氧化锆固定相反相高效液相色谱法测定碱性化合物的离解常数

研究了烷基键合氧化锆微球固定相(C12-ZrO2）的化学稳定性及其对碱性化合物的色谱保留特征,发现C12-ZrO2在pH为2~12时稳定,碱性化合物在该固定相上为典型的反相色谱保留机理。基于对碱性化合物的保留因子与流动相pH关系的考察,建立了碱性化合物离解常数的测定方法。测定了13种典型芳香胺和吡啶衍生物的离解常数,与文献结果对比,其差值在-0.27～0.35 pH单位范围内,说明该方法能够用于碱性化合物离解常数的快速测定。     

多壁碳纳米管键合硅胶固定相的保留机理研究

制备了3种不同键合量的多壁碳纳米管键合硅胶固定相。以芳香族化合物为目标分析物,甲醇-水为流动相,分别考察了其在不同流动相比例、流速、柱温条件下,酸性、中性、碱性化合物的色谱保留行为,并通过计算分离过程中焓变、熵变和吉布斯自由能等热力学参数,探讨了色谱柱的保留机理。结果表明,碳纳米管键合硅胶与未键合的硅胶固定相分离对氨基苯磺酸和尿嘧啶时,因碳纳米管的加入增强了其疏水作用,保留机理与反相色谱柱相似。而分离中性化合物时,因加入的碳纳米管引入π-π作用,增强了对化合物的保留,有效地提高了色谱柱的柱效。碳纳米管的加入使溶质分子在固定相上的保留增强,溶质分子从杂乱无序排列转为有序排列,且溶质分子在不同碳纳米管键合量的色谱柱上的保留并非由单一机理支配,而是由多种作用相互协同的结果,这使碳纳米管键合硅胶固定相在分离和固相萃取领域展现出良好的应用前景。     

1-萘甲膦酸改性氧化锆固定相分离芳胺类化合物的色谱性能研究

研究了一些芳胺类化合物在1-萘甲膦酸改性氧化锆固定相上的色谱行为。分别考察了流动相中甲醇含量、缓冲液pH值和离子强度等对芳胺类化合物色谱保留的影响,并对这类化合物在该固定相上的保留机理进行了探讨。研究结果表明,芳胺类化合物在该固定相上表现出反相和阳离子交换的混合保留模式。以pH 10.1的Tris-甲醇(60/40,V/V)溶液为流动相,在1-萘甲膦酸改性氧化锆固定相上成功分离了间苯二胺、邻甲苯胺、N-甲苯胺、对硝基苯胺、邻硝基苯胺和α-甲萘胺6种芳胺类化合物。     

生物碱在十八烷基膦酸改性锆-镁复合氧化物固定相上的色谱行为

研究了某些生物碱在十八烷基膦酸改性锆-镁复合氧化物固定相(C18PZM)上的色谱行为。通过考察流动相参数如甲醇含量、缓冲液pH值和离子强度对生物碱保留的影响,对这类化合物在该固定相上的保留机理进行了探讨。结果表明,在实验色谱条件下,生物碱在C18PZM上表现出反相和阳离子交换的混合保留模式机理。锆-镁基质上化学吸附的十八烷基膦酸和其对流动相中路易斯碱的吸附以及锆羟基本身均有可能是该固定相的离子交换作用位点的来源。高pH值流动相,溶质大部分以分子状态使用形式存在,因此其保留以疏水作用为主。在甲醇-pH 10.1 Tris缓冲液,生物碱的分离取得了满意的结果。与传统的烷基键合硅胶反相固定相相比,C18PZM表现出了更优越的化学稳定性,对于碱性化合物,尤其是具有高pKa值的碱性化合物的分离分析有着广泛的应用前景,有望发展为与硅胶键合固定相互补的一类反相HPLC的固定相。     

柱温对胆固醇键合固定相分离黄酮苷的影响及其热力学分离机理研究

柱温属于高效液相色谱(HPLC)的可调参数之一,但在实际操作过程中,柱温对溶质保留行为的影响通常被忽略,不作为色谱条件优化参数.本研究分别以甲醇-0.02 mol/L乙酸(30∶70,V/V)及甲醇-0.02 mol/L乙酸(25∶75,V/V)为流动相,讨论了柱温对6种黄酮苷在一种新型色谱固定相-胆固醇键合固定相以及C18键合固定相上分离的影响.结果表明,随着柱温升高,不同于十八烷基键合固定相,黄酮苷在胆固醇键合固定相上的分离效果得到改善,且峰形变好.同时,拟合了25℃～55℃温度范围内的van't Hoff方程,从热力学角度比较了黄酮苷在胆固醇键合固定相和十八烷基键合固定相上的保留机理.结果表明,黄酮苷在两种色谱柱上的van't Hoff方程均具有良好的线性关系(R2 ＞0.99),且拟合参数相近(△H0＜0,△S0＜0),表明这些物质在胆固醇键合固定相上的保留机理与在十八烷基键合固定相上相似,以单一的疏水性保留机理为主导,均属于焓驱动过程.本实验证实,在使用胆固醇键合固定相时,柱温可作为一项重要调节参数,参与色谱优化过程,从而使液相色谱从两变量调节方式(流动相种类和流动相比例)变为三变量调节方式(流动相种类、比例和柱温),从而为色谱条件优化提供了更多选择.     

十四烷基胺键合固定相的反相色谱性能

制备了一种新型反相液相色谱固定相──十四烷基胺硅胶键合固定相。以甲醇和水为二元流动相,评价了该固定相的疏水性、选择性和残留硅醇基活性。同时分离了包括碱性、酸性和中性有机化合物在内的混合物。结果表明,在该固定相上,碱性化合物的色谱峰对称性较好,硅酸基活性受到抑制,并具有良好的选择性。     

碱基在十二胺-N,N-二亚甲基膦酸改性氧化锆固定相上色谱行为的研究

研究了碱基在十二胺-N,N-二亚甲基膦酸(DDPA)改性氧化锆固定相（DPZ）上的色谱保留行为,考察了流动相中甲醇含量、流动相pH值、缓冲溶液中离子类型和离子强度对碱基保留的影响,对DDPA在氧化锆表面的吸附方式进行了研究。研究结果表明,DDPA仅以一个膦酸基与氧化锆结合,因而DPZ固定相表面上除了有长链的疏水烷基外,还有酸性的膦酸基和碱性的氨基。碱基分子中也存在氨基和酰胺基等极性基团,因此碱基在DPZ固定相上除了有疏水作用外,还具有电荷排斥作用、离子交换作用等多种保留机理。由于多种保留机理的存在,使得碱基在DPZ固定相上具有较好的分离选择性,在酸性条件下对碱基混合样品的分离取得了满意的结果。     

高效液相苯胺甲基键合硅胶固定相的保留机理研究

 制备了 3种不同键合量的苯胺甲基键合硅胶固定相 ,分别在正、反相条件下研究了它们对芳烃及其极性、酸性、碱性取代衍生物的保留和分离选择性 ,探讨了该固定相的保留机理 ,并考察温度对溶质在具有不同键合量的固定相上保留的影响。结果表明 :苯胺甲基键合硅胶固定相对溶质的保留是疏水、π π、偶极 偶极和电荷转移等多种作用的结果 ,在反相模式中 ,疏水作用对溶质的保留起主要作用。     

对-叔丁基杯[8]芳烃键合固定相的制备及表征

合成了一种新的对-叔丁基杯[8]芳烃的高效液相色谱键合固定相,考察了多环芳烃、苯甲酸酯、邻苯二甲酸酯、苯的单官能团取代物在该键合相上的反相液相色谱保留行为,并以甲醇-水作为流动相分离了氨基苯酚的邻、间、对取代位置异构体．研究结果发现,该键合相具有明显的反相特征,并讨论了可能的分离机理．     

酸性化合物在十二胺-N,N-二亚甲基膦酸改性氧化锆固定相上的分离

酸性化合物在十二胺-N; N-二亚甲基膦酸改性氧化锆固定相上的分离;氧化锆;色谱固定相;十二胺-N; N-二亚甲基膦酸     

氨基甲酸酯功能化离子液体高效液相色谱固定相的制备与初步评价

合成一种了氨基酸衍生物：4,4′-二苯亚甲基桥联-二[2-(1-咪唑基)-3-苯基丙醇氨基甲酸酯](ImPh-Carb),并将其键合到硅胶上制备了一种新的氨基甲酸酯功能化的离子液体HPLC固定相（ImPh-Carb-Silica）。 利用1H NMR、13C NMR、MS和FTIR对ImPh-Carb进行了表征;通过FTIR和元素分析对ImPh-Carb-Silica固定相进行了表征,根据N含量计算得到ImPh-Carb-Silica的键合量为0.19 mmol/g。 以5种芳烃、5种酚类化合物和4种有机磷农药为分析物,分别在正相和反相色谱模式下对固定相的色谱分离性能进行了评价,同时考察了流动相的变化与溶质保留因子lg k之间的关系。 结果表明,该固定相与溶质分子间存在多重作用力,如疏水、氢键、π-π和偶极-诱导偶极作用等,使其能同时在正相和反相色谱模式下使用;在正相色谱条件下固定相对酚类化合物和有机磷农药表现出较好的分离选择性。     

Retention behavior of basic compounds on alkylphosphonate-modified magnesia-zirconia composite stationary phase in RPHPLC

Summary The chromatographic properties of an alkylphosphonate-modified magnesia-zirconia composite stationary phase have been investigated by reversed-phase high-performance liquid chromatography with basic compounds as probes. The influence of organic modifier composition and mobile phase pH was studied. The new stationary phase, similar to a silica-based reversed-phase stationary phase, has hydrophobic properties, but greater pH stability. Use of the phase results in more symmetric peaks for basic compounds. A possible mechanism of retention of basic solutes on the new stationary phase is discussed. The chromatographic behavior of the basic solutes depends mainly on hydrophobic interactions between the solutes and the hydrophobic moiety of the stationary phase. Br?nsted acidic and basic sites on the surface of the new stationary phase play an important role in the retention of ionized solutes by ion-exchange interaction. Promising separations of some basic compounds have been achieved by use of methanolic TRIS buffer, pH 10.0, as the mobile phase.     

Phenylaminopropyl silica--a new specific stationary phase for high-performance liquid chromatography of phenols

The chromatographic properties of a new stationary phase, phenylaminopropyl silica (PhA-silica), containing phenylaminopropyl residues covalently bonded to the silica surface were studied. The presence of secondary amino groups, phenyl rings and alkyl linkers in the attached molecule makes it especially suitable for the separation of phenols by mixed mode retention mechanism including a combination of hydrogen-bonding, hydrophobic, electrostatic and pi-pi interactions with the stationary phase. The effects of mobile phase pH, ionic strength, nature and concentration of organic modifier on the retention of phenols on PhA-silica were investigated under conditions of reversed-phase HPLC. To elucidate the role of the amino group in the attached molecule in retention of phenols the selectivity of PhA-silica was compared with that obtained for phenylpropyl silica in the framework of a linear solvation energy relationship (LSER) model. The isocratic separation of phenol, and its nine methyl-, chloro- and nitro-substituted derivatives was achieved on a 150x4.6 mm I.D. chromatographic column packed with 7 microm particles of PhA-silica.     

Dipyridine modified silica--a novel multi-interaction stationary phase for high performance liquid chromatography

A novel multi-interaction stationary phase based on 4,4'-dipyridine modified silica was synthesized and characterized, by infrared spectra, X-ray photoelectron spectroscopy and elemental analysis. Mechanism involved in the chromatographic separation is the multi-interaction including π-π, hydrophobic, hydrogen-bonding, electrostatic and anion-exchange interactions. Based on these interactions, polycyclic aromatic hydrocarbons and phenols were successfully separated respectively in reversed-phase chromatography; inorganic and organic anions were also separated individually in anion-exchange chromatography by using the same column. Furthermore, the simultaneous separation of neutral organics, inorganic and organic anions was obtained on this stationary phase with the appropriate mobile phase. Therefore, such stationary phase has the characteristics of multi-interaction mechanism and multi-modal separation, and has potential application on complex samples.     

A multiple-function stationary phase based on perhydro-26-membered hexaazamacrocycle for high-performance liquid chromatography

A perhydro-26-membered hexaazamacrocycle-based silica (L¹GlySil) stationary phase for high-performance liquid chromatography (HPLC) was prepared using 3-glycidoxypropyltrimethoxysilane as coupling reagent. The structure of new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance and retention mechanism of the new phase were evaluated in reversed-phase (RP) and normal-phase (NP) modes using different solute probes including aromatic compounds, organophosphorus pesticides, carbamate pesticides and phenols. The results showed that L¹GlySil was a sort of multimode-bonded stationary phase with excellent chromatographic properties. The new phase could provide various action sites for different solutes, such as hydrophobic, hydrogen bonding, π–π, dipole–dipole interactions and acid–base equilibrium. The presence of phenyl rings, secondary amino groups and alkyl linkers in the resulting material made it suitable for the separation of above-mentioned analytes by multimode retention mechanisms.     

氮杂冠醚键合固定相的RP-HPLC色谱性能研究

报道在硅胶表面进行固-液相反应合成的3-(氮杂-18-冠-6)丙基键合固定相对金属离子的络合能力和色谱性能,研究了流动相组成、pH值、金属离子对极性二取代苯保留值的影响,探讨色谱分离机理。这种键合相通过对金属离子的络合,显示多种色谱分离机理,对极性二取代苯异构体分离选择性、分析速度均优于对比的C₁₈键合固定相反相色谱。     

Silica-Based Phenyl and Octyl Bifunctional Imidazolium as a New Mixed-Mode Stationary Phase for Reversed-Phase and Anion-Exchange Chromatography

In this study, octylbenzimidazolium-modified silica (BeImC8-Sil) was prepared by covalent attachment of 1-octylbenzimidazole to γ-chloropropyl silica. The synthesized materials were characterized by the elemental analysis, IR spectrum, and thermogravimetric analysis. Due to the introduction of phenyl and octyl groups on the quaternary imidazolium, the developed BeImC8-Sil column can function via both reversed-phase and anion-exchange retention mechanisms. The chromatographic properties of the synthesized material were investigated by the separations of polycyclic aromatic hydrocarbons, mono-substituted derivatives of benzene, anilines, and phenols, revealing the existence of multiple interactions, including hydrogen bonding, π–π stacking, electrostatic forces, and hydrophobic interactions in reversed-phase mode; inorganic and organic anions were also separated mainly through anion-exchange interaction. The proposed BeImC8-Sil is a promising mixed-mode stationary phase for the separation of complex samples in high-performance liquid chromatography.

     

Development of a new C14 monolithic silica column containing embedded polar groups for pressurized capillary electrochromatography

Monolithic columns have been prepared with a novel bonded silica stationary phase, tetradecylamine bonded silica (TDAS), and used in pressurized capillary electrochromatography (pCEC). The monolithic silica column matrix was prepared by a sol-gel process and then chemically modified with the spacer (3-glycidoxypropyl)trimethoxysilane and tetradecylamine. The introduced embedded polar amine groups dominated the charge on the surface of the monolithic stationary phase and generated an EOF from cathode to anode under acidic conditions. The tetradecyl hydrophobic chains in TDAS provide chromatographic interactions. The chromatographic characteristics of the prepared monolithic column were studied. Some aromatic compounds including alkylbenzenes, aromatic hydrocarbons, phenols, and anilines were successfully separated on the TDAS monolithic column in pCEC mode. As expected, the TDAS monolithic stationary phases exhibit typical reversed-phase electrochromatographic behavior toward neutral solutes due to the introduced tetradecyl groups. Hydrophobic as well as electrophoretic migration processes within the monoliths were observed in the separation of basic anilines. Symmetrical peaks can be obtained for anilines because the embedded polar amine groups on the surface can effectively shield the adsorption of positively charged analytes onto the stationary phase.     

基于二醛微晶纤维素功能化C18的反相/亲水色谱固定相的制备

通过十八烷基胺的氨基与二醛微晶纤维素的醛基共价键合,制备了基于二醛微晶纤维素(DMCC)官能化C₁₈的新型反相/亲水色谱固定相(C₁₈-DMCC/SiO₂),该色谱固定相被用于反相色谱(RPLC)和亲水相互作用色谱(HILIC)模式。C₁₈-DMCC/SiO₂色谱柱展现了良好的疏水选择性和芳香选择性,在反相色谱模式下可分离烷基苯和多环芳烃(PAHs)。苯胺类、酚类和糖苷类等极性化合物被用于评估该色谱柱在反相色谱模式下的极性选择性,商品C₁₈柱作对照柱,色谱评价结果令人满意。核酸碱基被用于评估C₁₈-DMCC/SiO₂色谱柱的亲水色谱性能。通过考察有机溶剂含量对分析物保留的影响,发现该新型色谱固定相具有反相/亲水色谱的典型特征。     

Chromatographic evaluation of reversed-phase/anion-exchange/cation-exchange trimodal stationary phases prepared by electrostatically driven self-assembly process

This work describes chromatographic properties of reversed-phase/cation-exchange/anion-exchange trimodal stationary phases. These stationary phases were based on high-purity porous spherical silica particles coated with nano-polymer beads using an electrostatically driven self-assembly process. The inner-pore area of the material was modified covalently with an organic layer that provided both reversed-phase and anion-exchange properties while the outer surface was coated with nano-sized polymer beads with strong cation-exchange characteristics. This design ensured spatial separation of the anion-exchange and the cation-exchange regions, and allowed reversed-phase, anion-exchange and cation-exchange retention mechanisms to function simultaneously. Chromatographic evaluation of ions and small molecules suggested that retention of ionic analytes was influenced by the ionic strength, pH, and mobile phase organic solvent content, and governed by both ion-exchange and hydrophobic interactions. Meanwhile, neutral analytes were retained by hydrophobic interaction and was mainly affected by mobile phase organic solvent content. Depending on the specific application, selectivity could be optimized by adjusting the anion-exchange/cation-exchange capacity ratio (selectivity), which was achieved experimentally by using porous silica particles with different surface areas.