Repeatability in column preparation of a reversed-phase C18 monolith and its application to separation of tocopherol homologues.

This work investigated the repeatability of column preparation for a reversed-phase C18 monolith, namely stearyl methacrylate-co-ethylene glycol dimethacrylate (SMA-EDMA). The columns were thermally polymerised using three commonly available heating devices (GC oven, hot air oven and water bath) and their chromatographic performance evaluated using micro-liquid chromatography for separation of five test compounds. Precision in terms of %RSD of retention times were 9.

Evaluation of Chinese medicinal herbs fingerprinting by HPLC-DAD for the detection of toxic aristolochic acids.

Aristolochic acids are known to contribute to various renal disorders; therefore, expanding the availability of analytical methodology to detect these compounds is important in order to assess the quality of Chinese herbal medicines in which they can be found. Twelve medicinal herbal samples were procured from various sources and extracted in duplicate prior to a "fingerprint" analysis using conventional HPLC-DAD. Multivariate analysis was performed on the entire chromatographed fingerprints.

Preparation and application of hydrophilic monolithic columns.

Hydrophilic interaction chromatography (HILIC) has experienced increasing attention in recent years. Much research has been carried out in the area of HILIC separation mechanisms, column techniques and applications. Because of their good permeability, low resistance to mass transfer and easy preparation within capillaries, hydrophilic monolithic columns represent a trend among novel HILIC column techniques.

Fluorinated monolithic column for CEC.

In order to overcome the drawbacks associated with particle-based fluorinated stationary phases, a fluorinated cationic monolith was successfully synthesized by the in situ copolymerization of a 45% monomer mixture and 55% porogens with thermal initiation using 0.1% initiator with respect to the monomer mixture. The monomer mixture was composed of perfluorododecyl acrylate (49.

Monolithic and packed particle materials for in-line pre-concentration in capillary electrophoresis for 4-hydroxy-3-methoxy-methamphetamine and terbutaline.

In-line solid-phase extraction (SPE) for capillary electrophoresis (CE) was investigated using a synthesized monolith and a commercial packing material. Terbutaline (TER) and 4-hydroxy-3-methoxy-methamphetamine (HMMA) with benzyl alcohol as the electroosmotic flow marker were employed as model compounds. Two types of methacrylate-based monoliths, namely methacrylic acid-ethylene dimethacrylate and butylmethacrylate-ethylene dimethacrylate were examined.

Highlighting the role of the hydroxyl position on the alkyl spacer of hydroxypropyl-beta-cyclodextrin for enantioseparation in capillary electrophoresis.

This work investigates the resolving power of 2,3-dihydroxypropyl-beta-CD (2,3-DHP-beta-CD) and 3-hydroxypropyl-beta-CD (3-HP-beta-CD) as chiral mobile phase additives (CMPAs) using CE. The effects of experimental parameters (CD concentration, buffer pH, and buffer concentration) on enantiorecognition were investigated. More than 20 basic chiral drugs were resolved with satisfactory enantioselectivity.

Assessment of Chinese medicinal herb metabolite profiles by UPLC-MS-based methodology for the detection of aristolochic acids.

In this study, aristolochic acid in different herbal medicines containing a mixture of varying herb species was identified through fingerprint pattern similarities. Aristolochic acid I and II are nephrotoxic compounds naturally present in the Aristolochia plant species that are commonly used in Chinese herbal medicines. Twenty-four commercially available herbal formulations were extracted into an aqueous solution and injected into a UPLC-MS system.

Preparation and characterization of long alkyl chain methacrylate-based monolithic column for capillary chromatography.

This paper describes the fabrication of long alkyl chain methacrylate monolithic materials for using as stationary phases in capillary liquid chromatography. Following deactivation of the capillary surface with 3-(trimethoxysilyl)propyl methacrylate (gamma-MAPS), monoliths were formed by co-polymerisation of stearyl methacrylate (SMA) with ethylene glycol dimethacrylate (EDMA) in the presence of the initiator AIBN and a mixture of porogens including iso-amyl alcohol and 1,4-butanediol. The monoliths were prepared in 100 microm i.

A 150 micron id packed column for the separation of soybean proteins by elution gradient mu-HPLC: simultaneous separation of soybean proteins from cereal and milk proteins.

Mu-HPLC has previously been used to increase the resolution and sensitivity of protein separations but never for the analysis of soybean proteins. In this work, soybean proteins were, for the first time, separated using a capillary column with an internal diameter of 150 microm packed with a Genesis C18 stationary phase (4 microm, 300 angstroms) and UV detection. TFA and acetic acid were investigated as ion-pairing reagents in order to optimise water-ACN gradients to achieve this separation.

Separation of biomolecules by micro-high-performance anion-exchange chromatography using a tentacle-like stationary phase.

A variety of biomolecules and their variants, which have previously been problematic to separate, have been analysed using a novel anion-exchange resin based on a non-porous polystyrene polymeric support with a hydrophilic coating and grafted tentacular quaternary ammonium functional groups. The hydrophilic coating results in minimal interaction between the support and the biomolecule, while the highly flexible tentacular-like anion-exchange groups increase the ionic interaction potential and act as an umbrella to hold the proteins away from the surface. Because of the removal of silanophilic interactions, minimisation of hydrophobic interactions, and the highly flexible nature of the tentacle-like ion exchangers, ionic interactions can therefore dominate the separation.

Comparison of styrene-divinylbenzene-based monoliths and Vydac nano-liquid chromatography columns for protein analysis.

This report details the fabrication of polystyrene-based nano-LC monolithic columns for the separation of protein molecules. The report focuses on the practical advantages of monolithic columns when compared to conventional packed columns. Capillary columns were made to 100 and 50 microm i.