Separations in Thin Layer and High Performance Liquid Chromatography Using Alkyl Silica Gel Bonded Phases

Abstract

Separations in thin layer (TLC) and high performance liquid chromatography (HPLC) using alkyl bonded phases were carried out under optimum solvent conditions for each of three phases, RP-2, RP-8 and RP-18. The phases were tested for their efficiency and resolving power using three groups of compounds in three binary organic-water mobile phases. The organic solvents were acetonitrile, methanol and tetrahydrofuran, which are widely used as solvent modifiers in reversed phase liquid chromatography.

The results showed that, unlike HPLC, TLC using RP-18 plates was the most, and RP-2 plates the least, efficient. A naphthalene and biphenyl mixture which was resolved by HPLC using any of the three solvents and columns was not resolved by TLC using any plate or solvent combination, unless the plate was prewashed with an organic modifier. The addition of NaCl (1–2% wt/vol) to the solvent for TLC speeded development unless an alcohol was used, but did not greatly affect the separation.     

用于固相萃取的聚乙二醇交联辛烷基、苯基、氨基和氰基固定相

用简单的方法合成了用于固相萃取的填料,填料含辛烷基,苯基,氨基或氰基及聚乙二醇链。这种固定相属于混合功能限进介质。其特点为表面有亲水性和一定程度的疏水性,只吸附少量蛋白质,蛋白质在4种固定相上的吸附量为0．98－3．62mg/g,苯基,氨基和氰基的聚乙二醇交联固定相在pH值4．5对蛋白质的吸附能力最大,而辛烷基聚乙二醇交联固定相在pH值2．5对蛋白质的吸附能力最大,固定相的塔板数能满足固相萃取的要求,含蛋白质的药物样品回收率为92％－115％,合成的固定相可用作生物样品的预处理。     

Chiral Separations by Capillary Electrochromatography on Multiple-Interaction Based Stationary Phases

Summary The direct resolution of neutral amino acid and amino alcohol derivatives by pressurized capillary electrochromatography (p-CEC) is reported. Separations were performed on columns packed with multiple-interaction based chiral stationary phases (CSPs) in reversed-phase mode, using borate buffer/acetonitrile mixtures as the eluent. Two CSPs were used: 3,5-dinitrobenzoyl-(R)-phenylglycine (DNB-PGLY)- and 3,5-dinitrobenzoyl-(R)-naphthylglycine (DNB-NGLY)-silica bonded, respectively. Baseline separations of N-benzoyl--naphthylamide derivatives of phenylalanine and leucine were accomplished on DNB-PGLY-CSP in less than three minutes, and on DNB-NGLY-CSP within about 3.5 minutes, with a comparable efficiency of 160.000 plates per meter. As expected, DNB-NGLY-CSP showed higher selectivity for the compounds under study. The R-isomer eluted before the S-isomer on both CSPs. The effect of the buffer pH on the efficiency of the columns was also studied. With buffer pH over the values of 8–8.5, free residual -aminopropyl groups on the silica particles seemed do affect neither selectivity nor resolution. At these mobile phase conditions calculated efficiency against electroosmotic flow plot is consistent with that generally obtained in CEC, providing a reduced plate height of about 1.8 at a linear velocity of 0.5 mm s^–1. With buffer pH values under 7.0, protonation of the free aminopropyl groups strongly affected the resolution with the result of higher retention and lower solute mass transfer.     

碳十八键合锆胶固定相的制备与色谱性能评价

用诱导聚合胶体凝聚法（PICA）制得的二氧化锆微球与碳十八三乙氧基硅烷反应制备了碳十八键合锆胶固定相（ODZ）,评价了该柱填料的色谱性能,并用此固定相分离了中性和碱性化合物。     

A Novel Method for the Preparation of Octyl Bonded Styrene-divinylbenzene HPLC Packings

Monodisperse octyl bonded poly（styrene-divinylbenzene） （C8-PS-DVB） beads were prepared via a single-step swelling and polymerization method. Fourier transform infrared and chromatographic evaluation were used to confirm the reaction between the octene and divinylbenzene.     

Aligned Carbon Nanotube Stationary Phases for Electrochromatographic Chip Separations

This paper reports a novel approach for developing a microfluidic electrochromatographic chip device using patterned vertically aligned carbon nanotubes as the stationary phase material. Patterned growth of nanotubes in a specific location of the channel is carried out using a solid phase Fe–Al catalyst as well as a vapor deposited ferrocene catalyst. Proof-of-concept applications are demonstrated using reversed phase capillary electrochromatographic separations as well as solid phase extraction of a glycosylated protein using concanavalin A immobilized onto the nanotube bed.     

键合反相硅胶的简单制备方法

用柱层析分离天然有机物时，经常遇到的困难是：尽管选用了各种各样的淋洗剂体系，还是不能得到满意的分离效果。据笔者经验，这时若变换固定相（如将硅胶换成氧化铝、聚酰胺、硅藻土或采用反相键合硅胶等），可能会得到满意的分离效果。可见，丰富固定相的种类对有机化合...     

Separation of Cyclodextrins Using Cyclodextrin Bonded Phases

Abstract

Two different cyclodextrin bonded phases (α and β) were used for the separation of α-, β-and γ-cyclodextrins. The β-cyclodextrin phase was found to be, in general, more effective at resolving the cyclodextrins than the α-cyclodextrin bonded phase. Acetonitrile/water mixtures were used as mobile phases. The effect of mobile phase composition on retention and resolution is examined. The elution order was found to be size dependent. The results are discussed in terms of the overall retention mechanism.     

多功能基和氮杂冠醚键合固定相的制备与鉴定

在全多孔微粒硅胶表面进行连续固－液相反应,制备氯丙基（ＣＰＳ）、乙二醇氨丙基（ＤＥＡＰ）、３－［氮杂１８－冠－６］－丙基（ＢＣＰ）键合固定相。采用有机元素分析、功能基分析、热分析、红外光谱和金属离子络合容量测定等对键合相进行鉴定和表征。化学和仪器分析结果表明,键合反应按预定路线进行。键合固定相具有各种色谱性能,其极性效应对分离选择性起重要作用。     

Comparison of Solvent Adsorption on Chemically Bonded Stationary Phases in RP-LC

The excess adsorption isotherms of organic modifiers (methanol and acetonitrile) from water on chemically bonded stationary phases were studied, using seven different packed columns with different organic ligand lengths from C4 to C30. Isotherms were measured using the minor disturbance method. Excess isotherms can give useful information about the structure of the stationary phase. The amount of “adsorbed” solvent can indicate the type of distribution mechanism.     

Separation of Proteins on Polar Bonded Phases by Hydrophobic Interaction Chromatography

Abstract

Hydrophobic interaction chromatography (HIC) with a polar bonded phase (“Acetamide”) developped for size exclusion chromatography (SEC) is described. Retention of proteins depends on the surface area of the stationary phase, the pH and ionic strength of the eluent. For efficient separation the pore diameter should be 25 nm or more. The surface area should be large to achieve retention even at low ionic strength. Separation is only possible with a gradient from high to low ionic strength. Gradient volumes of 10 empty column volumes with column lengths above 15 cm are recommended. Selectivity can be optimized via pH adjustment. The advantage of this column packing is its applicability for two different separation modes: SEC and HIC.     

A Geometrical Model for Chemically Bonded TMS and PDS Phases

Abstract

A geometrical model is developed for monomeric TMS and PDS phases that are chemically bonded to silica. Using experimental data for maximum surface coverage and considering amorphous silica as a collection of distorted crystals, we calculate that each nm² of the silica surface contains 2.3 modified hydroxyl groups, 1.3 free hydroxyl. groups and 0.6 pairs of bonded hydroxyl groups, respectively. From the dimensions of the silane molecule it is concluded that for maximum coverage the TMS and PDS molecules are rigidly attached to the silica surface with an Si-O-Si bond angle between 120 and 140 degrees. The unreacted hydroxyl groups are not completely screened but will be quite inaccessible on either phase. Very little free surface area remains on the silica surface.     

Preparation of Various Bonded Phases for HPLC Using Monochlorosilanes

Abstract

Monochlorosilanes have been prepared with yields of about 80% through a catalytic hydrosilylation of terminal olefins. Subsequently, the silanes are chemically bonded to silica to obtain: (i) n-octyldimethylsilyl bonded phases with reproducible surface coverage ranging from 0.8 to 3.5 μmol/m², (ii) propyldimethylsilyl bonded phases with different functional groups at the γ-position, all showing a nearly equal surface coverage of some 3.3 μmol/m², and (iii) n-alkyldimethylsilyl bonded phases with chainlengths ranging from 1 to 22 carbon atoms and with surface coverages ranging from 3.9 μmol/m² for RP-1 to 3.0 μmol/m² for the RP-22 bonded phase. A simplified model based on the pore structure of silica allows an explanation and estimation of the maximum surface coverage as a function of the chainlength of the bonded phase.     

高效液相色谱环糊精键合固定相

环糊精是由Ｄ（＋）－葡萄糖单元通过α－１，４糖苷键连接的环状齐聚糖，其最典型的性质是能与许多客体分子形成包容配合物。高效液相色谱环糊精键合固定相广泛用于对映异构体，非对映异构体，结构异构体和常规化合物的分离。     

高效液相色谱烷基硅胶键合固定相

综述了高效液相色谱烷基硅胶键合固定相研究的最新进展,参考文献４０篇。     

Determination of Surface Silanols of Silica Gels and HPLC Bonded Phases

Abstract

A rapid method determining the surface silanols of silica gels and HPLC bonded phases involves a titration of silica gel with sodium hydroxide, in a medium of any of the following 10% aqueous salts: sodium chloride, sodium nitrate, sodium sulfate, potassium chloride, potassium nitrate and potassium sulfate. The silanols are quantified as m eg/g. It is possible to determine cation exchange capacity of a cation-exchanger due to an acid as an end group and surface silanols separately.     

Retention Behavior of some Alkaloids in Thin Layer Chromatography with Bonded Stationary Phases and Binary Mobile Phases

JPC – Journal of Planar Chromatography – Modern TLC - The retention behavior of twenty-four alkaloids has been investigated in normal-phase systems on thin layers of aminopropylsilica...     

Reverse-Phase HPLC of Proteins: Effects of Various Bonded Phases

Abstract

A variety of organic phases bonded to silica can be used effectively for the reverse-phase high performance liquid chromatography of large proteins. These include octyl, octadecyl, cyanopropyl and diphenyl bonded phases. The differences in retention characteristics and selectivity among these bonded phases is demonstrated with several standard proteins.