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Dicoumarol is a mycotoxin, that acts as a blood anticoagulant, is formed during the microbial action of molds and fungi in spoiled hay or silage containing high-coumarin plant. A HPLC-DAD method for determination of coumarins, including dicoumarol, coumarin, and 4-hydroxycoumarin was developed. Methanol and acetic acid were used as mobile phase with gradient elution. The simultaneous separation was performed using C18 type of stationary phase. The recoveries were 88.6 – 92.6 %, 91.8 – 95.0 %, and 89.7 – 94.1 % (evaluated for three concentration levels) for dicoumarol, coumarin, and 4-hydroxycoumarin respectively. The parameters of system suitability (repeatability of retention times and peak areas) were determined for evaluation of the method. The method showed a good linearity in the concentration range 0.7 – 100 μg.mL−1 for dicoumarol, 0.05 – 100 μg.mL−1 for coumarin and 4-hydroxycoumarin with correlation coefficients higher than 0.9885. Extracts of sweet clover herb, hay, and spoiled hay were subjected to HPLC-DAD analysis. The most abundant compound in sweet clover herb and hay extracts was coumarin. In spoiled sweet clover hay extract the 4-hydroxycoumarin was detected in addition. The formation of 4-hydroxycoumarin was also observed in the synchronous fluorescence spectra recorded at the wavelength difference of 90 nm (difference between emission and excitation wavelength).

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Four macrocyclic glycopeptide chiral stationary phases (CSPs) based on native teicoplanin (Chirobiotic T), methylated teicoplanin aglycone (Chirobiotic m‐TAG), teicoplanin aglycone (Chirobiotic TAG), and vancomycin (Chirobiotic V) were compared for the high performance liquid chromatographic (HPLC) separation of enantiomers of 1‐methyl‐2‐piperidinoethylesters of 2‐, 3‐and 4‐ alkoxyphenylcarbamic acid (potential local anaesthetic drugs). The enthalpies (Δ H i ), entropies (Δ S i ), and Gibbs energies (Δ G i ) of transfer were evaluated for the separation of these compounds. The enantiomers were separated isothermally in the range of 0–50°C with 10°C increments, in the polar organic mode. The thermodynamic parameters were calculated in order to gain an understanding of the driving forces for retention in this chromatographic system. From these results, it is evident that the elongation of the alkoxy‐chain has major influence on the values of (Δ S i ) when using the vancomycin CSP and on the values of (Δ H i ) using the teicoplanin‐type CSPs. [ABSTRACT FROM AUTHOR]

In the present study, the HPLC method on a C 18 column with on-line spectrophotometric and fluorimetric detection was used for separation and determination of dehydroabietic acid and abietic acid in propolis. The samples of propolis tincture were prepared prior to the HPLC analysis. The mobile phase for isocratic elution was methanol-water 87:13 containing 0.05% formic acid. Abietic acid was detected with spectrophotometric detection at 238 nm, and dehydroabietic acid was detected with fluorimetric detection (excitation 225 nm, emission 285 nm). The limits of determination (signal/noise ratio 10) were 100 ng/mL for dehydroabietic acid and 200 ng/mL abietic acid. The calibration graphs were linear over a wide interval from the limit of determination to 1 mg/mL. Analytical recovery and reproducibility exceeded more than 89%. The developed method was used for analysis of propolis from Slovakia. Mass spectrometry was used for identification of the studied acids. The results demonstrated that dehydroabietic acid was present in all tested samples of propolis. Its content was different (3.7 µg/g–44.7 µg/g of propolis) depending on the source of propolis. [ABSTRACT FROM AUTHOR]

The isocratic retention of enantiomers of chiral analytes (1-methyl-2-piperidinoethylesters of 2-, 3-, and 4-alkoxyphenylcarbamic acid, potential local anaesthetic drugs) was studied on a methylated teicoplanin CSP, at different temperatures (in the range of 0–50°C with 10°C increments) in the polar organic mode (the mobile phase composition consisted of methanol with 17.5 mmol/L acetic acid and 4.8 mmol/L diethylamine). The natural logarithms of the retention factors (ln ki) of the investigated chiral compounds depended linearly on the inverse of temperature (1/T). van't Hoff plots afforded thermodynamic parameters, such as the apparent change in enthalpy (ΔHi), the apparent change in entropy (ΔSi), and the apparent change in Gibbs free energy (ΔGi) for the transfer of analyte between the mobile phase and the stationary phase. The thermodynamic parameters were calculated in order to promote an understanding of the thermodynamic driving forces for retention in this chromatographic system. Enthalpy–entropy compensation plots showed that all of the compounds in this study separate via the same enthalpy driven chiral recognition mechanism. [ABSTRACT FROM AUTHOR]

It has been found that the teicoplanin aglycone (CHIROBIOTIC TAG) chiral stationary phase is a useful column for the high performance liquid chromatographic (HPLC) separation of enantiomers of 1-methyl-2-piperidinoethylesters of 2-, 3- and 4-alkoxy-phenylcarbamic acid (potential local anaesthetic drugs) in the polar organic mode. The enantiomers were separated on a CHIROBIOTIC TAG column, isothermally in the range of 0–50°C with 10°C increments, using methanol [100 mL (v)] containing 17.5 mmol L−1 acetic acid and 4.8 mmol L−1 diethylamine as a mobile phase. van't Hoff plots (dependence of ln ki on 1/T, where k is the retention factor of a solute i and T is the temperature) were linear in the studied temperature interval. This allowed the determination of interaction enthalpies (ΔHi), entropy (ΔSi), and Gibbs energies (ΔGi). This thermodynamic information was used to evaluate the retention and resolution of enantiomers of studied analytes in this HPLC system. [ABSTRACT FROM AUTHOR]

The melting temperature of nine piperidinoethyl esters of alkoxyphenylcarbamic acid (hexaoxy-octyloxy) including all site isomers was investigated. The analyses were performed using DSC apparatus, sample mass ranged from 0.2 to 2.5 mg, heating rate was 5 K min-1 and in static air atmosphere. On the basis of melting peak, thermodynamic figures like: enthalpy, entropy, height and area of the peak and temperature of the partial peak were fixed. For evaluation of the results Principal Component Analysis was applied. Thanks to this method the influence of length (mass) and position of alkoxy substituents on the thermodynamic parameters of melting of compounds under investigation were determined. [ABSTRACT FROM AUTHOR]

The HPLC by using chiral stationary phases based on macrocyclic antibiotics, dimethylphenyl carbamate cyklofructan 7 and β-cyclodextrin in terms of polar-organic separation mode (mobile phase methanol/acetonitrile/acetic acid/triethylamine) were used for enantioseparation of alkoxy derivatives of phenylcarbamic acid. The effect of the analyte structures on the efficiency of enantioseparation was investigated. The most suitable stationary phase was teicoplanin aglycone, where the separations of the enantiomers were obtained (the resolution value from 0.65 to 2.90, depending on the structure of the analyte). Significant effect on the resolution of the enantiomers has position of alkoxy substituent in the hydrophobic part of the molecule. The enantiorecognition was achieved for 3-alkoxysubstituted derivatives.