O. A. Shpigun

Chiral analysis of pharmaceuticals by capillary electrophoresis using antibiotics as chiral selectors

The review summarizes the use of the chiral capillary electrophoresis (CE) with different class of antibiotics as chiral selectors in the pharmaceutical field. Basic factors influencing the enantioseparation are shortly discussed. Non-aqueous capillary electrophoresis is also included as well as the coupling of CE to MS. The selection of a chiral selector according the ionic state and structure of the analyte is described. Summary of pharmaceutical applications of chiral CE is given.

Countercurrent chromatography in analytical chemistry (IUPAC Technical Report)

Countercurrent chromatography (CCC) is a generic term covering all forms of liquid-liquid chromatography that use a support-free liquid stationary phase held in place by a simple centrifugal or complex centrifugal force field. Biphasic liquid systems are used with one liquid phase being the stationary phase and the other being the mobile phase. Although initiated almost 30 years ago, CCC lacked reliable columns. This is changing now, and the newly designed centrifuges appearing on the market make excellent CCC columns. This review focuses on the advantages of a liquid stationary phase and addresses the chromatographic theory of CCC. The main difference with classical liquid chromatography (LC) is the variable volume of the stationary phase. There are mainly two different ways to obtain a liquid stationary phase using centrifugal forces, the hydrostatic way and the hydrodynamic way. These two kinds of CCC columns are described and compared. The reported applications of CCC in analytical chemistry and comparison with other separation and enrichment methods show that the technique can be successfully used in the analysis of plants and other natural products, for the separation of biochemicals and pharmaceuticals, for the separation of alkaloids from medical herbs, in food analysis, etc. On the basis of the studies of the last two decades, recommendations are also given for the application of CCC in trace inorganic analysis and in radioanalytical chemistry.

Recent progress in capillary electrophoresis of metal ions.

Advances in the fundamental studies and methodology of capillary electrophoresis (CE) as applied to metal ion analysis over the last two years are reviewed, with the objective of providing the interested reader with a state‐of‐the‐art picture of techniques potentialities in the area. In particular, novel strategies for separation selectivity control and CE system innovations designed to enhance the detection sensitivity are described. In addition, a brief overview of the primary metal analytes and samples for which the technique appears to be best suited is given. The current limitations of the technique regarding most of all the implementation for routine use are considered along with the approaches on how they could be addressed. Finally, some pointers as to the likely trends in the future research are discussed.

Use of cationic polymers for the simultaneous determination of inorganic anions and metal-4-(2-pyridylazo)resorcinolato chelates in kinetic differentiation-mode capillary electrophoresis

Abstract Three cationic polymers were used as electroosmotic flow and selectivity modifiers for simultaneous determination of inorganic anions and metal-4-(2-pyridylazo)resorcinolato (PAR) chelates. It was shown that the ability of polymers to associate with analytes decreased in the order: poly-(N-ethyl-4-vinylpyridinium bromide)>poly-(diallyldimethylammonium chloride)>Polybrene. CrO42− was chosen as a background electrolyte anion, because it enables indirect UV detection of transparent analytes at 254 nm and do not affect the detection sensitivity of chelates at 490 nm. Rapid (4 min) separation of Co(II), Ni(II), and Fe(II)-PAR chelates and of 11 inorganic anions was demonstrated.

Polyelectrolyte sorbents based on aliphatic ionenes for ion chromatography

2-4, 3-4, 2-8, 3-8, 3-6, 4-6, 6-8, 6-10-ionenes (polymers with quaternary nitrogen atoms in the main chain) served as modifiers in synthesizing polyelectrolyte sorbents for ion chromatography. The approaches to the synthesis and their stability are discussed. Cluster analysis was applied to separate aliphatic ionenes to three groups as chromatographic modifiers, namely hydrophilic, hydrophobic, and intermediate. Each group is characterized by a certain selectivity to sulfate, perchlorate, iodide and thiocyanate. The sorbents show high selectivity and efficiency up to 15,000 theoretical plates per meter.

Selectivity of chemically bonded zwitterion-exchange stationary phases in ion chromatography

A number of zwitterion-exchange stationary phases were prepared by immobilization of amino acids of different structure (Asp, Glu, Val, Tyr, Pro, Hypro, Arg and Lys) on a silica surface. The occurrence of oppositely charged groups in a single ion-exchange site provided cation-, anion- and zwitterion-exchange properties. The chromatographic behaviour of these stationary phases was evaluated by the retention of a series of test organic compounds of different ionogenic nature. The role of the type and structure of the ion-exchange site was considered. The structure of the bonded molecules and the pH of the eluent were shown to be key parameters influencing the ion-exchange properties of amino acid-bonded silicas. The cation-exchange selectivity of phases containing primary or secondary amino groups was investigated for alkali and alkaline earth metal ions. The application of amino acid-bonded silicas to the ion chromatographic separation of anions and cations is described.

Ion-exchange properties of glutamic acid-bonded silica

The chromatographic behaviour of alkali, alkaline earth and some transition metals on the glutamic acid-bonded silica stationary phase was investigated using dilute solutions of perchloric acid as eluent. The effect of different classes of organic modifiers as well as the influence of temperature on the retention of cations were studied. Sorption heats for cations under different conditions were calculated. These investigations allowed the chromatographic separation conditions, under which either complex forming or ion-exchange mechanisms prevail, to be determined.

Direct liquid chromatographic determination of hydrazines: A review

Today the determination of hydrazines is an important application in analytical chemistry. This review shows the current state-of-the-art analyses and discusses the merits of the direct chromatographic methods for the determination of hydrazines such as ion-, ion-exclusion, ion-pair and hydrophilic interaction chromatography. The methodological aspects of the separation and detection of hydrazines are considered for these methods. Examples of hydrazine determination in real samples are presented.

Determination of gallic acid with 4-nitrobenzenediazonium tetrafluoroborate by diffuse reflectance spectrometry on polyurethane foam

AbstractThe present work describes a rapid and cost-effective analytical procedure for the determination of gallic acid. It is basedon the solid-phase extraction of gallic acid in the form of the azo compound by polyurethane foam (PUF) and measurementby diffuse reflectance spectrometry. The calibration graphs are linear over the range 0.2–6 gml −1 . The developed procedurewas applied to the determination of gallic acid in alcoholic beverages.© 2002 Elsevier Science B.V. All rights reserved. Keywords: Gallic acid; Polyurethane foam; Sorption; Diffuse reflectance spectrometry 1. IntroductionGallic acid (2,3,4-trihydroxybenzoic acid) is a natu-ral phenolic compound which is widely distributed inplants. Some pharmacological properties of this sub-stance have been described previously. For example,it has strong antimutagenic, anticarcinogenic and an-tioxidant activities [1–3]. The antioxidant activity andantiradicalar power of gallic acid have been estimatedquantitatively [1].Along with other polyphenolic compounds, gallicacid is often used as an indicator of adulteration of fruitjuices [2,4] and different alcoholic beverages [5–7].For instance, cognac and scotch whisky contain gal-lic acid, and as was shown [5], there was a good

Modified silica as a stationary phase for ion chromatography

The possibility of the rapid preparation of agglomerated anion exchangers was demonstrated on a reversed-phase silica support with the polymeric agents poly(N-ethyl-4-vinylpyridinium bromide), poly(dimethyldiallylammonium chloride), poly(hexamethyleneguanidinium hydrochloride) and 2,5-ionene as modifiers. A 90-min sorbent preparation and column packing allowed an efficiency of more than 10000 theoretical plates per metre to be obtained for 10-μm spherical beads. The polymeric agents showed different selectivity, stability and capacity for the resulting anion exchangers (owing to changes in the structure and the density of functional groups in the polymer chain). The sorbents were used for the simultaneous determination of weakly and strongly retained anions and some heavy metals with EDTA solutions as eluent.