Ionic Liquids as Mobile Phase Additives for Separation of Nucleotides in High-Performance Liquid Chromatography

Ionic liquids are a type of salts that are liquid at low temperature (＜100℃). Because of their some special properties, they have been widely used as new “green solvents” for many chemical reactions and liquid-liquid extraction in the past several years. In this paper, a new method for the separation of nucleotides is developed and the essential feature of the method is that 1-alkyl-3-methylimidazolium salts are used as mobile phase additives, resulting in a baseline separation of nucleotides without need of gradient elution and need of organic solvent addition as currently used in RP-HPLC. This study shows the potential application of ionic liquids as mobile phase additives in reversed-phase liquid chromatograohy.     

Determination of Methanol Increment in Mobile Phase Consisting of Methanol and Water by On—line UV Spectrometry in Reversed Phase Liquid Chromatography

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Surface Confined Ionic Liquid—A New Stationary Phase for the Separation of Ephedrines in High-performance Liquid Chromatography

In this article, a new and effective stationary phase based on ionic liquid modified silica is first reported and used for the separation of ephedrines in high-performance liquid chromatography (HPLC). The separation results indicate the high efficiency and reproducibility of the stationary phase. The electrostatic interaction, ion-exchange interaction between the solutes and the stationary phase are considered to attribute the effective separation. Moreover, the free silanols on the surface of the silica are effectively masked by the immobilized ionic liquid, a result of which is to decrease the non-specific absorption.     

Dependence of Elution Curve and Adsorption Isotherms of Insulin on composition of Mobile Phase of Frontal Analysis in Reversed Phase Liquid Chromatography

With frontal analysis(FA),the dependence of adsorption isotherms of insulin on the composition of mobile phase in reversed phase liquid chromatography (RPLC) has been investigated,This is also a good example to employ the stoichiometric displacement theory (SDT) for ivestigating solute adsorption in physical chemistry.Six kinds of mobile phase in RPLC were employed to study the effects on the elution curves and adsorption isotherms of insulin.the key points of this paper are:(1) the stability of insulin due to delay time after preparing,the organic solvent concentration,the kind and the concentration of ion-pairing agent in mobile phase were found to affect both elution curve and adsorption isotherm very seriously.(2)To obtain a valid and comparable result,the composition of the mobile phase employed in FA must be as same as possible to that in usual RPLC of either analytical scale or preparative purpose.(3)Langmuir Equation and the SDT were employed to imitate these obtained adsorption isotherms.The expression for solute adsorption from solution of the SDT was found to have a better elucidation to the insulin adsorption from mobile phase in RPLC.     

A Direct Evidence of Stoichiometric Displacement between Insulin and Methanol in Reversed Phase Liquid Chromatography

Ｗith four kinds of mobile phases,methanol-water,ethanol-water,2-propanol and acetonitrile-water(all containing 0.1％rifluroacetic acid),the displacement between solute and solvent in RPLC was proved to be universal in frontal analysls(FA).Based on the measured Z value in usual RPLC to be a constant and the quantitative determination of methanol increment in mobile phase in FA,the stoichiometric displacement(SD)between insulin and methanol was directly proved by the experiment.The SD was also proved to occur only on about the one-fourth of the maximum amount of adsorbed methanol in the bonded phase layer(BPL)without any dynamic problem of mass transfer,while in FA,the SD firstly occurs on the surface of the BPL and then gradually sinks into the deeper sites companied with a dynamic problem.Although the displaces soplvent by the same solute is less in the former case,the SD is independent of how deep of the solute enters the BPL.In addition,the adsorbed amount of solute on and adsorbent not only depends on the numbers of the adsorbed layer on the adsorbent surface,but also on the extent of the complete removal of the displace able solvent in the BPL.The pyhsical fundamental of the SD and the methodoloby for investigation were also discussed.     

Characters of the Plateau of Methanol Increment in Frontal Analysis in Reversed Phase Liquid Chromatography

With insulin methanol-water,and the ion-pairing agent,hydrochloric acid and trifluroacetic acid(TEA),the character of the first plateau(FP)on the elution curve of frontal analysis in reversed phase liquid chromatography(RPLC)was investigated by on-line UV-spectrometry and identified with nuclear magnetic resonance(NMR) spectrometry and mass spectrometry.The profile of the FP is the same as that of a usual elution curve of methanol in frontal analysis(FA).When the insulin concentration was limited to a certain range,the height of the FP was found to be proportional to the insulin concentration in mobile phase and its length companying to shorten,The FP profile on the intersection of two tangents reflects the components of the microstructure in the depth direction of the bonded stationary phase layer and the desorption dynamics of the displaced components.The displaced methanol was quantitatively determined by NMR and on-line UV spectrometries.TFA with high UV absorbance can not be used as an ionpairing agent for the investigation of the FP in RPLC,but if can be used as a good marker to investigate the complicated transfer process of components in the stationary phase in RPLC.A stoichiometric displacement process between solute and solvent was proved to be valid in both usual and FA in RPLC.From the point of view of dynamics of mass transfer, the solutes can only contact to the surface of stationary phase in usual RPLC,while solute can penetrate into it in FA of RPLC.The solvation of insulin in methanol and water solution as an example indicating the usage of the FP in the FA was also investigated in this paper.     

Diethyl Tartrate on Polystyrene Bead as Chiral Stationary Phase in Liquid Chromatography

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Experimental Design Optimization of Solid‐Phase Microextraction Conditions for the Determination of Heterocyclic Aromatic Amines by High‐Performance Liquid Chromatography

Abstract

Solid‐phase microextraction, using Carbowax‐Templated Resin fiber, coupled with high performance liquid chromatography ultra violet/diode array detector (HPLC‐UV/DAD) has been optimized for the determination of the heterocyclic aromatic amines (HAs). Three variables (absorption time, soaking time, and desorption time) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using two level factorial and Doehlert matrix designs. Absorption time and soaking time were significant variables, and 15 min for each one of the variables was chosen for the best response. The optimized procedure allowed the determination of HAs with detection limits that ranged from 1.58 to 16.8 ng/L (except PhIP: 23.8 ng/L). The reproducibility of the method (n=5), expressed as relative standard deviation was between 2.21% and 28.3%. The method was applied to the analysis of a meat extract sample and the range of recoveries for the amines was 64.14%–112.72%.     

Determination of Cotinine in Urine by Molecularly Imprinted Polymer Solid Phase and Liquid–Liquid Extraction Coupled with Gas Chromatography

A comparison between molecularly imprinted solid phase extraction (MISPE) and liquid–liquid extraction (LLE) was performed for cotinine in human urine followed by gas chromatography analysis. The molecularly imprinted polymer (MIP) was synthesized via bulk methodology employing cotinine, methacrylic acid, and ethylene glycol dimethacrylate as template, functional monomer, and cross-linker, respectively. Both methods were validated with good precision and accuracy. The LLE method (limit of quantification = 10 nanograms per milliliter) was slightly more sensitive than the MISPE (limit of quantification = 15 nanograms per milliliter) procedure, but both methods were able to determine cotinine at typical concentrations in urine. An important advantage of the molecularly imprinted polymer approach was its ability to be reused up to at least 100 times. Other advantages of the MISPE include simple manipulation, low solvent consumption, and low worker exposure.     

Reversed‐Phase High‐Performance Liquid Chromatography with Electrochemical Detection of Anthocyanins

Abstract

Anthocyanins, flavonoid compounds present in grapes and wines, were determined by reverse‐phase high‐performance liquid chromatography (RP‐HPLC) with electrochemical detection (RP‐HPLC‐ED). The method developed consists of RP‐HPLC gradient elution with voltammetric detection using a glassy carbon electrode after separation in an Inertsil ODS‐3V analytical column. Good peak resolution was obtained following direct injection of a 50 µL sample of anthocyanins in a mobile phase of pH 2.20. The results show that six different anthocyanins: cyanidin‐3‐O‐glucoside chloride (kuromanin chloride), cyanidin‐3,5‐di‐O‐glucoside chloride (cyanin chloride), malvidin‐3‐O‐glucoside chloride (oenin chloride), malvidin‐3,5‐di‐O‐glucoside chloride (malvin chloride), delphinidin‐3‐O‐glucoside chloride (myrtillin chloride), and peonidine‐3‐O‐glucoside chloride, all with antioxidant properties, can be separated in a single run by direct injection of solution. The limit of detection (LOD) for these compounds was lower than 0.3 µM. The method can also be applied to the analysis of these compounds in red wines and in skins and pulp extracts of red grapes, since all these antioxidants are electroactive.     

Determination of Fluoroquinolone Antibiotics in Industrial Wastewater by High-Pressure Liquid Chromatography and Thin-Layer Chromatography—Densitometric Methods

JPC – Journal of Planar Chromatography – Modern TLC - Two methods were described for the simultaneous determination of ciprofloxacin HCl (CIP) and moxifloxacin HCl (MOX) in their binary...     

Chitin as Stationary Phase in Thin-Layer Chromatography–Application of Chromatographic Process Optimization Theory for Chitin Layers

Abstract

This paper describes initial of two basic theories of adsorption thin-layer chromatography potimization namely thermodynamic adsorption theory and theory based on mass action law, so called Snyder s theory in chromatographic systems containing chitin as stationary phase on wchich various amino acids were chromatographed. The results obtained were comparable to those obtained for analogous chromatographic systems containing silica gel as stationary phase. Comparison of applicability of these theories for well investigated silica gel and for not enough investigate chitin will permit to draw introductory conclusions about the processes carrying in the chromatographic systems containing chitin as stationary phase.     

Determination of Organotins in Seafood by Novel Extraction Procedures and High Performance Liquid Chromatography–Inductively Coupled Plasma-Mass Spectrometry

Triorganotins in seafood are a risks to human health, but due to their low concentrations, their determination is challenging. In this study, a simple and rapid method was developed to isolate triorganotins from seafood by microwave-assisted extraction coupled with magnetic nanoparticle-based purification. The magnetic nanoparticles were coated with octanoic acid. Triethyltin chloride, tributyltin chloride, triphenyltin chloride, and azocyclotin were determined by high performance liquid chromatography– inductively coupled plasma mass spectrometry (HPLC–ICP-MS). Various parameters including the temperature, time, and volume of solvent were optimized to improve the extraction efficiency. Under the optimized conditions, the average recoveries (n = 6) of the triorganotins (fortified at 0.01, 0.02, and 0.05 µg g^?1) were between 73.8% and 105.4% and the relative standard deviations were less than 10.4%. The procedure was successfully applied to seafood, and the analytes were measured at concentration levels between 2.93 and 11.26 ng g^?1.     

Identification of Carbofuran And Methiocarb and their Transformation Products in Estuarine Waters by On-line Solid Phase Extraction Liquid Chromatography—Mass Spectrometry

Abstract

The degradation of the carbamate insecticides carbofuran and methiocarb in distilled and natural waters was determined. Degradation studies were carried out both under a xenon arc irradiation and natural sunlight at pesticide concentrations of 50–100 μg/L. 50–100 mL water sample were preconcentrated using automated online solid phase extraction (SPE) followed by liquid chromatography (LC), UV detection or post column fluorescence detection (EPA method 531.1 for carbamate insecticides). Structure identification was carried out by on-line SPE-LC-MS either with thermospray and/or high flow pneumatically assisted electrospray interfaces. Half-lives varying between 4–12.5 days for carbofuran and methiocarb were determined under natural sunlight exposure, being chemical hydrolysis the major degradation pathway. When using xenon arc lamp irradiation both pesticides degraded very rapidly with half-lives varying from 0.3–1.7 hours. The various degradation products identified were: methiocarb sulfoxide, 4-methylthio-3, 5-dimethylphenol, 3-hydroxy-7-carbofuranphenol and 2-hydroxy-3-(2-methylprop-1-enyl)-phenyl-N-methylcarbamate.     

Determination of Phthalate Esters in Wine Using Dispersive Liquid–Liquid Microextraction and Gas Chromatography

A simple and rapid efficient method was developed for the determination of phthalate esters using dispersive liquid–liquid microextraction followed by gas chromatography with flame ionization detection. A mixture of isopropanol (0.75 mL, dispersant) and carbon tetrachloride (30 µL, extractant) with sodium chloride (1%, w/v) was used for extraction. Under optimum conditions, the method provided linear calibration curves between 0.5 and 200 µg L^?1 for dibutyl phthalate, and 1.0 and 200 µg L^?1 for butyl benzyl phthalate, diethyl phthalate, and diisooctyl phthalate. The relative standard deviations for intra-day and inter-day analyses were less than 5.8% and 6.9%, respectively, with enrichment factors between 229 and 424. Two wine samples were analyzed with recoveries between 70.1% and 119.3%.     

Preparation and Characterization of Bonded Stationary Phase Containing Monoaza Crown Ether for High-Performance Liquid Chromatography

Themonoa-zacrownetheramphiphilicmolecu1escontainingalonghydrophobicchainhavebeenwidelyusedinanalyticalchemistry,andprovidedwithsomecharacteristicsofselectivecoordinationwithsomemetalionsl-3.TheaPp1icationofcrownetherinhigh-performanceliquidchromatograPhy(HPLC)isanimportantfie1dofresearchindevelopinghost-guestandmultimodalstationaryphaseforLC'-'.Theworkpresentedinthispaperreportsthepreparationofmonoazacrownetherbondedphaseviaaseriesofsyntheticreactionsthatenabledmonoazacrownethertobebondedto…     

An Integrated Theory of Adsorption and Partition Mechanism and Eash Contribution to Solute Retention in Reversed Phase Liquid Chromatography

With the combination of the the stoichiometric displacement model for retention (SDM-R) in reversed phase liquid chromatography (RPLC) and the stoichiometric displacement model for adsorption (SDM-A) in physical chemistry,the total number of moles of the re-solvated methanol of stationary phase side.nr,and that of solute side in the mobile phase,q,corresponding the one mole of the desorbing solute,were separately determined and referred as the characterization parameters of the contributions of the adsorption mechanism and partition mechanism to the solute retention,respectively.A chromatographic system of insulin,using mobile phase consisting of the pseudo-homologue of alcohols(methanol,ethanol and 2-propanol)-water and trifluoroacetic acid was employed.The maximum number of the methanol layers on the stationary phase surface was found to be 10.6,only 3 of which being valid in usual RPLC,traditionally referred as a volume process in partition mechanism.However,it still follows the SDM-R.Both of q and nr of insulin were found not to be zero,indicating that the retention mechanism of insulin is a mixed mode of partition mechanism and adsorption mechanism.When methanol is used as the organic modifier,the ratio of q/nr was 1.13,indicating the contribution to insulin retention due to partition mechanism being a bit greater than that due to adsorption mechanism.A linear relationship between q,or nr and the carbon number of the pseudo-homologue in the mobile phase was also found.As a methodology for investigating the retention mechanism retention and behavior of biopolymers.a homologue of organic solvents as the organic modifier in mobile phase has also been explored.     

Influence of Mobile Phase Composition on the Enantioseparation of Meythoxyl Flavanones with Self—prepared CDMPC Column and Chiral Recogniton Mechanism

The influence of different alcohol modifiers in mobile phase on the chiral separation of 4‘‘‘‘‘‘‘‘-methoxyl flavanone,5-methoxyl flavanone and 6-methoxyl flavanone on cellulose tris(3,5-dimethylphenylcarbamate)(CDMPC)column was studied and the chiral recognition mechanism was discussed.Using hexane-tert-butanol(1.31molL^-1) as the mobile phase,those three methoxyl flavanones were excellently separated on CDMPC chiral column.     

A Dissipative Reaction Network Drives Transient Solid–Liquid and Liquid–Liquid Phase Cycling of Nanoparticles

Transient states maintained by energy dissipation are an essential feature of dynamic systems where structures and functions are regulated by fluxes of energy and matter through chemical reaction networks. Perfected in biology, chemically fueled dissipative networks incorporating nanoscale components allow the unique properties of nanomaterials to be bestowed with spatiotemporal adaptability and chemical responsiveness. We report the transient dispersion of gold nanoparticles in water, powered by dissipation of a chemical fuel. A dispersed state that is generated under non-equilibrium conditions permits fully reversible solid–liquid or liquid–liquid phase transfer. The molecular basis of the out-of-equilibrium process is reversible covalent modification of nanoparticle-bound ligands by a simple inorganic activator. Activator consumption by a coupled dissipative reaction network leads to autonomous cycling between phases. The out-of-equilibrium lifetime is tunable by adjusting the pH value, and reversible phase cycling is reproducible over several cycles.