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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]

The enantiomers of 1-methyl-2-piperidinoethylesters of 3- and 4-alkoxyphenylcarbamic acid were separated on vancomycin(CHIROBIOTIC V) and teicoplanin(CHIROBIOTIC T) columns isothermally in the range of 0–50°C at 10°C increments, using methanol containing 17.5 mmol/L acetic acid and 4.8 mmol/L diethylamine as the mobile phase. Lower temperatures produced the expected increase in retention of the studied enantiomers and improved their separation. The retention factors ki(as well as the resolutions Rij) were higher on the teicoplanin chiral stationary phase(CSP) compared with the vancomycin CSP. Van't Hoff plots(dependence of ln ki on 1/T) were linear within the temperature interval studied, and they also were used to determine thermodynamic data, such as the(ΔHi) and(ΔSi) of transfer of the enantiomers between mobile and stationary phases. From these results, it is evident that the prolongation of carbon atoms in the alkoxy-chain has a major influence on the values ofΔ(ΔS2,1) using the vancomycin CSP, and on the values ofΔ(ΔH2,1) using the teicoplanin CSP. However, when the alkoxy-substituent on the phenylcarbamic acid ring system is in the 3- and 4-positions, there seems to be little difference in the thermodynamic parameters. [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 Whelk-O 1 chiral stationary phase (CSP) is an useful column for the high performance liquid chromatographic (HPLC) resolution of enantiomers of 2-methoxy-1-[(4-methylpiperazino)methyl]ethyl esters of N-(2-,3-, and 4-alkoxyphenyl)carbamic acid (group of the local anaesthetic drugs) in the polar organic mode and the reversed mode. According to the results of enantiomeric separations in different mobile phases [containing organic modifiers (methanol, acetonitrile, water), with different additives of acetic acid and trimethylamine], it can be postulated that the piperazino part of the phenylcarbamic acid compound is essential because the separation of piperidino, pyrrolidino, and perhydroazepino esters of alkoxy phenylcarbamic acid were not observed. Also the influence of the environment near the analyte's stereogenic is important for enantioseparation. A comparison of the enantiomeric elution order and the configuration of the chiral selector shows that R-(−) enantiomers are more retained on the (R,R) Whelk-O 1 column and S-(+) enantiomers are more retained on the (S,S) Whelk-O 1 column. [ABSTRACT FROM AUTHOR]

Enantiomeric separation of alkoxysubstituted esters of phenylcarbamic acid (local anesthetic drugs) is carried out using high performance liquid chromatography (HPLC) with two chiral stationary phases. The teicoplanin chiral stationary phase—chirobiotic T and the teicoplanin chiral stationary phase without the pendant carbohydrate moieties—chirobiotic teicoplanin aglycone (TAG) were used. The influence of the sugar units, the concentration of the ionic modifiers (diethylamine), the influence of the position and of number of carbon atoms in the analytic alkoxychain substituent, and the composition of the mobile phase; on retention factors and resolution of enantiomers were investigated. By comparison of chromatographic parameters obtained by using both chiral stationary phases, the influence of carbohydrate moieties on the mechanism of chiral separation could be evaluated. The interaction mechanism of the enantiomeric separations is discussed. Better separation, in terms of—greater values of Rij of enantiomers—was achieved with the chirobiotic TAG column. [ABSTRACT FROM AUTHOR]