分散液相微萃取-气相色谱法测定水样中六种芳香胺

建立了分散液相微萃取-气相色谱同时测定环境水样中氟苯胺等6种芳香胺的方法.确定了色谱条件,在4 min内实现了对6种芳香胺的分离与测定;对萃取剂种类及用量、分散剂种类及用量;水样pH值、NaCl加入量等前处理条件进行了优化,使得水样中6种芳香胺得到了同时提取和富集.在最佳实验条件下,建立了6种物质的工作曲线,其相关系数...     

电-多相催化反应器强化处理苯胺废水的研究

本文设计一种新型的电-多相催化反应器处理苯胺废水.考察外加电压,电解时间,初始pH值以及支持电解质浓度等工艺条件对电解效果的影响.实验表明,在外加电压30 V、电解时间l h、初始pH=7和支持电解质Na2SO4溶液浓度为800 mg/L的条件下,该反应器对苯胺有最佳的处理效果,优于单独电化学处理体系.     

苯胺及其衍生物的毛细管电泳行为研究

采用紫外吸收检测，毛细管电泳分离，研究了九种苯胺及其衍生物在毛细管区带电泳(CZE)体系和胶束电动毛细管色谱(MECC)体系中的行为特征。讨论了缓冲溶液的浓度与pH、胶束浓度及混合胶束等在不同体系中对分离组分的影响，发现在CZE体系中，控制分离的主要因素是pKb值；在MECC体系中，控制分离的主要因素是溶质分子中碳原子数。建立了一种分离测定九种苯胺及其衍生物的高效毛细管电泳方法。     

液相微萃取-毛细管电泳联用对汗液基质中4种芳香胺的同时测定

采用纤维膜三相液相微萃取(HF-LLLME)技术,对汗液基质中的苯胺、邻甲苯胺、对氯苯胺、对硝基苯胺进行了分离富集。以正辛醇为有机相,在供体相pH为9.0,NaCl质量浓度为200g/L,接收相pH为1.0,萃取时间为60min的条件下,4种芳香胺的富集倍数为410～1250倍。将接收相直接进行毛细管电泳(CE)测定,样品相中4种芳香胺的质量浓度在10～100μg/L范围内与电泳峰面积呈良好线性,相关系数均大于0.992,4种芳香胺的检出限为1～10μg/L。运用该法对偶氮染料汗液环境下光致降解过程中产生的苯胺进行测定,回收率为91%～93%,结果满意。     

核苷与碱基的苯胺甲基键合硅胶固定相高效液相色谱分离

建立苯胺甲基键合硅胶固定相(PAMS)高效液相色谱分离核苷与碱基的方法；研究流动相有机溶剂浓度、磷酸缓冲液pH值、离子强度对核苷和碱基在该键合固定相上的色谱保留及分离选择性的影响，用磷酸缓冲液(pH＝4)为流动相快速分离了部分核苷与碱基。     

咖啡因及其9种类似物的胶束电动毛细管分析研究

 以十二烷基硫酸钠 (SDS)胶束为准固定相 ,考察了咖啡因及其 9种类似物在胶束电动毛细管 (MECC)分离模式下的分离行为。研究了运行缓冲液的 pH值、磷酸盐浓度、SDS浓度、甲醇体积分数、分离电压、分离温度等因素对这 10种化合物的迁移时间和分离效果的影响。结果发现 ,这些因素对上述 10种化合物的分离有显著的影响 ,尤以pH值为最。它不仅影响化合物的迁移时间和分离效率 ,还改变其出峰顺序 ,这与碱性条件下化合物仲胺基上氢的电离有关。优化后的分离条件 :运行缓冲液为 2 0mmol/L磷酸盐 2 0mmol/LSDS(pH 11 0 ) ,分离电压为2 5kV。     

DNA-Lipid探针用于细胞膜外pH值的原位成像

将二酰基脂质体自动偶联到两端标有Cy3和Cy5的具有i-motif结构的DNA链上,形成二酰基脂质体-DNA共轭物(DNA-lipid)探针。二酰基脂质体与细胞膜之间强烈的疏水作用可使该探针直接插入细胞膜表面,实现缺氧和常氧条件下细胞外pH值的比率型检测。在高pH值条件下,具有i-motif结构的DNA链两端的荧光基团处于分离状态,无FRET效应;在低pH值条件下,具有i-motif结构的DNA链在细胞膜表面形成四聚体结构,两端的荧光基团相互靠近,产生强的FRET效应。通过测定两种荧光基团的荧光强度比值实现了pH值的定量检测。利用此探针对pH值的灵敏响应实现了对缺氧环境中细胞外pH值的精确测量,在生理病理学上具有重大意义。     

色氨酸及其主要代谢产物的分离和在生物样品中的测定

建立以乙酸缓冲系统和甲醇作流动相、电化学和紫外检测器联用的高效液相色谱法,分离和测定了色氨酸经5-羟色胺和犬尿酸原两条主要代谢途径的8种代谢物。使用三氯乙酸作离子对试剂以延长3-羟犬尿酸原的保留时间,分析了流动相pH值和三氯乙酸浓度对各物质分离的影响及检测条件。结果表明,pH值及三氯乙酸浓度对各物质保留时间有明显影响,可作为控制分离的主要因素。此外,对生物样品中各物质分离和检测条件进行了讨论。     

苯二酚异构体电迁移行为预测与研究

系统研究了邻、间、对苯二酚3种异构体在毛细管区带电泳中的迁移行为,从理论上分析了解离常数、缓冲液pH与迁移行为之间的关系,进行了定量预测。通过实验讨论了缓冲溶液类型及浓度、缓冲溶液的pH、分离电压等因素对三种异构体分离的影响,获得了优化的分离条件。结果表明,使用未涂层石英毛细管柱(50μmi.d.,50 cm,有效长度为45 cm),在检测波长225 nm,硼砂缓冲溶液30 mmol/L,pH为8.5~9.15,分离电压为10~25 kV的条件下,苯二酚3种异构体均可按对、间、邻的顺序得到基线分离,实验结果与理论预测相符。     

金纳米粒子在氨基表面上的组装-pH值的影响

用原子力显微镜（AFM）和表面增强喇曼光谱（SERS）研究了pH值对金纳米粒子在Au／巯基苯胺自组装膜表面上组装效果的影响．AFM结果表明，金纳米粒子在表面上的覆盖度随pH值表现出规律性的变化，巯基苯胺自组装膜的SERS强度随pH值的变化也有类似的趋势．在磁性环境下，氨基未质子化，金粒子难以组装上，而在酸性条件下，氨基质子化带正电，金粒子与基底容易结合．我们认为金纳米粒子和氨基之间的作用属于静电力，pH值同时影响膜表面氨基的质子化程度和金纳米粒子表面的带电量．     

Separation of positional isomers by cucurbit[7]uril-mediated capillary electrophoresis

A novel macrocyclic molecule, cucurbit[7]uril (CB[7]) was for the first time employed as an additive in capillary electrophoresis (CE). In similarity to other macrocyclic molecules, such as crown ethers, cyclodextrins (CDs) and calixarenes, CB[7] can form inclusion complexes with a variety of guest molecules due to its inner cavity. Thus, it can be used like other macrocyclic molecules to manipulate selectivities in CE. During the running process, CB[7] bears a positive charge under the studied pH range (pH 2.5-7) and can be adsorbed onto the inner wall of a fused-silica capillary, leading to a reversal of the electroosmotic flow (EOF). Electrophoretic behaviors of nitrotoluene, nitrophenol, nitroaniline, and methylaniline isomers were studied under various conditions. The electrophoretic separations of the isomers can be accomplished with a buffer containing CB[7]. Furthermore, a probable separation mechanism in the presence of CB[7] was also proposed.     

Simultaneous spectrophotometric determination of nitroaniline isomers after cloud point extraction by using least-squares support vector machines

Cloud point extraction has been used for the preconcentration of m-nitroaniline, o-nitroaniline and p-nitroaniline and later simultaneous spectrophotometric determination using polyethylene glycol tert-octylphenyl ether (Triton X-100) as surfactant. The resolution of a ternary mixture of the nitroaniline isomers (after extraction by cloud point) by the application of least-squares support vector machines (LS-SVM) was performed. The chemical parameters affecting the separation phase and detection process were studied and optimized. Under the optimum experimental conditions (i.e. pH 7.0, Triton X-100=0.6%, equilibrium time 20 min and cloud point 75 degrees C), calibration graphs were linear in the range of 0.2-20.0, 0.1-15.0 and 0.1-17.0 microg ml(-1) with detection limits of 0.08, 0.05 and 0.06 microg ml(-1) for m-nitroaniline, o-nitroaniline and p-nitroaniline, respectively. The experimental calibration matrix was designed with 21 mixtures of these chemicals. The concentrations were varied between calibration graphs concentrations of nitroaniline isomers. The root mean square error of prediction (RMSEP) for m-nitroaniline, o-nitroaniline and p-nitroaniline were 0.0146, 0.0308 and 0.0304, respectively. This procedure allows the simultaneous determination of nitroaniline isomers in synthetic and real matrix samples good reliability of the determination was proved.     

Positional and geometrical anionic isomer separations by capillary electrophoresis-electrospray ionization-mass spectrometry

Capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) was applied to the analysis of polar positional and geometrical anionic isomers. Since the investigated positional and geometrical anionic isomers have different pK(a) values, they could be separated by CE-ESI-MS under simple analytical conditions using a bare fused-silica capillary and volatile ammonium acetate buffer after optimizing buffer pH. Ortho-, meta-, para-hydroxybenzoate positional isomers were completely separated on a fused-silica capillary with 20 mM ammonium acetate buffer at pH 10.0, and cis-, trans-cyclohexane dicarboxylate geometrical isomers could be also separated with 20 mM ammonium acetate buffer at pH 4.0. Several analytical parameters affecting ESI-MS sensitivity were also investigated. It was found that both running buffer pH and sheath liquid pH had significant effects on the selectivity and the sensitivity on CE-ESI-MS analysis while sheath flow rate and other parameters had little influence. Under optimized conditions, linearity, detection limit, and repeatability of the analysis of hydroxybenzoate isomers were examined, and good results were obtained. It was found that the method presented in this paper is a simple, robust, and cost-effective method for simultaneous analysis of positional and geometrical anionic isomers as well as of other small anionic compounds.     

Separation and determination of nitroaniline isomers by capillary zone electrophoresis with amperometric detection

In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was firstly applied to the simultaneous separation and determination of nitroaniline positional isomers. The three analytes could be perfectly analyzed by using the buffer of extreme pH. The effects of several important factors were investigated to find optimum conditions. A carbon-disk electrode was used as working electrode. The optimal conditions were 40 mmol/L tartaric acid-sodium tartrate (pH 1.2) as running buffer, 17 kV as separation voltage and 1.10 V (versus saturated calomel reference electrode, SCE) as detection potential. Under the optimum conditions, o-, m- and p-nitroaniline were separated successfully and good linearity, reproducibility and recovery results were obtained. The detection limit for m-nitroaniline was as low as at 9.06 × 10⁻⁹ mol/L. This proposed method demonstrated long-term stability and reproducibility with relative standard deviations of less than 1.8% for migration time and 1.1% for peak areas. The utility of this method was demonstrated by monitoring dyestuff wastewater and the assay results were satisfactory.     

Graphene oxide and reduced graphene oxide as novel stationary phases via electrostatic assembly for open‐tubular capillary electrochromatography

We present here the application of graphene oxide (GO) and reduced graphene oxide (GOOH) sheet as novel stationary phases for open‐tubular CEC (OTCEC) separation based on electrostatic assembly. The inner walls of a bare capillary column was first modified by ionic assembly of poly (diallyldimethylammonium chloride) (PDDA), and then negatively charged GO or GOOH was easily assembled on a positively charged interior walls of the capillary by electrostatic force. Scanning Electron Microscope images showed that GO and GOOH can still maintain sheet‐layer‐like structure when coated onto the capillary via electrostatic assembly. The chromatographic properties of the GO and GOOH coated columns were evaluated via OTCEC separations of various kinds of analytes, including three acid nitrophenol isomers, three basic nitroaniline isomers, and four neutral PAHs. Efficient separations of all the analytes were achieved with optimized buffer pH and organic additive. The reproducibility and stability of the GO or GOOH coated columns were investigated. Our results indicate the capability of application GO or GOOH sheet in OTCEC separation, which can be coated on the inner wall of fused‐silica capillary via electrostatic assembly.     

High Performance Liquid Chromatography of Uroporphyrin Isomers

Abstract

The separation of uroporphyrin I and III isomers by reversed-phase high performance liquid chromatography on ODS-Hypersil with ammonium acetate buffer-acetonitrile solvent systems is described. The effects of buffer concentration, pH, organic modifier proportion and different organic modifiers on the resolution are studied. The optimum conditions for the separation were 12–13% acetonitrile in 1M ammonium acetate buffer pH 5.10–5.20. The method also separated uroporphyrin I and III from the II isomers but the resolution of uroporphyrin III and IV isomers was not achieved.     

Spectrophotometric simultaneous determination of nitroaniline isomers by orthogonal signal correction-partial least squares

The simultaneous determination of nitroaniline isomer mixtures by using spectrophotometric methods is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares (PLS), it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction (OSC) is a preprocessing technique used for removes the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for partial least squares calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 200–500 nm range for 21 different mixtures of nitroaniline isomers. Calibration matrices were containing 1–21, 1–15 and 1–18 μg ml⁻¹ of m-nitroaniline, o-nitroaniline and p-nitroaniline, respectively. The RMSEP for m-nitroaniline, o-nitroaniline and p-nitroaniline with OSC and without OSC were 0.6567, 0.2692, and 0.3134, and 1.3818, 1.2181, and 0.3953, respectively. This procedure allows the simultaneous determination of nitroaniline isomers in real matrix samples and good reliability of the determination was proved.     

HPLC separation of positional isomers on a dodecylamine-N, N-dimethylenephosphonic acid modified zirconia stationary phase

The chromatographic performance of a new zirconia stationary phase (DPZ) modified with dodecylamine-N,N-dimethylenephosphonic acid (DDPA) is studied by using positional isomers as probes. The DDPA modified zirconia via one phosphonic group has a polar inner-layer and a non-polar outer-layer on its surface. The alkyl chain of outer-layer provides the hydrophobic interaction, while the polar inner-layer that consists of an amine group and a free phosphonic group provided dipolar and ion-exchange/columbic repellent interaction sites. The effects of methanol content, ionic strength and pH of mobile phase on capacity factors of the solutes are studied in detail, and baseline separations of toluidine, nitroaniline, aminophenol, dihydroxybenzene, and nitrophenol isomers were achieved on the new zirconia stationary phase. In addition, retention mechanism of the isomers on the DDPA-modified zirconia stationary phase is also proposed.     

改良型单纯形法优化硝基喜树碱的毛细管电泳分离

使用改良型单纯形法优化硝基喜树碱(Nitrocamprothecinum,NC)一对同分异构体的毛细管电泳分离。考察了运行电压、缓冲液的pH、硼砂和十二烷基磺酸钠(SDS)的浓度等4个影响因子,与传统的单因子优化方法及其结果进行比较。改良型单纯形法(采用CRS函数为响应函数)在分析方法的建立过程中显著减少了实验步骤,获得了更好的电泳分离条件。     

Separation and migration behavior of positional and structural naphthalenesulfonate isomers by cyclodextrin-mediated capillary electrophoresis

The effects of the type of buffer system, buffer pH, the polarity of electrode, and both the type and the concentration of cyclodextrins (CDs) on the separation and migration behavior of seven positional and structural naphthalenesulfonate isomers in CD-mediated capillary electrophoresis were systematically investigated. The most effective separation conditions were to use 20 mM phosphate buffer with beta-CD at pH 3.0, while the polarity of the electrodes were reversed across the capillary. Under such conditions, these isomers can be separated in 10 min. The results also indicate that the interactions of naphthalenesulfonate derivatives with CDs are strongly affected by the position of the substituent(s) on the aromatic ring. The inclusion complex formation constants of these compounds were evaluated to improve our understanding of the interaction between the naphthalenesulfonate derivatives and CDs. Moreover, the formation constants of naphthalene-2-sulfonate to beta-CD agreed closely with the data in the literature obtained by a spectrophotometric method and by CE methods in various pH buffers.