The Enantioselective Potential of NicoShell and TeicoShell Columns for Basic Pharmaceuticals and Forensic Drugs in Sub/Supercritical Fluid Chromatography.

The enantioselective potential of two macrocyclic glycopeptide-based chiral stationary phases for analysis of 28 structurally diverse biologically active compounds such as derivatives of pyrovalerone, ketamine, cathinone, and other representatives of psychostimulants and antidepressants was evaluated in sub/supercritical fluid chromatography. The chiral selectors immobilized on 2.7 µm superficially porous particles were teicoplanin (TeicoShell column) and modified macrocyclic glycopeptide (NicoShell column). The influence of the organic modifier and different mobile phase additives on the retention and enantioresolution were investigated. The obtained results confirmed that the mobile phase additives, especially water as a single additive or in combination with basic and acidic additives, improve peak shape and enhance enantioresolution. In addition, the effect of temperature was evaluated to optimize the enantioseparation process. Both columns exhibited comparable enantioselectivity, approximately 90% of the compounds tested were enantioseparated, and 30% out of them were baseline enantioresolved under the tested conditions. The complementary enantioselectivity of the macrocyclic glycopeptide-based chiral stationary phases was emphasized. This work can be useful for the method development for the enantioseparation of basic biologically active compounds of interest.

The effect of tandem coupling of NicoShell and TeicoShell columns in sub/supercritical fluid chromatography on enantioresolution.

The coupling of columns in sub/supercritical fluid chromatography presents a great opportunity for influencing the separation efficiency and extending the selectivity of the separation system. Combinations of different types of chiral stationary phases could positively affect the enantioresolution if single ones are complementary to each other. In this work, two superficially porous particle (2.7 µm) macrocyclic glycopeptide-based columns, namely TeicoShell and NicoShell, were serially coupled and tested in sub/supercritical fluid chromatography for the first time. The influence of the column arrangement on the enantioseparation of structurally diverse biologically active compounds was examined. The obtained results showed how the column order crucially affected the enantioresolution of compounds tested, but the retention was negligibly affected in most cases. We also demonstrated that single TeicoShell and NicoShell columns are very promising towards the development of highly efficient and fast/ultrafast sub/supercritical fluid chromatography methods for structurally different chiral compounds. The optimized methods for sub-minute enantioselective separation of certain biologically important compounds were proposed.

Enantioseparation performance of superficially porous particle vancomycin-based chiral stationary phases in supercritical fluid chromatography and high performance liquid chromatography; applicability for psychoactive substances.

Novel psychoactive substances (NPS) are synthetic compounds that have been designed to produce the physiological and psychological effects of known recreational drugs, while circumventing current drug control laws and scheduling guidelines. Such "designer drugs" pose problems in detection and prevention of use, and they are no less dangerous than known controlled substances. Among the various classes of NPS, many are chiral. As they are synthetic products, most are racemates. Not unexpectedly, there is limited information about different the pharmacological and toxicological properties of their pure enantiomers. Hence, fast and reliable enantioselective methods are of great interest. In this work, superficially porous particle (SPP) vancomycin-based chiral stationary phases were used for development of fast enantioselective separation methods for various classes of NPS in supercritical fluid chromatography and liquid chromatography. The NPS tested included pyrovalerones, benzofurans, phenidines and phenidates. The effect of mobile phase composition on the retention and resolution of NPS in supercritical fluid chromatography was examined. The amount as well as the ratios of additives used is crucial for enantioseparation efficiency. Results showed the high enantioselective potential of vancomycin-based columns in both chromatographic techniques; 88% of NPS tested were enantioseparated in supercritical fluid chromatography and 69% of NPS tested were enantioseparated in liquid chromatography. Moreover, under optimized conditions, simultaneous enantioseparations of some NPS were achieved, which indicates great suitability of vancomycin-based columns for this purpose. The proposed methods can serve as guides for method development and for enantioseparation of further upcoming NPS.

Macrocyclic glycopeptide-based chiral selectors for enantioseparation in sub/supercritical fluid chromatography.

Increasing number of reported works dealing with macrocyclic glycopeptide-based columns in sub/supercritical fluid chromatography (SFC) points to the growing interest in this area. With the development and production of sub 2 µm fully porous particles and superficially porous particles with bonded macrocyclic glycopeptides, significant improvements have been made in ultrafast high efficiency chiral SFC. This review article gives an overview of macrocyclic glycopeptide-based chiral selectors that were used in theoretical studies and/or applications in SFC. The review covers the period from 1997 when macrocyclic glycopeptides were first used in SFC till the end of July 2020 according to Web of Science. This work can also be helpful to analysts searching for an appropriate method for the separation/determination of enantiomers of their interest.

Method for evaluation of ionic interactions in liquid chromatography.

In this work we utilized basic and acidic analytes to investigate the ionic interaction participation in retention behavior of selected reversed-phase and polar columns. The test analytes included nitrate, benzenesulfonate and trimethylphenylammonium ions. The fully aqueous mobile phase comprising 10 mM dichloroacetic acid buffered with ammonia solution to desirable pH was used for retention experiments. Developed method was utilized to study the ionic interactions of stationary phases in pH range between 2.5 and 9.0. We demonstrate that selected sorbents used for reversed-phase and hydrophilic interaction chromatography separations exhibit cation- or anion-exchange interactions. We compare the results to novel Atlantis PREMIER BEH C18 AX mixed-mode column that combines reversed-phase and anion-exchange interaction modes. We evaluated the relative retention strength of selected columns for anionic and cationic analytes.

Enantiorecognition ability of different chiral selectors for separation of liquid crystals in supercritical fluid chromatography; critical evaluation.

Comprehensive study of enantioselective potential of eight different chiral stationary phases for chiral liquid crystal-forming molecules was conducted. The tested columns were: (i) polysaccharide-based Trefoil AMY1, CEL1 and CEL2 and (ii) superficially porous particles packed TeicoShell, VancoShell, TagShell, DMP-MaltoShell, and NicoShell. To test their enantioselective potential for these separations, twenty racemic mixtures of rod-like liquid crystalline materials comprising three different types of chiral centres and various other structural differences were used. Mobile phases consisting of supercritical carbon dioxide and alcohol as cosolvent were used; selected alcohols were methanol, ethanol and propan-2-ol. Effect of acidic and/or basic additives on enantioselectivity was also evaluated. Chiral stationary phases based on polysaccharides were found to have the greatest enantioselective potential for rod-like molecules that form liquid crystals, followed by TeicoShell, which proved suitable for enantioseparation of non-halogenated liquid crystals with lactic acid-based chiral centre.

Enantioselective potential of teicoplanin- and vancomycin-based superficially porous particles-packed columns for supercritical fluid chromatography.

Application of the superficially porous particles (SPPs) grafted with chiral selectors can substantially improve resolution in chromatographic techniques. In this work, we carried out a deeper study on supercritical fluid chromatography systems with 2.7 µm SPPs bonded with teicoplanin and vancomycin. Fast separations of the majority of enantiomers of phytoalexins, substituted tryptophans, and ketamine derivatives, as representatives of important biologically active and structurally diverse chiral compounds have been achieved. The chromatographic behavior of the structurally different analytes served to characterize these separation systems. The influence of separation conditions, namely mobile phase composition, i.e. type of co-solvent and additive on retention, enantioselective resolution and enantioselectivity was examined. The success rate of baseline and partial separations in individual groups of compounds differed with the chiral stationary phase and also with mobile phase composition. The best, baseline separations for the phytoalexins were achieved on the TeicoShell column using methanol as a co-solvent and trifluoroacetic acid as an additive if used. Mostly partial separations were achieved on the vancomycin-based column for all groups of analytes. Complementary separation behavior of these CSPs was confirmed for the majority of the chiral compounds examined in this work.

The degree of substitution affects the enantioselectivity of sulfobutylether-ß-cyclodextrin chiral stationary phases.

Three chiral stationary phases were prepared by dynamic coating of sulfobutylether-ß-cyclodextrin (SBE-ß-CD) with different degrees of substitution, onto strong anion-exchange stationary phases. The enantioselective potential and stability of newly prepared chiral stationary phases were examined using a set of structurally different chiral analytes. Measurements were performed in RP-HPLC. Mobile phases consisted of methanol/formic acid, pH 2.10, and methanol/10 mM ammonium acetate buffer, pH 4.00, in various volume ratios. SBE-ß-CDs with degrees of substitution (DS) 4, 6.3, and 10 proved suitable for the enantioseparation of 14, 11, and 8 analytes, respectively. The SBE-ß-CD DS 4 based chiral stationary phase enabled the enantioseparation of the nearly all basic and neutral compounds. Chiral stationary phases with higher sulfobutylether-ß-cyclodextrin substitution (especially DS 10) yielded higher enantioresolution values for acidic compounds.