E. N. Shapovalova

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.

Enantiorecognition of profens by capillary electrophoresis using a novel chiral selector eremomycin

The evaluation of a macrocyclic glycopeptide antibiotic, eremomycin, as a chiral selector in capillary electrophoresis (CE) has been performed. The stability of eremomycin in solution and capillary electrolyte, as well as its optical and electrophoretic properties have been discussed. The effect of experimental parameters influencing the enantioseparation of several profens has been studied. Excellent enantioseparation of profens has been achieved and migration order has been validated. Comparison of enantioseparations of profens in CE by using eremomycin-mediated electrolytes and in HPLC with eremomycin immobilized on silica has revealed similar trends for both methods.

Clarithromycin as a chiral selector for enantioseparation of basic compounds in nonaqueous capillary electrophoresis

The first use of macrolide antibiotic clarithromycin (CLM) in nonaqueous media for enantioseparation (partial or baseline) of the following compounds: alprenolol, atenolol, metoprolol, clenbuterol, methoxyphenamine, pindolol, propranolol, sotalol, synephrine, labetalol, and fenoterol is reported. Each analysis took less than 15 min. To find optimal separation conditions, some properties of CLM (adsorption, solubility), as well as the effect of experimental parameters on the enantioseparation of analytes (background electrolyte composition, chiral selector concentration, temperature, and applied voltage) were studied. The best chiral resolution was achieved in methanolic solution of 100 mM citric acid, 10 mM NaOH, 240–300 mM H3BO3, and 60–75 mM CLM. Using the proposed procedure, adsorption of CLM on the capillary wall was negligible and the repeatability of the migration times (RSD) was as good as 1.6%. For the analysis of propranolol, the linearity was achieved in the concentration range 2.5 × 10−2– 3.0 × 10−1 mg/mL with the LODs (3 × S/N) being equal 2.6 × 10−3 mg/mL and 2.8 × 10−3 mg/mL for the first and the second enantiomers, respectively. Linear range for metoprolol enantiomers was 1.0 × 10−2 –1.6 × 10−1 mg/mL. The LODs (3 × S/N) were determined as 2.8 × 10−3 and 3.0 × 10−3 mg/mL for the first and the second enantiomers, respectively.

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.

Preconcentration of 2,4-dichlorophenoxyacetic acid on molecularly imprinted polymers and its subsequent determination by high performance liquid chromatography

The potency of molecularly imprinted polymers (MIP) for 2,4-dichlorophenoxyacetic acid (2,4-D) in the dynamic sorption preconcentration (solid phase extraction) of 2,4-D and three other structurally related species (2,4-dichlorophenol, 2-chlorophenol, and dikamba) from aqueous solutions is assessed. The optimal conditions for preconcentration are found: 0.01 M HCl, 25–100 mL of solution, flow rate of solution 0.7 mL/min, column (15 × 2.7 mL), and sorbent weight 0.04 g. The analytes are desorbed with 1 mL of methanol and detected in the eluate by reversed-phase HPLC with spectrophotometric detection at 225 nm. The detection limit for 2,4-D makes 0.4 μg/mL without preconcentration and 0.01 μg/mL with preconcentration from a volume of 100 mL. The procedure is applied to the analysis of model mixtures based on fresh river water.

On-line sorption-chromatographic determination of phenols with amperometric detection

Conditions of the preconcentration of phenol on a microcolumn filled with MN-200 hypercrosslinked polystyrene were determined using the linear sorption dynamics model. Conditions of the on-line determination of phenol and its chloro derivatives by reversed-phase high-performance liquid chromatography with amperometric detection were optimized. The detection limit of phenol and chlorophenols for preconcentration from 30 mL of a sample was 3 and 15 ng/L, respectively. The proposed procedure was used for the determination of phenols in tap and river water.

Preconcentration of polycyclic aromatic hydrocarbons on polyurethane foams and their determination in waters with the use of luminescence and high-performance liquid chromatography

A technique was developed for the sorption preconcentration of polycyclic aromatic hydrocarbons on polyurethane foams in the batch and dynamic modes providing their simultaneous quantitative extraction. A procedure was proposed for screening waters for polycyclic aromatic hydrocarbons based on the preconcentration of these compounds with polyurethane foam, determination of their total amount by the luminescence method, desorption of adsorbed compounds with acetonitrile, and determination of individual compounds in the eluate by high-performance liquid chromatography with fluorescence detection. The procedure was tested with model and real samples of water.

Enantioseparation of organic acids of pharmaceutical interest using eremomycin as a chiral selector.

Strong adsorption of eremomycin on the fused‐silica capillary wall was used for separation of enantiomers by CE. The capillary with adsorbed chiral selector was shown to be easily prepared and has reproducible properties. The effect of the chiral selector concentration, pH and composition of the BGE, and applied voltage on enantioseparation of acidic compounds, such as profens and aromatic carboxylic acids, was investigated. Two native α‐amino acids, aspartic acid and glutamic acid, were enantioseparated. Fourteen tested compounds (including amino acids) were baseline resolved. Good selectivity of separation (α>1.09) was achieved. The migration order of ibuprofen and ketoprofen enantiomers was determined. The procedures were proposed for the analysis of flurbiprofen and warfarin in pharmaceuticals. Linearity was achieved in the concentration range of 4.0×10−5–2.0×10−3 M for flurbiprofen and 3.2×10−6–4.9×10−6 M for warfarin. The detection limits were found to be about 1×10−5 M for flurbiprofen and 1×10−6 M for warfarin.

Separation of pesticides by high-performance liquid chromatography with amperometric detection

The possibility of the amperometric detection of a number of pesticides, such as benomyl, thiram, linuron, metoxuron, desmedipham, dicuron, lenacil, and fludioxonil, widely used in agrochemical practice was studied. The effect of the working electrode material (glassy carbon, nickel, and gold) and the type of the electrochemical cell on the value of the analytical signal was studied using the example of thiram. It was found that the optimum potential of the working electrode in analyzing a pesticide mixture was 1400 mV. The dependence of the analytical signal on the pesticide concentration was shown to be linear. The detection limits for the analytes were calculated. Using a 100-μL sample loop, all of the studied pesticides can be determined at the level of the maximum permissible concentration (MPC). The amperometric determination of seven pesticides at the level of MPC in real samples was shown by the examples of model mixtures dissolved in tap water and beetroot juice.

Ion-Pair Chromatography of Metal Complexes of Unithiol in the Presence of Quaternary Phosphonium Salts

The chromatographic behavior of heavy-metal (Pb, Cd, Cu, Hg, and Ni) complexes of unithiol was studied by ion-pair reversed-phase chromatography using new ion-pair reagents: tetrabutylphosphonium and tributylhexadecylphosphonium bromides. The dependence of the retention of metal unithiolates on the nature and concentration of ion-pair reagents, concentrations of an organic solvent and inorganic salts in the mobile phase, and the pH of the mobile phase was studied. It was found that the retention of complexes increases upon increasing the hydrophobicity and concentration of the ion-pair reagent and upon decreasing the concentrations of acetonitrile and inorganic salts (NaClO4 and NaNO3). Optimal conditions of the separation of Pb, Cd, Cu, Hg, and Ni unithiolates were selected, and the possibility of their separate determination in a mixture was demonstrated. Concentrations of metals in process water were determined.