNPs efficiently absorbed the laser radiation and transferred the energy to the analyte forthe desorption/ionization process. The unique features of AuNPs such as large surface area and high absorption coefficientlead not only to high resolution, low interference and low limit of detection, but also offered selective detectionfor certain species. AuNPs provided an excellent surface for the analysis of several species such as small molecules, biomarkers, proteins and cells (pathogenic bacteria or cancer cells). AuNPs played many roles such as surface for LDI-MS, probe and stationary phasefor separation or preconcentration. AuNPs modified various surface chemistry was applied for a wide range of different wavelength. AuNPs severed as a source of Au(+) ions that were suitable for analyte cationisation. Characterization of Au nanoclusters (AuNCs) by mass spectrometry, pros and cons were also highlighted. Graphical Abstract Schematic representation of the analysis by Gold Nanoparticles Assisted Laser Desorption/Ionization Mass Spectrometry (GALDI-MS).

Gold nanoparticles grafted modified silica gel as a new stationary phase for separation and determination of steroid hormones by thin layer chromatography

A new thin layer chromatographic layer using gold nanoparticles grafted 3-triethoxysilyl propylamine modified silica gel (Au NPs-APTS modified silica gel) was developed as a stationary phase for separation and determination of two steroid hormones, namely progesterone and testosterone. Acetone–n-hexane 25:75 (v/v) was used as the mobile phase, and the results were compared with those obtained using plain (i.e., unmodified) silica gel plates. Some chromatographic parameters used for separation of the two steroids on an Au NPs-APTS modified silica gel plate as well as on a plain silica gel plate, including ΔRF, separation factor (α), and resolution (RS), were evaluated and compared. The reproducibility of RF values was also determined by analysis of the two steroids in 7 consecutive days on both plates. Validity of the method was investigated, and a wide linear range of 1–200 ng per spot, and low detection limits of 0.16 ng and 0.13 ng per spot, low quantification limits of 0.51 ng and 0.40 ng per spot, and good precision (expressed as percent relative standard deviation) lower than 3.1% and 2.7% were obtained for progesterone and testosterone, respectively. As the results revealed, the proposed method is rapid and sensitive, and it is applicable to separation and determination of progesterone and testosterone in biological matrices such as urine samples.

A new imidazolium ionic polymer as a gas chromatography stationary phase for separation of high and wide temperature range complex samples

A new imidazolium ionic liquid polymer was synthesized and prepared as GC stationary phase for separation of coal tar samples. The coated capillary GC columns exhibited good thermal stability from room temperature to 380 °C, high separation efficiencies for coal tar samples, phthalates, PAHs and a maximum programmable temperature up to 400 °C.

Preparation of a Novel Stationary Phase for Separation of Ethylbenzene Hydroperoxides

The novelty of this work is preparation of a special stationary phase for selective separation of hydroperoxides. This column can be used widely in the polymerization industries where a variety of initiators (mainly the hydroperoxides) are used. In this work, the ionic liquid-based silica particles were prepared and used as a novel stationary phase for separation of ethylbenzene hydroperoxides. The mobile phase of methanol/acetonitrile from 90:10 to 70:30 (v v−1) was used to separate three isomers of ethylbenzene hydroperoxide. A satisfactory linearity was obtained from 1.0 to 110.0 mg mL−1 (RSD <4.0 %). The stationary phase performed stably and produced reproducible results, highlighting its potential as a separation material.

Poly(ethylene oxide)-bonded stationary phase for separation of inorganic anions in capillary ion chromatography

A tosylated-poly(ethylene oxide) (PEO) reagent was reacted with primary amino groups of an aminopropylsilica packing material (TSKgel NH2-60) in acetonitrile to form PEO-bonded stationary phase. The reaction was a single and simple step reaction. The prepared stationary phase was able to separate inorganic anions. The retention behavior of six common inorganic anions on the prepared stationary phase was examined under various eluent conditions in order to clarify its separation/retention mechanism. The elution order of the tested anions was iodate, bromate, bromide, nitrate, iodide, and thiocyanate, which was similar as observed in common ion chromatography. The retention of inorganic anions could be manipulated by ion exchange interaction which is expected that the eluent cation is coordinated among the PEO chains and it works as the anion-exchange site. Cations and anions of the eluent therefore affected the retention of sample anions. We demonstrated that the retention of the analyte anions decreased with increasing eluent concentration. The repeatability of retention time for the six anions was satisfactory on this column with relative standard deviation values from 1.1 to 4.3% when 10mM sodium chloride was used as the eluent. Compared with the unmodified TSKgel NH2-60, the prepared stationary phase retained inorganic anions more strongly and the selectivity was also improved. The present stationary phase was applied for the determination of inorganic anions contained in various water samples.

Synthesis and characterization of new optically active polymers carrying calix[4]arene and amino acid units in the main chain and their binding properties towards toxic heavy metals

BACKGROUND: A series of novel optically active polymers containing upper rim calix[4]arene was prepared from the polycondensation reaction of calix diamine derivative 2 with two optically active diacid chlorides. RESULTS: The optically active compounds were prepared from the reaction of a pyromellitic dianhydride with two chiral amino acids. The optically active polymers were obtained in a yield of 80–86% and had an inherent viscosity of 0.20–0.26 dL g−1. The polymers were characterized using Fourier transform infrared and 1H NMR spectroscopy and elemental analysis. Studies of the complexation of the polymers towards some alkali metal and toxic transition metal cations were performed using solid–liquid sorption procedures and comparisons made with the starting monomer. CONCLUSION: It is evident from the complexation studies that the polymers investigated are good polymeric ionophores for alkali metal cations like Na+ and K+, for Ag+ and for toxic heavy metal cations such as Cu2+, Co2+, Cd2+ and Hg2+. These polymers are good candidates for use in chiral stationary phases for separation of enantiomers in ionic media, as well for removing metal ions. Copyright © 2009 Society of Chemical Industry

Titania-based stationary phase in separation of ondansetron and its related compounds

Improvements in stationary phase stability have been and remain a great task for research of new stationary phases. Metal oxide-based stationary phases appear as one of perspective alternatives to classical silica based stationary phases regarding to their similar effectiveness, different selectivity, different retention mechanism and mainly better chemical and thermal stability. In this study, the retention behaviour of ondansetron and its five pharmacopoeial impurities on TiO 2-based reversed phase was investigated. The influence of buffer type, pH and concentration on retention was studied. Different types and amount of organic solvent in mobile phase were tested. The effect of temperature and flow rate on separation was investigated. The separation conditions were optimized and developed method validated. The retention parameters – retention time ( t R), retention factor ( k′), theoretical plate number ( N), resolution between peaks due to nearby peaks ( R s) and symmetry factor ( A s) have been compared to parameters achieved on polybutadiene-coated zirconia column. The thermodynamic parameters of retention of analysed compounds – enthalpy, entropy and Gibbs free energy – were calculated and compared to those achieved on polybutadiene-coated zirconia column. This work proves similarity of retention behaviour of ondansetron and its five related compounds on zirconia-based and titania-based stationary phases and potential utilisation of polyethylene covered TiO 2-based reversed stationary phase as an alternative to polybutadiene-coated ZrO 2 stationary phase in pharmaceutical analysis of ondansetron.

Application of Humic Acid Bonded‐Silica as a Hydrophilic‐interaction Chromatographic Stationary Phase in Separation of Polar Compounds

In this paper, humic acid bonded silica (HAAS) stationary phase was prepared through the spacer of aminoalkyl silanes. The high performance liquid chromatographic behavior of several polar compounds, including four alkaloids and clenbuterol, was studied on HAAS. The effect of mobile phase variables such as organic solvent content, buffer pH, and ionic strength on their chromatographic behavior was investigated. The retention mechanism of tested compounds on the stationary phase was elucidated. The results indicate that the HAAS stationary phase behaved as hydrophilic interaction chromatographic packing, using high content organic solvent as mobile phase, and the stationary phase showed good separation selectivity for four alkaloids and clenbuterol.

Comparison of the performance of chiral stationary phase for separation of fluoxetine enantiomers

Separation of fluoxetine enantiomers on five chiral stationary phases (chiralcel OD-H, chiralcel OJ-H, chiralpak AD-H, cyclobond capital I, Ukrainian 2000 DM and kromasil CHI-TBB) was investigated. The optimal mobile phase compositions of fluoxetine separation on each column were hexane/isopropanol/diethyl amine (98/2/0.2, v/v/v), hexane/isopropanol/diethyl amine (99/1/0.1, v/v/v), hexane/isopropanol/diethyl amine (98/2/0.2, v/v/v), methanol/0.2% triethylamine acetic acid (TEAA) (25/75, v/v; pH 3.8) and hexane/isopropanol/diethyl amine (98/2/0.2, v/v/v), respectively. Experimental results demonstrated that baseline separation (R(S)>1.5) of fluoxetine enantiomers was obtained on chiralcel OD-H, chiralpak AD-H, and cyclobond capital I, Ukrainian 2000 DM while the best separation was obtained on the last one. The eluate orders of fluoxetine enantiomers on the columns were determined. The first eluate by chiralcel OJ-H and kromasil CHI-TBB is the S-enantiomer, while by chiralpak AD-H and cyclobond I 2000 DM is the R-enantiomer.

Surface engineering of microchannel walls for protein separation and directed microfluidic flow

The preparation of surfaces in microfluidic devices that selectively retain proteins may be difficult to implement due to the incompatibility of derivatization methods with microdevice fabrication techniques. This review describes recently reported developments in simple and rapid methods for engineering the surface chemistries of microchannels based on construction of press-fit microdevices. These devices are fabricated by placing a glass fiber on a PDMS film and pressing the film on a silicon wafer or a microscope slide that has been derivatized with octadecyltrichlorosilane (ODS). The film adheres to the slide and forms an elliptically shaped channel around the fiber. The combination of surface wettability of a hydrophilic glass microfiber and the surrounding hydrophobic microchannel surfaces directs a narrow boundary layer of liquid next to the fiber in order to bring the sample in contact with the separation media and results in selective retention of proteins. This phenomenon may be exploited to enable microscale separation applications since there are a wide variety of fibers available with different chemistries. These may be used to rapidly fabricate microchannels that serve as stationary phases for separation at a microscale. The fundamental properties of such devices are discussed.

Comparison of Series 5 gas chromatography column performances from a variety of manufacturers for separation of chlorinated dibenzo- p-dioxins and dibenzofurans using high-resolution mass spectrometry

An extended study of seven fused silica capillary gas chromatographic (GC) columns has been conducted with regard to separation of international toxic equivalent factor (I-TEF) isomers (tetra- through octa-chlorinated at 2,3,7,8 positions) of polychlorinated dibenzo- p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) from closely co-eluted other isomers using high-resolution gas chromatography–high-resolution mass spectrometry (HRGC–HRMS). The data are explicated in mass chromatograms of Series 5 GC columns from a variety of manufacturers (Varian CP-Sil 8 CB LowBleed/MS, Phenomenex ZB-5UMS, Agilent HP-5MS, Restek Rtx-5MS, Supelco Equity-5, J&W Scientific DB-5 and DB-5MS), according to relative retention times, and 2,3,7,8-substituted isomer concentrations for each of the columns tested. Results showed differences between 5% phenyl methyl silicone and 5% silphenylene (Si-arylene) silicone polymer type GC stationary phases in separation of 2,3,7,8-substituted PCDDs/PCDFs from closely co-eluted isomers. The separation differences for Si-arylene type columns resulted in lower toxic equivalence (TEQ) values compared to the siloxane-based columns. Because of differences in product nomenclature and manufacturing practices by various manufacturers, incorrect assumptions and comparisons may be made regarding the interchangeability of these columns for PCCD/PCDF separations. The data presented are the most comprehensive to date and provide a valuable addition to operational criteria for the standard US Environmental Protection Agency methods 1613b and 8290.

Separation of racemic 2,4-dinitrophenyl amino acids on zirconia-immobilized quinine carbamate in reversed-phase liquid chromatography.

Zirconia is known to be one of the best chromatographic support materials due to its excellent chemical, thermal, and mechanical stability. A quinine carbamate-coated zirconia was prepared as a chiral stationary phase for separation of enantiomers of DNP-amino acids in reversed-phase liquid chromatography. Retention and enantioselectivity of this phase were compared to those for quinine carbamate bonded onto silica. Most amino acids studied were separated on the quinine carbamate-zirconia CSP although retention was longer and chiral selectivity was somewhat lower than on the corresponding silica CSP. Increased retention and decreased selectivity are probably due to strong non-enantioselective Lewis acid-base interactions between the amino acid molecule and the residual Lewis acid sites on the zirconia surface.

The effect and model of silica concentrations on physical properties and particle sizes of three-dimensional SBA-16 nanoporous materials

Pore size, wall thickness, and microporosity of cubic SBA-16 with 3D, super-large channel can be bridled simply by varying silica concentrations. A reasonable model is also proposed and is applicable to other system such as SBA-15. Ultra-thick wall thickness of 8.5–9.1 nm for SBA-16 has not been reported and may lead to higher thermal and hydrothermal stability of calcined SBA-16. Particle size in the range of 1.5–10 μm can be controlled similarly and is a fairly important parameter for the application on the stationary phase for separation.

Chromatographic cross-fractionation

Chromatographic cross-fractionation applies current equipment and separation techniques to evaluate the molar mass distribution and chemical composition distribution of co-polymers. In comparison with traditional procedures based on fractional precipitation, chromatographic cross-fractionation offers the advantage of a wider range of application through the participation of stationary phases in separation, saving of time per analysis by a factor of 10 3 and reduction of sample size by a factor of 10 4. It also gives the possibility of automation and computerization of analyses.