Hydrophobicity of polymer based anion-exchange columns for ion chromatography.

The regularities of the retention of alkanoic and alkanesulfonic acids homologues were investigated for the set of 36 anion-exchange columns produced by various manufacturers. The role of hydrophobic and electrostatic interactions in the retention and separation of organic anions was studied. The methylene selectivity increments α(CH) were measured for the studied columns with 10 mM sodium hydroxide eluent.

Porous layer open tubular columns in capillary liquid chromatography.

This review covers the latest developments and applications of porous layer open tubular columns in capillary liquid chromatography. Here, the authors provide a concise background on the fundamentals of porous layer open tubular columns, their fabrication and application. Over the past two decades, growing interest in the areas of proteomics and hyphenated LC-MS techniques have played a large part in the development of porous layer structures within capillary formats due to their high permeability, excellent efficiency and exceptional peak capacity.

A new N-hydroxyethyliminodiacetic acid modified core-shell silica phase for chelation ion chromatography of alkaline earth, transition and rare earth elements.

Bare core-shell silica (1.7μm) has been modified with iminodiacetic acid functional groups via standard silane chemistry, forming a new N-hydroxyethyliminodiacetic acid (HEIDA) functionalised core-shell stationary phase. The column was applied in high-performance chelation ion chromatography and evaluated for the retention of alkaline earth, transition and heavy metal cations.

Fabrication and characterization of nanotemplated carbon monolithic material.

A novel hierarchical nanotemplated carbon monolithic rod (NTCM) was prepared using a novel facile nanotemplating approach. The NTCM was obtained using C60-fullerene modified silica gels as hard templates, which were embedded in a phenolic resin containing a metal catalyst for localized graphitization, followed by bulk carbonization, and template and catalyst removal. TEM, SEM, and BET measurements revealed that NTCM possessed an integrated open hierarchical porous structure, with a trimodal pore distribution.

Nano-particle modified stationary phases for high-performance liquid chromatography.

This review covers the latest developments and applications of nano-materials in stationary phase development for various modes of high-performance liquid chromatography. Specific attention is placed upon the development of new composite phases, including the synthetic and immobilisation strategies used, to produce either encapsulated nano-particles, or surface attached nano-particles, layers, coatings and other structures. The resultant chromatographic applications, where applicable, are discussed with comment upon enhanced selectivity and/or efficiency of the nano-particle modified phases, where such effects have been identified.

In-process phase growth measurement technique in the fabrication of monolithic porous layer open tubular (monoPLOT) columns using capacitively coupled contactless conductivity.

A technique for the in-process measurement of polymer stationary phase growth inside fused silica capillaries during the fabrication of monolithic porous layer open tubular (monoPLOT) columns is presented. In this work, capacitively coupled contactless conductivity detection (C4D) was applied as an online measurement tool for porous polymer layer growth within fused silica capillaries. The relationship between effective capillary diameter and C4D response was investigated for two polymers, butyl methacrylate-ethylene dimethacrylate (BuMA-EDMA) and polystyrene-divinylbenzene (PS-DVB) over a range of capillary diameters and layer thicknesses.

Chelation ion chromatography of alkaline earth and transition metals a using monolithic silica column with bonded N-hydroxyethyliminodiacetic acid functional groups.

A commercially available porous silica monolithic column (Onyx Monolithic Si, 100 mm×4.6 mm I.D.

Porous graphitized carbon monolith as an electrode material for probing direct bioelectrochemistry and selective detection of hydrogen peroxide.

For the first time, graphitized carbon particles with a high surface area have been prepared and evaluated as a new material for probing direct electrochemistry of hemoglobin (Hb). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging revealed that the carbon monolithic skeleton was constructed by a series of mesopores with irregular shapes and an average pore diameter of ~5.6 nm.

Zwitterionic ion-exchangers in ion chromatography: A review of recent developments.

Significant advances within the field of ion chromatography (IC) have often had their roots in research focussed on the development of new phase technologies, aimed to both simultaneously increase efficiency and vary selectivity. To increase selectivity it is necessary to develop new selective ion-exchangers, achieved by varying the nature of functional groups and the matrix of the stationary phase. In this comprehensive review, developments over the past decade in the production and application of zwitterionic and amphoteric ion-exchangers are presented and discussed.

Simultaneous separation of inorganic anions and metal-citrate complexes on a zwitterionic stationary phase with on-column complexation.

The retention and separation selectivity of inorganic anions and on-column derivatised negatively charged citrate or oxalate metal complexes on reversed-phase stationary phases dynamically coated with N-(dodecyl-N,N-dimethylammonio)undecanoate (DDMAU) has been investigated. The retention mechanism for the metal-citrate complexes was predominantly anion exchange, although the amphoteric/zwitterionic nature of the stationary phase coating undoubtedly also contributed to the unusual separation selectivity shown. A mixture of 10 inorganic anions and metal cations was achieved using a 20 cm monolithic DDMAU modified column and a 1 mM citrate eluent, pH 4.

Anion-exchange chromatography on short reversed-phase columns modified with amphoteric (N-dodecyl-N,N-dimethylammonio)alcanoates.

Short reversed-phase columns (50 mm x 4.6 mm Gemini C(18)) were dynamically coated with carboxybetaines of the general structure, C(12)H(25)N(+)(CH(3))(2)(CH(2))(n)COOH, namely (N-dodecyl-N,N-dimethylammonio)undecanoate, DDMAU (n=10) and (N-dodecyl-N,N-dimethylammonio)butyrate, DDMAB (n=3), and investigated for the separation of inorganic anions in ion chromatography. The role of the ionic strength of coating surfactant solutions on their adsorption and resultant column capacity was studied.

Separation of nucleic acid precursors on an amphoteric surfactant modified monolith using combined eluent flow, pH and concentration gradient.

An RP monolithic column coated with an amphoteric carboxybetaine type surfactant has been used with a combined triple eluent concentration, pH and flow gradient ion chromatography technique for the simultaneous separation of up to 18 nucleotides, nucleosides and nucleobases. The separation of up to eight precursors on a 1 cm long monolithic microcolumn using the combined gradient approach is also shown. The method was applied to the separation of the above nucleic acid precursors in perchloric acid extracts of yeastolates samples.

Flow gradient liquid chromatography using a coated anion exchange microcolumn.

Ion chromatography on a 4.0-mm-long (3.0 mm ID) ion exchange column is presented.