Ivan Skačáni

The Use of Molecularly Imprinted Polymer for Selective Extraction of (+)‐Catechin

Abstract Molecularly imprinted polymer (MIP) was prepared using acrylamide and ethylene glycol dimethacrylate (EDMA) as functional and crosslinking monomers, respectively. (+)‐Catechin (C) was chosen as the template molecule and solvent acetonitrile as porogen. The polymer was investigated as solid‐phase extraction (SPE) sorbent for the clean‐up of organic extracts of green tea. Specific binding capacity of prepared MIP was evaluated by comparison of specifically and nonspecifically [on blank polymer (BP)] bound amounts of C. Different media were tested for this purpose: acetonitrile, methanol, and water and the results were compared. The best specific capacity (3.84 µg/100 mg of MIP) was obtained in acetonitrile, which was used as porogen. This solvent was chosen for the next evaluation of the binding capacity of polymer for the other six catechins that occur in green tea. The MIP showed good selectivity towards C in the presence of structurally related compounds. Next, several washing solvents were applied to the developed SPE procedure with the aim to obtain maximum recovery for C. Acetonitrile, water, and methanol, with different additions of acetic acid, were used for this purpose. It was observed that water and acetonitrile are suitable for washing out of interferences, and the best elution solvent was methanol without any presence of acid. Very good recovery (95%) for C was obtained using the developed molecularly imprinted SPE (MISPE) procedure. The results of the presented work show that prepared MIP can be used as SPE sorbent for the clean‐up of methanol extract of green tea.

Isotachophoretic determination of naproxen in the presence of its metabolite in human serum

An isotachophoretic method with conductivity detection was developed to determine naproxen in the presence of its metabolite 6-O-desmethylnaproxen in human serum. The leading electrolyte contained 10 mM hydrochloric acid, beta-alanine, pH 4.0 and 0.1% methylhydroxypropylcellulose. The terminating electrolyte was 10 mM 2-(N-morpholino)ethanesulfonic acid-tris(hydroxymethyl)aminomethane, pH 6.9, containing 20% (v/v) of ethanol. Naproxen was determined in serum supernatant after simple deproteination of the sample with ethanol. The isotachophoretic results were compared with those obtained by synchronous fluorescence spectrometry.

GAS CHROMATOGRAPHIC SEPARATION OF PCB ATROPISOMERS ON CYCLODEXTRIN STATIONARY PHASES

Gas chromatographic study on chiral separation of PCBs was performed in a series of capillary columns coated with 0.1-μm film of modified cyclodextrin (CD) stationary phases. The preparation of columns included the investigation into the effect of the content of cyclodextrin derivative in polysiloxane, the type of polysiloxane and temperature of analysis on the quality of separation and retention of atropisomers of 15 selected PCB congeners. The separation properties towards PCBs of stationary phase heptakis(2,3-di-O-methyl-6-O-tert-butyl-dimethylsilyl)-β-CD dissolved in SE-30, SE-54, and OV-1701, were compared with those of 6-monokis-octamethylene-permethyl-β-CD anchored to polydimethylsiloxane polymer (ChirasilDex column, Chrompack, Middelburg, The Netherlands) and octakis(2,6-di-O-methyl-3-O-pentyl)-γ-CD in OV-1701 (MEGA, Legnano (MI), Italy). The correctness of quantitative enantiomer ratio determination was assesed by splitless analysis of PCBs reference solutions in concentration of 1.25–125 ng/ml (PCBs 45 and 91) and 2.5–250 ng/ml (PCB 95) (the PCB congeners are numbered according to IUPAC). Chirality 10:540–547, 1998.

Isolation of L‐Theanine from Plant Material using a Molecularly Imprinted Polymer

Abstract Nylon‐6 was used as a molecularly imprinted polymer (MIP). For imprinting L‐theanine (5‐N‐ethylglutamine) in the polymer, 2.0 g of Nylon‐6, 0.8 g (MIP 1), and 1.2 g (MIP 2), respectively, of L‐theanine templates and 7.2 g of formic acid was used for the phase inversion process in water. The resulting polymers, including the template molecule, were washed with acetic acid solution to extract the template from the polymers. The polymers were investigated as solid phase extraction (SPE) sorbents for the cleanup of water extracts of green tea. Various amounts of the template in the polymerization mixture had no influence on sorptive properties of MIPs in the range under study. Water was found as a suitable solvent for sample loading. The selective binding capacity of MIPs was 3.49 µg/1 g MIP. Water with addition of acetic acid (2% by volume) was used as an elution solvent. The recovery of the MISPE procedure was 87.8%±5.5%.

Isolation of Some Derivatives of Phenylcarbamic Acid from Human Plasma using Molecularly Imprinted Polymers

Abstract Two molecularly imprinted polymers for 1–methyl–2–piperidinoethyl ester of 4–decyloxyphenylcarbamic acid (template) have been synthesized using a non–covalent imprinting approach. Acrylamid and methacrylic acid, respectively, were used as the functional monomers. Imprinted polymers were used as the sorbents for solid phase extraction (MISPE). The capacity and selectivity of prepared imprinted polymers was investigated. The non-imprinted (blank) polymers were prepared by the same way, without the template, to study the non-specific interactions. Molecularly imprinted polymers were used to extract derivatives of alkoxyphenylcarbamic acid from spiked human plasma. C18 sorbent was also used for SPE to compare the efficiency of the procedure.

On the calculation of Gibbs energy corresponding to enantioselective interactions at a direct HRGC separation of enantiomers.

A novel procedure is proposed for the calculation of Gibbs energy corresponding to enantiospecific interactions of 2-(2, 4-dinitrophenoxy)-, 2-phenoxy-, and 2-halogen-n-pentane enantiomers with a beta-cyclodextrin (ChirasilDex) stationary phase under gas chromatographic conditions. This energy is calculated from retention data as a difference between the Gibbs energy of an enantiomer and its corresponding achiral congener. The procedure for the determination of 2-(2,4-dinitrophenoxy)-, 2-phenoxy- and 2-halogen- n-pentane achiral congener retention data is discussed in detail.

Molecularly Imprinted Solid-Phase Extraction of 1-Methyl-2-piperidinoethylesters of Alkoxyphenylcarbamic Acid from Human Plasma, Comparison with Classical Solid-Phase Extraction

Abstract Molecularly imprinted polymers for 1-methyl-2-piperidinoethylester of 2-methoxyphenylcarbamic acid (template) have been synthesised using a non-covalent imprinting approach. Acrylamid and methacrylic acid, respectively, were used as the functional monomers. Imprinted polymers were used as the sorbents for solid-phase extraction (MISPE). The capacity and selectivity of prepared imprinted polymers was investigated. The non-imprinted (blank) polymers were prepared by the same way without template to study the non-specific interactions. Molecularly imprinted polymer prepared from methacrylic acid was used to preconcentrate 1-methyl-2-piperidinoethylester of 2-methoxyphenylcarbamic acid and its analogues from spiked human plasma.

Determination of fendiline and gallopamil by capillary isotachophoresis

Capillary isotachophoresis was applied for the determination of fendiline and gallopamil--calcium antagonists--in serum. The cationic electrolyte system containing Na+ with acetic acid as a counter constituent was used as a leading electrolyte with the pH 4.7 and the terminating electrolyte was beta-alanine. Most of the proteins were precipitated with methanol, ethanol and dimethylketone. The lowest limits of quantitation were obtained for the pretreatment of serum with methanol. The recoveries of both compounds varied from 91.3 to 97.5%. The relative standard deviations varied from 0.6 to 7.7%.