Operating mode and parameter selection in liquid-liquid chromatography

Recent advances in methods of extraction, pre-concentration, purification, identification, and quantification of kaempferol

As a naturally widely-occurring dietary, cosmetic, and therapeutic flavonoid, kaempferol has gained much consideration for its nutritional and pharmaceutical properties in recent years. Although there have been performed a high number of studies associated with different aspects of kaempferol's analytical investigations, the lack of a comprehensive summary of the various methods and other plant sources that have been reported for this compound is being felt, especially for many biological applications. This study, aimed to provide a detailed compilation consisting of sources (plant species) and analytical information that was precisely related to the natural flavonoid (kaempferol). There is a trend in analytical research that supports the application of modern eco-friendly instruments and methods. In conclusion, ultrasound-assisted extraction (UAE) is the most general advanced method used widely today for the extraction of kaempferol. During recent years, there is an increasing tendency towards the identification of kaempferol by different methods.

Extrapolation of cytotoxic masked effects in planar in vitro assays

The masking of specific effects in in vitro assays by cytotoxicity is a commonly known phenomenon. This may result in a partial or complete loss of effect signals. For common in vitro assays, approaches for identifying and quantifying cytotoxic masking are partly available. However, a quantification of cytotoxicity-affected signals is not possible. As an alternative, planar bioassays that combine high-performance thin layer chromatography with in vitro assays, such as the planar yeast estrogen screen (p-YES), might allow for a quantification of cytotoxically affected signals. Affected signals form a typical ring structure with a supressed or completely lacking centre that results in a double peak chromatogram. This study investigates whether these double peaks can be used for fitting a peak function to extrapolate the theoretical, unaffected signals. The precision of the modelling was evaluated for four individual peak functions, using 42 ideal, undistorted peaks from estrogenic model compounds in the p-YES. Modelled ED50-values from bisphenol A (BPA) experiments with cytotoxically disturbed signals were 13 times higher than for the apparent data without compensation for cytotoxicity (320 ± 63 ng versus 24 ± 17 ng). This finding has a high relevance for the modelling of mixture effects according to concentration addition that requires unaffected, complete dose-response relationships. Finally, we applied the approach to results of a p-YES assay on leachate samples of an elastomer material used in water engineering. In summary, the fitting approach enables the quantitative evaluation of cytotoxically affected signals in planar in vitro assays and also has applications for other fields of chemical analysis like distorted chromatography signals.

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.

Multistep pH-peak-focusing liquid chromatography with a hydrophilic polymer gel column for separation of rare earth elements

Multistep pH-peak-focusing liquid chromatography with a column packed with a hydrophilic polymer gel (a cross-linked hydroxylated methacrylic polymer gel) was developed for separation of rare earth metal ions. Metal ions in a sample solution introduced to the column are chromatographically extracted into the stationary gel phase at the top of the column equilibrated with a basic solution used as the first mobile phase containing acetylacetone and 1,10-phenanthroline by synergistic extraction effect. After the sample solution is introduced, the mobile phases are delivered into the column by stepwise gradient elution in order of decreasing pH. Each metal ion is concentrated at a pH border formed between the zones of different pH in the column and moves toward the outlet of the column with the pH border. Mutual separation of La(III), Ce(III), Nd(III), Eu(III), Y(III), Tb(III), and Yb(III) was achieved by the present method for an 1-mL sample injection with the column of which the inner volume is 11.8 mL. The multistep pH-peak-focusing liquid chromatography with a hydrophilic polymer gel column developed in this study has great potential as a useful method for the separation of rare earth metal ions on a preparatory scale.

Dynamic Interfacial Tension Measurement for the Kinetic Study of Eu(III) Extraction in the NaNO3/Tributyl Phosphate System Based on an Increase in Interfacial Tension

We demonstrated for the first time that interfacial tension measurements can be used to evaluate the kinetics of the solvent extraction of metal ions. The Eu(III) extraction mechanism in the nitrate ion/tributyl phosphate (TBP) system was investigated on the basis of dynamic interfacial tension. Interestingly, the interfacial tension of the TBP droplet (γ) increased with Eu(III) extraction. This behavior can be explained by the electrocapillary effect. The time dependence of γ was kinetically analyzed, and we demonstrated that the rate-determining process was the interfacial reaction of Eu(III). Furthermore, the dependence of the mass transfer rate constant upon the concentration of the nitrate ions revealed that two nitrate ions were involved in the interfacial reaction during Eu(III) extraction. However, no change in the rate constant upon TBP concentration was observed, because the change in the TBP concentration did not affect the electrocapillary effect. We determined the forward and backward reaction rates to be k1 = (1.5 ± 0.7) × 10-6 m M-2 s-1 and k-MT = (6.9 ± 3.9) × 10-7 m s-1. Therefore, for the first time, we demonstrated that dynamic interfacial tension, which is involved in the electrocapillary effect, can be used to elucidate the kinetics of Eu(III) extraction. We expect that this study will attract the attention of researchers in several fields, including physical and analytical chemistry.

Modeling of analytical, preparative and industrial scale counter-current chromatography separations

Analytical, preparative and industrial scale counter-current chromatography (CCC) processes differ in the volumes of the loaded solution of components to be separated and in the design of the equipment. Preliminary mathematical modeling is necessary for selection of the optimal design and operation mode of these CCC separations. This study aims to compare simulations of CCC separations at different scales, using an exact description based on the model of equilibrium cells and a much simpler approximate solution based on the Gaussian distribution. Equations for modeling CCC separations of different scales and examples of simulation these separations are presented. It is shown that the discrepancy between the two simulations increases with an increase in the volume of the loaded solution of the components and a decrease in the number of equilibrium cells of a CCC device. In analytical and preparative separations, which are based on complex centrifugal devices, and relatively small sample volumes are injected, approximate equations can be used to simulate various options of CCC separation. In industrial-scale CCC separations, large volumes of the solution of components may be loaded, and as we have proposed previously, these separations can be based on a cascade of mixer-settler extractors. In this case, a more accurate mathematical description based on the cell model equations should be used for modeling.

Investigating hydrophobic environment in alkyl-group-functionalized silica particle with various chain lengths using absorption microspectroscopy

A well-known solvatochromic dye, Reichardt's dye (R-dye), was used to evaluate the hydrophobicity of alkyl-group-functionalized silica particles (ASPs) with different chain lengths. The absorption spectra of R-dye were measured in a single ASP in a mixed solution of water and an organic solvent (methanol (MeOH), ethanol (EtOH), acetonitrile (ACN), tetrahydrofuran (THF), or N,N-dimethylformamide (DMF)) using absorption microspectroscopy. The polarity parameter in the ASPs (ET), determined by the absorption maximum, was observed to be smaller than those in bulk solutions, indicating that R-dye was present in a more hydrophobic environment. In EtOH, THF, and DMF, R-dye was distributed within the alkyl chain layer including the organic solvent. An increase in the organic solvent content of the bulk solution led to a higher organic solvent concentration in the alkyl chain layer, resulting in a decrease in ET. In MeOH and ACN, the R-dye was distributed within the alkyl chain layer and concentrated phase. Moreover, with the increase in the organic molecule content, the distribution of R-dye in the concentrated phase became dominant in MeOH and ACN system, leading to an increase in the ET value. The findings presented in this paper are expected to attract the attention of a wide range of researchers in chromatography.

Nonlinear liquid-liquid chromatography: Modeling a binary mixture separation

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.

Modeling a pesticide remediation strategy for preparative liquid chromatography using high-performance liquid chromatography

BACKGROUND

Cannabis sativa L. also known as industrial hemp, is primarily cultivated as source material for cannabinoids cannabidiol (CBD) and ∆9-tetrahydrocannabinol (∆9-THC). Pesticide contamination during plant growth is a common issue in the cannabis industry which can render plant biomass and products made from contaminated material unusable. Remediation strategies to ensure safety compliance are vital to the industry, and special consideration should be given to methods that are non-destructive to concomitant cannabinoids. Preparative liquid chromatography (PLC) is an attractive strategy for remediating pesticide contaminants while also facilitating targeted isolation cannabinoids in cannabis biomass.

METHODS

The present study evaluated the benchtop-scale suitability of pesticide remediation by liquid chromatographic eluent fractionation, by comparing retention times of 11 pesticides relative to 26 cannabinoids. The ten pesticides evaluated for retention times are clothianidin, imidacloprid, piperonyl butoxide, pyrethrins (I/II mixture), diuron, permethrin, boscalid, carbaryl, spinosyn A, and myclobutanil. Analytes were separated prior to quantification on an Agilent Infinity II 1260 high performance liquid chromatography with diode array detection (HPLC-DAD). The detection wavelengths used were 208, 220, 230, and 240 nm. Primary studies were performed using an Agilent InfinityLab Poroshell 120 EC-C18 3.0 × 50 mm column with 2.7 μm particle diameter, using a binary gradient. Preliminary studies on Phenomenex Luna 10 μm C18 PREP stationary phase were performed using a 150 × 4.6 mm column.

RESULTS

The retention times of standards and cannabis matrices were evaluated. The matrices used were raw cannabis flower, ethanol crude extract, CO₂ crude extract, distillate, distillation mother liquors, and distillation bottoms. The pesticides clothianidin, imidacloprid, carbaryl, diuron, spinosyn A, and myclobutanil eluted in the first 3.6 min, and all cannabinoids (except for 7-OH-CBD) eluted in the final 12.6 min of the 19-minute gradient for all matrices evaluated. The elution times of 7-OH-CBD and boscalid were 3.44 and 3.55 min, respectively.

DISCUSSION

7-OH-CBD is a metabolite of CBD and was not observed in the cannabis matrices evaluated. Thus, the present method is suitable for separating 7/11 pesticides and 25/26 cannabinoids tested in the six cannabis matrices tested. 7-OH-CBD, pyrethrins I and II (RT_A: 6.8 min, RT_B: 10.5 min), permethrin (RT_A: 11.9 min, RT_B: 12.2 min), and piperonyl butoxide (RT_A: 8.3 min, RT_B: 11.7 min), will require additional fractionation or purification steps.

CONCLUSIONS

The benchtop method was demonstrated have congruent elution profiles using preparative-scale stationary phase. The resolution of pesticides from cannabinoids in this method indicates that eluent fractionation is a highly attractive industrial solution for pesticide remediation of contaminated cannabis materials and targeted isolation of cannabinoids.

Intermittent sample loading technique as a tool for obtaining high- concentration elution bands in recycling liquid-liquid chromatography: Theoretical study of periodic and semi-continuous separation processes

To improve the efficiency of countercurrent chromatography (CCC) separations, we have previously proposed a new sample loading method called intermittent sample loading (ISL), in which continuous sample feed alternates with short periods of "clean" mobile phase feed to the CCC device. In semi-continuous separation processes, during sample feed periods, the sample is loaded in separate batches, each consisting of a series of intermittent sample loads. It was shown that the application of the intermittent sample loading method in the conventional isocratic CCC separations significantly increased process productivity and the concentration of compounds in the separated fractions. In this study, to further improve the CCC separations with intermittent sample loading, we discuss the application of the ISL method in the processes of close-loop recycling counter-current chromatography (CLR CCC). The advantage of the ISL CLR CCC over the ISL CCC is higher resolution and lower solvent consumption. Equations are presented that allow the simulation of periodic and semi-continuous ISL CLR CCC separations and the selection of optimal operational conditions for these separation processes. It is shown that the use of ISL technique in CLR CCC separations makes it possible to produce fractions of compounds with a much higher concentration than when using the conventional single sample loading method.

Innovative Purification Method of Ovatodiolide from Anisomeles indica to Induce Apoptosis in Human Gastric Cancer Cells

Ovatodiolide (Ova), found in the plant Anisomeles indica (AI), has been reported to have an anti-proliferation effect in various cancer cells. However, little information is available regarding the anti-cancer effect of Ova in human gastric cancer cells. In this study, we investigated the inhibitory effects and the mechanisms of action responsible for these effects on human AGS cell lines from a newly developed purification technique for Ova from AI extract. Extract obtained at the optimum condition of 95% ethanol extraction of AI was sequentially partitioned by using different polarity solvents. Enriched content of Ova (35.9% purity) from the n-hexane fraction was then applied to the purification by using centrifugal partition chromatography (CPC) in a two-phase solvent system consisting of n-hexane:ethyl acetate:methanol:water (1.0:1.0:1.0:1.0, v/v/v/v) to reach purity over >95.0%. In evaluation of the anti-proliferation effect on AGS cells, Ova induced cell apoptosis with IC₅₀ values of 13.02 and 6.18 μM at 24 and 48 h, respectively, and arrested the cells at the G2/M phase. Quantification of Bax/Bcl2 mRNA expressions using qPCR showed a 2.5-fold increase in the Ova (5 μM)-treated cells at 48 h than in the control group. Specific protein expression data warrant further research to further confirm the proposed Ova-induced apoptotic pathway in AGS cells.

Alternative Extraction and Downstream Purification Processes for Anthocyanins

Anthocyanins are natural pigments displaying different attractive colors ranging from red, violet, to blue. These pigments present health benefits that increased their use in food, nutraceuticals, and the cosmetic industry. However, anthocyanins are mainly extracted through conventional methods that are time-consuming and involve the use of organic solvents. Moreover, the chemical diversity of the obtained complex extracts make the downstream purification step challenging. Therefore, the growing demand of these high-value pigments has stimulated the interest in designing new, safe, cost-effective, and tunable strategies for their extraction and purification. The current review focuses on the potential application of compressed fluid-based (such as subcritical and supercritical fluid extraction and pressurized liquid extraction) and deep eutectic solvents-based extraction methods for the recovery of anthocyanins. In addition, an updated review of the application of counter-current chromatography for anthocyanins purification is provided as a faster and cost-effective alternative to preparative-scale HPLC.

Separation of minor cannabinoids from hemp extract with trapping multiple dual mode liquid-liquid chromatography

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.

Closed-Loop Recycling Dual-Mode Counter-Current Chromatography with Specified Sample Loading Durations: Modeling of Preparative and Industrial-Scale Separations

We previously reported on a new counter-current chromatography (CCC) operating mode called closed-loop recycling dual-mode counter-current chromatography (CLR DM CCC), which incorporates the advantages of closed-loop recycling (CLR) and dual-mode (DM) counter-current chromatography and includes sequential separation of compounds in the closed-loop recycling mode with the mobile x-phase and in the inverted-phase counter-current mode with the mobile y-phase. The theoretical analysis of several implementations of this separation method was carried out under impulse sample injection conditions. This study is dedicated to the further development of CLR DM CCC theory applied to preparative and industrial separations, where high-throughput operation is required. Large sample volumes can be loaded via continuous loading within a specified time. To simulate CLR DM CCC separations with specified sample loading durations, equations are developed and presented in "Mathcad" software.

Liquid-Liquid Chromatography Separation of Guaiane-Type Sesquiterpene Lactones from Ferula penninervis Regel & Schmalh. and Evaluation of Their In Vitro Cytotoxic and Melanin Inhibitory Potential

Ferula penninervis Regel & Schmalh. is a perennial plant used in Kazakh traditional folk medicine to treat epilepsy, neurosis, rheumatism, gastroduodenal ulcers, dyspepsia, wounds, abscesses or tumors. The aim of this work was to isolate series of sesquiterpene lactones from a crude methanolic root extract and investigate their in vitro cytotoxic potential against androgen-dependent prostate cancer LNCaP and epithelial prostate PNT2 cells, as well as to evaluate their melanin production inhibitory effects in murine melanoma B16F10 cells stimulated with α-melanocyte-stimulating hormone (αMSH). Two new (penninervin P and penninervin Q) and five known (olgin, laferin, olgoferin, oferin and daucoguainolactone F) guaiane-type sesquiterpene lactones were isolated with the use of a simple and fast liquid-liquid chromatography method. Olgin and laferin showed the most promising cytotoxic effects in LNCaP cells (IC₅₀ of 31.03 and 23.26 μg/mL, respectively). Additionally, olgin, laferin, olgoferin, and oferin (10 μg/mL) potently impaired melanin release (40.67–65.48% of αMSH + cells) without influencing the viability of B16F10 cells. In summary, our findings might indicate that guaiane-type sesquiterpene lactones from F. penninervis could be regarded as promising candidates for further research in discovering new therapeutic agents with anti-prostate cancer and skin depigmentation properties.

Liquid-Liquid Chromatography: Current Design Approaches and Future Pathways

Since its first appearance in the 1960s, solid support-free liquid-liquid chromatography has played an ever-growing role in the field of natural products research. The use of the two phases of a liquid biphasic system, the mobile and stationary phases, renders the technique highly versatile and adaptable to a wide spectrum of target molecules, from hydrophobic to highly polar small molecules to proteins. Generally considered a niche technique used only for small-scale preparative separations, liquid-liquid chromatography currently lags far behind conventional liquid-solid chromatography and liquid-liquid extraction in process modeling and industrial acceptance. This review aims to expose a broader audience to this high-potential separation technique by presenting the wide variety of available operating modes and solvent systems as well as structured, model-based design approaches. Topics currently offering opportunities for further investigation are also addressed.

A simple and highly efficient counter-current chromatography method for the isolation of concentrated fractions of compounds based on the sequential sample loading technique: Comparative theoretical study of conventional multiple and intermittent sample loading counter-current chromatography separations

A new modification of the conventional multiple sample loading (MSL) mode - sequential sample loading (SSL) - is suggested to enhance further the performance of the counter-current chromatography (CCC) separation processes. The sequential sample loading technique is simple and easy to implement: the continuous sample solution supply to a CCC column is alternated (interrupted) with short periods of the "pure" mobile phase supply. Periodic (batch) and continuous SSL CCC separations can be designed and implemented. In continuous processes, the sample solution loading is carried out in the form of separate series, consisting of a number of sequential sample solution loads. In this work, the modeling of the conventional multiple sample loading and the sequential sample loading counter-current chromatography is used to compare the two operating modes considered. Equations for the calculation of band profiles, the recovery yield and the purity are given. Equations are also derived permitting the calculation of the optimum operating parameters of the separation processes. It is shown that the use of sequential sample loading makes it possible to produce fractions of purified compounds with a much higher concentration than in the original sample solution. The simulations of the conventional multiple sample loading and the sequential sample loading counter-current chromatography separations are presented in "Mathcad" software.

Coumarins from Seseli devenyense Simonk.: Isolation by Liquid-Liquid Chromatography and Potential Anxiolytic Activity Using an In Vivo Zebrafish Larvae Model

Different types of anxiety disorders have become the number one mental health issue in developed countries. The search for new, safer and effective drug-like molecules among naturally derived substances faces two difficulties: an efficient method of isolation compounds with a high-purity and high-throughput animal model for activity assay. Thus, the aim of the present study was to isolate by liquid–liquid chromatography high-purity rare coumarins from the fruits of Seseli devenyense Simonk. and evaluate their anxiolytic effect (defined as reversed thimotaxis) using a 5-days post-fertilization (dpf) Danio rerio larvae model. Liquid–liquid chromatography enabled the isolation of one simple hydroxycoumarin (devenyol) and four pyranocoumarins (cis-khellactone, d-laserpitin, isolaserpitin and octanoyllomatin). The anxiolytic effect was defined as a decrease in the time spent in the boundaries of the living space (also described as reversed thigmotaxis). Our results show that all isolated courmarins exerted a significant influence on the anxiety behavior (anxiolytic activity) in the zebrafish larvae model. According to our knowledge, this is the first report of anxiolytic activity of pyranocoumarins and devenyol.

Target separation and antitumor metastasis activity of sesquiterpene-based lysine-specific demethylase 1 inhibitors from zedoary turmeric oil

Lysine-specific histone demethylase 1 (LSD1) was the first histone demethylase identified in epigenetics and has recently emerged as an attractive therapeutic target for treating tumors. To date, almost all reported LSD1 inhibitors have been chemosynthesized; however, natural products possess pharmacological and biological activity and can be sources for drug development. Here, we established a target separation countercurrent chromatography technique to isolate LSD1 inhibitors from zedoary turmeric oil. Four sesquiterpene-based LSD1 inhibitors were efficiently obtained with an inhibition ratio equal to or less than that of the positive control drug. Compound 2 showed the most potent inhibitory activity, with a half-maximal inhibitory concentration of 3.97 μM, and was further tested to determine its ability to inhibit LSD1 and its antitumor metastatic effects in MDA-MB-231 cells. These four compounds are the first sesquiterpene-based natural LSD1 inhibitors to be characterized. Our findings provide a new molecular framework for studying LSD1 inhibitors and offer a template for designing more sesquiterpene-based LSD1 inhibitors with potential antitumor activity.

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.

Recovery and recycling of solvent of counter-current chromatography: The sample of isolation of zeaxanthin in the Lycium barbarum L. fruits

An efficient method of recovering and recycling solvent for counter-current chromatography was established by which zeaxanthin was separated from Lycium barbarum L. fruits. A column with activated carbon combined with high performance counter-current chromatography formed the recovering and recycling solvent system. Using the solvent system of n-hexane-ethyl acetate-ethanol-water (8:2:7:3, v/v) from the references, five injections were performed with an almost unchanged purity of zeaxanthin (80.9, 81.2, 81.5, 81.3, and 80.2% respectively) in counter-current chromatography separation. Meanwhile, the mobile phase reduced by half than conventional counter-current chromatography. By this present method, an effective improvement of counter-current chromatography solvent utilization was achieved.

Trapping multiple dual mode liquid-liquid chromatography: Preparative separation of nootkatone from a natural product extract

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.