^35Cl的核磁共振法研究高氯酸钙的离子缔合和离子溶剂化

本文研究了在10种溶剂中0.5mol/L的Ca(ClO4)2中^35Cl的峰宽和6种溶剂中^35Cl峰宽随盐浓度的变化，讨论了离子缔合与溶剂性质及离子性质的关系；以乙晴或乙醇作溶剂，在Ca(ClO4)2浓度固定时，观察^35Cl峰宽随第2溶剂组分B（此处B为H2O或DMF）的加入量（以[B]/[Ca^2 ]表示）的变化，讨论了变化规律、原因及钙离子被水或DMF的溶剂化数；还结合电导数据，讨论了Ca^2 离子与ClO4^-离子的相互作用和缔合形式。     

高氯酸锂甲醇溶液中离子溶剂化和离子缔合现象

通过红外光谱技术探讨了高氯酸锂甲醇溶液中离子与溶剂、离子与离子之间的相互作用。红外光谱分析结果表明:锂离子与溶剂发生了相互作用导致甲醇分子的O-H伸缩振动区蓝移,ClO4-的特征谱带的变化表明了溶液中存在离子缔合。根据密度泛函理论,对不同溶剂化数的配合物结构和两种离子对形式进行优化及热力学性质的计算。     

LiNO3在DMF中的离子溶剂化和离子缔合的红外光谱

LiNO3在DMF中的离子溶剂化和离子缔合的红外光谱;硝酸锂;N;N-二甲基甲酰胺;离子溶剂化;离子缔合;红外光谱法     

整体柱离子对色谱快速分析高氯酸盐

研究了用硅胶整体柱和直接电导检测的离子对色谱快速分析高氯酸盐的方法。实验采用Chromolith Speed ROD RP-18e色谱柱,以氢氧化四丁铵(离子对试剂) 邻苯二甲酸 乙腈(有机改进剂)为淋洗液,讨论了离子对试剂浓度、有机改进剂浓度、pH、色谱柱温度和流速对ClO4-保留时间的影响。确定最佳色谱条件为:0.25mmol/L氢氧化四丁铵 0.18mmol/L邻苯二甲酸 7%乙腈(pH5.5)作为淋洗液,柱温30℃,流速6.0mL/min。在此条件下,ClO4-的保留时间在1min之内。其它常见阴离子(Cl-、NO3-、SO42-和I-)不干扰测定。方法的检出限为1.56mg/L;工作曲线的线性范围是2.4~100mg/L;峰面积的相对标准偏差(RSD,n=5)为1.9%。将本方法应用于测定加标果汁和加标地下水中的ClO4-,加标回收率分别为98.2%和97.6%。     

高浓度LiClO4/丙酮溶液中离子-溶剂和离子-离子的相互作用

利用红外和拉曼光谱技术研究了不同浓度LiClO₄/丙酮溶液中离子-溶剂和离子-离子的相互作用. 红外和拉曼光谱的分析表明, Li^＋与丙酮分子发生了强烈的相互作用, 导致丙酮C—C伸缩振动谱带、C＝O伸缩振动谱带等发生了分裂. Li^＋的溶剂化数随溶液浓度的增加逐渐降低, 在所研究的LiClO₄浓度范围(0.31～3.98 mol•kg^－1)内由3.4减小到1.9. 此外, 根据的谱带变化确定了溶液中存在的多种离子对的形式, 计算了缔合平衡常数, 并与电导实验结果进行了比较, 解释了这两种方法测定的离子缔合常数存在差异的主要原因.     

高浓度LiClO4/丙酮溶液中离子-溶剂和离子-离子的相互作用

利用红外和拉曼光谱技术研究了不同浓度LiClO₄/丙酮溶液中离子-溶剂和离子-离子的相互作用. 红外和拉曼光谱的分析表明, Li^＋与丙酮分子发生了强烈的相互作用, 导致丙酮C—C伸缩振动谱带、C＝O伸缩振动谱带等发生了分裂. Li^＋的溶剂化数随溶液浓度的增加逐渐降低, 在所研究的LiClO₄浓度范围(0.31～3.98 mol•kg^－1)内由3.4减小到1.9. 此外, 根据的谱带变化确定了溶液中存在的多种离子对的形式, 计算了缔合平衡常数, 并与电导实验结果进行了比较, 解释了这两种方法测定的离子缔合常数存在差异的主要原因.     

用13C NMR弛豫研究星形聚苯乙烯在溶液中的分子运动(Ⅱ)

对不同支化度和不同支链链长的20%(W/V)星形聚苯乙烯溶液测定了¹³CNMR弛豫参数,用1g-x²分布、Cole-Cole分布和构象跳跃模型对主链的分子运动进行了分析讨论,并对芳环侧基的内旋转运动也进行了分析,求出了活化能和跳跃速率。结果表明,轻度化学交联对相关时间分布有一定影响,对链段运动的势垒没有明显影响。支链链长对¹³CNMR弛豫的影响和对线形聚合物的影响是类似的。     

在i-PrOH-H2O混合溶剂中硫酸镁离子对缔合热力学研究

50年代,Nair等利用电动势法研究了硫酸镁离子对缔合过程的热力学量,Chand等也对水溶液中硫酸镁离子对的性质做过研究,宋彭生和孙柏对硼酸镁和硼酸钙离子对做了研究,目前,还没有人研究有机溶剂对[MgSO4]^0离子对标准缔合常数Kb的影响,本文在278.15-318.15K温度范围内,测定了无液接电池（A）,（B）的电动热E：Pt,H2(101.325kPa)|(HCl(m1),H2SO4(m2),i-PrOH(x),H2O(1-x)|AgCl-Ag(A) Pt,H2(101.325kPa)|(HCl(m1),MgSO4(m2),i-PrOH(x),H2O(1-x)|AgCl-Ag(B)其中,mi为物质i的质量摩尔浓度,x表示异丙醇i-PrOH在混合溶剂中的摩尔分数,保持x=0.05。利用电池A的电动势,在Debye-Hueckel理论基础上,确定了H2SO4在混合溶剂中的二级标准解离常数K2;利用电池B的电动势,确定了[MgSO4]^0离子在对沸合溶剂中的标准缔合常数KD,根据实验结果计算了离子缔合熵和焓,讨论了异丙醇对KD的影响,指出离子缔合熵是形成离子对的推动力。     

溶液中尼龙11的NMR弛豫研究

用2D NMR(HMQC)技术归属了溶液中尼龙11分子的主要1H和13C-NMR共振信号 ,并通过变温和变浓度1H-NMR弛豫时间的测定 ,得到了尼龙11溶液中氢键结构变化的动力学信息 .结果表明 ,溶液中尼龙11分子的弛豫行为与一般高聚物不同 ,随着温度升高 ,尼龙链间相互作用逐渐减弱 ,尼龙分子与溶剂小分子间相互作用逐渐增强 ,尼龙链间氢键逐渐离解 ,而离解出来的自由NH和CO基团又与溶剂小分子间生成氢键 .尼龙11链卷曲堆积成无规线团状,一部分溶剂被包裹在内部并和α-CO质子成为一个整体而一起运动 .变浓度实验弛豫过程呈现双指数特性,快弛豫部分随体系浓度增加而增多,表明聚合物溶液中凝聚缠结含量的增大 ,这种凝聚缠结是由溶液中氢键引起分子链物理交联成网而形成的.随着浓度增加,溶液逐渐变成局部粘度较大的类似软固体.     

Performance optimization in electric field gradient focusing

Electric field gradient focusing (EFGF) is a technique used to simultaneously separate and concentrate biomacromolecules, such as proteins, based on the opposing forces of an electric field gradient and a hydrodynamic flow. Recently, we reported EFGF devices fabricated completely from copolymers functionalized with poly(ethylene glycol), which display excellent resistance to protein adsorption. However, the previous devices did not provide the predicted linear electric field gradient and stable current. To improve performance, Tris–HCl buffer that was previously doped in the hydrogel was replaced with a phosphate buffer containing a salt (i.e., potassium chloride, KCl) with high mobility ions. The new devices exhibited stable current, good reproducibility, and a linear electric field distribution in agreement with the shaped gradient region design due to improved ion transport in the hydrogel. The field gradient was calculated based on theory to be approximately 5.76 V/cm² for R-phycoerythrin when the applied voltage was 500 V. The effect of EFGF separation channel dimensions was also investigated; a narrower focused band was achieved in a smaller diameter channel. The relationship between the bandwidth and channel diameter is consistent with theory. Three model proteins were resolved in an EFGF channel of this design. The improved device demonstrated 14,000-fold concentration of a protein sample (from 2 ng/mL to 27 μg/mL).     

Calculation of the deuterium electric field gradients in HD and LiD using a variation-perturbation method with a Gaussian basis set

Summary We present calculations of the deuterium electric field gradients in the HD and LiD molecules obtained with a variation-perturbation method using Gaussian atomic orbitals. The differences between our theoretical values and the corresponding experimental or best calculated values are 2%. We conclude that high accuracy can be obtained with the variation-perturbation method using either Gaussian or Slater orbitals.     

离子色谱法测定化肥中高氯酸盐

本文研究了化肥中高氯酸盐含量的离子色谱分析方法.选择超声波萃取为样品提取方法并优化了萃取时间.筛选了离子色谱柱,确定使用IonPac AG21+AS21为分离柱;优化了淋洗液浓度和流速,确定以10 mmol/L NaOH为淋洗液,流速为0.3mL/min;进样体积为200μL.方法线性范围为0.1～10 mg/L,相关...     

Synthesis of Oxygen‐Containing Spirobipyrrolidinium Salts for High Conductivity Room Temperature Ionic Liquids

Synthesis of ionic liquids (IL) based on oxygen‐containing spirobipyrrolidinium salts with BF₄, BF₃C₂F₅, and NTf₂ as counterions was undertaken. Their physical and electrochemical properties were evaluated for suitability for Room Temperature Ionic Liquids (RTIL) application. Reduction in melting point occurred upon exchange of C(2) by an O‐atom of spirobipyrrolidinium, without sacrificing the electrochemical stability; while introduction of alkyl groups between the N‐ and O‐atoms led to incorporation of asymmetry, and hence reduced the melting points, and viscosity.     

改进的离子色谱法测定环境水样中的高氯酸盐

以亲水性阴离子交换柱IonPac AS16为分析柱, 以NaOH、乙腈和水的混合溶液为淋洗液, 采用电导检测法测定了环境水样中的痕量高氯酸盐. 通过添加有机改进剂有效地解决了4-氯苯磺酸和高氯酸盐共淋洗的问题. 实验考察了4种有机溶剂对高氯酸盐和4-氯苯磺酸保留时间的影响, 最终选定乙腈作为有机改进剂. 为了提高方法的灵敏度, 以AG19为浓缩柱对样品进行在线预浓缩. 采用预浓缩技术可使方法的检出限低至0.1 μg/L. 在0.2~200 μg/L线性范围内线性相关系数为0.9989, 将0.5 μg/L 高氯酸盐溶液连续进样测定11次, 所得峰面积的相对标准偏差(RSD)为4.2%. 将该方法应用于环境水样的测定, 加标回收率为93%~113%.     

Bilinear electric field gradient focusing

Electric field gradient focusing (EFGF) uses an electric field gradient and a hydrodynamic counter flow to simultaneously separate and focus charged analytes in a channel. Previously, most EFGF devices were designed to form a linear field gradient in the channel. However, the peak capacity obtained using a linear gradient is not much better than what can be obtained using conventional CE. Dynamic improvement of peak capacity in EFGF can be achieved by using a nonlinear gradient. Numerical simulation results indicate that the peak capacity in a 4-cm long channel can be increased from 20 to 150 when changing from a linear to convex bilinear gradient. To demonstrate the increased capacity experimentally, an EFGF device with convex bilinear gradient was fabricated from poly(ethylene glycol) (PEG)-functionalized acrylic copolymers. The desired gradient profile was confirmed by measuring the focusing positions of a standard protein for different counter flow rates at constant voltage. Dynamically controlled elution of analytes was demonstrated using a monolith-filled bilinear EFGF channel. By increasing the flow rate, stacked proteins that were ordered but not resolved after focusing in the steep gradient segment were moved into the shallow gradient segment, where the analyte peak resolution increased significantly. In this way, the nonlinear field gradient was used to realize a dynamic increase in the peak capacity of the EFGF method.     

Analysis of selected ionic liquid cations by ion exchange chromatography and reversed-phase high performance liquid chromatography

The chromatographic behavior of 8 ionic liquids - 7 homologues of 1-alkyl-3-methylimidazolium and 4-methyl-N-butylpyridinium - has been investigated with a strong cation exchange adsorbent. In particular, the dependence of the retention properties of these solutes on mobile phase composition, pH, and buffer concentration was evaluated with the aim of optimizing and improving the selectivity and retention of solute separation. While using the SCX stationary phase, several interactions occurred with varying strengths, depending on the mobile phase composition. Cation exchange, nonspecific hydrophobic interactions, and adsorption chromatography behavior were observed. Reversed phase chromatography occurred at low concentrations of acetonitrile, electrostatic and adsorption interactions at higher organic modifier concentrations. Elevated buffer concentrations lowered the retention factors without affecting the selectivity of ionic liquids. Obtained results were further compared to the chromatographic behaviour of ionic liquids in the reversed phase system. All analyzed ionic liquids follow reversed-phase behavior while being separated. Much lower selectivity in the range of highly hydrophilic compounds is obtained. This suggests preferred use of ion chromatography for separation and analysis of compounds below 4 carbon atoms in the alkyl side chain.