聚苯胺/石墨烯涂覆型阴离子交换固定相的制备及表征

该文以聚苯胺/石墨烯复合材料为涂覆材料,制备了一种涂覆型阴离子交换固定相。首先以苯胺和石墨烯为原料制备聚苯胺/石墨烯复合材料,并通过物理吸附涂覆在聚苯乙烯-二乙烯苯微球表面;然后以聚苯胺中的氮原子为反应位点,通过季铵化制备一系列具有不同交换容量的涂覆型阴离子交换固定相。通过扫描电镜(SEM)、傅里叶红外光谱(FT-IR)和元素分析(EA)对该涂覆型阴离子交换固定相进行表征,结果表明聚苯胺/石墨烯成功地涂覆在微球表面且发生了季铵化。通过分离常规阴离子和有机酸,对自制阴离子交换色谱柱的色谱性能进行评价。结果显示,8次季铵化的聚苯胺/石墨烯涂覆聚苯乙烯-二乙烯苯阴离子交换色谱柱对常规阴离子和有机酸呈现良好的分离效果。     

Application of bromoacetate‐substituted β‐CD‐bonded silica particles as chiral stationary phase for HPLC

Bromoacetate‐substituted [3‐(2‐O‐β‐cyclodextrin)‐2‐hydroxypropoxy]propylsilyl‐appended silica particles (BACD‐HPS), an important and useful synthetic intermediate for preparation of novel types of macrocycles‐capped β‐CD‐bonded silica particles including crown ether/cyclam/calix[4]arene‐capped β‐CD‐bonded silica particles, have been prepared and used as chiral stationary phase for HPLC. This synthetic stationary phase is characterized by means of elemental analysis. For the first time, the chromatographic behavior of BACD‐HPS was systematically evaluated with several disubstituted benzenes and some chiral drug compounds under both normal and RP conditions in HPLC. The results show that BACD‐HPS has excellent selectivity for the separation of aromatic positional isomers and chiral isomers of some drug compounds when used as stationary phase in HPLC.     

乳胶附聚型阴离子交换固定相的制备及表征

以烯丙基缩水甘油醚（AGE）为乳胶聚合单体,制备了一种乳胶附聚型阴离子交换固定相。通过无皂化乳液聚合法,以AGE和苯乙烯（ST）为共聚单体制备AGE-ST共聚乳胶。将该乳胶季铵化后附聚在磺化的聚苯乙烯-二乙烯苯（PS-DVB）微球表面,制备一种乳胶附聚型阴离子交换色谱固定相。通过扫描电镜（SEM）、傅里叶红外光谱（FT-IR）和元素分析（EA）等对该乳胶附聚型阴离子交换色谱固定相的理化性质进行表征,结果显示季铵化的AGE-ST共聚乳胶成功附聚在磺化的PS-DVB微球表面,并通过分离常规阴离子和有机酸对制得的阴离子交换剂的色谱性能进行评价。AGE以其良好的pH耐受性和活泼的反应活性为离子交换色谱固定相的制备提供一个新的选择。     

2,3-聚季铵盐附聚型离子色谱固定相的制备及其在SO42-分析中的应用

以四甲基乙二胺和1,3-二溴丙烷为原料,合成了聚电解质阳离子功能基--2,3-聚季铵盐功能基。以聚苯乙烯为种子,通过种子溶胀法制备了多孔型聚(苯乙烯-二乙烯基苯)微球(PS-DVB),并对其进行磺化。以附聚的方式在磺化的PS-DVB微球上附聚2,3-聚季铵盐功能基,得到附聚型离子交换固定相,通过匀浆法装入色谱柱,并将其用于SO₄^2-的分离分析。SO₄^2-能与其他常见的6种阴离子在8 min内完成分离,实现SO₄^2-的快速测定。其中,SO₄^2-的线性范围为0.5~50 mg/L,线性相关系数r为0.9992;加标回收率在99.2%~101.8%之间;峰面积和保留时间的相对标准偏差分别为2.4%和3.1%;根据信噪比(S/N=3)计算出检出限为0.04 mg/L。结果表明该自制色谱柱适用于复杂基质中SO₄^2-的快速测定。     

Iodide analysis by ion chromatography on a new stationary phase of polystyrene-divinylbenzene agglomerated with polymerized-epichlorohydrin-dimethylamine

A new stationary phase for iodide ion analysis has been developed. The cationic polymerepichlorohydrin-dimethylamine(PEPI-DMA) was served as modifier in synthesizing polyelectrolyte sorbents and the macroporous polystyrene-divinylbenzene(PS-DVB) resin was used as support. The positively charged polymer(PEPI-DMA) was electrostatically bonded to a negatively charged particle(PS-DVB sulfonated). The new stationary phase was characterized by scanning electron microscopy(SEM), Fourier transform infrared(FTIR), elemental analysis, chemical adsorption and desorption measurements. The chromatographic evaluation of the new stationary phase was performed using various anions with a conductivity detector. The new stationary phase was also applied to the determination of iodide directly with a DC amperometric detector using a platinum working electrode and an Ag/Ag Cl reference electrode. The chromatographic conditions were optimized and the eluent solution contained 5 mmol/L HNO3 and 15 mmol/L Na NO3 at a flow rate of 1.0 m L/min and column temperature of 30 8C. The applied voltage of the DC amperometric detector was 0.9 V. Under the optimum conditions, the linear range of the method was 0.2–50 mg/L for iodide ion with a correlation coefficient of 0.9990. The detection limit was 0.05 mg/L(calculated at S/N = 3) and the relative standard deviations(RSD, n = 6) were all less than 1% for retention time, peak area and peak height. This method was also utilized for the determination of iodide ions in samples of povidone iodine solution and kelp samples with satisfactory results.     

Prediction of retention behaviour and evaluation of pka values of peptides and quinolones in liquid chromatography.

The present paper examines the effect of the solute ionisation on the retention behaviour in liquid chromatography of a series of peptide and quinolone compounds of biological interest, using acetonitrile-water media as mobile phases and a polymeric-based stationary phase. Polymeric columns with polystyrene-divinylbenzene (PS-DVB) polymer show advantages over silica-based reversed-phase packings since the former are stable in a wide pH range. (s)(s)pKa values have been evaluated using chromatographic data in acetonitrile-water mixtures with acetonitrile percentages of 30, 35, 40 and 50% (v/v) for quinolones and 12.5 and 20% (v/v) for peptides. The quinolones show great retention on PS-DVB phase stationary. It was thus necessary to work with a higher acetonitrile content in the mobile phase than for the less retained peptides. The pH values were measured in the hydroorganic mixtures, used as mobile phases, instead of in water and account was taken of the effect of activity coefficients. The derived equations permit the chromatographic determination of (s)(s)pKa. values of the peptides and quinolones in acetonitrile-water mixtures by fitting it to the experimental data in a nonlinear least-square procedure and also permit the prediction of the effect of (s)(s)pH on their chromatographic behaviour. We have also compared the obtained (s)(s)pKa values with those previously obtained in acetonitrile-water mixtures from potentiometric measurements.     

Intermolecular interactions of substituted benzenes on multi-walled carbon nanotubes grafted on HPLC silica microspheres and interaction study through artificial neural networks

Purified multi-walled carbon nanotubes (MWCNTs) grafted onto silica microspheres by gamma-radiation were applied as a HPLC stationary phase for investigating the intermolecular interactions between MWCNTs and substituted benzenes. The synthetic route, simple and not requiring CNTs derivatization, involved no alteration of the nanotube original morphology and physical–chemical properties. The affinity of a set of substituted benzenes for the MWCNTs was studied by correlating the capacity factor (k′) of each probe to its physico-chemical characteristics (calculated by Density Functional Theory). The correlation was found through a theoretical approach based on feedforward neural networks. This strategy was adopted because today these calculations are easily affordable for small molecules (like the analytes), and many critical parameters needed are not known. This might increase the applicability of the proposed method to other cases of study. Moreover, it was seen that the normal linear fit does not provide a good model. The interaction on the MWCNT phase was compared to that of an octadecyl (C18) reversed phase, under the same elution conditions. Results from trained neural networks indicated that the main role in the interactions between the analytes and the stationary phases is due to dipole moment, polarizability and LUMO energy. As expected for the C18 stationary phase correlation, is due to dipole moment and polarizability, while for the MWCNT stationary phase primarily to LUMO energy followed by polarizability, evidence for a specific interaction between MWCNTs and analytes. The CNT-based hybrid material proved to be not only a chromatographic phase but also a useful tool to investigate the MWCNT-molecular interactions with variously substituted benzenes.     

Improving selectivity in gas chromatography by using chemically modified multi-walled carbon nanotubes as stationary phase

Amino-terminated alkyl MWCNTs (MWCNTs-R-NH₂), synthesized by chemical modification of the nanotube skeleton by nucleophilic substitution with 2,2′-(ethylenedioxy)diethylamine, were successfully used as stationary phases for gas chromatographic separation of esters and chloroaromatics. The presence of alkyl chains with polar embedded groups made the functionalized MWCNTs (f-MWCNTs) a mixed-mode GC separation material able to interact in different ways with the analytes. Compared with non-functionalized MWCNTs (nf-MWCNTs), MWCNTs-R-NH₂ had higher selectivity, enhanced resolution, and optimum retention behaviour, and they were proved to perform better than the commercial stationary phase Porapak QS (PQS), claimed to be suitable for similar applications. The so-prepared stationary phase was used for analysis of a synthetic mixture containing different classes of analytes, viz. esters, ketones, alcohols, alkanes, and aromatic hydrocarbons, and finally used for investigation of similar real matrices. In particular, the constituents of a commercial paint thinner were determined by direct injection of the sample, with good reproducibility (inter-day precision RSDs from 5 to 19%). Two unknown samples of commercial white spirit were also analysed for determination of the aromatic hydrocarbon content, and their composition was profiled on the basis of the different compounds identified.     

Surface Polymers on Multiwalled Carbon Nanotubes for Selective Extraction and Electrochemical Determination of Rhodamine B in Food Samples

In this study, we combine magnetic solid phase extraction (MSPE), with the screen-printed carbon electrode (SPCE) modified by a molecular imprinted polymer (MIP) for sensitive and selective extraction and electrochemical determination of Rhodamine B in food samples. A magnetic solid phase extraction (MSPE) was carried out using magnetic poly(styrene-co-divinylbenzene) (PS-DVB) and magnetic nanoparticles (MNPs) synthetized on the surface of multiwalled carbon nanotubes (MWCNTs). An MIP was prepared on the surface of MWCNTs in the presence of titanium oxide nanoparticles (TiO₂NPs) modifying the SPCE for the rapid electrochemical detection of Rhodamine B. The MIPs synthesis was optimized by varying the activated titanium oxide (TiO₂) and multiwalled carbon nanotubes (MWCNTs) amounts. The MSPE and electrochemical detection conditions were optimized as well. The present method exhibited good selectivity, high sensitivity, and good reproducibility towards the determination of Rhodamine B, making it a suitable method for the determination of Rhodamine B in food samples.     

一种表面共聚氢氧根选择性阴离子色谱固定相

报道了一种基于聚(苯乙烯-二乙烯基苯)微球(PS-DVB)的表面共聚氢氧根选择性阴离子固定相。它以烯丙基缩水甘油醚(AGE)为功能单体、通过自由基引发直接与PS-DVB微球表面残留的悬挂双键共聚,再通过醇胺开环得到。考察了两种醇胺试剂对分离的影响;扫描电镜、红外光谱、元素分析表征结果表明:表面共聚反应成功在微球表面引入季胺基团,且对微球理化性质无显著影响;所得固定相表现氢氧根淋洗液的高选择性,对常规无机阴离子表现出良好的分离性能(分离度>1.5)和运行稳定性(保留时间的相对标准偏差<1.13%),其实用性通过分析茶叶样品中无机阴离子进行了展示。     

Characterisation of stationary phases in subcritical fluid chromatography with the solvation parameter model IV. Aromatic stationary phases

The purpose of the present work was to systematically study the chromatographic behaviour of different aromatic stationary phases in a subcritical fluid mobile phase. We attempted to assess the chemical origin of the differences in retention characteristics between the different columns. Various types of aromatic stationary phases, all commercially available, were investigated. The effect of the nature of the aromatic bonding on interactions between solute and stationary phases and between solute and carbon dioxide-methanol mobile phase was studied by the use of a linear solvation energy relationship (LSER): the solvation parameter model. This study was performed to provide a greater knowledge of the properties of these phases in subcritical fluid chromatography, and to allow a more rapid and efficient choice of aromatic stationary phase in regard of the chemical nature of the solutes to be separated. Charge transfer interactions naturally contribute to the retention on all these stationary phases but are completed by various other types of interactions, depending on the nature of the aromatic group. The solvation vectors were used to compare the different phase properties. In particular, the similarities in the chromatographic behaviour of porous graphitic carbon (PGC), polystyrene-divinylbenzene (PS-DVB) and aromatic-bonded silica stationary phases are evidenced.     

Quantification of lactobionic acid and sorbitol from enzymatic reaction of fructose and lactose by high-performance liquid chromatography

Experimental conditions for complete separation and quantification of mixtures containing lactobionic acid, sorbitol, lactose and fructose are discussed for the first time. These mixtures appear in the enzymatic bioconversion of fructose and lactose catalyzed by glucose-fructose oxidoreductase (GFOR) and glucono-delta-lactonase (GL) enzymes of Zymomonas mobilis cells. The high-performance liquid chromatography (HPLC) separation was carried out in a strong cation ion exchange resin (hydrogen form) based on a copolymer of styrene divinylbenzene (PS-DVB). A stationary phase of beta-cyclodextrin was also evaluated. An efficient separation was obtained with PS-DVB column eluted with sulfuric acid 0.450 mM solutions (pH 3.0-3.2) at 75 degrees C. The formation of lactones was observed, which is associated with the dissolution of lactobionic acid crystals; however, by dissolving the lactobionic acid crystals on alkaline calcium hydroxyde solution in equimolar ratio a single lactobionic acid chromatographic peak without lactobionolactone is obtained.     

A single pump column-switching technique coupled with polystyrene-divinylbenzene-carbon nanotubes column for the determination of trace anions in different concentrated organic matrices by ion chromatography

An ion chromatographic method with on-line sample pretreatment was developed for the trace analysis of seven common anions in concentrated matrices. The pretreatment column used in this study consisted of polystyrene-divinylbenzene (PS-DVB) and multi-walled carbon nanotubes (MWCNTs). It was too hydrophobic to retain different inorganic anions, but it showed a strong affinity for organic compounds. Thus, this chromatographic system could be used to detect trace anions in organic solvents, organic acids and relevant salts. The addition of MWCNTs decreased the surface areas of stationary phases and the retention times of organic matrices were shortened. Compared with conventional column-switching technique, only a single instrument (ICS2100) was needed in this system, including a pump, a conductivity detector, an eluent generator, a six-port valve and a ten-port valve. An electrochemical self-generating suppressor (ESGS) was adopted to convert the eluent of KOH into water for the matrix elimination. Two different eluent were employed in the chromatographic system, one for separation and the other for matrix elimination. The sample pretreatment and analysis were realized simultaneously. After optimization of this system, a calibration study was conducted by preparing and analyzing eight concentrations (between 5 and 5000 μg L(-1)) of mixture standards of seven anions in deionized water. The linearity was between 0.9990 and 0.9998, and the detection limits ranged from 0.41 to 3.17 μg L(-1). A spiking study was performed on three representative organic chemicals with satisfactory recoveries between 88.1% and 118.5% when the concentrations of the matrices did not exceed 10 g L(-1).     

Preparation and evaluation of packed capillary columns for the separation of nucleic acids by ion-pair reversed-phase high-performance liquid chromatography

Oligonucleotides and double stranded DNA fragments were separated in 200 microm I.D. capillary columns packed with micropellicular, octadecylated, 2.1 microm poly(styrene-divinylbenzene) particles by ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC). Both the length and the diameter of the connecting capillaries (150 x 0.020 mm I.D.) as well as the detection volume (3 nl) had to be kept to a minimum in order to maintain the high efficiency of this chromatographic separation system with peak widths at half height in the range of a few seconds. Three different types of frits, namely sintered silica particles, sintered octadecylsilica particles, and monolithic poly(styrene-divinylbenzene) (PS-DVB) frits were evaluated with respect to their influence on chromatographic performance. Best performance for the separation of oligonucleotides and long DNA fragments was observed with the PS-DVB frits, whereas the short DNA fragments were optimally resolved in columns terminated by octadecylsilica frits. The maximum loading capacity of 60 x 0.20 mm I.D. columns ranged from 20 fmol (7.7 ng) for a 587 base pair DNA fragment to 500 fmol (2.4 ng) for a 16-mer oligonucleotide. Lower mass- and concentration detection limits in the low femtomol and low nanomol per liter range, respectively, make capillary IP-RP-HPLC with UV absorbance detection highly attractive for the separation and characterization of minute amounts of synthetic oligonucleotides, DNA restriction fragments, and short tandem repeat sequences amplified by polymerase chain reaction.     

Latex-functionalized monolithic columns for the separation of carbohydrates by micro anion-exchange chromatography

A novel stationary phase for micro ion chromatography has been prepared by coating a porous poly(butyl methacrylate-co-ethylene dimethacrylate-co-2-acrylamido-2-methyl-1-propanesulfonic acid) monolith with quaternary amine-functionalized latex particles via simple electrostatic binding. This stationary phase enabled the separation of saccharides in the mobile phase with a high-pH value consisting of aqueous ammonia solution in anion-exchange mode using evaporative light scattering for detection. Effects of both porous properties of the monolithic stationary phase and chromatographic conditions on the separation ability were studied. Under optimized conditions, an efficient separation of seven saccharides was achieved in less than 10 min. The stationary phase also enables the separation of saccharides obtained by the enzymatic hydrolysis of corn starch.     

Carbon nanotube and carbon nanorod-filled polyacrylonitrile electrospun stationary phase for ultrathin layer chromatography

The application of carbon nanotube or nanorod/polyacrylonitrile (PAN) composite electrospun nanofibrous stationary phase for ultrathin layer chromatography (UTLC) is described herein. Multi-walled carbon nanotubes (MWCNTs) and edge-plane carbon (EPC) nanorods were prepared and electrospun with the PAN polymer solution to form composite nanofibers for use as a UTLC stationary phase. The analysis of laser dyes demonstrated the feasibility of utilizing carbon nanoparticle-filled electrospun nanofibers as a UTLC stationary phase. The contribution of MWCNT or EPC in changing selectivity of the stationary phase was studied by comparing the chromatographic behavior among MWCNT–PAN plates, EPC–PAN plates and pure PAN plates. Carbon nanoparticles in the stationary phase were able to establish strong π–π interactions with aromatic analytes. The separation of five polycyclic aromatic hydrocarbons (PAHs) demonstrated enhanced chromatographic performance of MWCNT-filled stationary phase by displaying substantially improved resolution and separation efficiency. Band broadening of the spots for MWCNT or EPC-filled UTLC stationary phases was also investigated and compared with that for pure PAN stationary phases. A 50% improvement in band dispersion was noted using the MWCNT based composite nanofibrous UTLC plates.     

表面接枝型离子色谱固定相的制备

以苯乙烯-二乙烯基苯微球为基质,建立了一种新型离子色谱固定相的制备方法。在基质微球表面合成一层聚缩水甘油甲基丙烯酸酯聚合物层(GMA),随后与甲胺及1,4-丁二醇二环氧甘油醚(BDDE)交替反应,与其表面接枝上带正电荷的季铵基团,可用于阴离子的分离。通过改变接枝反应的次数,控制交换树脂的交换容量。自制色谱固定相能够用于7种常规阴离子分离分析,并用于自来水中常规阴离子的检测。分离检测结果可与商用离子色谱柱相比,同时水负峰能与氟离子完全分离,不影响氟离子的定量检测。     

磷酰胆碱色谱固定相的制备及其在分离生物大分子中的应用

以三氯氧磷、氯化胆碱和甲基丙烯酸-2-羟乙酯(HEMA)为原料合成了含磷酰胆碱的单体2-甲基丙烯酰氧乙基磷酰胆碱(MPC). 在硅胶表面嫁接聚合MPC, 得到磷酰胆碱两性离子交换色谱填料. 研究了该填料对标准蛋白的分离性能及pH对蛋白质保留的影响. 结果表明, 该填料对溶菌酶和牛血清白蛋白的动态吸附容量分别为13.8和18.7 mg/g, 其基质磷酰胆碱色谱固定相可同时基线分离两种酸性和两种碱性蛋白.     

Dynamic chelation ion chromatography of transition and heavy metal ions using a mobile phase containing 4-chlorodipicolinic acid

The chromatographic behaviour of selected transition and heavy metal ions, the lanthanides, uranium and aluminium, on a neutral polystyrene-divinylbenzene (PS-DVB) stationary phase (7 microm Hamilton PRP-1) dynamically modified with 4-chlorodipicolinic acid, was investigated to evaluate retention characteristics. Complicated retention factor against pH plots were found for these metals demonstrating changes in retention order. It was concluded that complexation between the metal ions and the ligand adsorbed on the resin was strongly influenced by the decrease in dynamic loading with increase in pH, coinciding with changes in the metal-to-ligand ratio in the mobile phase. Possible reversed-phase interactions between metal-chlorodipicolinic acid complexes and the hydrophobic PS-DVB stationary phase also could not be ruled out. An eluent of 0.25 mM chlorodipicolinic acid, I M potassium nitrate at pH 2.2 was suitable for the separation of seven transition and heavy metal ions in under 20 min on a 250 x 4.6 mm column (with 50-mm guard column), determined in a certified water sample with good accuracy (R2 > or = 0.994) and reproducibility (RSD 1-4.2%). Pb(II), Cd(II) and Cu(II) were additionally analysed in <10 min in a more complicated certified rice flour matrix, using the same eluent but adjusted to pH 1.5, again with good accuracy (R2 > or = 0.998) and reproducibility (RSD 0.48-1.38%).     

Analysis of carbohydrates using different quaternized polystyrene-divinylbenzene particles and pulsed amperometric detection

Summary This paper reports on the use of a polymer-based, strong anion-exchange stationary phase for rapid, selective and sensitive analysis of physiological important mono-, di- and oligosaccharides by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) under alkaline conditions. The adsorbent was obtained by direct nitration of 3 and 5 μm, spherical non-porous highly cross-linked, styrene-divinylbenzene copolymer (PS-DVB) beads, followed by reduction of superficially introduced nitro groups with nascent hydrogen and quaternization of the resultant amino groups with iodomethane. Extended exposure to high pressure and strong alkaline conditions did not have any untoward effect on mechanical stability and chromatographic performance. A comparison of the 3 and 5 μm beads showed, that the synthesized 3 μm highly cross-linked PS-DVB particles are the preferred phases for the separation of monosaccharides and the 5 μm particles are preferable for the separation of oligosaccharides. To demonstrate the suitability for the analysis of complex samples, the optimized and validated system was used for the determination of glucose, fructose and sucrose in apple juice and other soft drinks such as Coca Cola. Finally, analysis within a few minutes without sample pretreatment down to a lower limit of detection of 0.174–0.504 μg mL⁻¹ at a linearity with R²>0.994 and a repooducibility higher than 98% further confirmed the efficiency of these polymeric sorbents.