Strategies for predictive modeling of overloaded oligonucleotide elution profiles in ion-pair chromatography

Impact of ion-pairing systems choice on diastereomeric selectivity of phosphorothioated oligonucleotides in reversed-phase liquid chromatography

Ion-pairing reversed-phase liquid chromatography was utilized for the analysis of native and phosphorothioated oligonucleotides differing in the length (2-6mers and 21mer) and the number and position of phosphorothioate modifications. We investigated the influence of counterion (acetate vs. hexafluoroisopropanol) on the adsorption of eleven alkylamines on the stationary phases. A stronger adsorption of charged alkylamines on octadecyl- and phenyl-based stationary phases led to greater retention of oligonucleotides, and the adsorption of alkylamines was promoted with greater concentration of hexafluoroisopropanol in the mobile phase. Selected amines (triethylamine, dipropylamine, hexylamine) were used to study the resolution of n and n-x mers (main peak and its impurities shortened at 5´end), and diastereomeric separation of phosphorothioated oligonucleotides. The results confirmed a crucial role of alkylamine and counterion choice on the diastereomeric separation. The increasing hydrophobicity of alkylamine led to diminished diastereomeric selectivity which produced narrower phosphorothioated oligonucleotides peaks and led to improved n/n-x separation. Using hexafluoroisopropanol instead of acetate as counterion further enhances this effect (except for 100 mM concentration of hexafluoroisopropanol in combination with highly hydrophobic hexylamine). The elevated column temperature led to suppression of the diastereomeric resolution and improved resolution of n and n-x mers oligonucleotides. Baseline separation of oligonucleotides with different number of phosphorothioate linkages was achieved; this may be useful for therapeutic oligonucleotide analysis.

Sequential purification of cannabidiol by two-dimensional liquid chromatography combined with modeling and simulation of elution profiles

Cannabidiol (CBD) has garnered significant attention for its neuroprotective properties, and research on its therapeutic effects has increased dramatically in recent years. However, the systematic purification of CBD through scalable processes has remained bottleneck due to the structural similarities of the cannabinoids. Although preparative chromatography is considered as a potential solution, it is usually time-consuming and expensive. Therefore, the development of scalable strategy via fast and accurate optimization approach is crucial. The present study aimed to develop a sequential process for the scalable purification of CBD through an eco-friendly ethanolic extraction using ultrasonic assisted extraction, decarboxylation of cannabidiolic acid optimized by response surface methodology, followed by the development of off-line two-dimensional semi-preparative chromatography, boosted with stacked injection overloading. In the first dimension, a column packed with macroporous resin allows to enrich the target substance and then, the behavior of resin column for scale-up procedure were predicted and optimized by developed mathematical model. A C18 column was used in the second dimension. The CBD purity and recovery obtained were 94.3 and 82.1 %, respectively. A robust and reliable method was employed for CBD enrichment/purification, which can be generalized to other bioactive compounds in complex matrices.