A. V. Pirogov

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.

Ion chromatography as a tool for the investigation of unsymmetrical hydrazine degradation in soils

A new procedure for the determination of 1,1-dimethylhydrazine (UDMH) in soil samples was developed. This involves the distillation of UDMH from an alkaline suspension of soil and ion chromatographic analysis of the distillate. The separation was performed on a silica cation-exchanger column with ammonium acetate buffer solution as mobile phase and amperometric detection at +1.2 V. Hydrazine (Hy) and methylhydrazine (MH), which are decomposition products of UDMH, can be determined simultaneously. The limits of detection in aqueous solutions were 0.2, 0.5 and 1 µg L−1 for Hy, MH and UDMH, respectively. The developed technique was used for investigating the behaviour of UDMH in spills of rocket fuels on soils. It was found that the addition of 4 kg m−2 UDMH resulted in a 0.02% residue one year after the soil treatment. The vertical migration of UDMH in soil was less than 50 cm.

Ion-chromatographic selectivity of polyelectrolyte sorbents based on some aliphatic and aromatic ionenes

An aliphatic ionene with hydroxyl group (2HP-8 ionene), mixed aliphatic-aromatic ionenes (3-X and 6-X ionenes), aromatic ionene (Ph-X ionene), and viologen (Dp-X ionene) - polymers with quaternary nitrogen atoms in the main chain served as modifiers in synthesising polyelectrolyte sorbents for ion chromatography. The selectivity of produced and several previously prepared anion exchangers was compared with those of aliphatic ionenes. It was found that aromatic ionenes having a rigid structure of polymer chains are similar to their aliphatic analogues with shorter chains with a high charge density. Polyelectrolyte sorbents based on aromatic ionenes show higher selectivity to aromatic acids (e.g., 1-naphthalenesulfonic acid) as compared with aliphatic ionenes due to specific pi-pi interactions.

Ionene-coated sulfonated silica as a packing material in the packed-capillary mode of electrochromatography

An aliphatic ionene (2-10-ionene) has been selected as a modifier to prepare a novel polymer-coated packing material for capillary electrochromatography. The packing material was produced by dynamical modification of a commercially available sulfonated silica Exsil-100 SCX. Strong ion-exchange interactions in the capillary packed with ionene-modified sulfonated silica have been demonstrated by the example of the retention of p-aminobenzoic acid. The total calculated anion-exchange capacity of the sorbent in the capillary was about 4 x 10(-9) mol. A fast separation (about 15 min) of several aromatic acids was achieved with the packing material. The highest number of theoretical plates obtained was about 120,000. Limits of detection of the aromatic acids were 2-5 microg/ml. The advantages and lacks of the approach are discussed briefly.

Determination of underivatized glucosamine in human plasma by high-performance liquid chromatography with electrochemical detection: Application to pharmacokinetic study

A simple, rapid and sensitive high-performance liquid chromatography method with electrochemical detection was developed for the determination of glucosamine in human plasma. Plasma samples were analyzed after a simple two-step procedure of protein precipitation with subsequent dilution. The chromatographic separation was performed on a Carbopack column (3 mm x 150 mm) with a mobile phase consisting of water and 200 mM sodium hydroxide. Detection was performed electrochemically in a pulsed voltammetry mode. The limit of detection was 2.0 ng/ml, inter- and intra-day precision were less than 10%. The method was successfully applied to the investigation of the pharmacokinetics of glucosamine in healthy man volunteers.

Use of ionenes as capillary modifiers in the simultaneous determination of azide, chlorate, and perchlorate ions by capillary electrophoresis

It was demonstrated that Cl–, SO42-, NO3-, N3-, ClO3–, and ClO4– ions can be simultaneously and selectively determined by capillary electrophoresis using 2,4-ionene as a capillary modifier. The effect of n-butanol additives to the buffer electrolyte on the migration times of ions was shown. The optimum buffer electrolyte contained 0.5 mM Na2CrO4, 0.05% 2,4-ionene, 10%n-butanol, and 7% methanol. It was shown that azide can be identified in wash solutions obtained at the place of lead azide explosion. The detection limit for azide was 1–3 mg/L.

Separation and enantioseparation of derivatized amino acids and biogenic amines by high-performance liquid chromatography with reversed and chiral stationary phases

This study demonstrates that an amino-beta-cyclodextrin-bonded phase column exhibits enantioselectivity for various amino acid derivatives. Mixtures of methanol, acetonitrile, tetrahydrofuran or dioxan and triethylamine buffers (pH 4.0-7.0) were used as mobile phases. The effect of the mobile phase on the resolution process was studied by varying the mobile phase composition (type and percentage of organic modifiers, pH, and ionic strength of the buffer solution). The 1-octanol-water partition coefficients are calculated and tabulated for 16 derivatized amino acids. The chromatographic data for 42 pairs of derivatized amino acids resolved on the amino-beta-cyclodextrin-bonded phase are summarised. The separation of adrenaline, noradrenaline and amphetamine on a novel vancomycin stationary phase is demonstrated.

Simultaneous determination of fat- and water-soluble vitamins by microemulsion electrokinetic chromatography

A new procedure was developed for the simultaneous determination of water- and fat-soluble vitamins by microemulsion electrokinetic chromatography. Using microemulsions based on sodium dodecyl sulfate, Brij 35, 1-butanol, and heptane, 10 vitamins were separated (4 water-soluble and 6 fat-soluble) within 35 min. The efficiency of the separation was 800000 theoretical plates (effective capillary length, 40 cm). To enhance the selectivity, 2-propanol was used as a hydrophobizing addition into the microemulsion. The procedure was used for analyzing a kaolin-based vitamin premix. The use of microemulsion as an agent for extracting vitamins from the support considerably simplifies the sample preparation.

Synthesis of polymeric anion exchangers bearing dimethylhydrazine and alkylammonium functional groups and comparison of their chromatographic properties

A new anion exchanger for ion chromatography bearing an N,N-dimethylhydrazine functional group was synthesized by chloromethylation followed by the amination of a copolymer of styrene and divinylbenzene with a crosslinking degree of 50%. Its chromatographic properties were studied in a two-column mode of ion chromatography with conductometric detection. The anion exchanger obtained is characterized by better selectivity and efficiency than ion exchangers bearing alkylammonium functional groups, namely, trimethylamine, triethylamine, N,N,N′,N′-tetramethyldiaminomethane, N,N,N′,N′-tetramethylethylenediamine, and pyridine. Addition of p-hydroxybenzonitrile in the eluant improved the shape of the peak of the nitrate ion and allowed the simultaneous determination of fluoride, chloride, nitrate, phosphate, and sulfate ions.

Simplex-optimization with a new criterion. Applications to dual-column ion chromatography

A new optimization criterion for chromatography is presented. It was designed to evaluate the quality of chromatograms in a way similar to human estimation. Selectivity, efficiency, and time of analysis as well as the number of peaks were taken into account. The criterion has been tested in comparison with expert estimations and some modern criteria. A better agreement of the new criterion with human estimation of chromatographic quality compared to some literature criteria is shown. A number of successful optimization runs has been performed using the criterion together with simplex optimization.