Szabolcs Fekete

University of Lausanne, Lausanne, Vaud, Switzerland

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Publications (76)

  • Szabolcs Fekete · Alain Beck · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: Cation exchange chromatography (CEX) is a well established strategy for the characterization of monoclonal antibodies (mAbs). The optimization of mobile phase conditions is well described in the literature, but there is a lack of information about CEX stationary phases for the analysis of therapeutic proteins. The aim of this study was to compare five state-of-the-art CEX stationary phases based on the retention, selectivity and resolving power achieved in pH- and salt-gradient modes, with various therapeutic mAbs and their variants. The Sepax Antibodix WCX-NP3, Thermo MAbPac SCX-10 RS, YMC BioPro SP-F, Waters Protein-Pak Hi Res SP and Agilent Bio mAb NP1.7 SS were considered in this study. In terms of retention, the YMC Bio Pro SP-F material was the less retentive one, while the Agilent Bio mAb NP1.7 SS provides the highest retention. Regarding the selectivity achieved between the main mAbs isoforms and their variants, the Thermo MabPac SCX column generally gave the highest selectivity. Finally, it was hard to rank columns in term of kinetic performance since their performance is strongly solute (mAb) and elution mode (pH or salt gradient) dependent. However, the highest resolution - in most cases - was observed on the strong cation exchanger YMC Bio Pro SP-F material. Copyright © 2015 Elsevier B.V. All rights reserved.
    Article · Apr 2015 · Journal of pharmaceutical and biomedical analysis
  • Szabolcs Fekete · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: The goal of this work was to evaluate the changes in retention induced by frictional heating, pressure and temperature under ultra high pressure liquid chromatography (UHPLC) conditions, for four model proteins (i.e. lysozyme, myoglobin, fligrastim and interferon alpha-2A) possessing molecular weights between 14 and 20kDa. First of all, because the decrease of the molar volume upon adsorption onto a hydrophobic surface was more pronounced for large molecules such as proteins, the impact of pressure appears to overcome the frictional heating effects. Nevertheless, we have also demonstrated that the retention decrease due to frictional heating was not negligible with such large biomolecules in the variable inlet pressure mode. Secondly, it is clearly shown that the modification of retention under various pressure and temperature conditions cannot be explained solely by the frictional heating and pressure effects. Indeed, some very uncommon van't Hoff plots (concave plots with a maximum) were recorded for our model/therapeutic proteins. These maximum retention factors values on the van't Hoff plots indicate a probable change of secondary structure/conformation with pressure and temperature. Based on these observations, it seems that the combination of pressure and temperature causes the protein denaturation and this folding-unfolding procedure is clearly protein dependent. Copyright © 2015 Elsevier B.V. All rights reserved.
    Article · Mar 2015 · Journal of Chromatography A
  • Szabolcs Fekete · Alain Beck · Jean-Luc Veuthey · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: Ion-exchange chromatography (IEX) is a historical technique widely used for the detailed characterization of therapeutic proteins and can be considered as a reference and powerful technique for the qualitative and quantitative evaluation of charge heterogeneity. The goal of this review is to provide an overview of theoretical and practical aspects of modern IEX applied for the characterization of therapeutic proteins including monoclonal antibodies (Mabs) and antibody drug conjugates (ADCs). The section on method development describes how to select a suitable stationary phase chemistry and dimensions, the mobile phase conditions (pH, nature and concentration of salt), as well as the temperature and flow rate, considering proteins isoelectric point (pI). In addition, both salt-gradient and pH-gradient approaches were critically reviewed and benefits as well as limitations of these two strategies were provided. Finally, several applications, mostly from pharmaceutical industries, illustrate the potential of IEX for the characterization of charge variants of various types of biopharmaceutical products. Copyright © 2015 Elsevier B.V. All rights reserved.
    Article · Feb 2015 · Journal of pharmaceutical and biomedical analysis
  • Michael W. Dong · Davy Guillarme · Szabolcs Fekete · [...] · Nik P. Chetwyn
    [Show abstract] [Hide abstract] ABSTRACT: In this article, we present experimental results and method validation data from two analytical case studies of complex small-molecule pharmaceuticals to illustrate the utility and potential advantages of ultrahigh-pressure liquid chromatography (UHPLC) in high-resolution separations, particularly for quality control purposes. The focus is on the use of UHPLC in potency assays and purity analysis of complex drug substances and drug products using UV detection, where resolution of all analytes is required. Finally, we discuss some potential technical issues and mitigation strategies for conducting these high-resolution chromatographic analyses in a regulated environment.
    Article · Feb 2015 · LC GC Europe
  • Szabolcs Fekete · Alain Beck · Elsa Wagner · [...] · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: The poor recovery of large biomolecules is a well-known issue in reversed-phase liquid chromatography. Several papers have reported this problem, but the reasons behind this behaviour are not yet fully understood. In the present study, state-of-the-art reversed-phase wide-pore stationary phases were used to evaluate the adsorption of therapeutic monoclonal antibodies. These biomolecules possess molar mass of ∼150 000 g/mol and isoelectric points between 6.6 and 9.3. Two types of stationary phases were tested, the Phenomenex Aeris Widepore (silica based), with 3.6 μm superficially porous particles and the Waters Acquity BEH300 (ethylene-bridged hybrid) with 1.7 μm fully porous particles. A systematic investigation was carried out using 11 immunoglobulin G1, G2 and G4 antibodies, namely, panitumumab, natalizumab, cetuximab, bevacizumab, trastuzumab, rituximab, palivizumab, belimumab, adalimumab, denosumab and ofatumumab. All are approved by the Food and Drug Administration and the European Medicines Agency in various therapeutic indications and are considered as reference antibodies. Several test proteins such as human serum albumin, transferrin, apoferritin, ovalbumin and others, possessing a molar mass between 42 000 and 443 000 g/mol, were also evaluated to draw reliable conclusions. The purpose of this study was to find a correlation between the adsorption of monoclonal antibodies and their physicochemical properties. Therefore, the impact of isoelectric point, molar mass, protein glycosylation and hydrophobicity was investigated. The adsorption of intact antibodies on the stationary phase was significantly higher than that of proteins of similar size, isoelectric point or hydrophobicity. The present study also demonstrates the unique behaviour of monoclonal antibodies contributing some unwanted and unpredictable strong secondary interactions. This article is protected by copyright. All rights reserved.
    Article · Jan 2015 · Journal of Separation Science
  • Szabolcs Fekete · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: The pharmaceutical market has markedly changed over the past few years, and there are today an increasing number of therapeutic drugs produced from biological sources. These biopharmaceuticals include recombinant peptides, proteins, and monoclonal antibodies (mAbs). Their detailed characterization could be difficult and time consuming, so it requires powerful chromatographic and spectroscopic methods. In this context, the use of columns packed with sub-2-µm particles at very high pressure, also known as ultra-high performance (or pressure) liquid chromatography (UHPLC) has been reported as successful. Various modes of chromatography are compatible with UHPLC columns and conditions, including reversed-phase liquid chromatography (RPLC), size-exclusion chromatography (SEC), ion-exchange chromatography (IEX) and hydrophilic interaction chromatography (HILIC).
    Article · Dec 2014 · TrAC Trends in Analytical Chemistry
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    [Show abstract] [Hide abstract] ABSTRACT: Since its commercial introduction in 2004, there has been a considerable interest in ultra-high-performance (pressure) liquid chromatography (UHPLC), which dramatically increases the throughput of regular HPLC methods. Although the ability to achieve fast separations and good resolution are the main drivers for the increasing use of UHPLC, we describe a number of other trends in this review, such as: (1) use of UHPLC technology to perform high-resolution analysis of complex samples; (2) development of columns packed with sub-2-µm particles to achieve different chromatographic modes (i.e. chiral LC, SEC, IEX, HILIC, and SFC); (3) evaluation of higher pressure drop, higher temperature, smaller particle sizes and sub-2-µm core-shell particles, to further improve kinetic performance; (4) use of UHPLC for enhancing the characterization of biopharmaceuticals; and, (5) development of UHPLC-MS for applications, including bioanalysis, multi-residue screening, and metabolomics.
    Full-text Article · Dec 2014 · TrAC Trends in Analytical Chemistry
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    Balázs Bobály · Davy Guillarme · Szabolcs Fekete
    [Show abstract] [Hide abstract] ABSTRACT: A new superficially porous material possessing a carbon core and nanodiamond-polymer shell and pore size of 180Å was evaluated for the analysis of large proteins. Because the stationary phase on this new support contains a certain amount of protonated amino groups within the shell structure, the resulting retention mechanism is most probably a mix between reversed phase and anion exchange. However, under the applied conditions (0.1-0.5% TFA in the mobile phase), it seemed that the main retention mechanism for proteins was hydrophobic interaction with the C18 alkylchains on this carbon based material. In this study, we demonstrated that there was no need to increase mobile phase temperature, as the peak capacity was not modified considerably between 30 and 80°C for model proteins. Thus, the risk of thermal on-column degradation or denaturation of large proteins is not relevant. Another important difference compared to silica-based materials is that this carbon-based column requires larger amount of TFA, comprised between 0.2 and 0.5%. Finally, it is important to mention that selectivity between closely related proteins (oxidized, native and reduced forms of Interferon α-2A variants) could be changed mostly through mobile phase temperature. Copyright © 2014 Elsevier B.V. All rights reserved.
    Full-text Article · Nov 2014 · Journal of Pharmaceutical and Biomedical Analysis
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    [Show abstract] [Hide abstract] ABSTRACT: The goal of this study was to evaluate the combination of powerful chromatographic methods and compact single quadrupole MS device for simple in vitro cytochrome P450 (CYP) inhibition assay, instead of more expensive triple quadrupole MS/MS detectors. For this purpose, two modern chromatographic approaches (ultra-high pressure liquid chromatography (UHPLC) and ultra-high performance supercritical fluid chromatography (UHPSFC)) were tested in combination with simple MS detector. To show the applicability for an in vitro CYP-mediated metabolism assay using the cocktail approach, a method was first developed in UHPLC-MS to separate a mixture of 8 probe substrates and 8 CYP-specific metabolites. A screening procedure was initially applied to determine the best combination of a column, an organic modifier and a mobile-phase pH, followed by fine tuning of the conditions (i.e., gradient profile, temperature and pH) using HPLC modeling software. A similar sequential method development procedure was also evaluated for UHPSFC-MS. For method development where peak tracking is necessary, the use of single quadrupole MS was found to be extremely valuable for following the investigated analytes. Ultimately, a baseline separation of the 16 compounds was achieved in both UHPLC-MS and UHPSFC-MS with an analysis time of less than 7 minutes. In a second series of experiments, sensitivity was evaluated, and LOQ values were between 2 and 100 ng/mL in UHPLC-MS, while they ranged from 2 to 200 ng/mL in UHPSFC-MS. Based on the concentrations employed for the current in vitro phase I metabolism assay, these LOQ values were appropriate for this type of application. Finally, the two analytical methods were applied to in vitro CYP-dependent metabolism testing. Two well-known phytochemical inhibitors, yohimbine and resveratrol, were investigated, and reliable conclusions were drawn from these experiments with both UHPLC-MS and UHPSFC-MS. At the end, the proposed strategy of optimized chromatography combined with simple MS device has been shown to potentially compete with the widely used combination of generic chromatography and highly selective MS/MS device for simple in vitro CYP inhibition assays. In addition, our analytical method may be easier to use in a routine environment; the instrument cost is significantly reduced and the two developed method fit for purpose.
    Full-text Article · Oct 2014 · Journal of Chromatography A
  • Szabolcs Fekete · Alain Beck · Jenő Fekete · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: Ion exchange chromatography (IEX) is a historical technique widely used for the detailed characterization of therapeutic proteins and can be considered as a reference and powerful technique for the qualitative and quantitative evaluation of charge variants. When applying salt gradient IEX approach for monoclonal antibodies (mAbs) characterization, this approach is described as time-consuming to develop and product-specific. The goal of this study was to tackle these two bottle-necks. By modeling the retention of several commercial mAbs and their variants in IEX, we proved that the mobile phase temperature was not relevant for tuning selectivity, while optimal salt gradient program can be easily found based on only two initial gradients of different slopes. Last but not least, the dependence of retention vs. pH being polynomial, three initial runs at different pH were required to optimize mobile phase pH. Finally, only 9h of initial experiments were necessary to simultaneously optimize salt gradient profile and pH in IEX. The data can then be treated with commercial modeling software to find out the optimal conditions to be used, and accuracy of retention times prediction was excellent (less than 1% variation between predicted and experimental values). Second, we also proved that generic IEX conditions can be applied for the characterization of mAbs possessing a wide range of pI, from 6.7 to 9.1. For this purpose, a strong cation exchange column has to be employed at a pH below 6 and using a proportion of NaCl up to 0.2M. Under these conditions, all the mAbs were properly eluted from the column. Therefore, salt gradient CEX can be considered as a generic multi-product approach.
    Article · Sep 2014 · Journal of Pharmaceutical and Biomedical Analysis
  • Róbert Kormány · Imre Molnár · Jenő Fekete · [...] · Szabolcs Fekete
    [Show abstract] [Hide abstract] ABSTRACT: This paper describes a new and fast ultra-high pressure liquid chromatographic separation of amlodipine and bisoprolol and all their closely related compounds, for impurity profiling purposes. Computer-assisted method development was applied and the impact of several state-of-the-art stationary phase column chemistries (50 × 2.1 mm, sub-2 μm, and core–shell type materials) on the achievable selectivity and resolution was investigated. The work was performed according to quality by design principles using design of experiment with three experimental factors; namely the gradient time (t G), temperature (T), and mobile phase pH. Thanks to modeling software, it was proved that the separation of all compounds was feasible on numerous column chemistries within <10 min, by proper adjustments of variables. It was also demonstrated that the reliability of predictions was good, as the predicted retention times and resolutions were in good agreement with the experimental ones. The final, optimized method separates 16 peaks related to amlodipine and bisoprolol within 7 min, ensuring baseline resolution between all peak-pairs.
    Article · Sep 2014 · Chromatographia
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    [Show abstract] [Hide abstract] ABSTRACT: Superficially porous particles (SPP), or core shell particles, which consist of a non-porous silica core surrounded by a thin shell of porous silica, have gained popularity as a solid support for chromatography over the last decade. In the present study, five unbonded silica, one diol, and two ethylpyridine (2-ethyl and 4-ethyl) SPP columns were evaluated under SFC conditions using two mixtures, one with 17 drug-like compounds and the other one with 7 drug-like basic compounds. Three of the SPP phases, SunShell™ 2-ethylpyridine (2-EP), Poroshell™ HILIC, and Ascentis(®) Express HILIC, exhibited superior performances relative to the others (reduced theoretical plate height (hmin) values of 1.9-2.5 for neutral compounds). When accounting for both achievable plate count and permeability of the support using kinetic plot evaluation, the Cortecs™ HILIC 1.6μm and Ascentis(®) Express HILIC 2.7μm phases were found to be the best choices among tested SPPs to reach efficiencies up to 30,000 plates in the minimum amount of time. For desired efficiencies ranging from 30,000 to 60,000 plates, the SunShell™ 2-EP 2.6μm column clearly outperformed all other SPPs. With the addition of a mobile phase additive such as 10mM ammonium formate, which was required to elute the basic components with sharp peaks, the Poroshell™ HILIC, SunShell™ Diol and SunShell™ 2-EP phases represent the most orthogonal SPP columns with the highest peak capacities. This study demonstrates the obvious benefits of using columns packed with SPP on current SFC instrumentation.
    Full-text Article · Aug 2014 · Journal of Chromatography A
  • Szabolcs Fekete · Jenő Fekete · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: In this study, the retention changes induced by frictional heating were evaluated for model small compounds (150-190Da) and a small protein, namely insulin (5.7kDa). For this purpose, the effect of longitudinal temperature gradient caused by frictional heating was experimentally dissociated from the combined effect of pressure and frictional heating, by working either in constant and variable inlet pressure modes. Various columns packed with core-shell and fully porous sub-2μm particles were tested. It appears that frictional heating was less pronounced on the column packed with smallest core-shell particles (1.3μm), compared to the ones packed with core-shell and fully porous particles of 1.7-1.8μm. This observation was attributed to the low permeability of this material and the fact that it can only be employed in a restricted flow rate range, thus limiting the generated heat power. In addition, the thermal conductivity of the solid silica core of superficially porous particles (1.4W/m/K) is known to be much larger than that of fully porous silica. Then, the heat dissipation is improved. However, if systems with higher pressure capability would be available and the mechanical stability of 1.3μm core-shell material was extended to e.g. 2000bar, the retention would be more severely impacted. At 2000bar, ∼4.4W heat power and +30°C increase at column outlet temperature is expected. Last but not least, when analyzing large molecules, the impact of pressure overcomes the frictional heating effects. This was demonstrated in this study with insulin (∼5.7kDa).
    Article · Jul 2014 · Journal of Chromatography A
  • Michael W. Dong · Szabolcs Fekete · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: Columns packed with superficially porous particles (SPPs) have created considerable excitement over the last few years. Indeed, this column technology manifests the advantages of fully porous material (loading capacity, retention) and some beneficial properties of nonporous particles (kinetic performance). This review provides an updated overview of the theory behind the success of SPP technology, trends, benefits, and limitations. It also summarizes the latest developments of sub-2-μm SPPs and instrumental constraints associated with their use. Finally, it describes several applications to illustrate the performance and the universal applicability of these newly engineered particles.
    Article · Jun 2014 · Lc Gc North America
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    Szabolcs Fekete · Alain Beck · Jean-Luc Veuthey · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: Size exclusion chromatography (SEC) is a historical technique widely employed for the detailed characterization of therapeutic proteins and can be considered as a reference and powerful technique for the qualitative and quantitative evaluation of aggregates. The main advantage of this approach is the mild mobile phase conditions that permit the characterization of proteins with minimal impact on the conformational structure and local environment. Despite the fact that the chromatographic behavior and peak shape are hardly predictable in SEC, some generic rules can be applied for SEC method development, which are described in this review. During recent years, some improvements were introduced to conventional SEC that will also be discussed. Of these new SEC characteristics, we discuss (i) the commercialization of shorter and narrower columns packed with reduced particle sizes allowing an improvement in the resolution and throughput; (ii) the possibility of combining SEC with various detectors, including refractive index (RI), ultraviolet (UV), multi-angle laser light scattering (MALLS) and viscometer (IV), for extensive characterization of protein samples and (iii) the possibility of hyphenating SEC with mass spectrometry (MS) detectors using an adapted mobile phase containing a small proportion of organic modifiers and ion-pairing reagents.
    Full-text Article · Apr 2014 · Journal of pharmaceutical and biomedical analysis
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    Balázs Bobály · Davy Guillarme · Szabolcs Fekete
    [Show abstract] [Hide abstract] ABSTRACT: The aim of this study was to evaluate the possibilities/limitations of recent RP-LC columns packed with 1.6 μm superficially porous particles (Waters Cortecs) and to compare its potential to other existing sub-2 μm core-shell packings. The kinetic performance of Kinetex 1.3 μm, Kinetex 1.7 μm and Cortecs 1.6 μm stationary phases was assessed. It was found that the Kinetex 1.3 μm phase outperforms its counterparts for ultra-fast separations. Conversely, the Cortecs 1.6 μm packing seemed to be the best stationary phase for assays with longer analysis time in isocratic and gradient modes, considering small molecules and peptides as test probes. This exceptional behaviour was attributed to its favourable permeability and somewhat higher mechanical stability (ΔPmax of 1200 bar). The loading capacity of these three columns was also investigated with basic and neutral drugs analyzed under acidic conditions. It appears that the loading capacities of Cortecs 1.6 μm and Kinetex 1.7 μm were very close, while it was reduced by 2-7-fold on the Kinetex 1.3 μm packing. However, this observation is dependent on the nature of the compound and certainly also on mobile phase conditions. This article is protected by copyright. All rights reserved.
    Full-text Article · Feb 2014 · Journal of Separation Science
  • Róbert Kormány · Jenő Fekete · Davy Guillarme · Szabolcs Fekete
    [Show abstract] [Hide abstract] ABSTRACT: In this contribution, the possibility to automatically transfer RPLC methods between different column dimensions and instruments was evaluated using commercial modelling software. The method transfer reliability was tested with loratadine and its 7 related pharmacopeial impurities. In this study, state-of-the-art columns packed with superficially porous particles of 5, 2.6, 1.7 and 1.3μm particles were exclusively employed. A fast baseline separation of loratadine and related impurities (Rs,min=2.49) was achieved under the best analytical conditions (i.e. column of 50mm×2.1mm, 1.3μm, 10-90% ACN in 5min, T=40°C, pH=3, F=0.5ml/min). This optimal method was successfully tested on columns packed with other particle sizes, namely 1.7 and 2.6μm, to reduce pressure drop. The selectivities and retentions remained identical, while the peak widths were logically wider, leading to a reduction of peak capacity from 203 to 181 and 159 on the 1.3, 1.7 and 2.6μm particles, respectively. On the minimum, the resolution was equal to 1.54 on the 50mm×2.1mm, 2.6μm stationary phase. Next to this, the method was transferred to columns of different lengths, inner diameters and particle sizes (100mm×3mm, 2.6μm or 150mm×4.6mm, 5μm). These columns were used on other LC instruments possessing larger dwell volumes. The modelling software employed for developing the original method was able to calculate the new gradient conditions to be used. The accuracy of prediction was excellent, as the average retention time errors between predicted and observed chromatograms were -0.11% and 0.45% when transferring the method to 100mm×3mm and 150mm×4.6mm columns, respectively. This work proves the usefulness and validity of HPLC modelling software for transferring methods between different instruments, column dimensions and/or flow rates.
    Article · Jan 2014 · Journal of pharmaceutical and biomedical analysis
  • Róbert Kormány · Jenő Fekete · Davy Guillarme · Szabolcs Fekete
    Article · Jan 2014
  • Róbert Kormány · Jenő Fekete · Davy Guillarme · Szabolcs Fekete
    [Show abstract] [Hide abstract] ABSTRACT: The goal of this study was to evaluate the accuracy of simulated robustness testing using commercial modelling software (DryLab) and state-of-the-art stationary phases. For this purpose, a mixture of amlodipine and its seven related impurities was analyzed on short narrow bore columns (50×2.1mm, packed with sub-2μm particles) providing short analysis times. The performance of commercial modelling software for robustness testing was systematically compared to experimental measurements and DoE based predictions. We have demonstrated that the reliability of predictions was good, since the predicted retention times and resolutions were in good agreement with the experimental ones at the edges of the design space. In average, the retention time relative errors were <1.0%, while the predicted critical resolution errors were comprised between 6.9 and 17.2%. Because the simulated robustness testing requires significantly less experimental work than the DoE based predictions, we think that robustness could now be investigated in the early stage of method development. Moreover, the column interchangeability, which is also an important part of robustness testing, was investigated considering five different C8 and C18 columns packed with sub-2μm particles. Again, thanks to modelling software, we proved that the separation was feasible on all columns within the same analysis time (less than 4min), by proper adjustments of variables.
    Article · Nov 2013 · Journal of pharmaceutical and biomedical analysis
  • Szabolcs Fekete · Davy Guillarme
    [Show abstract] [Hide abstract] ABSTRACT: The aim of this work was to evaluate the practical possibilities in gradient elution mode of a column packed with 1.3μm core-shell particles recently released on the market. For this purpose, two types of analytes possessing different diffusion coefficients were selected (small molecule and peptide). It appears that the new 1.3μm material was particularly well suited for fast separations, compared to other existing core-shell particle dimensions in gradient mode. The new material systematically outperforms the other existing ones for peak capacity up to 300 for small molecules and 700 (corresponding to t0=15min) for peptides. Based on these cut-off values, the advantage of column packed with 1.3μm was much more obvious for peptides vs. small molecules analysis. Further improvements in terms of column mechanical stability and system upper pressure capability could expand the limits of separation speed and efficiency to a different level. Again, because of the current pressure limitation and low permeability, a column length of more than 5-8cm is never desired for small molecules analysis in gradient elution. On the contrary, longer columns were useful for peptide analysis. As example, a column of 28cm packed with 1.3μm particles provides a peak capacity of 1000 in the case of peptides analysis. All the predicted values were experimentally confirmed using a standardized extract of Ginkgo biloba and a tryptic digest of a monoclonal antibody (Panitumumab). For the plant extract, the better performance was always achieved with a 5cm long column (P=267 and 268 for the 5 and 15cm, respectively, using a gradient time of 10 and 40min, respectively). Finally, in the case of peptide mapping, a 15cm long column packed with 1.3μm particles was the best choice (P=176 and 311 for the 5 and 15cm, respectively, using a gradient time of 10 and 40min, respectively).
    Article · Oct 2013 · Journal of Chromatography A