Determination of inorganic anions by capillary electrochromatography

Reverse-Polarization High-Performance Layer Electrochromatography-A New Approach to Anion Separation

High-performance layer electrochromatography (HPLEC) combines the advantages of overpressured-layer chromatography (OPLC) and pressurized planar electrochromatography (PPEC) while overcoming some of their limitations. HPLEC equipment can work in various HPLEC, OPLC, and PPEC modes. The equipment enables HPLEC analysis also with an electroosmotic effect directed against the hydrodynamic flow of the mobile phase. The change in the electric field direction in the separation system does not result in a change in either the direction of the mobile phase flow or the direction of solute migration. The hydrodynamic flow generated by the pump dominates the electroosmotic effect and enables separation against the direction of the latter. Reversed-polarization HPLEC may be advantageous for the analysis of anionic compounds, as it facilitates faster and more selective separation than OPLC performed in similar conditions. This separation mode provides a new possibility to develop and optimize separation methods by performing separation against the electroosmotic effect and without need of any modification of the adsorbent surface. A drawback of this separation mode is the increase in the backpressure at the mobile phase inlet and the limitation of the mobile phase flow rate. Currently, contrary to the single-channel mode, multi-channel reverse-polarity HPLEC still requires some technical and methodological improvements.

Determination of inorganic anions in uranium ore concentrate reference materials

The determination of inorganic anions in uranium ore concentrates (UOCs) is useful to nuclear forensics for establishing the provenance of sample materials. In this collaborative study, quantitation of inorganic anions was carried out on three UOC reference materials from the National Research Council Canada: UCLO-1 (https://doi.org/10.4224/crm.2020.uclo-1), UCHI-1 (https://doi.org/10.4224/crm.2020.uchi-1), and UPER-1 (https://doi.org/10.4224/crm.2020.uper-1). The analytes were extracted into water and characterized by ion chromatography with combined standard uncertainties (uc) between 1.6 and 11%. The highest contributor to uc was homogeneity. Sulfate was the most abundant anion (2000–12,000 mg/kg SO42−). Other anions were in the 15–500 mg/kg range.

Determination of organic acids by CE and CEC methods

A comprehensive overview of the analysis of low-molecular-mass organic acids employing electromigration methods in the capillary format is given. This review includes papers published since 2003 and can be seen as an update of the review paper published by Galli et al. in 2003. Tables included in this review contain application papers describing the determination of organic acids from a variety of fields like the analysis of food and beverages, environmental samples, samples from clinical origin, and from natural products.

Evaluation of capillary ion exchange stationary phase coating distribution and stability using radial capillary column contactless conductivity detection

The use of radial (across) capillary column capacitively coupled contactless conductivity detection is demonstrated as a simple and rapid technique for visualisation of stationary phase longitudinal coverage and coating stability in capillary ion exchange chromatography.

Review coupling of capillary electrochromatography to mass spectrometry

This review discusses the development of capillary electrochromatography (CEC) coupled to mass spectrometric (MS) detection over the last few years. Major topics addressed are instrumental setups employed and applications of this technology published in the recent literature. The instrumental section includes a discussion of the most commonly used interfaces for the hyphenation of CEC and MS as well as ionization techniques. Applications reviewed in this paper come from a variety of different fields such as the analysis of biomolecules like proteins, peptides, amino acids or carbohydrates, chiral separations or the analysis of pharmaceutical an their metabolites in a series of matrices.

Recent highlights in stationary phase design for open-tubular capillary electrochromatography

This review examines the most recent innovations made to achieve high performance in open-tubular capillary electrochromatography (OT-CEC) separations, focusing on the ingenious chemical and physical solutions made to increase the surface area and equip the stationary phase with exploitable selectivity. Among the approaches taken are chemically bonded ligands, etching with chemical bonding, sol-gels, molecularly imprinted polymers, porous layers, physically attached or adsorbed phases, and nanoparticle coatings. Particularly noteworthy are modern developments with macrocyclic receptor ligands, nanoparticles and open channel electrochromatography on-chip.

Relation between Electrophoretic Behavior and Molecular Shapes of Aromatic Anions

The capillary electrophoretic behavior of 44 aromatic organic ions was investigated. The observed ionic radii (r(obs0)) for the aromatic organic ions were obtained from the electrophoretic mobilities of sodium tetraborate (pH 9.2), potassium tetraborate (pH 9.2), ammonium borate (pH 9.2), and trisodium phosphate (pH 11.7) buffers with zero ionic strength. The linear relationships between the r(obs0)) values and the ionic radii (r(calc)), calculated by either the AM1 or PM3 method, were determined for benzyltrialkylammonium and aromatic sulfonate ions. However, the r(obs0)) values were constant for the aromatic carboxylate ions in buffers, in spite of the different r(calc) values. This indicates that aromatic carboxylate ions, such as benzenecarboxylate, pyridinecarboxylate, naphthalenecarboxylate, and anthracenecarboxylate ions, migrate as planar ions in buffers, whereas aromatic sulfonate ions could migrate as approximately spherical ions.