Introducing online multicolumn two-dimensional liquid chromatography screening for facile selection of stationary and mobile phase conditions in both dimensions

Two-dimensional liquid chromatography with reversed phase in both dimensions: A review

Two-dimensional liquid chromatography (2D-LC), and in particular comprehensive two-dimensional liquid chromatography (LC×LC), offers increased peak capacity, resolution and selectivity compared to one-dimensional liquid chromatography. It is commonly accepted that the technique produces the best results when the separation mechanisms in the two dimensions are completely orthogonal; however, the use of similar separation mechanisms in both dimensions has been gaining popularity as it helps avoid difficulties related to mobile phase incompatibility and poor column efficiency. The remarkable advantages of using reversed phase in both dimensions (RPLC×RPLC) over other separation mechanisms made it a promising technique in the separation of complex samples. This review discusses some physical and practical considerations in method development for 2D-LC involving the use of RP in both dimensions. In addition, an extensive overview is presented of different applications that relied on RPLC×RPLC and 2D-LC with reversed phase column combinations to separate components of complex samples in different fields including food analysis, natural product analysis, environmental analysis, proteomics, lipidomics and metabolomics.

Theoretical and practical guidelines for solvent dilution between the two dimensions in online comprehensive two-dimensional liquid chromatography

Online comprehensive two-dimensional liquid chromatography (online LC x LC) has become increasingly popular. Among the different chromatographic modes that can be combined, hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RPLC) are particularly interesting because they offer a high degree of orthogonality. However, this combination remains complex due to the incompatibility of the solvents in the two dimensions. To avoid this problem, it is possible to dilute the first dimension (1D) effluent with (zdilution -1) volumes of a weaker solvent added to one volume of 1D-effluent, where zdilution represents the extent to which the fraction volume has been multiplied. This can be done using either active solvent modulation technology or an additional pump, prior to the second dimension analysis. The objective of this study was to develop theoretical models to predict whether or not dilution can be effective, and, if so, what is the minimum zdilution value required. This approach is based on the calculation of the ratio (called xdilution) between the peak standard deviation due to the injection process and the peak standard deviation in the absence of extra-column dispersion. xdilution was calculated from theoretical relationships and plotted as a function of zdilution, to predict the value required to obtain good peak shapes for the compound of interest. The maximum xdilution value was found to be of the order of 1 for chromatographically acceptable peak shapes. The proposed theoretical approach was experimentally validated on a number of representative small molecules and peptides. Agreement between experimental results and theoretical models was very high, especially for small molecules. Finally, it is shown that this approach helps to predict the most appropriate set of conditions in HILIC x RPLC, depending on the compounds to be separated.

Computer-assisted multifactorial method development for the streamlined separation and analysis of multicomponent mixtures in (Bio)pharmaceutical settings

The (bio)pharmaceutical industry is rapidly moving towards complex drug modalities that require a commensurate level of analytical enabling technologies that can be deployed at a fast pace. Unsystematic method development and unnecessary manual intervention remain a major barrier towards a more efficient deployment of meaningful analytical assay across emerging modalities. Digitalization and automation are key to streamline method development and enable rapid assay deployment. This review discusses the use of computer-assisted multifactorial chromatographic method development strategies for fast-paced downstream characterization and purification of biopharmaceuticals. Various chromatographic techniques such as reversed-phase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC), ion exchange chromatography (IEX), hydrophobic interaction chromatography (HIC), and supercritical fluid chromatography (SFC) are addressed and critically reviewed. The most significant parameters for retention mechanism modelling, as well as mapping the separation landscape for optimal chromatographic selectivity and resolution are also discussed. Furthermore, several computer-assisted approaches for optimization and development of chromatographic methods of therapeutics, including linear, nonlinear, and multifactorial modelling are outlined. Finally, the potential of the chromatographic modelling and computer-assisted optimization strategies are also illustrated, highlighting substantial productivity improvements, and cost savings while accelerating method development, deployment and transfer processes for therapeutic analysis in industrial settings.

Recent developments in the high-throughput separation of biologically active chiral compounds via high performance liquid chromatography

Bioactive compounds, including active pharmaceutical ingredients (APIs), are often chiral molecules where stereoisomers have different biological and therapeutic activity. Nevertheless, the preparation of these molecules can lead to racemic or scalemic mixtures (it is not trivial to produce just the optically pure compound). The evaluation of the enantiomeric purity of bioactive compounds, and therefore quality, is indeed of fundamental importance for regulatory scopes. Chiral high performance liquid chromatography (HPLC) is the gold standard technique to separate and to purify enantiomers. This comes from the wide availability of commercial chiral stationary phases (CSPs) and operational modes, which makes the technique extremely versatile. In recent years, the most relevant trend in the field of chiral analytical HPLC has been the development of CSPs suitable for fast or even ultrafast separations, thus favoring the high throughput screening of biologically active chiral compounds. This process has somehow lagged behind compared to achiral HPLC, due to a series of practical and fundamental issues. The experience has shown how in chiral chromatography even very basic concepts, such as the supposed kinetic superiority of core-shell (pellicular) particles over fully porous ones to improve the chromatographic efficiency, cannot be taken for granted. In this review, the most relevant fundamental and practical features that must be taken into consideration to design successful high-throughput, fast enantioseparations will be discussed. Afterwards, the main classes of CSPs and the most relevant, recent (last five-year) high-throughput applications in the field of the separation of chiral bioactive compounds (for pharmaceutical, forensic, food, and omics applications) will be considered.

Comprehensive reversed-phase×chiral two-dimensional liquid chromatography coupled to quadrupole-time-of-flight tandem mass spectrometry with post-first dimension flow splitting for untargeted enantioselective amino acid analysis

This work describes a comprehensive achiral × chiral two-dimensional liquid chromatography separation for enantioselective amino acid analysis coupled to electrospray ionization-tandem mass spectrometry detection using data-independent acquisition. Flow splitting after the first and second dimension separation was utilized for volumetric flow reduction and for enabling a multi-detector approach (with ultraviolet, fluorescence, charged aerosol, and MS detection), respectively. Derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate provided a chromophore, a fluorophore, and an efficient mass tag for efficient ionization in positive electrospray ionization-mass spectrometry. Chiral columns often have limitations in terms of their chemoselectivity, which may be a problem when complex sample mixtures with structurally related compounds need to be separated. It can be alleviated by a reversed-phase×chiral two-dimensional-liquid chromatography setup, in which the first dimension provides the chemoselectivity and a chiral tandem column constituted of quinine-carbamate derived weak anion-exchanger and zwitterionic ion-exchanger in the second dimension separation of D- and L-amino acid enantiomers. The method was used to control the stereointegrity of the therapeutic peptide octreotide. After hydrolysis, all amino acid constituents were detected with the correct configuration and composition. Some options for flow splitting and integration of destructive detectors in the first dimension separation are outlined.

A strategy for assessing peak purity of pharmaceutical peptides in reversed-phase chromatography methods using two-dimensional liquid chromatography coupled to mass spectrometry. Part I: Selection of columns and mobile phases

The current study describes the development of a 2D-LC-MS-based strategy for assessing main peak purity in the analysis of pharmaceutical peptides. The focus is on 2D-LC using reversed-phase (RP) separations in both dimensions, and particularly peptide isomer selectivity, since compounds with the same mass to charge ratio are not readily differentiated by mass spectrometry and therefore must be separated chromatographically. Initially, 30 column / mobile phase combinations were evaluated for both general separation performance (i.e., selectivity and peak shape) and isomer selectivity using forcibly degraded peptide samples and mixtures of synthetic diastereomers. A ranking of more than 300 UV and MS chromatograms suggests that when developing a new method, screening a set of four columns and four volatile mobile phases with differing characteristics should be adequate to both cover the selectivity space, and yield good separation performance. When 2D-LC-MS is to be used to evaluate peak purity for a new method, our results show that a second-dimension separation comprising a C8/C18 column possessing no ionic functionality, and an acetic acid / ammonium acetate mobile phase buffered at pH 5, provides good selectivity at 25 °C for peptide isomers with a MW <10 kDa. Retention data for 29 diverse peptides (1 < MW < 14 kDa, 3.7 < pI < 12.5) measured in this study using a variety of column and mobile phase conditions (i.e., 30 in total) are consistent with the classification of these various chromatographic conditions using the previously reported Peptide RPC Column Characterisation Protocol. For the investigated peptides trifluoroacetic acid was found to reduce selectivity differences between columns of diverse properties, probably due to its potential to form ion-pairs with peptides. Trifluoroacetic acid often improves peak shape for very large peptides (i.e. MW > 10 kDa). In the current dataset which also contain smaller peptides it received the highest ranking for 40% of the column and mobile phase combinations due to better selectivity and/or peak shape. The reported work here constitutes part one of a series of two papers. The second paper focuses on the use of retention modelling for rapid and accurate selection of the shallow gradients (i.e., << 1% ACN/min) required to obtain sufficient peptide isomer retention and separation in the second dimension. The overall results presented in this series of papers provides the guidance needed to develop a 2D-LC-MS method from start to finish for the analysis of main peak purity of therapeutic peptides.

Multi-2D LC × LC as a Novel and Powerful Implement for the Maximum Separation of Complex Samples

Achieving complete information about the chemical composition of complex samples requires the use of multianalytical platforms able to maximize the acquisition of high-quality data for unequivocal identification. However, this process requires long analysis times and several instruments. Food analysis is one of the analytical fields where the analysis of very complex samples has a huge impact. One of these complex samples is vermouth, a fortified wine based on the maceration of a large number of herbs, fruits, barks, seeds, and leaves. The application of conventional or even advanced analytical techniques like comprehensive two-dimensional (2D) liquid chromatography (LC × LC) does not provide enough separation power to resolve the complete profile of this sample. In this work, a novel 2DLC strategy called multi-²D LC × LC is developed. This new setup consists of the use of two different columns with different separation properties in the second dimension (²D) that can be selected during the LC × LC analysis accordingly to the chemical nature of the compounds eluted from the first dimension (¹D). The vermouth sample was analyzed using a ¹D-PFP and a combination of HILIC (from 0 to 30 min) and C18 (from 30 to the end) columns in the ²D. This setup increased both the peak capacity and the orthogonality of the analysis in comparison to the use of only one of the columns in the ²D. Multi-²D LC × LC is presented as an integrated 2DLC tool that maximizes the separation capacity for very complex samples.

Comprehensive Online Reversed-Phase × Chiral Two-Dimensional Liquid Chromatography-Mass Spectrometry with Data-Independent Sequential Window Acquisition of All Theoretical Fragment-Ion Spectra-Acquisition for Untargeted Enantioselective Amino Acid Analysis

This work presents an advanced analytical platform for untargeted enantioselective amino acid analysis (eAAA) by comprehensive achiral × chiral 2D-LC hyphenated to ESI-QTOF-MS/MS utilizing data-independent SWATH (sequential window acquisition of all theoretical fragment-ion spectra) technology. The methodology involves N-terminal pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC; AccQ) as retention, selectivity, and MS tag, supporting retention and UV detection in RPLC (¹D), chiral recognition, and thus enantioselectivity by the core-shell tandem column composed of a quinine carbamate weak anion exchanger (QN-AX) and a zwitterionic chiral ion-exchanger (ZWIX(+)) (²D) as well as the ionization efficiency during positive electrospray ionization due to a high proton affinity of the AQC label. Furthermore, the urea-type MS tag gives rise to the generation of AQC-tag characteristic signature fragments in MS². The latter allows the chemoselective mass spectrometric filtering of targeted and untargeted N-derivatized amino acids or related labeled species. The chiral core-shell tandem column provides a complete enantioselective amino acid profile of all proteinogenic amino acids within 1 min, with full baseline separation of all enantiomers, but without resolution of isomeric Ile/allo-Ile (aIle)/Leu, which can be resolved by RPLC. The entire LC × LC separation occurs within a total run time of 60 min (¹D), with the chiral ²D operated in gradient elution mode and a cycle time of 60 s. A strategy to mine the 2D-LC-SWATH data is presented and demonstrated for the qualitative eAAA of two peptide hydrolysate samples of therapeutic peptides containing common and uncommon as well as primary and secondary amino acids. Absolute configuration assignment of amino acids using template matching for all proteinogenic amino acids was made feasible due to method robustness and the inclusion of an isotopically labeled L-[U-¹³C¹⁵N]-AA standard. The quantification performance of this LC × LC-MS/MS assay was also evaluated. Accuracies were acceptable for the majority of AAs enabling AA composition determination in peptide hydrolysates simultaneously with configuration assignment, as exemplified by oxytocin. This methodology represents a step toward truly untargeted 2D enantioselective amino acid analysis and metabolomics.

Emerging analytical techniques for pharmaceutical quality control: Where are we in 2022?

Quality control is a fundamental and critical activity in the pharmaceutical industry that guarantees the quality of medicines. QC analyses are currently performed using several well-known techniques, mainly liquid and gas chromatography. However, current trends are focused on the development of new techniques to reduce analysis time and cost, to improve the performances and decrease ecological footprint. In this context, analytical scientists developed and studied emerging technologies based on spectroscopy and chromatography. The present review aims to give an overview of the recent development of vibrational spectroscopy, supercritical fluid chromatography and multi-dimensional chromatography. Selected emerging techniques are discussed using SWOT analysis and published pharmaceutical QC applications are discussed.

Expediting the chromatographic analysis of COVID-19 antibody therapeutics with ultra-short columns, retention modeling and automated method development

The COVID-19 pandemic necessitated the emergency use authorization (EUA) of several new therapeutics and vaccines. Several monoclonal antibodies (mAbs) were among those authorized for use, and they have served a purpose to provide passive immunity and to help minimize dangerous secondary effects in at-risk and hospitalized patients infected with SARS-CoV-2. With an EUA submission, scientific data on a drug candidate is often collected near simultaneously alongside drug development. In such a situation, there is little time to allow misguided method development nor time to wait on traditional turnaround times. We have taken this dilemma as a chance to propose new means to expediting the chromatographic characterization of protein therapeutics. To this end, we have combined the use of automated, systematic modeling and ultrashort LC columns to quickly optimize high throughput RP, IEX, HILIC and SEC separations for two COVID-19-related mAbs. The development and verification of these four complementary analytical methods required only 2 days of experimental work. In the end, one chromatographic analysis can be performed with a sub-2 min run time such that it is feasible to comprehensively characterize a COVID-19 mAb cocktail by 4 different profiling techniques within a 1-hour turnaround time.

Nonlinear Predictive Modelling Enables In Silico Optimization of Chromatographic Methods for Complex Stationary Phase‑Analyte Interactions

The development of robust analytical assays for separation and analysis of complex multicomponent mixtures can often be challenging, reflecting the increased complexity of new medicine and vaccine processes. In silico liquid chromatography (LC) method development strategies for small molecules have reached a mature stage across the pharmaceutical industry. However, a straightforward approach for large molecules remains elusive because of conformational changes that can often influence chromatographic retention. Nonetheless, an excellent correlation between experimental and predicted retention time is possible by deploying the correct regression retention models in terms of ln k vs. %B and ln k vs. 1/T (ΔtR < 0.1%). Excellent outcomes generated through in silico chromatographic method development of large molecules using different chaotropic and denaturing mobile phases are illustrated. Linear and nonlinear (polynomial regression) retention models using readily available software were deployed as a function of several chromatographic parameters (gradient slope and column temperature) for a variety of proteins (12–670 kDa) and peptides.

Trapping-Enrichment Multi-dimensional Liquid Chromatography with On-Line Deuterated Solvent Exchange for Streamlined Structure Elucidation at the Microgram Scale

At the forefront of chemistry and biology research, development timelines are fast-paced and large quantities of pure targets are rarely available. Herein, we introduce a new framework, which is built upon an automated, online trapping-enrichment multi-dimensional liquid chromatography platform (TE-Dt-mDLC) that enables: 1) highly efficient separation of complex mixtures in a first dimension (¹ D-UV); 2) automated peak trapping-enrichment and buffer removal achieved through a sequence of H₂ O and D₂ O washes using an independent pump setup; and 3) a second dimension separation (² D-UV-MS) with fully deuterated mobile phases and fraction collection to minimize protic residues for immediate NMR analysis while bypassing tedious drying processes and minimizing analyte degradation. Diverse examples of target isolation and characterization from organic synthesis and natural product chemistry laboratories are illustrated, demonstrating recoveries above 90 % using as little as a few micrograms of material.

Automated ion exchange chromatography screening combined with in silico multifactorial simulation for efficient method development and purification of biopharmaceutical targets

Bioprocess development of increasingly challenging therapeutics and vaccines requires a commensurate level of analytical innovation to deliver critical assays across functional areas. Chromatography hyphenated to numerous choices of detection has undeniably been the preferred analytical tool in the pharmaceutical industry for decades to analyze and isolate targets (e.g., APIs, intermediates, and byproducts) from multicomponent mixtures. Among many techniques, ion exchange chromatography (IEX) is widely used for the analysis and purification of biopharmaceuticals due to its unique selectivity that delivers distinctive chromatographic profiles compared to other separation modes (e.g., RPLC, HILIC, and SFC) without denaturing protein targets upon isolation process. However, IEX method development is still considered one of the most challenging and laborious approaches due to the many variables involved such as elution mechanism (via salt, pH, or salt-mediated-pH gradients), stationary phase's properties (positively or negatively charged; strong or weak ion exchanger), buffer type and ionic strength as well as pH choices. Herein, we introduce a new framework consisting of a multicolumn IEX screening in conjunction with computer-assisted simulation for efficient method development and purification of biopharmaceuticals. The screening component integrates a total of 12 different columns and 24 mobile phases that are sequentially operated in a straightforward automated fashion for both cation and anion exchange modes (CEX and AEX, respectively). Optimal and robust operating conditions are achieved via computer-assisted simulation using readily available software (ACD Laboratories/LC Simulator), showcasing differences between experimental and simulated retention times of less than 0.5%. In addition, automated fraction collection is also incorporated into this framework, illustrating the practicality and ease of use in the context of separation, analysis, and purification of nucleotides, peptides, and proteins. Finally, we provide examples of the use of this IEX screening as a framework to identify efficient first dimension (¹D) conditions that are combined with MS-friendly RPLC conditions in the second dimension (²D) for two-dimensional liquid chromatography experiments enabling purity analysis and identification of pharmaceutical targets.

Comprehensive profiling of Sanguisorba officinalis using off-line two-dimensional mixed-mode liquid chromatography × reversed-phase liquid chromatography, tandem high-resolution mass spectrometry, and molecular network

The profiling of natural products is important in modern biological sciences and new drug development. However, the separation and characterization of complex herbal extracts are significantly challenging for researchers in the biochemical field. Herein, an off-line two-dimensional mixed-mode LC × reversed-phase LC system is developed. Our system exhibits high orthogonality and is composed of a newly prepared stationary phase in the first dimension and a traditional C₁₈ phase in the second dimension, and is operated in combination with high-resolution MS and molecular network. Sanguisorba officinalis L. is studied using the proposed method owing to its bioactivity. With the aid of orthogonal separation, the ionization of the individual components is improved. The number of detected compounds and separated peaks are significantly increased when one-dimensional-LC is upgraded to two-dimensional-LC. In addition, 270 compounds (127 of which are tentatively characterized as new compounds, and further confirmation is needed) are successfully characterized based on their fragmentation patterns under the guidance of molecular network, while only 95 compounds are characterized using one-dimensional-LC and high-resolution MS. The results indicate that the developed off-line two-dimensional mixed-mode LC × reversed-phase LC, tandem high-resolution MS, and molecular network method is effective for profiling complex samples. This article is protected by copyright. All rights reserved.

In Silico Method Development of Achiral and Chiral Tandem Column Reversed-phase Liquid Chromatography for Multicomponent Pharmaceutical Mixtures

Tandem column liquid chromatography (LC) is a convenient, cost-effective approach to resolve multicomponent mixtures by serially coupling columns on readily available one-dimensional separation systems without specialized user training. Yet, adoption of this technique remains limited, mainly due to the difficulty in identifying optimal selectivity out of many possible tandem column combinations. At this point, method development and optimization require laborious "hit-or-miss" experimentation and "blind" screening when investigating different column selectivity without standard analytes. As a result, many chromatography practitioners end up combining two columns of similar selectivity, limiting the scope and potential of tandem column LC as a mainstay for industrial applications. To circumvent this challenge, we herein introduce a straightforward in silico multifactorial approach as a framework to expediently map the separation landscape across multiple tandem columns (achiral and chiral) and eluent combinations (isocratic and gradient elution) under reversed-phase LC conditions. Retention models were built using commercially available LC simulator software showcasing less than 2% difference between experimental and simulated retention times for analytes of interest in multicomponent pharmaceutical mixtures (e.g., metabolites and cyclic peptides).

Enantioselective UHPLC Screening Combined with In Silico Modeling for Streamlined Development of Ultrafast Enantiopurity Assays

Enantioselective chromatography has been the preferred technique for the determination of enantiomeric excess across academia and industry. Although sequential multicolumn enantioselective supercritical fluid chromatography screenings are widespread, access to automated ultra-high-performance liquid chromatography (UHPLC) platforms using state-of-the-art small particle size chiral stationary phases (CSPs) is an underdeveloped area. Herein, we introduce a multicolumn UHPLC screening workflow capable of combining 14 columns (packed with sub-2 μm fully porous and sub-3 μm superficially porous particles) with nine mobile phase eluent choices. This automated setup operates under a vast selection of reversed-phase liquid chromatography, hydrophilic interaction liquid chromatography, polar-organic mode, and polar-ionic mode conditions with minimal manual intervention and high success rate. Examples of highly efficient enantioseparations are illustrated from the integration of chiral screening conditions and computer-assisted modeling. Furthermore, we describe the nuances of in silico method development for chiral separations via second-degree polynomial regression fit using LC simulator (ACD/Labs) software. The retention models were found to be very accurate for chiral resolution of single and multicomponent mixtures of enantiomeric species across different types of CSPs, with differences between experimental and simulated retention times of less than 0.5%. Finally, we illustrate how this approach lays the foundation for a streamlined development of ultrafast enantioseparations applied to high-throughput enantiopurity analysis and its use in the second dimension of two-dimensional liquid chromatography experiments.

Enantioselective multiple heart cutting online two-dimensional liquid chromatography-mass spectrometry of all proteinogenic amino acids with second dimension chiral separations in one-minute time scales on a chiral tandem column

In this work, we present a unique, robust and fully automated analytical platform technology for the enantioselective amino acid analysis using a multiple heart cutting RPLC-enantio/stereoselective HPLC-ESI-QTOF-MS method. This 2D-LC method allows the full enantioselective separation of 20 proteinogenic AAs plus 5 isobaric analogues, namely allo-Threonine (aThr), homoserine (Hse), allo-isoleucine (aIle), tert-Leucine (Tle) and Norleucine (Nle), after pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC; AccQ). This N-terminal AA-derivatization method introduces on the one hand beneficial chromatographic properties for ¹D RP-LC (stronger retention) and ²D chiral separation (better chiral recognition), and on the other hand favorable detection properties with its chromophoric, fluorophoric, and easily ionizable quinoline mass tag. The entire separation occurs within a total 2DLC run time of 45 min, which includes the ¹D-RP run and the 68 s ²D chiral separations of 30 heart-cuts (from the ¹D-RP-run) on a chiral quinine carbamate (core-shell QNAX/fully porous ZWIX) tandem column. This relatively short overall run time was only possible by utilizing the highly efficient "smart peak parking" algorithm for the heart cuts and the resulting optimized analysis order thereof. ¹D retention time precisions of <0.21% RSD were a requirement for the time-based sampling mode and finally led to a robust, fully automated enantioselective amino acid analysis platform. This achiral-chiral 2DLC method was applied for the amino acid stereoconfiguration assignment of three peptides (aureobasidin A, a lipopeptide research sample, and octreotide) using an L-[u-¹³C¹⁵N] labelled internal AA standard mix spiked to each sample. The isotopically labelled L-AA standard allowed an easy and straightforward identification and configuration assignment, as well as the relative quantification of amino acids within the investigated peptides, allowing the direct determination of the number of respective amino acids and their chirality within a peptide.

Ultra-high-throughput SPE-MALDI workflow: Blueprint for efficient purification and screening of peptide libraries

At the forefront of synthetic endeavors in the pharmaceutical industry, including drug discovery and high-throughput screening, timelines are tight and large quantities of pure chemical targets are rarely available. In this regard, the development of novel and increasingly challenging chemistries requires a commensurate level of innovation to develop reliable analytical assays and purification workflows with rapid turnaround that enables accelerated pharmacological evaluation. A small-scale automation platform enabling high-throughput analysis and purification to streamline the selection of candidate leads would be a transformative advance. Herein, we introduce an automation-friendly solid-phase extraction-matrix-assisted laser desorption/ionization (SPE-MALDI) platform applied to the high-throughput purification and analysis of peptide libraries. This advance enabled us to purify peptides from microgram levels in less than a day with results comparable to traditional high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS).

Mapping the Separation Landscape in Two-Dimensional Liquid Chromatography: Blueprints for Efficient Analysis and Purification of Pharmaceuticals Enabled by Computer-Assisted Modeling

Recent developments in two-dimensional liquid chromatography (2D-LC) now make separation and analysis of very complex mixtures achievable. Despite being such a powerful chromatographic tool, current 2D-LC technology requires a series of arduous method development activities poorly suited for a fast-paced industrial environment. Recent introductions of new technologies including active solvent modulation and a support for multicolumn 2D-LC are helping to overcome this stigma. However, many chromatography practitioners believe that the lack of a systematic way to effectively optimize 2D-LC separations is a missing link in securing the viability of 2D-LC as a mainstay for industrial applications. In this work, a computer-assisted modeling approach that dramatically simplifies both offline and online 2D-LC method developments is introduced. Our methodology is based on mapping the separation landscape of pharmaceutically relevant mixtures across both first (¹D) and second (²D) dimensions using LC Simulator (ACD/Labs) software. Retention models for ¹D and ²D conditions were built using a minimal number of multifactorial modeling experiments (2 × 2 or 3 × 3 parameters: gradient slope, column temperature, and different column and mobile phase combinations). The approach was first applied to online 2D-LC analysis involving achiral and chiral separations of complex mixtures of enantiomeric species. In these experiments, the retention models proved to be quite accurate for both the ¹D and ²D separations, with retention time differences between experiments and simulations of less than 3.5%. This software-based concept was also demonstrated for offline 2D-LC purification of drug substances.

Achiral-Chiral Two-Dimensional Liquid Chromatography Platform to Support Automated High-Throughput Experimentation in the Field of Drug Development

Automated high-throughput experimentation (HTE) is a powerful tool for scientists to explore and optimize chemical transformations by simultaneously screening yield, stereoselectivity, and impurity profiles. To analyze the HTE samples, high-throughput analysis (HTA) platforms must be fast, accurate, generic, and specific at the same time. A large amount of high-quality data is critical for the success of machine learning models in the era of big data. Conventional chiral liquid chromatography-mass spectrometry (LC/MS) HTE methods are hampered by compound co-eluting, possible ion suppression, and limited chiral column lifetime in the presence of crude reaction mixtures or complex sample matrices. To overcome these limitations, a generic and fast achiral-chiral heart-cutting two-dimensional (2D)-LC method has been developed to determine both the yield and stereoselectivity of chemical transformations within a 10 min run time. Successful implementation of the 2D-LC HTA platform in a routine drug development environment was achieved for real-world project support, with the analysis so far of over 2000 reaction mixtures prepared in the 96-well plate format. Excellent performance of the method was demonstrated by relative standard deviation (RSD) lower than 0.83% for the ¹D and ²D retention times, and determination coefficients higher than 0.99. The presented HTA 2D-LC platform has had a significant impact on drug development by analyzing the HTE samples rapidly with unambiguous peak tracking and providing a robust approach for accurately generating a large amount of high-quality data in a short time.