Mechanism of formation of system peaks in ion-exclusion chromatography.

Single or multiple system peaks can be observed in ion-exclusion chromatography (IEC) based on whether the eluent is composed of single or multiple active eluent constituents. It was confirmed experimentally that the number of system peaks is always equal to or lower than (when co-elution occurs) the number of active eluent components. Positive and negative system peaks can be recorded in the IEC systems.

Computational method for modeling of gradient separation in ion-exchange chromatography.

A model for the simulation of the gradient separation in ion-exchange chromatography is presented. It is based on discontinuous plate model and simulates the distribution of analytes in the ion-exchange column during the separation process. It enables calculations of chromatograms for the analytes with integer and non-integer effective charges under complex gradient profiles.

Hard modeling of ion chromatography separations on hydroxide-selective stationary phase.

In the present paper the development and testing of the computer software for the simulation of the on-column ion chromatography separation processes are presented. The computer algorithm based exclusively on the selectivity coefficients of the tested analytes has been upgraded to cope with the 2:1 and 1:1 ratios of the analyte-to-eluent ion charge. The analytical solution of the cubic equation, which is needed for calculation of chromatograms for doubly charged analytes in the presence of singly charged eluent, is presented.

Analyte-stationary phase interactions in ion-exclusion chromatography.

The currently accepted analyte-stationary phase interactions occurring in ion-exclusion chromatography are re-examined. In particular, the requirement for the existence of a Donnan membrane separating the flowing, interstitial eluent from the static, occluded, liquid acting as the stationary phase is scrutinized, together with the role of hydrophobic adsorption effects in the retention of aromatic analytes. Plots showing the interconversion of the column between the analyte and eluent forms are used to highlight some shortcomings of the currently accepted mechanism for ion-exclusion chromatography.

Determination of bisphosphonates by ion chromatography-inductively coupled plasma mass spectrometry.

An ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) was introduced in the analysis of bisphosphonates. Two compounds (alendronic acid and etidronic acid) were separated on a Dionex AS-7 anion-exchange column with dilute nitric acid employed as the mobile phase. The analytes were detected at m/z 31, as they contain phosphorus.

Determination of epichlorohydrin by sulfite derivatization and ion chromatography: characterization of the sulfite derivatives by ion chromatography-mass spectrometry.

This work is an upgrade of a previously developed method (J. Chromatogr. A 884 (2000) 251] for epichlorohydrin determination by ion chromatography (IC) and conductivity detection.

Interference of some matrix ions in cation-exchange chromatography.

Ion chromatographic analysis of ions in samples containing complex matrix composition strongly depends on the on-column co-processes caused by sample matrix components. In the present publication studies of different separation phenomena in cation-exchange chromatography are described. The studies were performed at 'non-linear' chromatographic conditions, when the concentration of matrix (interfering) ions significantly exceeded the concentration of the eluent ions.

Efficiency and characteristics of solid-phase (ion-exchange) extraction for removal of Cl- matrix.

Certain types of samples contain chloride in concentrations that are too high to accurately determine other anions by ion chromatography without any pretreatment. One of the most widely used approaches for such samples is matrix elimination using disposable cartridges containing a cation-exchange resin in the Ag+ form. The efficiency and characteristics of the commercially available cartridge for Cl- removal were tested by the on-line connection of the cartridge effluent to an inductively coupled plasma mass spectrometer.

Optimization of artificial neural networks used for retention modelling in ion chromatography.

The aim of this work is the development of an artificial neural network model, which can be generalized and used in a variety of applications for retention modelling in ion chromatography. Influences of eluent flow-rate and concentration of eluent anion (OH-) on separation of seven inorganic anions (fluoride, chloride, nitrite, sulfate, bromide, nitrate, and phosphate) were investigated. Parallel prediction of retention times of seven inorganic anions by using one artificial neural network was applied.

On-line pH modification of carbonate eluents using an electrolytic potassium hydroxide generator for ion chromatography.

Classical gradient elution, based on the application of a gradient pump used for mixing two or more prepared eluent components in pre-determined concentrations, was replaced by a chromatography system equipped with an isocratic pump and an electrolytic KOH generator. The isocratic pump delivered a constant concentration eluent composed of pure hydrogencarbonate solution. Carbonate ions, the main component of carbonate/hydrogencarbonate-based eluents, were formed by titration of hydrogencarbonate with KOH formed on-line in the electrolytic KOH generator.

Simple and rapid determination of iodide in table salt by stripping potentiometry at a carbon-paste electrode.

A simple and rapid procedure, utilising constant-current stripping analysis (CCSA) at a carbon-paste electrode containing tricresyl phosphate as a pasting liquid (TCP-CPE), has been developed for the determination of iodide in table salt. Because of a synergistic accumulation mechanism based on ion-pairing and extraction of iodide in combination with electrolytic pretreatment of the TCP-CPE, the method is selective for iodide and enables direct determination of iodide in samples of table salt containing anti-caking agents such as K(4)[Fe(CN)(6)] (food additive "E 536") or MgO. The iodide content (calculated as KI) can be determined in a concentration range of 2 to 100 mg kg(-1) salt, with a detection limit (S/N=3) of 1 mg kg(-1), and a recovery from 90 to 115%.