A sequence optimization strategy for chromatographic separation in reversed‐phase high‐performance liquid chromatography

A sequence optimization strategy combining an artificial neural network (ANN) and a chromatographic response function (CRF) for chromatographic separation in reversed‐phase high‐performance liquid chromatography has been proposed. Experiments were appropriately designed to obtain unbiased data concerning the effects of varying the mobile phase composition, flow‐rate, and temperature. The ANN was then used to simultaneously predict the resolution and analysis time, which are the two most important features of chromatographic separation. Subsequently, a CRF consisting of resolution and analysis time was used to predict the optimum operating conditions for different specialized purposes. The experimental chromatograms were consistent with those predicted for given conditions, which verified the applicability of the method. Furthermore, the proposed optimization strategy was applied to literature data and very good agreement was obtained. The results show that a strategy of sequential combination of ANN and CRF can provide a more flexible and efficient optimization method for chromatographic separation. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Kinetic of epoxy resin formation by high‐performance liquid chromatography

This article is focused on the following of the cure of an epoxy resin by high‐performance liquid chromatography (HPLC) and the comparison of the data obtained with those obtained by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques usually employed for characterize curing processes. A reversed‐phase HPLC method with UV detection is developed to study the kinetic of the curing reaction of diglycidyl ether of bisphenol A (DGEBA) with 1,3‐cyclohexanebismethylamine (1,3‐BAC) at 60, 70, and 80°C, before and after gelation. The limits of quantification obtained permit the application of the proposed method until the last steps of the formation kinetic. HPLC and DSC analysis show a good correlation. The gel conversions obtained by HPLC and DMA agree well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 497–504, 2003     

Investigation of alkaline hydrolysis of phthalimide‐based azo dye and its application to after‐treatment optimisation for high‐fastness dyeing of polyesters

4‐Amino‐N‐methylphthalimide was prepared from phthalimide for use as a diazo component and was coupled with N,N‐Diethylaniline to produce a phthalimide‐derived monoazo disperse dye. The pseudo first‐order kinetics were confirmed by analyzing the dye hydrolysis under alkaline conditions using high performance liquid chromatography, and the optimal dyeing pH and alkali‐clearing conditions were proposed. The synthesised phthalimidyl disperse dyes exhibited excellent colour fastness with a mild alkaline after‐treatment instead of reduction clearing which results in a high biological oxygen demand and pH in conventional disperse dyeing wastewater.     

Identification of early synthetic dyes in historical Chinese textiles of the late nineteenth century by high‐performance liquid chromatography coupled with diode array detection and mass spectrometry

In the present study, five classes of synthetic dyes – nitrophenol (picric acid), azo (Orange II), diarylmethane (auramine O), triarylmethine (fuchsine, methyl violet, and malachite green), and anthraquinone (alizarin) dyes – were identified in late‐nineteenth‐century textiles from the China National Silk Museum by high‐performance liquid chromatography coupled with diode array detection and mass spectrometry. Data‐dependent acquisition of tandem mass spectra provided some information not only on the molecular mass but also on the fragment ions obtained from precursor ions. These fragmentation patterns, obtained in a single experiment, proved to be useful for identification of the synthetic dyes extracted from the textile samples. In addition, it is worth noting that two anthraquinones, which are probably anthrapurpurin and flavopurpurin, and which were detected in printed cotton, can be used as the markers for distinguishing synthetic alizarin from natural alizarin.     

Separation of asymmetric triacylglycerols into their enantiomers by recycle high‐performance liquid chromatography

A recycle HPLC system equipped with a polysaccharide‐based chiral column was used for the enantiomeric separation of asymmetric triacylglycerols (TAGs). When the chiral columns were screened by the resolution of 1,2‐dipalmitoyl‐3‐oleoyl‐rac‐glycerol separation was achieved only with the cellulose tris‐ (3,5‐dimethylphenylcarbamate) chiral selector. The resolution of other TAG enantiomers was also examined, and 1,2‐dioleoyl‐3‐palmitoyl‐rac‐glycerol, 1,2‐dipalmitoyl‐3‐linoleoyl‐rac‐glycerol, 1,2‐dipalmitoyl‐3‐eicosapentaenoyl‐rac‐glycerol, 1,2‐dipalmitoyl‐3‐docosahexaenoyl‐rac‐glycerol, and 1,2‐docosahexaenoyl‐3‐palmitoyl‐rac‐glycerol were resolved into their respective enantiomers. However, neither 1,2‐dioleoyl‐3‐linoleoyl‐rac‐glycerol, consisting of only unsaturated fatty acids, nor 1,2‐dipalmitoyl‐3‐stearoyl‐rac‐glycerol, consisting of only saturated fatty acids, was resolved. In addition, 1,2‐eicosapentaenoyl‐3‐palmitoyl‐rac‐glycerol was not resolved clearly, even in the recycle runs. These results suggest that asymmetric TAGs having both a palmitic acid moiety and an unsaturated fatty acid moiety at the sn‐1 or sn‐3 positions might be resolved on a cellulose tris‐ (3,5‐dimethylphenylcarbamate) chiral column.     

New insight into the kinetics of diisocyanate‐alcohol reactions by high‐performance liquid chromatography and mass spectrometry

The uncatalyzed reactions of 2,4‐TDI (2,4‐ toluenediisocyanate ) and MDI (4,4 ′ ‐ diphenylmethane‐diisocyanate ) with alcohols including butan‐1‐ol, butan‐2‐ol, diethylene glycol monomethylether (DEGME) were studied by high ‐ performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI‐MS). The reactions were carried out at different temperatures from 22°C to 75°C using high molar ratios of alcohols to diisocyanates. It was found that the first isocyanate group of the MDI reacts about 1.5 times faster with the alcohols than the second one. The relative reactivities of the isocyanate groups (para and ortho) of 2,4‐TDI as a function of the temperature was also deduced. From the temperature dependence of the rate constants the apparent activation energies were determined. Furthermore, the dependence of the apparent rate constant on the concentration of alcohols was also investigated and a mechanism was proposed for the reaction of diisocyanates with alcohols. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42127.     

Rosin‐based molecularly imprinted polymers as the stationary phase in high‐performance liquid chromatography for selective separation of berberine hydrochloride

A novel method for the separation of berberine hydrochloride has been developed. Berberine hydrochloride molecularly imprinted polymers were prepared by suspension polymerization in the aqueous phase using berberine hydrochloride as the template, methyl acrylic acid as a functional monomer, and ethylene glycol maleic rosinate acrylate (which contains a phenanthrene ring skeleton) and ethylene glycol dimethacrylate as combinatorial crosslinkers. The imprinted polymers were successfully used as a selective stationary phase in high‐performance liquid chromatography. Separation performance of the chromatographic column was determined from the selectivity (evaluated by separation factor) and sorption selectivity (evaluated by imprinting factor) of the molecularly imprinted and non‐imprinted polymers towards the template. The optimum conditions to maximize separation and imprinting factors were investigated. Acetic acid–methanol solution (0.05% v/v) was selected as the optimum mobile phase, while 0.2 mL min^?1 was chosen as the optimized flow rate for selective separation of berberine hydrochloride. The highest imprinting and separation factors obtained were 1.924 and 18.52, respectively. Simultaneously, the chromatographic column backpressure was stable and showed good permeability. The chromatographic column was used to separate effectively template molecules from coptis root extract and other analogues. Such chromatographic columns with high selectivity can be used to selectively separate berberine hydrochloride from other compounds. © 2014 Society of Chemical Industry     

Reversed‐phase analysis of triacylglycerols by ultra performance liquid chromatography‐evaporative light scattering detection (UPLC‐ELSD)

An improved reversed‐phase (RP) method has been developed for the analysis of triacylglycerols (TAG) in fats and oils. This method has shown superior performance over traditional reversed‐phase liquid chromatographic (LC) methods in speed and resolution, and equivalent to superior performance in quantitation accuracy (101%–109%) and reproducibility (1.3%–5.8% RSD). The method can easily be adjusted for use with different oils by simple modification of the gradient and run time. Additionally, a mobile phase is used that is compatible with liquid chromatography/mass spectrometry (LC/MS) that when required, can aid in identification of TAG, for which many standards do not exist. This method is suited to a broad number of applications including (but not limited to) research and development of new oils, quality control, production of industrial or edible oils, and seed strain selection.     

High‐performance liquid chromatography of some natural dyes: analysis of plant extracts and dyed textiles

In this study, wool fibre samples were mordanted by means of 25% alum mordant solution. The mordanted wool samples were dyed in 50%Reseda luteola L. (weld), 20%Rhamnus petiolaris Boiss (buckthorn) and 50%Datisca cannabina L. (bastard hemp) dyebaths. A reverse‐phase high‐performance liquid chromatography with diode‐array detection method was utilised for the identification of dyes in the dyed wool samples and the plant extracts. The extraction of dyes was carried out with a hydrogen chloride/methanol/water (2:1:1; v/v/v) mixture.     

Coating of porous silica beads by in situ polymerization/crosslinking of 2‐hydroxypropyl β‐cyclodextrin for reversed‐phase high performance liquid chromatography applications

Porous silica beads were coated with a crosslinked β‐cyclodextrin polymer by in situ polymerization/crosslinking of 2‐hydroxypropyl β‐cyclodextrin with 1,6‐hexamethylenediisocyanate in anhydrous dimethylsulfoxide. This method was developed for the preparation of reversed‐phase high performance liquid chromatography stationary phases. The mass of polymer immobilized onto the silica surface was controlled by the amount of coupling agent, 1,6‐hexamethylenediisocyanate, added during the coating process. The influence of the polymer coating on the physical features of the beads was investigated by means of nitrogen adsorption/desorption methods, scanning electron microscopy and energy dispersion X‐ray analysis. The column lifetime was found to be primarily dependent on the extent of crosslinking of the stationary phase. Moreover, it was demonstrated that the synthesis of highly crosslinked stationary phases with a reasonable column lifetime gave rise to a phase separation of the β‐cyclodextrin polymer. To prove their usefulness as reversed‐phase packing materials, they were used to separate mixtures of nitrophenol positional isomers, four pesticides, and drugs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1419–1426, 2004     

Characterization of ethylene‐propylene copolymers with high‐temperature gradient adsorption liquid chromatography and CRYSTAF

Blends of linear polyethylene (PE) and isotactic polypropylene (iPP) with different average molar masses and a series of ethylene‐propylene (EP) copolymers with different chemical composition as well as blends of PE, Ipp, and EP copolymers were separated using a carbon‐column packing (Hypercarb®) and gradients of 1‐decanol or 2‐ethyl‐1‐hexanol → 1,2,4‐trichlorobenzene (TCB). The separation is based on full adsorption of linear PE on the carbon sorbent at temperature 160°C. However, iPP is not adsorbed and elutes in size exclusion mode. The random EP copolymers have been adsorbed in the column packing and separated according to their average chemical composition after application of the gradient starting with alcohol and ending with pure TCB. The elution volumes of the copolymers depended linearly on the average concentration of ethylene in the copolymers. The HPLC elution profiles were correlated with the CRYSTAF elution profiles. In contrast to CRYSTAF, fully amorphous polyolefin samples were separated with the high‐temperature adsorption liquid chromatography. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of a pseudo‐template imprinted polymer with a chirality‐matching monomer for the separation of cinchona alkaloids by high‐performance liquid chromatography

A hydroquinidine‐imprinted stationary selector with chiral recognition for cinchona alkaloids was prepared by bulk polymerization with (+)‐(2R,3R)‐N,N′‐diallyl‐L ‐tartardiamide as a functional monomer, and the recognition properties of the polymers for quinidine (QD) were analyzed with high‐performance liquid chromatography. By optimizing the preparation conditions and chromatographic conditions, such as the ratio of the mobile phase and flow rate, QD and quinine could be completely separated to the best resolution of 2.25. The chiral molecularly imprinted polymers (CMIPs) combined the virtues of traditional brush‐type chiral selectors with existing CMIPs. The results show a substantial synergistic effect between the chiral monomer and the chiral cavity of the resulting CMIPs in chiral recognition. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

高效液相色谱-二极管阵列检测法测定马来酸和乙醛酸

建立了高效液相色谱-二极管阵列法同时测定乙醛酸和马来酸的高效液相色谱方法。色谱条件为:Shim-pack VP.ODS柱(250 mm×4.6 mm I.D.,5μm);二极管阵列检测器;流动相为甲醇/磷酸盐缓冲溶液(NaH2PO4浓度为0.1 mol/L,H3PO4调节至pH=2.98),体积比为5∶95,流速为1.0 mL/min,检测波长为195 nm,柱温为40℃。线性范围分别为79.6～26 660 mg/L和9.3～7 864 mg/L,检出限分别为39.4 mg/L和4.7 mg/L;日内、日间测定的相对标准偏差(RSD):乙醛酸为0.22%和0.46%,马来酸为0.02%和0.03%。     

Separation and identification of isomeric conjugated fatty acids by high-performance liquid chromatography with photodiode array detection

A simple, high-performance liquid chromatographic method is described for the separation of tetraenoic, trienoic and dienoic conjugated fatty acids on a Zorbax ODS reversed-phase column using acetonitrile/tetrahydrofuran (95∶5, vol/vol) at a flow rate of 1.2 mL/min as mobile phase. Also described is the separation of the isomeric conjugated fatty acids with acetonitrile/water/tetrahydrofuran (90∶90∶1, by vol) as mobile phase. The simultaneous detection and identification of the separated geometrical isomers in the eluant was accomplished using photodiode array detection.     

Magnetic molecularly imprinted polymer nanoparticles coupled with high performance liquid chromatography for solid‐phase extraction of carvedilol in serum samples

Herein, we report a magnetic molecularly imprinted polymers (m‐MIPs) using Fe₃O₄ as a magnetic component, carvedilol as a template molecule for the solid‐phase extraction (MISPE) as the sample clean‐up technique combined with high‐performance liquid chromatography (HPLC) and for the controlled release of carvedilol at different pH values of 1.0 (simulated gastric fluid), 6.8 (simulated intestinal fluid), and 7.4 (simulated biological fluid). The adsorption kinetics was modeled with the pseudo‐first‐order and pseudo‐second‐order kinetics, and the adsorption isotherms were fitted with Langmuir and Freundlich models. The performance of the m‐MIPs for the controlled release of carvedilol was assessed and results indicated that the magnetic MIPs also have potential applications in controlled drug release. Furthermore, the m‐MIPs were applied to the extraction of carvedilol from human blood plasma samples. Carvedilol can be quantified by this method in the 2–350 μg L^?1 concentration range. The limit of detection and limit of quantification in plasma samples are 0.13 and 0.45 μg L^?1. The results from HPLC showed good precision (3.5% for 50.0 μg L^?1) and recoveries (between 85 and 93) using m‐MIP from human plasma samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41209.     

Investigation on colour,fastness properties and HPLC‐DAD analysis of silk fibres dyed with Rubia tinctorium L. and Quercus ithaburensis Decaisne

Silk fabric samples were dyed according to the various procedures using madder (Rubia tinctorium L.) and walloon oak (Quercus ithaburensis Decaisne) extracts. The colour coordinates, K/S, as well as wash, light, rub and perspiration fastness values were determined. A reversed‐phase high‐performance liquid chromatography with diode‐array detection was utilised for the identification of the components of dyes present in the dyed fabrics and in the plant extracts.