Search

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. [ABSTRACT FROM AUTHOR]

• MAb dynamic binding capacity of the membrane adsorber was between 35 mg mL-1 and 59 mg mL-1. • Membrane utilization was up to 86 % higher in the RC-BioSMB than in the batch process. • Buffer consumption was lowest for the RC-BioSMB process. • Batch process outperformed the RC-PMCC and RC-BioSMB at low mAb concentrations and flow rates. • RC-BioSMB outperformed the batch and RC-PMCC at high mAb concentrations and flow rates. Protein A affinity membrane adsorbers are a promising alternative to resins to intensify the manufacturing of monoclonal antibodies. This study examined the process performance of convective diffusive membrane adsorbers operated in batch and continuous multi-column mode. Therefore, three different processes were compared regarding membrane utilization, productivity, and buffer consumption: the batch process, the rapid cycling parallel multi-column chromatography process, and the rapid cycling simulated moving bed process. The influence of the monoclonal antibody loading concentration (between 0.5 g L-1 and 5.2 g L-1) and the loading flow rate (between 1.25 MV min-1 and 10 MV min-1) on the monoclonal antibody binding behavior of the membrane adsorber were studied with breakthrough curve experiments. The determined breakthrough curves were used to calculate the monoclonal antibody dynamic binding capacity, the duration of the loading steps for each process, and the number of required membrane adsorbers for the continuous processes rapid cycling parallel multi-column chromatography and rapid cycling simulated moving bed. The highest productivity for the batch (176 g L-1 h-1) and rapid cycling parallel multi-column chromatography process (176 g L-1 h-1) was calculated for high monoclonal antibody loading concentrations and low loading flow rates. In contrast, the rapid cycling simulated moving bed process achieved the highest productivity (217 g L-1 h-1) for high monoclonal antibody loading concentrations and loading flow rates. Furthermore, due to the higher membrane utilization, the buffer consumption of the rapid cycling simulated moving bed process (1.1 L g-1) was up to 1.9 times lower than that of the batch or rapid cycling parallel multi-column chromatography operation (2.1 L g-1). [ABSTRACT FROM AUTHOR]

Highlights • Two operating modes for separation of intermediately-eluting components evaluated. • Preferred mode dependent on separation factor and purity and yield requirements. • Trapping MDM extends the use of LLC to separation factors as low as 1.1. • Use of trapping MDM most advantageous for separation factors around 1.3. • Simpler batch injections preferred for separation factors of 1.5 or greater. Abstract Two operating modes that can be used for the separation of intermediately-eluting target components from complex mixtures using solid support-free liquid-liquid chromatography (LLC) include batch injections and trapping multiple dual mode (trapping MDM). Batch injections offer the advantage of simpler equipment and process design, while the trapping MDM process, although more complex, can provide improved resolution at low separation factors. In this study, a thorough comparison of batch injection and trapping MDM performance with respect to productivity is made using simulations for a wide range of separation tasks (target component/impurity separation factors; minimum purity and yield requirements). For each separation task, the maximum productivities obtained by the two operating modes were separately determined with respect to their independent parameters. The results indicate that trapping MDM can be used to extend the application of LLC down to separation factors as low as 1.1, with its use being most advantageous for separation factors of approximately 1.3. However, the simpler batch injection process remains preferable for separation factors around or greater than 1.5. [ABSTRACT FROM AUTHOR]

Highlights • Temperature influences the separation performance and resolution in CCC and CPC. • Temperature influences phase composition and physical properties. • Settling time and system stability exhibit temperature sensitivity. • Temperature control is essential for temperature sensitive system. Abstract In a biphasic liquid system, temperature affects the phase composition, so that a change in temperature can even turn the system into a single-phase system. Furthermore, temperature influences the physical properties of the phases, such as density, viscosity and interfacial tension. In this work, temperature was evaluated as an influencing factor for the separation performance in solid support-free liquid-liquid chromatography, i.e. countercurrent chromatography and centrifugal partition chromatography. To this end, two biphasic systems were selected: the non-aqueous solvent system n -hexane/ethyl acetate/acetonitrile (11.2/2.0/5.3 v/v/v at 25 °C) and the aqueous-organic system n -heptane/ethyl acetate/methanol/water (1/1/1/1 v/v/v/v at 25 °C). The effect of elevated temperature on the separation was systematically analyzed between 25 °C and 40 °C. The results were related to the changes in the liquid-liquid equilibria of the solvent systems and physical properties of the phases. The temperature influence on the stationary phase retention, column efficiency and separation resolution was analyzed. An appropriate temperature control of the column was shown to be essential in order to avoid destabilizing the biphasic system and enable a satisfactory separation for temperature sensitive systems. In this context, the influence of different column and mobile phase inlet temperature on the separation performance was investigated by pulse injections. In addition, the stability and settling time of the biphasic systems were evaluated as indicators whether temperature susceptibility needs to be considered during method development in order to prevent a decrease in separation resolution. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Evaluation of new centrifugal partition chromatography column (CPC) with spherical cells. • High mobile phase flow rates possible without significant decrease of stationary phase retention. • No decrease of resolution with increase of mobile phase flow rate. • Comparison to conventional CPC column with twin-cell design. • Theoretical study of productivity and solvent consumption. Abstract A new centrifugal partition chromatography (CPC) column with spherical cells, insignificant duct (channel) volume, and without PTFE plates between the disks was evaluated. Due to the reduced duct volume, almost the entire column volume is available for the separation. This allows operation at higher pressure drop and thus increased rotational speed and flow rates. The new column was characterized in terms of stationary phase retention, column efficiency and resolution as a function of flow rate and rotational speed. The separation performance was compared to that of two conventional twin-cell CPC columns of the same total volume. The new column leads to an increased productivity especially at higher flow rates and outperforms columns with smaller cells in terms of higher separation factors and reduced purity or recovery requirements. [ABSTRACT FROM AUTHOR]

Aqueous two‐phase systems (ATPSs) can be applied in centrifugal partition chromatography (CPC) to separate biomolecules. Two ionic liquids (ILs) served as modifying agents to tune partition coefficients in the separation of two model proteins, myoglobin and lysozyme. Myoglobin was not affected by the ILs, while the partition coefficient of lysozyme was lowered with addition of IL. High stationary phase retention was achieved with ATPSs in a CPC column with cell size and geometry specially designed for unstable biphasic systems. When ILs were used as modifying agents, no notable decrease in stationary phase retention was observed. The injection volume was increased to 20 % of the total column volume and process simulations indicate that a further increase in the injection volume is possible. Aqueous two‐phase systems help to separate biomolecules in centrifugal partition chromatography. The application of ionic liquids as modifying agents in protein separations with this kind of chromatography was demonstrated for two model proteins, myoglobin and lysozyme. Simulations and experimental studies were performed to evaluate possibilities for increasing the separation productivity. [ABSTRACT FROM AUTHOR]

The applicability of sequential centrifugal partition chromatography for continuous fractionation of multicomponent mixtures, represented here by a mixture of four parabens with very similar molecular structure, was studied. The fractionation of the quaternary feed mixture was regarded as a separation of a pseudo-binary mixture. The model-based approach was used to select the biphasic liquid system and the unit operating parameters. All desired fractions were recovered with purities >99%. The influence of the solute concentration on the density, viscosity and volume ratio of the phases as well as on the partitioning of the solutes between the two phases was investigated. According to these results, possibilities for increasing the throughput were proposed and validated experimentally. For example, butyl paraben with a purity ≥99% was continuously separated from the rest of the parabens in a 250 mL unit with a throughput of 3.24 g h−1 and a solvent consumption of 0.33 L g−1. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1659-1673, 2017 [ABSTRACT FROM AUTHOR]

Sequential centrifugal partition chromatography ( sCPC) is a novel cyclic liquid-liquid chromatographic process. Each cycle comprises two steps, which differ by the liquid phase used as a mobile phase (upper or lower phase) and its flow direction. The feed is continuously separated into two product streams, which are collected alternately. The process includes six (four flow rates and two-step durations) interconnected operating parameters. In this work, by imposing a complete separation of a binary feed mixture and using the assumption of instantaneous solutes partition equilibrium, a set of constraints on the sCPC unit operating parameters is derived. Using these constraints, a region of complete separation, composed of a set of combinations of the two-step times, can be defined for a preselected feed and mobile phase flow rates. The approach is validated by simulation of a binary mixture separation in a sCPC using the cell model. © 2012 American Institute of Chemical Engineers AIChE J, 59: 241-249, 2013 [ABSTRACT FROM AUTHOR]

Abstract: Sequential centrifugal partition chromatography (sCPC) is a novel continuous cyclic liquid–liquid chromatographic separation technology. Each cycle of the process comprises two steps, which differ by the liquid phase used as mobile phase (upper or lower phase) and its flow direction. The feed is introduced continuously in the unit and two product streams are collected alternately, in each step of the cycle. In this work, the sCPC was modeled using the stage (cell) model. The model was used to simulate a separation of a model binary mixture consisting of pyrocatechol and hydroquinone. The solutes distribution constants, system hydrodynamics and mass transfer parameters were determined experimentally and implemented in the model. Furthermore, a parameter study (variation of the feed concentration and step times) was performed by experiments and simulation. A recently developed method was used to select the operating parameters of the sCPC unit. [Copyright &y& Elsevier]

Abstract: The X-ray computed tomography (CT) is used to determine local parameters related to the column packing homogeneity and hydrodynamics in columns packed with spherically and irregularly shaped particles of same size. The results showed that the variation of porosity and axial dispersion coefficient along the column axis is insignificant, compared to their radial distribution. The methodology of using the data attained by CT measurements to perform a CFD simulation of a batch separation of model binary mixtures, with different concentration and separation factors is demonstrated. The results of the CFD simulation study show that columns packed with spherically shaped particles provide higher yield in comparison to columns packed with irregularly shaped particles only below a certain value of the separation factor. The presented methodology can be used for selecting a suited packing material for a particular separation task. [Copyright &y& Elsevier]

This work deals with chiral separation by Simulated Moving Bed (SMB) chromatography. A simulation package is used to predict the effect of the operating variables on the process performance. The "separation volume" methodology is used to study effect of the presence of mass transfer resistances presented by different particle sizes on operating conditions of the SMB unit with emphasis to the net flow in zone I and IV in terms of interstitial velocity ratio (γ1 and γ4). The experimental operation of the a pilot plant SMB unit LICOSEP 12-26 (Novasep, France) is carried out for the separation of enantiomers of R,S-α-Tetralol using the chiral adsorbent CHIRALPAK AD with particle size 20 µm. To obtain real insight to operation of the SB unit Licosep 12-26 the mathematical model accounts for all dead volumes inside of the SMB unit and time delay in shifting of injection and withdrawal points. Experimental and theoretical results based on the SMB model are compared in terms of process performance parameters and internal concentration profiles. [ABSTRACT FROM AUTHOR]

Abstract: The hydrodynamic, equilibrium and kinetics of adsorption in a silica-based monolithic preparative column Chromolith Prep. Si (Merck KgaA, Germany) have been studied. The inverse size-exclusion chromatography with polystyrene standards of narrow molecular size distribution and small tracer molecule has been used to measure the external and total porosity of the monolithic column. The column permeability was calculated according to the Darcy law for laminar flow. The efficiency of the monolithic column was characterized through the height equivalent to a theoretical plate (HETP) of phenol, ethyl vanillin and dimethyl phthalate. The separation efficiency does not decrease in the region of high flow rates. The adsorption isotherms of phenol, ethyl vanillin and dimethyl phthalate measured by frontal analysis were linear in the investigated concentration range. The 2D single channel mathematical model has been applied to describe the adsorption dynamics. The model assumes parabolic velocity profile, axial and radial diffusion in the monolith channel, linear driving force model for the mass transfer in the monolith channel skeleton wall and linear adsorption equilibrium. The model gives good prediction of the experimental breakthrough curves. [Copyright &y& Elsevier]

• Liquid-liquid chromatography separation of an intermediately-eluting component. • 5-step design approach applied to a complex natural product starting mixture. • Use of short-cut method for selection of trapping MDM step durations. • Target separation from >90 impurities at 79% purity and 85% yield. Trapping multiple dual mode (trapping MDM) is a preparative liquid-liquid chromatography (LLC) technique well-suited to difficult separations of intermediately-eluting components from similarly structured impurities. In this demonstrative study, a design approach for high process throughput is applied for the trapping MDM separation of a target component, nootkatone (NK), initially comprising 16.7% of an industrial side stream mixture with over 90 impurities. This design approach, previously developed and validated using ternary mixtures of model solutes, is applied to a complex real mixture for the first time. The approach consists of five steps: (1) determination of the maximum starting mixture concentration for feed preparation; (2) determination of the maximum flow rate for maintenance of the pre-set stationary phase fraction; (3) determination of the partition coefficients of the target and main impurities; (4) selection of step durations and number of cycles using an established short-cut method; (5) execution of the trapping MDM separation. The target, NK, was obtained along with a co-eluting component at 78.7% purity and 84.6% yield, demonstrating the effectiveness of trapping MDM for the separation of intermediately-eluting natural product target components from complex starting mixtures. [ABSTRACT FROM AUTHOR]

• Standard, extrusion, flow reversal, and continuous operating modes discussed. • Critique and unification of published design equations and short-cut models. • Operating mode selection based on sample and separation goal. • Preliminary separation design with simple equations. The presence of a liquid stationary phase in liquid–liquid chromatography (LLC) allows for high versatility of operation as well as adaptability to different sample types and separation tasks. LLC, also known as countercurrent chromatography (CCC) or centrifugal partition chromatography (CPC), offers the user a variety of operating modes, many of which have no direct equivalent in conventional preparative liquid–solid chromatography. These operating modes have the potential to greatly improve LLC separation performance compared to the standard "classical" isocratic batch injection mode, and they often require minimal to no addition of equipment to the standard set-up. However, reports of the use of alternative LLC operating modes make up only a fraction of the literature. This is likely due, at least in part, to the lack of clear guidelines and methods for operating mode and parameter selection, leaving alternative process options to be avoided and underutilized. This review seeks to remedy this by providing a thorough overview of the available LLC operating modes, identifying the key characteristics, advantages and disadvantages, and areas of application of each. Additionally, the equations and short-cut models aiding in operating mode and parameter selection are presented and critiqued, and their notation is unified for clarity. By rendering LLC and its alternative operating modes more accessible to current and prospective users, it is hoped to help expand the application of this technology and support the achievement of its full potential. [ABSTRACT FROM AUTHOR]

• THC-remediation of hemp extracts with liquid–liquid chromatography (LLC) was evaluated. • Two-column flow-reversal advanced LLC processes were investigated. • Operating parameters for the advanced modes were selected using mathematical models. • All chromatograms were successfully simulated based on the equilibrium-cell model. • The sequential mode continuously provided a THC-free extract with high productivity. The presence of tetrahydrocannabinol (THC) in cannabinoid-based materials, such as hemp flower extracts, can pose a severe commercialization burden. In this study, various operating modes of liquid–liquid chromatography (LLC), i.e., batch mode (conventional), trapping multiple dual mode (semi-continuous), and sequential mode (continuous), were evaluated for the THC-remediation of hemp extracts. The biphasic system composition, the feed concentration range, and the maximum flow rate were selected in preliminary experiments. The operating parameters were chosen using short-cut methods, whereas simulations were based on the equilibrium-cell model. Batch elution provided good productivity, easy operation, and yielded a THC-free hemp extract. Trapping multiple dual mode showed a lower productivity than batch, whereas the sequential mode afforded a THC-free extract with a similar composition to the batch mode and offered the advantage of continuous operation and superior productivity. The results of this work constitute a solid basis for the model-based design and optimization of LLC processes for the industrial remediation of hemp extracts. [ABSTRACT FROM AUTHOR]

Abstract: Sequential centrifugal partition chromatography (sCPC) is a cyclic solid support-free liquid–liquid chromatographic process, in which a continuously introduced feed mixture is separated into two sequentially collected product streams. The few experimental demonstrations of this concept already revealed its potential for the preparative separation of pharmaceuticals and fine chemicals. In this work not only the possibilities, but also the limits of the sCPC technology are explored. A feed mixture consisting of capsaicin and dihydrocapsaicin, whose molecular structure differs in only one double bond, was selected for this purpose. The sCPC unit operating parameters needed for a complete separation of the feed mixture were selected using the recently published approach, which uses the partition coefficient of the feed components and the hydrodynamic characteristics of the system as input data. A complete separation of capsaicin and dihydrocapsaicin with the solvent system heptane/ethyl acetate/methanol/water:1/1/1/1 (v/v/v/v) was achieved, although the separation factor was only 1.32. The sCPC unit separation performance was successfully simulated using the cell model. [Copyright &y& Elsevier]

Abstract: The selection of the mobile and the stationary phase in support-free liquid–liquid chromatography (centrifugal partition chromatography and counter-current chromatography) is equivalent to a selection of a biphasic liquid system and its global composition. There is an immense number of choices of biphasic liquid systems. On one hand what makes this technique extremely versatile, on the other hand turns the selection of the appropriate system for a particular separation problem into a challenging and demanding task. In this work a systematic procedure for the selection of biphasic liquid systems for preparative scale separations is presented. The procedure is adaptable to the production scale requirements including production cost and safety. The experimental effort of different stages of the selection procedure is minimized by using a fully predictive method, the conductor-like screening model for real solvents (COSMO-RS). The COSMO-RS is used to assess properties relevant for the selection of a biphasic liquid system, such as the solute solubility and the partition coefficient. [Copyright &y& Elsevier]

Abstract: The aim of this investigation was to minimize the experimental effort for solvent system selection in counter-current chromatography. The separation mechanism in counter-current chromatography is based exclusively on the partitioning of the solute between the two liquid phases. Therefore, a quantum chemical method combined with statistical thermodynamics (conductor-like screening model for real solvents, COSMO-RS) was used for the prediction of the partition coefficient. A comparison of the experimental and predicted data for five model solutes systems demonstrated the potential of the use of COSMO-RS as a screening tool for the solvent system selection. [Copyright &y& Elsevier]

• Separation of two solutes in nonlinear liquid-liquid chromatography (LLC) was modeled;. • The equilibrium-cell model and an empirical distribution isotherm were employed;. • The isotherm parameters were estimated from LLC experiments of single solutes;. • The LLC elution profiles of binary mixtures were successfully predicted;. • The modeling approach is general and applicable to different isotherm models. In liquid-liquid chromatography (LLC), mixture components are separated due to their different distribution between the phases of a biphasic liquid system composed of three or four solvents. LLC separations are typically modeled assuming that only the solutes distribute between the two liquid phases and their distribution can be described with a concentration-independent distribution constant. With increasing solute concentration, the physicochemical properties of the biphasic system change, and the distribution of the solutes becomes a function of their concentration. However, the experimental determination of liquid-liquid equilibria in multicomponent systems is time-intensive, and its prediction using thermodynamic models is often not sufficiently accurate for process design purposes. Thus, in this work, we propose a simple approach to model and simulate LLC separations in the nonlinear (concentration-dependent) range of the solutes' distribution equilibria, namely cannabidiol (CBD) and cannabigerol (CBG). Using the inverse method, the distribution equilibrium equation parameters were estimated from pulse injection experiments of single solutes at concentrations ranging from 1 to 100 mg/mL and 1–50 mg/mL for CBD and CBG, respectively. The obtained parameters were then successfully used to predict the elution profiles of binary mixtures of different compositions at 40 mg/mL total cannabinoid concentration. The approach was demonstrated and validated for CBD and CBG as model compounds and n -hexane/methanol/water 10/7.5/2.5 (v/v/v) as the biphasic solvent system. It should be noted that the applicability of the proposed approach is system-dependent, and hence, it should be evaluated for each separation task individually. [ABSTRACT FROM AUTHOR]

Petasites hybridus L. (butterbur, Asteraceae) is a well-known medicinal plant traditionally used as a remedy for neurological, respiratory, cardiovascular, and gastrointestinal disorders. Eremophilane-type sesquiterpenes (petasins) are considered to be the major bioactive constituents of butterbur. However, efficient methods to isolate high-purity petasins in sufficient amounts for further analytical and biological testing are lacking. In this study, various sesquiterpenes were separated from a methanol rootstock extract of P. hybridus with liquid-liquid chromatography (LLC). The appropriate biphasic solvent system was selected using the predictive thermodynamic model COSMO-RS and shake-flask experiments. After the selection of the feed (extract) concentration and operating flow rate, a batch LLC experiment was performed with n -hexane/ethyl acetate/methanol/water 5/1/5/1 (v/v/v/v). For those LLC fractions containing petasin derivatives with purities < 95%, a preparative high-performance liquid chromatography purification step followed. All isolated compounds were identified by state-of-the-art spectroscopic methods, i.e., liquid chromatography coupled with high-resolution tandem mass spectrometry and nuclear magnetic resonance techniques. As a result, six compounds were obtained, namely 8β-hydroxyeremophil-7(11)-en-12,8-olide, 2-[(angeloyl)oxy]eremophil-7(11)-en-12,8-olide, 8α/β-H-eremophil-7(11)-en-12,8-olide, neopetasin, petasin, and isopetasin. The isolated petasins can be further used as reference materials for standardization and pharmacological evaluation. [Display omitted] • Selection of conditions for isolation of butterbur compounds by LLC. • Screening of solvent system by predictive thermodynamic model. • Isolation of petasins with the use of CPC and preparative HPLC. • LC-HR-MS/MS and NMR characterization of the isolated compounds. [ABSTRACT FROM AUTHOR]

Tick-borne diseases raise serious health concerns for both humans and animals. Tick control and disease prevention largely depend on synthetic acaricides and repellents, often incriminated for high toxicity. To find alternative, safe, and efficient agents against ticks, research on plant-based volatile terpenes constitutes a promising direction. This study aimed to separate and identify hemp flower compounds with repellent properties against Hyalomma marginatum (Acari: Ixodidae). Produced by supercritical CO 2 extraction under different pressure (100–110 bar) and temperature (40–60 °C) conditions, the hemp extracts were tested in a moving object bioassay. The extract with the highest repellent power was further subjected to batch liquid-liquid chromatography (LLC). The biphasic solvent system (n -heptane/methanol/acetonitrile 10/5/10, v/v/v) for separating the major hemp terpenes was selected by combining the COSMO-RS-based distribution coefficient screening with experimental validation. Bisabolol (>99%), caryophyllene oxide (>98%), and caryophyllene/humulene (3.5/1, w/w, >95% purity) were thus isolated and assessed in the H. marginatum bioassay. The activity of bisabolol (20% w/w in hexane) was comparable to the synthetic repellent DEET at the same concentration. For the large-scale purification of bisabolol, trapping multiple dual mode, a semi-continuous flow-reversal LLC operating mode, was proposed and evaluated. Bisabolol was obtained with a solvent consumption 2.6-times lower and productivity 2.7-times higher than the batch process. In conclusion, using a multi-methodological computer-aided approach, bisabolol was efficiently identified and isolated as a good tick repellent agent from hemp flowers. • Terpene-rich hemp flower extracts were obtained with supercritical CO2 technology. • The Hyalomma marginatum repellency was evaluated in a moving object bioassay. • Hemp terpenes were separated by liquid-liquid chromatography (LLC). • Bisabolol was isolated and identified as the most potent tick repellent compound. • The large-scale purification of bisabolol was achieved by trapping multiple dual mode LLC. [ABSTRACT FROM AUTHOR]

• The first systematic study of liquid-liquid chromatography (LLC) in the nonlinear range of the distribution isotherm. • Pulse injection experiments with cannabidiol (CBD, 1–300 mg/mL) were performed in three units of different designs and volumes (20 mL-2 L). • At higher concentrations, the CBD elution profiles showed a diffusive front and sharp rear part. • The elution profiles were successfully simulated with the equilibrium-cell model and a nonlinear correlation describing the CBD distribution isotherm. • The distribution isotherm parameters were determined by the peak fitting method. Liquid-liquid chromatography (LLC) is a technique in which the separation of mixture components is achieved due to their different distribution between the two phases of a pre-equilibrated biphasic solvent system. In this work, the LLC operation in the nonlinear range of the distribution isotherm was systematically examined for the first time. The influence of the feed concentration on the elution profiles of a model component (cannabidiol, CBD) was studied in three LLC units of different types and sizes ranging from ∼20 mL to ∼2 L. A series of pulse injections with CBD concentrations varying from 1 to 300 mg/mL was performed with n -hexane/methanol/water 5/4/1 (v/v/v) in descending mode (lower phase as the mobile phase). The elution profiles were simulated using the equilibrium-cell model and an anti-Langmuir-like equation for describing the CBD distribution equilibria. The distribution equilibria equation parameters were fitted to the CBD elution profiles using the peak fitting method. The model was validated and provided good predictions of the CBD elution profiles in the entire concentration range for all three LLC units. [ABSTRACT FROM AUTHOR]

• Trapping MDM - a two column flow-reversal liquid-liquid chromatography process. • Semi-continuous separation of minor cannabinoids from hemp extracts. • Operating parameters selection using mathematical models and simulations. • Cannabinoids purities around 95% and yields of 73-95%. • Trapping MDM productivity twice higher than in conventional batch separation. Aside from Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), other less common cannabinoids have recently gained an increasing popularity, mostly due to their promising biological potential. However, time-saving and cost-effective methods for their preparative purification are missing. In this study, trapping multiple dual mode (MDM), a flow-reversal liquid-liquid chromatography (LLC) operating mode, was used for the separation of different minor cannabinoids from a hemp extract. Separation task specific biphasic solvent systems were selected for the purification of the target constituents, as follows: n-hexane/methanol/water 10/6.5/3.5 for cannabielsoin (CBE); n-hexane/methanol/water 10/7/3 for cannabidivarin (CBDV) and cannabigerol (CBG); n-hexane/methanol/water 10/8/2 for cannabinol (CBN) and n-hexane/methanol/water 10/9/1 for cannabichromene (CBC) and cannabicylol (CBL). For each separation task, the concentration of the hemp extract in the feed stream and mobile phase flow rate were selected by shake-flask and stationary phase retention experiments, respectively. For the determination of the trapping MDM operating parameters, the short-cut method was implemented and followed by equilibrium-cell model-based simulations. The trapping MDM allowed the separation of the targeted cannabinoids with purities of 93-99%, yields of 73-95%, solvent consumption 2-4-fold lower and productivities almost double than those obtained using batch separation. [ABSTRACT FROM AUTHOR]

• COSMO-RS was used to screen biphasic solvent systems for CBD isolation. • Three solvent systems were found as the best candidates for CBD isolation with LLC. • Oregon pesticides were divided into four groups: high, medium, low and non-critical. • A guideline for simultaneous CBD isolation and pesticide removal with LLC was proposed. • LLC experiments with a pesticide-hemp extract were performed for each solvent system. In this work, a computer-aided approach for selecting biphasic solvent systems for simultaneous cannabidiol (CBD) isolation and pesticide removal from hemp extracts with liquid-liquid chromatography (LLC) was investigated. By taking advantage of a fully predictive thermodynamic model (COSMO-RS), a considerable number of ternary solvent systems were screened and potential systems were identified with practically no experimental effort; the partition coefficient of the target component CBD was used as screening parameter. After the experimental validation, three solvent systems were chosen: solvent system I : n- heptane/methanol/water 4/3/1 v/v/v, solvent system II : n- heptane/acetone/water 2/5/1 v/v/v and solvent system III : n- heptane/acetonitrile/water 5/3/2 v/v/v. The 59 pesticides regulated by the state of Oregon in cannabis products were included in the next step with the aim to propose a classification system of the most critical pesticides for obtaining pesticide-free CBD. Based on CBD/pesticide separation factors (α CBD/PEST), four critical levels were defined. Depending on the solvent system, it was shown that 50–70 % of the Oregon-listed pesticides were found to be non-critical (α CBD/PEST > 4), while only 13–22 % were retrieved as highly and medium critical (α CBD/PEST < 2). Using the acquired knowledge, a guideline for the selection of the best solvent system candidate for the simultaneous LLC separation of CBD and removal of Oregon-listed pesticides from hemp extracts was proposed. Following a series of LLC experiments with a pesticide-spiked hemp extract, it was shown that the pesticide classification lists can be used to select the most promising solvent system to achieve the removal of most of the contaminating pesticides. [ABSTRACT FROM AUTHOR]