J. Lehotay

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.

QSRR models for potential local anaesthetic drugs using high performance liquid chromatography

Quantitative structure-retention relationships (QSRR) were proposed for Separon SGX C18 and Separon SGX Phenyl columns using physico-chemical molecular descriptors for the compounds, which are potential local anaesthetic drugs. Chemometrical methods were used for the QSRR studies of the HPLC retention factor k of 59 esters of alkoxyphenylcarbamic acid, which exhibit surface and/or infiltration anaesthetic activity. Four separation systems were used: phenyl column and acetonitrile/water mobile phase, phenyl column and methanol/water mobile phase, C18 column and acetonitrile/water mobile phase, and C18 column and methanol/water mobile phase. The values of logP and logS and ¹³C and ¹H NMR chemical shifts were simulated and utilized in calculating the corresponding QSRR models and predicting the retention factors by artificial neural networks (ANN). In addition, principal component analysis and cluster analysis were used for a closer characterization of alkoxyphenylcarbamic acid esters. The proposed ANN models, based on optimally selected species descriptors, showed a high degree of correlation between k predicted and k measured. The intercepts and the slopes of the obtained dependences were close to the theoretically expected values of 0 and 1, respectively.

In vitro study of enzymatic hydrolysis of diperodon enantiomers in blood serum by two-dimensional LC.

An on-line coupled HPLC system is described for the determination of the enantiomers of diperodon in blood serum. The method involves three steps: (i) off-line preconcentration and clean-up, (ii) separation of the diperodon enantiomers from the matrix components on a reversed-phase stationary phase, and (iii) separation of the racemate from the reversed-phase column on a teicoplanin chiral stationary phase. The method is suitable for simultaneous determination of both enantiomers in serum up to 0.5 microg/ml. The degradation of diperodon enantiomers was studied in serum by an in vitro method and the experimental rate constants were determined. The enantiomeric hydrolysis rates and half-lives for diperodon in serum are different.