Study on open tubular capillary affinity liquid chromatography.

A silica capillary of 50 μm internal diameter and 500 mm length (416 mm effective length) was chemically modified with 4-(trifluoromethoxy) phenyl isocyanate in the presence of dibutyl tin dichloride as catalyst. Sodium diethyl dithiocarbamate was reacted with the terminal halogen of the bound ligand to incorporate the initiator moiety, and in situ polymerization was performed using a monomer mixture of styrene, N-phenylacrylamide, and methacrylic acid. The resultant open tubular capillary column immobilized with the copolymer layer was used for the separation of tryptic digest of cytochrome C in capillary electrochromatography. The sample was well eluted and separated into many components. The elution patterns of tryptic digest of cytochrome C were studied with respect to pH and water content in the mobile phase. This preliminary study demonstrates that open tubular capillary electrochromatography columns with a modified copolymer layer composed of proper nonpolar and polar units fabricated by reversible addition-fragmentation transfer polymerization can be useful as separation media for proteomic analysis.

A novel type of glycopolymer brushes grafted open-tubular capillary column (OTCC) was developed for the polar compound separation. Briefly, the glycerol methacrylate (GMA) polymer brushes were grafted on the inner wall of OTCC by the surface initiated atom transfer radical polymerization (SI-ATRP). Next, glucose was coupled to the side chains of the GMA polymer brushes to obtain the hydrophilic stationary phase (PGMA-N-Glucose). The optimized SI-ATRP reaction conditions were GMA/CuCl/CuCl2/cyclohexanol system grafting at 25 degrees C for 1 h. After the glucose coupling, the column back pressure was about 3,585 kPa. The structure of the glycopolymer brushes on the inner surface of OTCC was characterized by scanning electron microscopy (SEM). The glycopolymer grafting resulted in the formation of three-dimensional wave-like polymer structure on the inner surface of OTCC and largely increased the interior surface area. Therefore, improved column efficiency and loading capacity can be achieved. Under the optimized conditions, the electro osmotic flow (EOF) strength of the glycopolymer brushes grafted OTCC was obviously less than that of the bare column when the pH value of the mobile phase ranging from 3 to 11. Using the glycopolymer brushes grafted OTCC, the baseline separations of polar molecules and proteins were obtained without peak tailing. The future work will focus on the further development of the glycopolymer brushes for the highly polar compound separation, such as glycans and glycoproteins.

A modified multiresidue capillary gas chromatographic (GC) procedure has been developed using automated headspace sampling and a wide-bore fused silica open-tubular (FSOT) capillary column for the determination of volatiles in water and milk. Compounds are quantitated by the method of standard additions. An IBM System 9000 computer with the CAPMC3 chromatographic applications package and a BASIC linear regression program are used for data reduction. Data are presented for solutions prepared by fortifying water and milk with volatile solvents such as acetone, methyl ethyl ketone, benzene, methylene chloride, and chloroform, which are commonly used in the manufacture of packaging materials and adhesives. The wide-bore FSOT capillary columns showed dramatically improved detection for certain compounds, compared with normal-bore capillary GC columns. Data presented for various chemicals demonstrate the improved limits of detection from the use of automated headspace gas chromatography with wide-bore capillary columns and flame ionization detection.

A new preparation method has been developed that uses silica‐oligomer for the sub‐micron silica‐gel layer for the open‐tubular capillary column (OTC). The silica‐gel layer has a unique sub‐micron cell structure, which was observed by scanning electron microscope, and this structure contributes to increasing its total surface area. Using ultrashort (2 cm long) OTCs modified with docosyl methyl dichloro silane, separation of neutral compounds has been demonstrated. The column shows a good performance, such as theoretical plate number 71,000 plates/m. The column gives a relatively high capacity factor, such as 1.85 for fluorine.

Automated in-tube solid-phase microextraction–liquid chromatography–electrospray ionization mass spectrometry for the determination of ranitidine

In this work, an open-tubular capillary liquid-phase column was prepared by modifying chain polymer on the inner surface of capillary and chemical bonding of metal organic frameworks, NH2 -UiO-66, to the brushes of chain polymer (poly(glycidyl methacrylate)). Besides advantages of facial preparation and good permeability, the chain polymer effectively increases the modification amount of NH2 -UiO-66 nanoparticles to increase the phase ratio of open-tubular capillary column and enhance the interactions with analytes. The results of scanning electron microscope energy-dispersive X-ray spectra indicated that NH2 -UiO-66 nanoparticles were successfully bonded to the chain polymer. Because of the hydrophobic interaction and hydrogen bonding interaction between the analytes and the ligand of NH2 -UiO-66, different analytes were well separated on the NH2 -UiO-66-modified poly(glycidyl methacrylate) capillary (1.12m × 25 μm id × 365 μm od) with the high absolute column efficiency reaching 121477 plates, benefiting from an open-tubular column and low mass transfer resistance provided by polymer brush and metal-organic framework crystal. The relative standard deviations of the retention time for run-to-run, day-to-day, and column-to-column (n=3) runs are below 4.28%, exhibiting good repeatability. Finally, the column was successfully applied to separation of flavonoids in licorice.

Chiral covalent organic framework-based open tubular capillary electrochromatography column for enantioseparation of selected amino acids and pesticides.

Chapter 28 - Capillary electrochromatography

Evaluation of microbore and packed capillary column chromatography with an ethylvinylbenzene—divinylbenzene polymeric packing material and supercritical ammonia as the mobile phase

The electrochromatographic separations of 2'-, 3'- and 5'-monophosphates of adenosine, guanosine, cytidine, and uridine were carried out with an open-tubular capillary column which was wall-coated with a highly selective reagent, 28-membered macrocyclic polyamine, 4, 8, 12, 18, 22, 26-hexaaza-1,15-dioxacyclooctaeicosane ([28]ane-N6O2). The effects of pH, composition and concentration of background electrolyte (BGE), applied voltage, column length, and the additive of the BGE, such as metal ions, borate, beta-cyclodextrin and organic solvent on the separation of these monophosphorylated nucleotide isomers were investigated. The results suggested that the interactions between analytes and the bonded groups on the wall predominantly comprise anion coordination and anion exchange in addition to the electrophoresis. A well-resolved electrochromatogram was obtained with the capillary column of 100 cm (75 cm effective length) x 75 microm inside diameter (ID), citrate buffer (20 mM, pH 3.99), applied voltage of -22 kV and detection at 254 nm. Column efficiency was found with the average theoretical plate numbers of 119,500/m and a low detection limit of 0.01 microM level could be achieved for the separation of these isomers.

High-performance capillary electrophoresis of proteins : Sodium dodecyl sulphate—polyacrylamide gel-filled capillary column for the determination of recombinant biotechnology-derived proteins

A 3 m zwitterionic polymeric porous layer open tubular column (3 m × 25 μm id × 375 μm od) with a polymeric porous layer thickness of 4 μm was fabricated by the copolymerization of [2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide and N,N'-methylenebis(acrylamide). The effects of the diameter of the capillary, reaction temperature, and polymerization time on the preparation of the open tubular column were investigated. Characterized by scanning electron microscopy, the zwitterionic layer was observed to be rough and throughout the fused-silica capillary homogenously, which increased the phase ratio. The separation of neutral, basic, and acidic compounds demonstrates the strong hydrophilicity of the poly[2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide coating. In addition, the poly[2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide porous layer open tubular column was applied for the analysis of flavonoids from the rootstalk of licorice, revealing the potential in separating complex samples. The relative standard deviation of retention time for run-to-run (n = 5), day-to-day (n = 3), and column-to-column (n = 3) of toluene, N,N-dimethylformamide, formamide, and thiourea were below 1.2%, exhibiting good repeatability.

In this work, a composite of polyethylene glycol (PEG) modified MoS2 (PEG-MoS2) was synthesized and used as the stationary phase of open-tubular capillary column via a chemical bonding strategy. The PEG-MoS2 exhibited a sphere-like architecture through characterization of scanning electronic microscopy. p-phenylenediboronic acid was introduced as a linker to combine the PEG-MoS2 with capillary column. A capillary electrochromatographic method was established for the determination of nine sulfonamides by using PEG-MoS2-coated capillary column. The intra-day, inter-day, and column-to-column relative standard deviations (RSDs) of migration time and peak area were in the range of 0.80–4.38% and 1.61–9.22%, respectively. The limits of detection were in the range of 20.4–64.8 ng/mL. The recoveries in environmental water and milk were from 83.26 to 116.29% and 80.86 to 118.22%. This work is the first report that PEG-MoS2 material is utilized as stationary phase for capillary electrochromatography.

Author response for "Separation of dithiothreitol and dithioerythritol by an open tubular capillary electrochromatographic column with a MOF modified by histidine as stationary phase"

A vancomycin chiral stationary phase modified open tubular capillary electrochromatography (OT-CEC) column has been prepared using a microwave irradiation method. Compared with the use of conventional heating, the microwave-assisted process improved the efficiency of the synthesis, led to a significant increase in the rate of the reaction, and reduced the preparation time from 12 h to 55 min. Four aromatic racemates were selected as model compounds to evaluate the performance of the vancomycin modified OT-CEC column. Using the optimized conditions, all four of these racemic compounds were successfully separated with a baseline resolution (RS) of more than 1.75. These results demonstrated that the vancomycin modified OT-CEC column prepared using the microwave-assisted process possessed excellent chiral recognition properties towards aromatic racemates, as well as showed good levels of stability and repeatability. This column is therefore suitable for use in chiral separations by CEC.