O. V. Krokhin

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.

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.

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.

Influence of cationic polymers on separation selectivity in kinetic differentiation mode capillary electrophoresis of metal-4-(2- pyridylazo)resorcinolato chelates

Abstract The influence of four kinds of cationic polymers on electrophoretic mobilities of V(V), Co(II), Ni(II), and Fe(II)–4-(2-pyridylazo)resorcinolato chelates was investigated in kinetic differentiation mode capillary electrophoresis (CE). It was shown that the addition of cationic polymers strongly changes selectivity of such a type of separation. Four parameters of carrier electrolyte (pH, counter-ion, polymer and acetonitrile concentrations) were changed to examine the elution order of the complexes. The behaviour of the chelates can be described in terms of ion-exchange separation. Fast separation of the four chelates with efficiency of more than 450u2008000 theoretical plates per meter in CE with reversed polarity power supply was easily performed.

Potential of ethylenediaminedi(o-hydroxyphenylacetic acid) and N,N′-bis(hydroxybenzyl)ethylenediamine-N,N′-diacetic acid for the determination of metal ions by capillary electrophoresis☆

Two aromatic polyaminocarboxylate ligands, ethylenediaminedi(o-hydroxyphenylacetic acid) (EDDHA) and N,N-bis(hydroxybenzyl)ethylenediamine-N,N-diacetic acid (HBED), were applied for the separation of transition and heavy metal ions by the ion-exchange variant of electrokinetic chromatography. EDDHA structure contains two chiral carbon centers. It makes it impossible to use the commercially available ligand. All the studied metal ions showed two peaks, which correspond to meso and rac forms of the ligand. The separation of metal-HBED chelates was performed using poly(diallyldimethylammonium) polycations in mixed acetate-hydroxide form. Simultaneous separation of nine single- and nine double-charged HBED chelates, including In(III), Ga(III), Co(II)-(III) and Mn(II)-(III) pairs demonstrated the efficiency of 40,000-400,000 theoretical plates. The separation of Co(III), Fe(III) complexes with different arrangements of donor groups and oxidation of Co(II), Mn(H), Fe(II) ions in reaction with HBED have been discussed.

Separation selectivity of some ethylenediaminetetraacetic acid and cyclohexane-1,2-diaminetetraacetic acid complexes in column and ion electrokinetic chromatography

The complexes of Mn2+, Cd2+, Fe3+, Pb2+, Ni2+, Co2+, Zn2+ and Cu2+ with EDTA and cyclohexane-1,2-diaminetetraacetic acid (CDTA) were separated and detected in column and ion electrokinetic chromatography with suppressed conductivity and direct UV detection, respectively. In column ion chromatography (IC) these complexes were separated on an IonPac AS4A anion-exchange column (Dionex, USA). Parameters of carrier electrolyte, which were examined in the ion electrokinetic chromatography (IEKC) mode, include polymer and sulfate concentrations. In IEKC separation selectivity of complexes with poly(diallyldimethylammonium) cation as modifier is similar as for an IonPac AS4A column both for EDTA and CDTA chelates. It was shown that the ion-exchange capacity of the electrokinetic system is more than 100-times lower than the capacity of the IC column for the same peak resolution. In comparison with column main advantages of electrokinetic version are high separation efficiency (220,000-390,000 theoretical plates) and the absence of the analyte interaction with the sorbent matrix.

Effect of Fluoride Anions on Gramicidin Photoinactivation Sensitized by Sulfonated Aluminum Phthalocyanines

Abstract Interaction of potent photodynamic agents, sulfonated aluminum phthalocyanines (AlPcSn where n is a number of sulfonic groups), with biological membranes was studied here using model systems: sensitized photoinactivation of gramicidin channels in planar lipid bilayers and adsorption on lipid monolayers. Fluoride anions known to form complexes with aluminum were found to inhibit both the adsorption of aluminum phthalocyanines on lipid monolayers, as measured with a Langmuir trough by surface pressure and surface potential changes, and photodynamic efficacy of the dyes, as studied by gramicidin channel photoinactivation. The similar effects were caused by the alkalinization of the medium. Fluoride anions appeared to be much more effective in the case of AlPcS4 as compared to AlPcS3. The suppression of the photodynamic potency of aluminum phthalocyanines was attributed to desorption of the dyes from lipid bilayers induced by fluoride or hydroxyl ions. With AlPcS4 an enhancement of the dye aggregation leading to a decrease in the sensitizing activity was probably involved in the fluoride effect as revealed by absorption and fluorescence spectral measurements. Capillary electrophoresis was employed to understand the mechanism of the dye desorption. The results of these experiments indicated that the reduction in the membrane affinity was associated with an increase in the negative charge of the dye molecules due to the binding of fluoride or hydroxyl ions.

New High-Performance Techniques for Ion-Exchange Separation

Results of the use of water-soluble cationic polymers for the synthesis of new anion exchangers for ion chromatography, capillary electrophoresis, and electrokinetic chromatography were summarized. The influence of functional groups in polymer molecules on the selectivity of the ion-chromatographic determination of ions and their mobility in capillary electrophoresis was considered.

Separation selectivity of anionic metal complexes of N,N′-bis(hydroxybenzyl)ethylenediamine-N,N′-diacetic acid in ion and ion electrokinetic chromatography

The complexes of Fe(III), Co(III), Mn(III), Al(III), Cu(II), Ni(II), Cd(II) and Zn(II) with N,N-bis(hydroxybenzyl)ethylenediamine-N,N-diacetic acid (HBED) were separated by ion exchange in different modes: ion chromatography (IC) and ion electrokinetic chromatography (IEKC). In column IC these complexes were separated on an IonPac AS4a anion-exchange column (Dionex, USA). Parameters of the background electrolyte that were examined in IEKC mode include polymer, competing ion concentration and pH. The use of poly(diallyldimethylammonium chloride) (PDADMACl) as a modifier in IEKC provides separation selectivity only slightly different from that observed in IC on the IonPac AS4a column. Optimal separation conditions were found to be: 0.1 mM HBED, 50 mM PDADMAOH, 10 mM Na2 B4 O7, pH adjusted to 10 with acetic acid. The use of an aromatic ligand allowed a 10-fold decrease in detection limits of metal ions in comparison with previously studied EDTA. A separation efficiency up to 400,000 theoretical plates was demonstrated for IEKC.

Chromatographic Determination of Silicon and Phosphorus as Molybdic Heteropoly Acids with Preconcentration

The chromatographic behavior of molybdic heteropoly acids of silicon and phosphorus as ion pairs with tetrabutylammonium bromide was studied by ion-pair high-performance liquid chromatography on the C18reversed phase (UV detection at 310 nm). Heteropoly acids were preconcentrated as ion pairs with tetrabutylammonium bromide to increase the sensitivity of the determination. Optimal conditions were selected for the chromatographic determination of silicon and phosphorus in water in the presence of each other. Detection limits for silicon and phosphorus are (1.1 × 0.3) × 10–3and (6.7 × 1.2) × 10–3μg/mL, respectively. Calibration plots are linear in the concentration ranges 0.01–0.1 μg/mL (silicon) and 0.02–0.15 μg/mL (phosphorus). The procedure was used for the analysis of distilled water.