An easy-to-use calculating machine to simulate steady state and non-steady-state preparative separations by multiple dual mode counter-current chromatography with semi-continuous loading of feed mixtures

Modeling the liquid-liquid chromatography separation of cannabinoids from hemp extracts

The separation of cannabinoids from hemp materials is nowadays one of the most promising industrial applications of liquid-liquid chromatography (LLC). Despite various experimental research efforts to purify cannabinoids, there are currently few works on process modeling. Thus, this study aimed to explore a straightforward approach to model the LLC separation of cannabinoids from two hemp extracts with different compositions. The feed materials were simplified to mixtures of preselected key components (i.e., cannabidiol, tetrahydrocannabinol, cannabigerol, and cannabinol). The elution profiles of cannabinoids were simulated using the equilibrium-cell model with an empirical nonlinear correlation. The model parameters were derived from the elution profiles of single-solute pulse injections. For the validation of the proposed approach, LLC separations with the two hemp extracts were performed in descending mode with the solvent system composed of hexane/methanol/water 10/8/2 (v/v/v). The injected sample concentrations were gradually increased from 5 to 100 mg/mL. The results showed that the approach could describe reasonably well the elution behavior of the cannabinoids, with deviations of only 1-2 min between simulated and experimental elution times. However, to improve the prediction accuracy, the model parameters can be refitted to the elution profiles of 3-4 systematically selected pulse injections with specific hemp extracts.

Comparison of two different multiple dual-mode counter-current chromatograph for separation of ketoconazole enantiomers

In this work, two different multiple dual-mode (MDM) counter-current chromatography methods, conventional MDM and modified MDM elution modes, were compared for the chiral separation of the ketoconazole enantiomers. The biphasic solvent system which consisted of n-hexane: isobutyl acetate: 0.1 mol/L phosphate buffer (2:4:6, v/v) (pH = 8.5) was employed as stationary phase and mobile phase. And the hydroxypropyl-β-cyclodextrin (HP-β-CD) with a concentration of 100 mmol/L was dissolved in the phosphate buffer, as the chiral selector. Under two different methods, dual-mode (DM) elution was performed to determine the time of the transformed phase roles and multiple cycles were performed to isolate ketoconazole, respectively. The result indicated that the modified MDM elution had a significant improvement on the separation, increasing the resolution from 0.51 to 1.19, while the resolution was increased from 0.40 to 0.79 by the conventional MDM elution. Ultimately, baseline separation of ketoconazole enantiomers was essentially achieved by high-speed counter-current chromatography under optimized modified MDM separation conditions. The final recoveries of the two enantiomers, R-(K) and S-(K), were 92.5 % and 83.3 %, respectively, corresponding to enantiomeric excess values of 99.0 % and 97.0 %, as determined by HPLC.

An overview of recent progress in multiple dual-mode counter-current chromatography

Counter-current chromatography is a chromatographic separation and purification technique being developed. The development of different elution modes has significantly contributed to this field. Multiple dual-mode elution is a method developed based on dual-mode elution, which consists of a series of changing cycles of the phase role and the direction by switching between normal and reverse elution modes of counter-current chromatography. This dual-mode elution method takes full advantage of the liquid nature of stationary and mobile phases of counter-current chromatography and effectively improves the separation efficiency. So, this unique elution mode has gained extensive attention for separating complex samples. This review mainly describes and summarizes in detail its development, applications, and characteristics in recent years. Meanwhile, its advantages, limitations, and future outlook also have been discussed in this paper.

Analytical, Preparative, and Industrial-Scale Separation of Substances by Methods of Countercurrent Liquid-Liquid Chromatography

Countercurrent liquid-liquid chromatographic techniques (CCC), similar to solvent extraction, are based on the different distribution of compounds between two immiscible liquids and have been most widely used in natural product separations. Due to its high load capacity, low solvent consumption, the diversity of separation methods, and easy scale-up, CCC provides an attractive tool to obtain pure compounds in the analytical, preparative, and industrial-scale separations. This review focuses on the steady-state and non-steady-state CCC separations ranging from conventional CCC to more novel methods such as different modifications of dual mode, closed-loop recycling, and closed-loop recycling dual modes. The design and modeling of various embodiments of CCC separation processes have been described.