Separation of cannabinoids on three different mixed-mode columns containing carbon/nanodiamond/amine-polymer superficially porous particles.

Three mixed-mode high-performance liquid chromatography columns packed with superficially porous carbon/nanodiamond/amine-polymer particles were used to separate mixtures of cannabinoids. Columns evaluated included: (i) reversed phase (C18 ), weak anion exchange, 4.6 × 33 mm, 3.6 µm, and 4.6 × 100 mm, 3.6 µm, (ii) reversed phase, strong anion exchange (quaternary amine), 4.6×33 mm, 3.6 µm, and (iii) hydrophilic interaction liquid chromatography, 4.6 × 150 mm, 3.6 µm. Different selectivities were achieved under various mobile phase and stationary phase conditions. Efficiencies and peak capacities were as high as 54 000 N/m and 56, respectively. The reversed phase mixed-mode column (C18 ) retained tetrahydrocannabinolic acid strongly under acidic conditions and weakly under basic conditions. Tetrahydrocannabinolic acid was retained strongly on the reversed phase, strong anion exchange mixed-mode column under basic polar organic mobile phase conditions. The hydrophilic interaction liquid chromatography column retained polar cannabinoids better than the (more) neutral ones under basic conditions. A longer reversed phase (C18 ) mixed-mode column (4.6 × 100 mm) showed better resolution for analytes (and a contaminant) than a shorter column. Fast separations were achieved in less than 5 min and sometimes 2 min. A real world sample (bubble hash extract) was also analyzed by gradient elution.

Influence of the mobile phase composition on chiral recognition of some pyrrolidin-2-ones in the liquid chromatographic system with polysaccharide stationary phases.

Chiral separations of a series of 15 pyrrolidin-2-ones on polysaccharide stationary phases in the HPLC system have been reported. Three stationary phases have been applied: Chiralpak AD, Chiralpak IA and Chiralcel OD. The changes of retention and enantioselectivity have been examined depending on the organic modifier (ethanol or 2-propanol). The addition of a small amount of water has also been studied. Amylose columns exhibit better enantioselectivity (higher alpha values) than cellulose ones. All compounds can be enantiomerically separated on a Chiralpak IA column with EtOH as the organic modifier. The separation of all compounds on a Chiralpak AD and Chiralcel OD columns required changes of mobile phase composition. Depending on the structure of the compounds, the type of stationary phase, as well as the composition of the mobile phase, different intermolecular interactions can play a key role in chiral discrimination.

Determination of diastereomerization barrier of some flavanones by high-performance liquid chromatography methods.

The rate constants and activation energy barriers DeltaG# of diastereomerization reaction of flavanones: naringin, narirutin, hesperidin and neohesperidin were determined. The stopped-flow HPLC (SFM-HPLC), dynamic HPLC (D-HPLC) and enantioselective HPLC combined with the classical kinetic method were applied for determination of these parameters. It was found that the rate constants of diastereomerization were about eight times higher for naringin and narirutin (1.9 x 10(-5) s(-1)) than for hesperidin and neohesperidin (2.4 x 10(-6) s(-1)). No significant differences in the rate of diastereomerization were found between neohesperidosides and corresponding rutinosides.

An HPLC method for the indirect quantification of a quinone adduct of the drug paroxetine.

An HPLC method has been developed which enables the quantification of low levels of a catechol derivative and a quinone adduct of paroxetine in the presence of excess drug substance. Due to its inherent instability, the paroxetine quinone adduct is not available as a pure compound so that an indirect method was developed for its quantification. This procedure is based on the assumption that one molecule of the catechol (or more precisely the corresponding 1,2-benzoquinone) reacts with one molecule of paroxetine to produce one molecule of paroxetine quinone adduct. In the presence of paroxetine excess, pseudo-first-order kinetics was used to study the formation of the unstable product. A detector response factor for the paroxetine quinone adduct was calculated as a function of the response factor for the paroxetine catechol derivative, after considering a mass balance of the reaction. Using the methodology outlined, quantitative analysis was carried out of the paroxetine catechol derivative and the paroxetine quinone adduct in batches of paroxetine drug substance.

Thermodynamic studies of complexation and enantiorecognition processes of monoterpenoids by alpha- and beta-cyclodextrin in gas chromatography.

Gas-liquid chromatography was applied in thermodynamic investigations of processes of complexation and enantioseparation by alpha- and [-cyclodextrins of chiral monoterpenoids. The distribution constants, stability constants and thermodynamic parameters enthalpy, entropy and free energy of the complexation processes were determined. It has been found that enantioseparation of monoterpenes by alpha- and beta-cyclodextrins is the result of formation of 1:2 stoichiometric complexes. When 1:1 stoichiometric complexes are formed, enantioselectivity is not observed. All investigated processes of complexation are enthalpy-driven regardless of the stoichiometry of the formed complexes. -deltaH, -TdeltaS and -deltaG of complexation process have higher values for bicyclic than for monocyclic monoterpenoids as well as for alpha-CD than for beta-CD. The first or second step of complexation may be responsible for enantioselectivity.

Evaluation of a new wide-pore superficially porous material with carbon core and nanodiamond-polymer shell for the separation of proteins.

In this study, reversed phase liquid chromatographic columns packed with superficially porous material made of a carbon core and nanodiamond-polymer shell were evaluated for the analytical characterization of proteins. The emphasis was put on the impact of pore size on the kinetic performance when analyzing large molecules. Three different types of columns possessing an average pore size of 120, 180, and 250Å were thus evaluated. As expected, the peak capacities were improved with the 180 and above all the 250Å pore size, while the kinetic performance achieved with the 120Å were systematically lower. It was also shown that a trifluoroacetic acid (TFA) concentration of 0.3-0.5% was required when analyzing proteins, to achieve suitable peak shapes (limited broadening and tailing) with this material. Elevated temperature (>60°C) is mandatory when analyzing proteins with silica-based stationary phases, but this was not the case with this particular column made with a carbon core and nanodiamond-polymer shell, since the peak capacities were not improved at high temperature. However, there was a need to increase mobile phase temperature in the range 70-90°C when analyzing monoclonal antibodies (mAbs), to limit adsorption that often occur in RPLC with this specific class of biomolecules. Finally, the FLARE(®) wide-pore column was applied to real life samples of native, oxidative stressed and reduced therapeutic proteins as well as reduced, digested mAbs and antibody drug conjugates (ADCs), to highlight the possibilities offered by this column technology.

Chiral separation of basic drugs by capillary electrophoresis with carboxymethylcyclodextrins.

Capillary electrophoresis (CE) with carboxymethylated beta- or gamma-cyclodextrins was used to achieve the rapid enantiomeric separation of a set of basic drugs. The enantiomers of 12 chiral amino-containing pharmaceutical compounds belonging to various therapeutic categories were analyzed by CE using an uncoated 60 cm x 75 microm I.D. silica capillary. Several experimental parameters such as the nature, concentration and pH of the buffer, nature and concentration of the anionic cyclodextrin and temperature were studied in order to optimize the enantiomeric separation. The variation of the solute partition coefficient for the chiral selector, the enantioselectivity and resolution factors are used to assess the quality of the chiral separation. It is shown that the solute affinity for the chiral selector is not related to its enantioresolution factor. None of the two cyclodextrin selectors used was able to separate the whole set of basic drugs.

Chiral HPLC method for chiral purity determination of paroxetine drug substance.

This article describes a chiral HPLC method for (+) trans isomer of paroxetine in a paroxetine drug substance. The method development was performed to establish a suitable HPLC system in order to separate both enantiomers. It was found that a system based on a Chiralpak AD column was suitable for the analysis. Proper column maintenance and the optimized eluent composition allowed good reproducibility and sensitivity for the method. The method was also checked on a number of different columns using different HPLC equipment and gave both reproducible chromatography and reproducible quantitative results.