十二烷基硫酸钠微乳色谱体系中pH值对其电渗流行为与微结构的影响

以十二烷基硫酸钠(SDS)/正己烷/正丁醇/硼砂微乳液为毛细管电色谱运行研究体系,以甲醇峰为微乳体系电渗流峰(EOF),考察不同pH值条件下微乳体系电渗流出峰时间(tEOF)和变化趋势.以微乳液滴粒径和ξ电位考察pH值对SDS缓冲溶液微乳体系微结构的影响,用微乳体系的电导值分析pH值条件下微乳液滴与氢氧根离子之间的相互...     

A new dodecylsulfate-selective supported liquid membrane electrode based on its N-cetylpyridinium ion-pair

A supported liquid and a poly(vinyl chloride) (PVC)-based membrane selective for dodecylsulfate (DS⁻) ion are described. The active element is a membrane containing a dissolved ion association complex of DS⁻ with cetylpyridinium (CP⁺) cation. The supported liquid membrane electrode (acetophenone as solvent) showed a Nernstian response towards the DS⁻ anion over the concentration range of sodium dodecylsulfate (SDS) from 8.3×10⁻³ to 1.0×10⁻⁶ mol dm⁻³ at 25 °C. The proposed electrode also showed a super-Nernstian potential response (108±2 mV decade⁻¹) at low concentrations (1.0×10⁻⁹ to 1.0×10⁻⁶ mol dm⁻³). Moreover, this electrode showed good selectivity and precision (R.S.D.?2.0%), and was usable within the pH range 4.0-6.8. The proposed electrode revealed a lower limit of detection of 6.3×10⁻⁷ mol dm⁻³ and improved selectivity in comparison with the some previously reported DS⁻ ion selective electrodes. The isothermal temperature coefficient of this electrode amounted to −0.001 V °C⁻¹. The liquid membrane electrode may find application in the direct determination of SDS by the standard addition method at pH 5.0, and in the physicochemical studies of surfactant solutions.     

Use of mobile phase 18-crown-6 to improve peak resolution between mono- and divalent metal and amine cations in ion chromatography

It is difficult to quantify NH4+ by ion chromatography in the presence of high concentrations of Na+ due to peak overlap. The Dionex IonPac CS15 column, which contains phosphonate, carboxylate, and 18-crown-6 functional groups, was originally developed to overcome this problem. We have found that the addition of 18-crown-6 to the eluent promotes improved peak resolution between Na+ and NH4+ even at concentrations as high as 60,000 to 1 using this column. Its use also improves the separation of alkali and alkaline earth metal and amine cations. Mobile phase 18-crown-6 increased the retention times of CH3NH3+, NH4+, and K+, and decreased the retention time of Sr2+. The retention times of Li+, Na+, Mg2+, Ca2+, (CH3)2NH2+, and (CH3)3NH+ were not affected. This method makes possible the direct analysis of ammonia from nitrogenase, the enzyme responsible for biological nitrogen fixation. The resolution of the NH4+ peak from the Na+ and Mg2+ peaks improved from zero resolution to values of 6.19 and 5.65, respectively. This technique considerably reduces the analysis time of NH4+ in the presence of high concentrations of Mg2+ and Na+ over traditional indophenol measurements.     

高效液相色谱法测定全血中直链烷基苯磺酸钠

提出了高效液相色谱法测定全血中直链烷基苯磺酸钠同系物的含量。全血样品用酸性提取溶液稀释,过Bakerbond SPE C18固相萃取小柱,经甲醇-乙酸-水(49+2+49)混合溶液淋洗后用甲醇-氨水(98+2)混合溶液洗脱。经纯化后的洗脱液在Wakopak WS AS-Aqua(250 mm×4.6 mm,5μm)柱上进行分离,流动相为乙腈与水(60+40)混合溶液,检测波长为228 nm。5种n-ABS同系物的C10~C14的质量分数在10.0~100.0 ng.g-1范围内与其峰面积呈线性关系,全血中各同系物回收率为78%~107%;日内相对标准偏差(n=5)≤10%,日间相对标准偏差(n=5)≤13%。     

离子色谱法测定混凝土外加剂中硫酸钠含量

建立了一种离子色谱法测定混凝土外加剂中硫酸钠含量的方法,外加剂试样溶于水中,采用反相柱去除溶液中有机物,进样量25μL。经Dionex IonPac AS18色谱柱分离,用30 mmol·L~(-1)氢氧化钾溶液作流动相,以1.0 mL·min~(-1)流量进行洗脱,按峰面积定量。方法的检出限(3S/N)为3μg·L~(-1)。该方法可实现硫酸钠与氯离子同时测定的优点。在3个浓度水平上对方法的精密度作了考核,测得其相对标准偏差(n=6)均小于1%。用标准加入法,以实样为基体作回收试验,测得回收率在98.7%～100.5%之间。     

Binary mixed micelles of chiral sodium undecenyl leucinate and achiral sodium undecenyl sulfate: I. Characterization and application as pseudostationary phases in micellar electrokinetic chromatography

Sodium 10-undecenyl sulfate (SUS), sodium 10-undecenyl leucinate (SUL) and their five different mixed micelles at varied percent mole ratios were prepared. The critical micelle concentration (CMC), C₂₀, γ_CMC, partial specific volume, methylene group selectivity, mobilities and elution window were determined using a variety of analytical techniques. These surfactant systems were then evaluated as novel pseudostationary phases in micellar electrokinetic chromatography (MEKC). As a commonly used pseudostationary phase in MEKC, sodium dodecyl sulfate (SDS) was also evaluated. The CMC values of SUS and SUL were found to be 26 and 16 mM, respectively, whereas the CMC of mixed surfactants was found to be very similar to that of SUL. The C₂₀ values decreased dramatically as the concentration of SUL is increased in the mixed micelle. An increase in SUL content gradually increased the methylene group selectivity making the binary mixed surfactants more hydrophobic. Linear solvation energy relationships (LSERs) and free energy of transfer studies were also applied to predict the selectivity differences between the surfactant systems. The cohesiveness and the hydrogen bond acidic character of the surfactant systems were found to have the most significant influence on selectivity and MEKC retention. The SUS and SDS showed the strongest while SUL showed the weakest hydrogen bond donating capacity. The basicity, interaction with n and π-electrons of the solute and dipolarity/polarizability were the least significant factors in LSER model for the surfactant systems studied. Free energies of transfer of selected functional groups in each surfactant systems were also calculated and found to be in good agreement with the LSER data.     

Analysis of amino acids and biogenic amines in breast cancer cells by capillary electrophoresis using polymer solutions containing sodium dodecyl sulfate

We describe simultaneous analysis of naphthalene-2,3-dicarboxaldehyde (NDA)-amino acid and NDA-biogenic amine derivatives by CE in conjunction with light-emitting diode-induced fluorescence detection using poly(ethylene oxide) (PEO) solutions containing sodium dodecyl sulfate (SDS). After sample injection, via EOF 0.1% PEO prepared in 100 mM TB solution (pH 9.0) containing 30 mM SDS entered a capillary filled with 0.5 M TB solution (pH 10.2) containing 40 mM SDS. Under this condition, 14 NDA-amino acid and NDA-amine derivatives were separated within 16 min, with high efficiency ((1.0–3.2) × 10⁵ theoretical plates) and sensitivity (LODs at S/N = 3 ranging from 2.06 to 19.17 nM). In the presence of SDS and PEO, analytes adsorption on the capillary wall was suppressed, leading to high efficiency and reproducibility. The intraday analysis RSD values (n = 3) of the mobilities for the analytes are less than 0.52%. We have validated the practicality of this approach by quantitative determination of 9 amino acids in breast cancer cells (MCF-7) and 10 amino acids in normal epithelial cells (H184B5F5/M10). The concentrations of Tau and Gln in the MCF-7 cells were different than those in the H184B5F5/M10 cells, respectively. Our results show the potential of this approach for cancer study.     

The aggregation of sodium dehydrocholate in water

 We used a battery of different methods to study the association in aqueous sodium dehydrocholate (NaDHC) solutions. This salt associates by a stepwise mechanism. Below (9.6 ± 4.2) × 10⁻⁴ mol dm⁻³ there is a molecular solution with some strongly insoluble dehydrocholic acid produced by hydrolysis. Between (9.6 ± 4.2) × 10⁻⁴ and (5.2 ± 2.2) × 10⁻³ mol dm⁻³, an aggregate similar to acid soap (NaDHC.HDHC) appears and its amount and the aggregate's size increase with concentration. At =(2.20 ± 0.85) × 10⁻² mol dm⁻³ the aggregates formed have properties usually associated with true micelles, such as solubilisation of water-insoluble dyes. These aggregates increase in size with concentration and change their shape at 8 × 10⁻² mol dm⁻³, giving nonsymmetrical aggregates. The changes in the solution physicochemical properties at these concentrations may be misinterpreted and this explains the different values of the critical micelle concentration reported in the literature for substances with similar structure, such as bile salts. Received: 14 May 2001 Accepted: 10 August 2001     

Synthesis of hollow spherical silica with MCM-41 mesoporous structure

Hollow spherical mesoporous silica was synthesized by using sodium silicate as a precursor and a low concentration of cetyltrimethylammonium bromide (CTAB) (0.154 mol dm^–3). The resulting hollow spherical particles were characterized with scanning electron microcopy (SEM), small-angle X-ray diffraction (SXRD), transmission electron microscopy (TEM), and N₂ gas adsorption and desorption techniques. The results showed that regular spherical mesoporous silica could be obtained only if the molar ratio of propanol to CTAB was in the range of approximately 8:1–9:1. The spherical particles were hollow (inside), and the shell consisted of smaller particles with a pore structure of hexagonal symmetry. With an increase of the molar ratio of propanol to CTAB, the distance (a value) between centers of two adjacent pores increased, and the pore structure of mesoporous silica became less ordered. N₂ adsorption–desorption curves revealed type IV isotherms and H1 hysteresis loops; with an increase of the molar ratio of propanol to CTAB, the pore size with Barrett–Joyner–Halenda (BJH) diameter of the most probable distribution decreased, but the half peak width of the pore size distribution peak increased