Semi-preparative high-resolution recycling liquid chromatography

Sustainable cannabinoids purification through twin-column recycling chromatography and green solvents

In the present study, twin-column recycling chromatography has been employed for the purification of a Cannabis extract by using a green solvent, ethanol, as the mobile phase. In particular, the complete removal of the psychoactive tetrahydrocannabinol (THC) from a Cannabis extract rich in cannabidiol (CBD) was achieved under continuous conditions. The performance of the method, in terms of compound purity, recovery, productivity and solvent consumption, was compared to that of traditional batch operations showing the potential of the twin-column recycling approach. The employment of a theoretical model to predict the band profiles of the two compounds during the recycling process has facilitated method development, thus further contributing to process sustainability by avoiding trial and error attempts or at least decreasing the number of steps significantly.

Momentum transport of morphological instability in fluid displacement with changes in viscosity

Saffman-Taylor instability exhibits a stepwise unstable morphology from a stable interface to viscous fingering, eventually leading to tip splitting. The nonlinear dynamics of the destabilized interface depends on various flow properties. However, the physicochemical mechanism that determines the transition point of the flow state is unclear. We studied the interfacial instability transition in miscible displacement from a thermodynamic perspective by calculating the momentum transport and entropy production. Using numerical analysis based on Darcy's law coupled with the convection-diffusion equation, the observed flux-dependent flow state transitions were attributed to the selection of the flow state with a higher entropy production.

Generation of potent antibacterial compounds through enzymatic and chemical modifications of the trans-δ-viniferin scaffold

Stilbene dimers are well-known for their diverse biological activities. In particular, previous studies have demonstrated the high antibacterial potential of a series of trans-δ-viniferin-related compounds against gram-positive bacteria such as Staphylococcus aureus. The trans-δ-viniferin scaffold has multiple chemical functions and can therefore be modified in various ways to generate derivatives. Here we report the synthesis of 40 derivatives obtained by light isomerization, O-methylation, halogenation and dimerization of other stilbene monomers. The antibacterial activities of all generated trans-δ-viniferin derivatives were evaluated against S. aureus and information on their structure-activity relationships (SAR) was obtained using a linear regression model. Our results show how several parameters, such as the O-methylation pattern and the presence of halogen atoms at specific positions, can determine the antibacterial activity. Taken together, these results can serve as a starting point for further SAR investigations.

Resolution limits of size exclusion chromatography columns identified from flow reversal and overcome by recycling liquid chromatography to improve the characterization of manufactured monoclonal antibodies

The flow reversal (FR) technique consists of reversing the flow direction along a chromatographic column. It is used to reveal the origin (such as poor column packing, active sites, or slow absorption/escape kinetics) for the resolution limit of 4.6 mm × 150 mm long columns packed with 1.7 μm 200 Å Bridge-Ethylene-Hybrid (BEHTM) Particles. These columns are used to separate manufactured monoclonal antibodies (mAb, ∼ 150 kDa) from their close impurities (or IdeS fragments, ∼ 100 kDa) by size exclusion chromatography (SEC). FR unambiguously demonstrates that the resolution limit of these SEC columns is primarily due to long-range flow velocity biases covering distances of at least 500 μm across the column diameter. This confirms the existence of center-to-wall flow heterogeneities which cause undesirable tailing for the mAb peak. Because the transverse dispersion coefficient (Dt=1.1 × 10-6 cm2/s) of mAbs across the column diameter is intrinsically low, the bandspreading of the mAb in a single flow direction is in part reversible upon reversing the flow direction. For the very same residence time in the column, the column efficiency is found to increase by +85% relative to that observed under conventional elution mode. The observed peak tailing of the mAb and its sub-units is not caused by active surface sites or by slow absorption/escape from the BEH Particles. Therefore, the most critical mAb impurities (hydrolytic degradation Fab/c and IdeS [Formula: see text] fragments) can only be successfully separated and quantified with acceptable accuracy by adopting alternate pumping recycling liquid chromatography (APRLC). APRLC enables the full baseline separation of the mAb and 100 kDa mAb fragments and partial separation of Fab/c and [Formula: see text] fragments after increasing the number of cycles to ten. It was made possible to accurately measure the relative abundances of the mAb (99.0 ± 0.1%), [Formula: see text] fragment (0.88 ± 0.03%), and Fab/c immunogenic fragment (0.13 ± 0.02%) in less than 45 min for a total mAb sample load of only 5 μg. Still, further improvements are needed to increase the sensitivity of the APRLC method and to reduce the solvent consumption by adopting narrow-bore 2.1 mm i.d. SEC columns.

Automated High-Resolution Semi-Preparative Gradient Recycling Liquid Chromatography: Principles, Design, and Applications

A semi-preparative twin-column recycling liquid chromatography (TCRLC) process was extended from isocratic to gradient elution mode. The main separation challenge is when the sample mixture contains early, nearly coeluting, and late impurities, all at the same time. To further improve classical isocratic TCRLC, the gradient TCRLC (GTCRLC) process was implemented with a 2-position 4-port valve in order to better shave the targeted sample from all these impurities. Prior to fully resolving the target compound(s) from the closest impurities by classical isocratic TCRLC, the added valve enabled full elimination by gradient elution mode of not only the early impurities but also any highly retained late impurities that could contaminate the collected fractions of the target compound(s). This GTCRLC process was entirely automated regarding the initial gradient applied, the recycling conditions, and the actuation times of the two valves. The GTCRLC process was applied for the isolation of a single polycyclic aromatic hydrocarbon (PAH), chrysene, present in a complex PAH mixture. In addition, the GTCRLC process was successfully applied to clean vitamins D2 and D3 from a milk extract and to baseline resolve them.

Rebirth of recycling liquid chromatography with modern chromatographic columns : Extension to gradient elution

Twin column recycling semi-preparative liquid chromatography (TCRLC) is revived to prepare small amount (∼ 1 mg) of a pure targeted compound, which cannot be isolated by conventional preparative liquid chromatography. In this work, TCRLC is extended to gradient elution. The first step of this modified process consists of a gradient step, which eliminates both early and late impurities. If not discarded, some late impurities could echo during the second isocratic recycling step of the process and compromise the purity level required for the targeted compound. Additionally, the entire gradient TCRLC (GTCRLC) process is automated regarding the eluent composition programmed and the actuation times of two valves: one two-position four-port divert valve enables to shave the targeted compound from early and late impurities during the initial gradient step. The second two-position six-port recycling valve ensures the complete baseline resolution between the band of the targeted compound and those of the closest impurities, which are not fully eliminated after the initial gradient step. The automation of the whole GTCRLC process is achieved by running four preliminary scouting gradient runs (at four different relative gradient times, t_gt₀= 2, 6, 18, and 54, where t₀ is the hold-up column time) for the accurate determination of the thermodynamics (lnk versus φ plots of the retention factor as a function of the mobile phase composition) of the first impurity, the targeted compound(s), and of the last impurity. The automated GTCRLC process was successfully applied for the isolation of a polycyclic aromatic hydrocarbon (PAH), chrysene, from a complex mixture of PAHs containing two nearly co-eluting impurities (benzo[a]anthracene and triphenylene) and nine other early/late impurities (sample volume injected: 1 mL, 7.8 mm × 150 mm Sunfire-C₁₈ column, acetonitrile/water eluent mixtures, T= 55 ^∘C, 20 cycles, baseline separation in less than two hours). Additionally, the GTCRLC process is advantageously used to isolate and baseline separate the vitamins D₂ and D₃ initially present in a milk extract mixture (0.3 mL sample injection volume, 7.8 mm × 150 mm Sunfire-C₁₈ column, methanol/water eluent mixtures, T= 65 ^∘C, 14 cycles needed in 1.5 hours). These results open promising avenues toward an effective preparation of unknown targeted compounds before further physico-chemical characterization and unambiguous identification.

Theoretical study of twin-column recycling chromatography with a solvent-gradient for preparative binary separations

Twin-column recycling chromatography with a solvent gradient (TCRC-SG) was investigated with the equilibrium-dispersive chromatography model. The solvent gradient caused by constant addition of a modifier between the two columns created a band compression effect to counterbalance band broadening, so that the target component band neither broadened nor shrunk. Meanwhile, band compression accelerated the separation but prevented excessive separation. Increasing the volume fraction of weak solvent in the modifier and reducing the modifier flowrate enhanced band compression and improved the separation. The effect of column efficiency (number of theoretical plates: 500-1500) on the separation was not significant. According to the separation behavior, a simple operation scheme is proposed to automatically control column switching without needing to determine the adsorption isotherm and designing operating conditions in advance. In comparison with simulated moving bed, TCRC-SG had a higher feed throughput, but consumed more solvent. The results showed that TCRC-SG is favorable for preparative separation.

Intelligent Multidimensional Purity Analysis and Confirmation Tool for Multiple Attribute Analysis

Chiral active pharmaceutical ingredients (APIs) are known to bind to chiral biological targets with better on-target specificity than achiral ones. However, the methods of synthesizing such APIs stereoselectively require the exhaustive optimization of multiple quality attributes of an asymmetric synthesis, wherein all critical quality attributes (for example, chemical and stereochemical purity of the API) are to be optimized in parallel and ideally from the beginning of the drug development program. A multidimensional liquid chromatographic tool capable of simultaneously measuring multiple quality attributes from a single analytical injection is reported. The tool is designed for the recirculation of chromatographic eluent bearing an analyte of interest through one or more stationary phases using a new and uniquely designed heart-cut valve. The iterative measurement of a target analyte from just one single injection will help scientists identify whether an unknown impurity is formed during reaction or during analysis. This chromatographic tool is particularly useful in the discovery of on-analysis artifacts, which is a resource-intensive exercise involving the identification, synthesis, and injection of impurity standards, all of which delay the drug development program.

The (CF3C(O)NH)(C6H5CH2NH)2P(O) phosphoric triamide as a novel carrier with excellent efficiency for Cu(ii) in a liquid membrane transport system

Transport of Ag(i), Cd(ii), Co(ii), Cu(ii), Ni(ii), Pb(ii) and Zn(ii) cations across a bulk liquid membrane (BLM) containing N,N′-dibenzyl-N′′-(2,2,2-trifluoroacetyl)-phosphoric triamide (PTC) as a new carrier is studied by atomic absorption spectrometry. The results show selective and efficient transport of the copper(ii) cation from aqueous solution in the presence of the other cations. Various factors are optimized in order to obtain maximum transport efficiency. The PTC ligand is characterized by single crystal X-ray diffraction analysis, IR, NMR (¹⁹F, ³¹P, ¹H, ¹³C) and mass spectroscopy. The complex formation reaction between copper(ii) and PTC is studied by a conductometric method, which shows the 1 : 1 stoichiometry for ligand and copper(ii).

Selective transport of Cu(ii) cation in the presence of six other cations across a bulk liquid membrane containing a novel phosphoric triamide carrier is studied.