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Deep eutectic solvents (DESs) were evaluated as solvents in centrifugal partition chromatography, a liquid-liquid chromatography separation technology. To this end, the partition coefficients of ten natural compounds of different hydrophobicity were determined in non-aqueous biphasic systems containing DES. The influence of the composition of DESs and the presence of water in the biphasic system on the partition coefficient were also examined. In addition, several process relevant physical properties of the biphasic system, such as the density and viscosity of the phases, were measured. A mixture of three to four hydrophobic compounds was successfully separated in a centrifugal partition extractor using a heptane/ethanol/DES biphasic system. [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]

The poor water solubility of active pharmaceutical ingredients (APIs) poses a significant challenge in pharmaceutical development, affecting their bioavailability and therapeutic efficacy. Consequently, there is an urgent demand for strategies to improve API solubility, with hydrotropy emerging as one of the most effective approaches. Hydrotropes, which can act as excipients in pharmaceutical formulations, enhance solubility by solubilizing hydrophobic compounds in aqueous solutions through mechanisms other than micellar solubilization. However, identifying the right hydrotropic agent requires a screening from a large pool of candidates. This work aims to analyze hydrotropy from a thermodynamic perspective by investigating the influence of the molecular interactions among the API, hydrotrope, and water on the API solubility in water at different temperatures. For this systematic study, hypothetical ternary systems were used and only liquid hydrotropes were considered. Utilizing the Two-Suffix Margules equation to model the liquid phase nonideality, the study revealed that strong API-hydrotrope interactions notably enhance the API solubility in water. Additionally, the interaction between the hydrotrope and water significantly influences API solubility; weaker hydrotrope-water interactions allow for increased API solubility in water. However, when hydrotrope-water interactions are stronger than API-hydrotrope interactions, this effect is diminished. The theoretical findings were validated using solubility experimental data of syringic acid with alkanediols in water from the literature. The results of this work will aid in selecting suitable liquid hydrotropes for enhancing the API solubility in aqueous solutions.

Harmonizing unit operations in the downstream process of monoclonal antibodies (mAbs) has a high potential to overcome throughput limitations and reduce manufacturing costs. This study proposes a streamlined clarification and capture (S-CC) process concept for the continuous processing of cell broth harvested from a connected bioreactor. The process was realized with a fluidized bed centrifuge connected to depth and sterile filters, a surge tank, and a multi-column chromatography (MCC) unit. The MCC unit was operated in the rapid cycling simulated moving bed (RC-BioSMB) mode with five convective diffusive membrane adsorbers (MAs). A control strategy and the surge tank were used to adjust the loading flow rate of the MCC unit. The mAb was recovered with a total process yield of 90%, with high removal of the process-related impurities HCP (2.1 LRV) and DNA (2.9 LRV). Moreover, the S-CC process productivity of 4.2 g h - 1 was up to 5.3 times higher than for comparable, hypothetical batch MA processes. In addition, the buffer consumption of the capture step could be reduced from 2.0 L g - 1 in batch mode to 1.2 L g - 1 in the RC-BioSMB mode. These results demonstrate the high potential of streamlined interconnected unit operations to improve the overall mAb downstream process performance., (© 2024 The Author(s). Biotechnology and Bioengineering published by Wiley Periodicals LLC.)

Oleaginous microorganisms are promising for the biotechnological production of valuable hydrophobic bioactive components. For an environmentally friendly extraction, we evaluated a two-step process for β-carotene and lipid isolation from wet Rhodosporidium toruloides biomass using biphasic green and biobased solvent systems: 2-methyl tetrahydrofuran (2-MeTHF) or cyclopentyl-methyl-ether (CPME) with ethanol or 1-butanol and water. Initially, components were extracted with a single-phase solvent mixture, followed by separating hydrophobic target components from polar impurities via phase separation. We employed the Conductor-like Screening Model for Real Solvents (COSMO-RS) to predict the solubility of β-carotene and select compositions with higher solubility. Our study highlights the potential of these solvent systems for extracting hydrophobic components and the importance of understanding the system's liquid-liquid equilibria for effective process design. We present a framework for evaluating new solvent systems for extracting hydrophobic bioactive compounds by demonstrating the impact of solvent composition selection on extraction yields and solvent consumption., Competing Interests: The authors declare no competing financial interest., (© 2025 The Authors. Published by American Chemical Society.)

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 )., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Fabian Schmitz reports a relationship with Sartorius Stedim Biotech GmbH that includes: employment. Markus Kampmann reports a relationship with Sartorius Stedim Biotech GmbH that includes: employment. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Downstream processing is the bottleneck in the continuous manufacturing of monoclonal antibodies (mAbs). To overcome throughput limitations, two different continuous processes with a novel convective diffusive protein A membrane adsorber (MA) were investigated: the rapid cycling parallel multi-column chromatography (RC-PMCC) process and the rapid cycling simulated moving bed (RC-BioSMB) process. First, breakthrough curve experiments were performed to investigate the influence of the flow rate on the mAb dynamic binding capacity and to calculate the duration of the loading steps. In addition, customized control software was developed for an automated MA exchange in case of pressure increase due to membrane fouling to enable robust, uninterrupted, and continuous processing. Both processes were performed for 4 days with 0.61 g L -1 mAb-containing filtrate and process performance, product purity, productivity, and buffer consumption were compared. The mAb was recovered with a yield of approximately 90% and productivities of 1010 g L -1  d -1 (RC-PMCC) and 574 g L -1  d -1 (RC-BioSMB). At the same time, high removal of process-related impurities was achieved with both processes, whereas the buffer consumption was lower for the RC-BioSMB process. Finally, the attainable productivity for perfusion bioreactors of different sizes with suitable MA sizes was calculated to demonstrate the potential to operate both processes on a manufacturing scale with bioreactor volumes of up to 2000 L., (© 2024 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals LLC.)

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., (© 2024 The Author(s). Journal of Separation Science published by Wiley‐VCH GmbH.)

Hemp ( Cannabis sativa L.) has been used for millennia as a rich source of food and fibers, whereas hemp flowers have only recently gained an increased market interest due to the presence of cannabinoids and volatile terpenes. Currently, the hemp flower processing industry predominantly focuses on either cannabinoid or terpene extraction. In an attempt to maximize the valorization of hemp flowers, the current study aimed to evaluate the phytochemical composition and antimicrobial properties of several extracts obtained from post-distillation by-products (e.g., spent material, residual distillation water) in comparison to the essential oil and total extract obtained from unprocessed hemp flowers. A terpene analysis of the essential oil revealed 14 monoterpenes and 35 sesquiterpenes. The cannabinoid profiling of extracts showed seven acidic precursors and 14 neutral derivatives, with cannabidiol (CBD) reaching the highest concentration (up to 16 wt.%) in the spent material extract. The antimicrobial assessment of hemp EO, cannabinoid-containing extracts, and single compounds (i.e., CBD, cannabigerol, cannabinol, and cannabichromene) against a panel of 20 microbial strains demonstrated significant inhibitory activities against Gram-positive bacteria, Helicobacter pylori , and Trichophyton species. In conclusion, this work suggests promising opportunities to use cannabinoid-rich materials from hemp flower processing in functional foods, cosmetics, and pharmaceuticals with antimicrobial properties.

Eutectic systems design requires an in-depth understanding of their solid-liquid equilibria (SLE). Modeling SLE in eutectic systems has as prerequisites, the melting properties and activity coefficients of components in the liquid phase. Thus, due to the unavailable melting properties of thermally unstable substances, it is impossible to estimate their activity coefficients from experimental SLE data and model the SLE phase diagram of their eutectic systems. Here, we evaluate the activity coefficients of thermally unstable constituents in the liquid phase, which were calculated independent of their melting properties by correlating the SLE data of their cocrystals. Differential scanning calorimetry and powder x-ray diffraction were employed to obtain the SLE phase diagram of three eutectic systems, i.e., tetramethylammonium chloride/catechol, tetraethylammonium chloride/catechol, and betaine/catechol systems, and identify the formation of nine cocrystals. The non-random, two-liquid equation was used to calculate the activity coefficients of the components in the liquid phase. The substantial negative deviation from ideality in the three studied systems indicated strong hydrogen bonding interactions in the liquid solution. Furthermore, modeling ion-ion interactions in eutectic systems containing ionic constituents is of utmost importance for understanding their nonideality., (© 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).)

Brewing espresso coffee (EC) is considered a craft and, by some, even an art. Therefore, in this study, we systematically investigated the influence of coffee grinding, water flow rate, and temperature on the extraction kinetics of representative EC components, employing a central composite experimental design. The extraction kinetics of trigonelline, caffeine, 5-caffeoylquinic acid (5-CQA), and Total Dissolved Solids (TDS) were determined by collecting and analyzing ten consecutive fractions during the EC brewing process. From the extraction kinetics, the component masses in the cup were calculated for Ristretto, Espresso, and Espresso Lungo. The analysis of the studied parameters revealed that flow rate had the strongest effect on the component mass in the cup. The intensity of the flow rate influence was more pronounced at finer grindings and higher water temperatures. Overall, the observed influences were minor compared to changes resulting from differences in total extracted EC mass.

Black pepper (P. nigrum L.) is considered one of the most valuable spices and a promising candidate in natural product research. In this study, the influence of different combinations of pressures (100-300 bar) and temperatures (40-60 °C) on the supercritical CO 2 (SC-CO 2 ) recovery of several key compounds from black pepper was evaluated systematically. The extraction curves showed that terpenes were recovered in a short time under all studied conditions. In contrast, higher pressure values were required to extract piperamides efficiently. Furthermore, the differences in the extraction kinetics of piperine, piperettine, pellitorine, guineensine, and N-isobutyl-2,4,14-eicosatrienamide were linked with several structural features, such as the nature of the amine group or the terminal part of the fatty acid. The data from the isocratic experiments represented the starting point for designing a two-step pressure gradient SC-CO 2 process in which one terpene-rich and one piperamide-rich product were successively obtained., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Supercritical fluid extraction from hops ( Humulus lupulus L.) can be used to extract essential oil for the flavoring of beer. With a special focus on the oil composition being linked to the hop aroma, the influence of pressure and temperature on the extraction kinetics of seven oil components (β-myrcene, α-humulene, β-caryophyllene, 2-methylbutyl isobutyrate, undecanone, linalool, and α-pinene) is analyzed and modeled in this article. Supercritical CO 2 extraction from hop pellets was conducted at pressure-temperature combinations of 90/100/110 bar and 40/45/50 °C. The extract composition over time, analyzed by gas chromatography, was used for the parameterization of two existing mechanistic models: an internal-mass-transfer-control (IMTC), and a broken-and-intact-cells (BIC) model. The IMTC model was found to effectively describe most extraction kinetics and hence applied in this study. In contrast to previous studies, the IMTC model parameters were not only fitted to individual extraction curves from different experiments but also correlated to temperature and pressure as a further step towards model-based prediction. Using the parameterized model, the extract composition was predicted at 95 bar/48 °C, 105 bar/42 °C, and 105 bar/48 °C. Extraction yields were found to be higher at lower temperatures and higher pressures in general. The sensitivity towards pressure was observed to differ between components and to be particularly higher for β-myrcene compared with α-humulene. Changes of the essential oil composition with a variation in pressure and temperature were predicted correctly by the model with a mean relative deviation from experimental data of 11.7% (min. 1.2%, max. 36.2%)., Competing Interests: The authors declare no competing interests., (© 2023 The Authors.)

The biotechnological production of the carotenoid astaxanthin is done with the microalgae Haematococcus pluvialis (H. pluvialis). Under nutrient deficiency and light stress, H. pluvialis accumulates astaxanthin intracellularly and forms a resistant cyst cell wall that impedes direct astaxanthin extraction. Therefore, a complex downstream process is required, including centrifugation, mechanical cell wall disruption, drying, and supercritical extraction of astaxanthin with CO 2 . In this work, an alternative downstream process based on the direct extraction of astaxanthin from the algal broth into ethyl acetate using a centrifugal partition extractor (CPE) was developed. A mechanical cell wall disruption or germination of the cysts was carried out to make astaxanthin accessible to the solvent. Zoospores containing astaxanthin are released when growth conditions are applied to cyst cells, from which astaxanthin can directly be extracted into ethyl acetate. Energy-intensive unit operations such as spray-drying and extraction with supercritical CO 2 can be replaced by directly extracting astaxanthin into ethyl acetate. Extraction yields of 85% were reached, and 3.5 g of oleoresin could be extracted from 7.85 g homogenised H. pluvialis biomass using a CPE unit with 244 mL column volume. A techno-economic analysis was done for a hypothetical H. pluvialis production facility with an annual biomass output of 8910 kg. Four downstream scenarios were examined, comparing the novel process of astaxanthin extraction from homogenised cyst cells and germinated zoospores via CPE extraction with the conventional industrial process using in-house or supercritical CO 2 extraction via an external service provider. After 10 years of operation, the highest net present value (NPV) was determined for the CPE extraction from germinated zoospores., (© 2021. The Author(s).)

The plant genus Piper comprises extensively consumed spice taxa like black pepper (P. nigrum L.) or long pepper (P. longum L.). The chronic dietary use of different Piper spices has been associated with different health benefits, though the molecular mechanisms remain poorly understood. The aim of this work was to perform the liquid-chromatography-high-resolution tandem mass spectrometry (LC-HRMS/MS) profiling and LC-DAD quantification of piperamides in several Piper species and varieties and study their ability to modulate the endocannabinoid system (ECS). LC-HRMS/MS analysis revealed a number of 42 piperamides grouped into six structural classes, with 22 of them, notably piperine, retrofractamide B, guineensine, piperchabamide C, being also quantified by LC-DAD. The multivariate analysis showed that P. nigrum and P. longum are very similar with respect to their piperamide profile, while the other Piper spices (P. retrofractum, P. guineense, P. cubeba, P. borbonense) might have significantly different metabolite patterns. The results from the biological assays confirmed that guineensine and total piperamides are strongly correlated with anandamide (AEA) cellular uptake inhibition. While none of the Piper spice extracts showed binding activity at cannabinoid CB 1 receptors, some P. nigrum varieties exhibited moderate binding interactions with CB 2 receptors. Overall, the analytical profiling enabled global annotations of piperamides associated to cannabimimetic effects in Piper spices., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The current situation with the SARS-CoV-2 pandemic indicates the importance of new approaches in vaccine design. In order to design new attenuated vaccines, to decrease virulence of virus wild types, it is important to understand what allows a virus to hijack its host cell's metabolism, a property of all viruses. RNA and protein sequences obtained from databases were used to count the number of atoms of each element in the virions of SARS, MERS and SARS-CoV-2. The number of protein copies and carbohydrate composition were taken from the literature. The number of lipid molecules was estimated from the envelope surface area. Based on elemental composition, growth equations were balanced, and thermodynamic properties of the viruses were determined using Patel-Erickson and Battley equations. Elemental and molecular compositions of SARS, MERS and SARS-CoV-2 were found, as well as their standard thermodynamic properties of formation and growth. Standard Gibbs energy of growth of virus nucleocapsids was found to be significantly more negative than that of their host tissue. The ratio of Gibbs energies of growth of virus nucleocapsids and host cell is greater than unity. The more negative Gibbs energy of growth of viruses implies that virus multiplication has a greater driving force than synthesis of host cell components, giving a physical explanation of why viruses are able to hijack their host cell's metabolism. Knowing the mechanism of viral metabolism hijacking can open new paths for vaccine design. By manipulating chemical composition of viruses, virulence can be decreased by making the Gibbs energy of their growth less negative, resulting in decreased multiplication rate, while preserving antigenic properties., (© 2020 Published by Elsevier Ltd.)

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., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier B.V.)

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., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Trapping multiple dual mode centrifugal partition chromatography (trapping MDM CPC) is an alternative to isocratic pulse injections for the separation of intermediately-eluting components from complex mixtures using liquid-liquid chromatography. In this work, a throughput maximization strategy is developed and validated to investigate the full potential of trapping MDM CPC as a preparative technique. In the proposed approach, shake flask and stationary phase retention experiments are used to determine the maximum feed concentration and flow rate, respectively. A model-based parameter selection process combining a mathematical short-cut method and simulations based on the equilibrium cell model is used to obtain the column loading and step durations resulting in maximized process throughput. The proposed throughput maximization strategy is experimentally validated for the separation of a ternary model mixture of parabens. A preliminary comparison of trapping MDM CPC separation performance to that of stacked pulse injections is also made., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The preparative separation of intermediately-eluting components in liquid-liquid chromatography is commonly performed with isocratic batch injections, a technique which often leads to low yield and/or purity as a result of peak overlap. Two-column trapping multiple dual mode centrifugal partition chromatography, an alternative discontinuous method for the separation of a mixture into three product fractions (early-, intermediately-, and late-eluting components) at full recovery, is presented in this work. A mathematical shortcut method based on equilibrium theory assumptions is derived for the determination of the key operating parameters (i.e., step durations and number of steps). The feasibility of the technique and the accompanying short-cut method is demonstrated by proof-of-concept experiments for the separation of two paraben model mixtures., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Tocopherols are a class of molecules with vitamin E activity. Among those, α-tocopherol is the most important vitamin E source in the human diet. The purification of tocopherols involving biphasic liquid systems can be challenging since these vitamins are poorly soluble in water. Deep eutectic solvents (DES) can be used to form water-free biphasic systems and have already proven applicable for centrifugal partition chromatography separations. In this work, a computational solvent system screening was performed using the predictive thermodynamic model COSMO-RS. Liquid-liquid equilibria of solvent systems composed of alkanes, alcohols and DES, as well as partition coefficients of α-tocopherol, β-tocopherol, γ-tocopherol, and σ-tocopherol in these biphasic solvent systems were calculated. From the results the best suited biphasic solvent system, namely heptane/ethanol/choline chloride-1,4-butanediol, was chosen and a batch injection of a tocopherol mixture, mainly consisting of α- and γ-tocopherol, was performed using a centrifugal partition chromatography set up (SCPE 250-BIO). A separation factor of 1.74 was achieved for α- and γ-tocopherol., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Aqueous two-phase systems composed of imidazolium-based ionic liquids and phosphate salts were evaluated for their applicability in liquid-liquid chromatography. The influence of the nature of ionic liquid anion and cation on the partitioning of bovine serum albumin, lysozyme and myoglobin was investigated. A mixture of K2HPO4 and KH2PO4 in a ratio of 1.82:1 wt/wt was used in all of the tested biphasic systems to adjust the pH to a range of 7-8. The results show that more hydrophobic cations decrease the partition coefficients of the proteins in the biphasic systems and outweigh the effect of the anion on the distribution of the macromolecules. Viscosities and densities of the biphasic systems were in a suitable range for liquid-liquid chromatography. Even though the partition coefficients were too high for a conventional batch operation mode, these aqueous two-phase systems show favorable properties for protein capturing in liquid-liquid chromatographic columns. Additionally, the possible application of ionic liquids as modifiers in polyethylene glycol (PEG)-based aqueous two-phase systems was investigated. It could be demonstrated that ionic liquids alter the partition coefficients of the proteins., (Copyright © 2015 Elsevier B.V. All rights reserved.)

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 © 2012 Elsevier B.V. All rights reserved.)

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 © 2012 Elsevier B.V. All rights reserved.)