Szabolcs Fekete

University of Lausanne, Lausanne, Vaud, Switzerland

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Publications (54)178.31 Total impact

  • Szabolcs Fekete, Davy Guillarme
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    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).
    Journal of Chromatography A 10/2013; 1320. DOI:10.1016/j.chroma.2013.10.061 · 4.26 Impact Factor
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    ABSTRACT: Recently, there has been a renewed interest in supercritical fluid chromatography (SFC), due to the introduction of state-of-the-art instruments and dedicated columns packed with small particles. However, the achievable kinetic performance and practical possibilities of such modern SFC instruments and columns has not been described in details until now. The goal of the present contribution was to provide some information about the optimal column dimensions (i.e. length, diameter and particle size) suitable for such state-of the-art systems, with respect to extra-column band broadening and system upper pressure limit. In addition, the reliability of the kinetic plot methodology, successfully applied in RPLC, was also evaluated under SFC conditions. Taking into account the system variance, measured at ∼85μL(2), on modern SFC instruments, a column of 3mm I.D. was ideally suited for the current technology, as the loss in efficiency remained reasonable (i.e. less than 10% decrease for k>6). Conversely, these systems struggle with 2.1mm I.D. columns (55% loss in N for k=5). Regarding particle size, columns packed with 5μm particles provided unexpectedly high minimum reduced plate height values (hmin=3.0-3.4), while the 3.5 and 1.7μm packing provided lower reduced plate heights hmin=2.2-2.4 and hmin=2.7-3.2, respectively. Considering the system upper pressure limit, it appears that columns packed with 1.7μm particles give the lowest analysis time for efficiencies up to 40,000-60,000 plates, if the mobile phase composition is in the range of 2-19% MeOH. The 3.5μm particles were attractive for higher efficiencies, particularly when the modifier percentage was above 20%, while 5μm was never kinetically relevant with modern SFC instruments, due to an obvious limitation in terms of upper flow rate value. The present work also confirms that the kinetic plot methodology could be successfully applied to SFC, without the need for isopycnic measurements, as the difference in plate count between predicted and experimental values obtained by coupling several columns in series (up to 400mm) was on average equal to 3-6% and with a maximum of 13%.
    Journal of Chromatography A 09/2013; 1314. DOI:10.1016/j.chroma.2013.09.039 · 4.26 Impact Factor
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    ABSTRACT: Innovative columns made with very small core-shell particles (1.0-1.4μm) were investigated over a wide experimental space using state-of-the-art ultra high performance liquid chromatography (UHPLC) instruments. Among the columns tested is one that is now commercially available and is made with 1.3μm core-shell particles consisting of non-porous cores about 0.9μm in size and porous shells <0.2μm thick. This work demonstrated that exceptionally low observed minimum plate heights of 2.2μm could be obtained using columns packed with 1.3μm particles, corresponding to a plate count of over 450,000 plates/m. It was shown that only low volume columns allow operation under optimal conditions with current top-of-the-line UHPLC instruments. It was also demonstrated that the loss in performance caused by frictional heating effects remains negligible. Finally, the practical utility of these columns was confirmed with several real-world applications requiring extreme resolving power (i.e. peptide mapping, sample typical of metabolomic studies and crude human insulin). The performance achieved was compared to that of a reference UHPLC column packed with 1.7μm fully porous particles. The column packed with 1.3μm particles gave peak capacity values that were 20-40% higher than the reference column for the same analysis time.
    Journal of Chromatography A 08/2013; DOI:10.1016/j.chroma.2013.08.065 · 4.26 Impact Factor
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    ABSTRACT: In this study, pressure induced changes in retention were measured for model peptides possessing molecular weights between ∼1 and ∼4kDa. The goal of the present work was to evaluate if such changes were only attributed to the variation of molar volume and if they could be estimated prior to the experiments, using theoretical models. Restrictor tubing was employed to generate pressures up to 1000bar and experiments were conducted for mobile phase temperatures comprised between 30 and 80°C. As expected, the retention increases significantly with pressure, up to 200% for glucagon at around 1000bar compared to ∼100bar. The obtained data were fitted with a theoretical model and the determination coefficients were excellent (r(2)>0.9992) for the peptides at various temperatures. On the other hand, the pressure induced change in retention was found to be temperature dependent and was more pronounced at 30°C vs. 60 or 80°C. Finally, using the proposed model, it was possible to easily estimate the pressure induced increase in retention for any peptide and mobile phase temperature. This allows to easily estimating the expected change in retention, when increasing the column length under UHPLC conditions.
    Journal of Chromatography A 08/2013; DOI:10.1016/j.chroma.2013.08.045 · 4.26 Impact Factor
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    ABSTRACT: When performing fast LC with 50mm narrow-bore columns packed with small particles, the LC instrumentation can give rise to non-negligible band broadening. In the present study, the loss in chromatographic efficiency attributed to nine different mass spectrometers of various brands, ionization source geometries and types of analyzers was assessed. In their standard configurations, the extra-column variance of these UHPLC-MS systems was estimated to vary from 20 to >100μL(2). However, it was demonstrated that these differences arise exclusively from the chromatographic system (i.e., injector, tubing, valves, heater) and from the tubing employed to interface the UHPLC instrument with the MS device. By minimizing the tubing used for each UHPLC system, the extra-column variance was reduced to approximately 17-19μL(2) at 600μL/min, for all types of configurations. To achieve optimal chromatographic performance, it is therefore of prime importance to optimize the UHPLC configuration prior to conducting MS. The tubing located between the UHPLC system and the ionization source entrance was found to be particularly critical, as it contributes to band broadening even in the gradient mode. Using an optimized UHPLC-MS configuration, the loss in efficiency with a 50×2.1mm I.D. column was negligible for k>7. However, the efficiency loss with 1mm I.D. columns remained non-negligible for all current instrumentation, even for solutes with a value of k>20. Indeed, for a mixture of isobaric substrates and metabolites analyzed in gradient mode, the peak widths decreased by approximately 50% between a standard and optimized UHPLC-MS configuration, considering a 50×2.1mm, 1.7μm column. The peak broadening was changed by 230% on a 50×1mm, 1.7μm stationary phase, for the same system configurations.
    Journal of Chromatography A 08/2013; DOI:10.1016/j.chroma.2013.08.001 · 4.26 Impact Factor
  • Szabolcs Fekete, Davy Guillarme
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    ABSTRACT: The goal of this study was to critically evaluate a new generation of columns packed with 1.3μm core-shell particles. The practical possibilities and limitations of this column technology were assessed and performance was compared with other reference columns packed with 1.7, 2.6 and 5μm core-shell particles. The column efficiency achieved with 1.3μm core-shell particles was indeed impressive, Hmin value of only 1.95μm was achieved, this would correspond to an efficiency of more than 500,000plates/m. The separation impedance of this column was particularly low, Emin=2000, mostly due to a reduced plate height, h of 1.50. Comparing the kinetic performance of 1.3μm core-shell particles to that of other particle dimensions tested in this study revealed that the 1.3μm material could provide systematically the shortest analysis time in a range of below 30,000 theoretical plates (N<30,000).Despite its excellent chromatographic performance, it was evident that this column suffers from the limitations of current instrumentation in terms of upper pressure limit and extra-column band broadening: (1) even at 1200bar, it was not possible to reach an optimal linear velocity showing minimal plate height value, due to the low permeability of this column (Kv=1.7×10(-11)cm(2)), and (2) for these short narrow bore columns packed with 1.3μm core shell particles, which is mandatory for performing fast-analysis and preventing the influence of frictional heat on column performance in UHPLC, it was observed that the extra-column band broadening could have a major impact on the apparent kinetic performance. In the present work, significant plate count loss was noticed for retention factors of less than 5, even with the best system on the market (σ(2)ec=2μL(2)).
    Journal of Chromatography A 08/2013; 1308. DOI:10.1016/j.chroma.2013.08.008 · 4.26 Impact Factor
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    ABSTRACT: In the present study, three types of silica-based monoliths, i.e., the first and second generations of commercial silica monolithic columns and a wide-pore prototype monolith were compared for the analysis of large biomolecules. These molecules possess molecular weights between 1 and 66 kDa. The gradient kinetic performance of the first-generation monolith was lower than that of the second generation, for large biomolecules (>14 kDa) but very close with smaller ones (1.3-5.8 kDa). In contrast, the wide-pore prototype column was particularly attractive with proteins larger than 19 kDa (higher peak capacity). Among these three columns, the selectivity and retention remained quite similar but a possible larger number of accessible and charged residual silanols was noticed on the wide-pore prototype material, which lead to unpredicted small changes in selectivity and slightly broader peaks than expected. The peak shapes attained with the addition of 0.1% formic acid in the mobile phase remained acceptable for MS coupling, particularly for biomolecules of less than 6 kDa. It was found that one of the major issues with all of these silica-based monoliths is the possible poor recovery of large biomolecules (principally with monoclonal antibody fragments of more than 25 kDa). This article is protected by copyright. All rights reserved.
    Journal of Separation Science 07/2013; 36(14). DOI:10.1002/jssc.201300323 · 2.59 Impact Factor
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    ABSTRACT: Monoclonal antibodies (mAbs) represent one of the fastest growing areas of new drug development. However, their analytical characterization is complex and generally requires an array of orthogonal analytical techniques. Reversed phase liquid chromatography is a valuable strategy due to its high resolving power and straightforward compatibility to mass spectrometry. The present study demonstrates that high peak capacity can be attained with intact mAb of ∼150kDa, reduced mAb fragments of ∼25-50kDa and also digested mAb generating numerous peptides of ∼0.5-3kDa. Several long columns packed with fully porous wide-pore sub-2μm particles were coupled in series to evaluate the effect of column length on peak capacity. By using three columns of 150mm length, a mobile phase temperature of 80°C and a gradient time of around 20min, peak capacities of 117 and 128 were obtained for a commercial intact mAb and its reduced mAb fragments, respectively. On the other hand, when peptide mapping was performed at 50°C, with a gradient time of 270min and a column length of 450mm, a peak capacity of more than 700 was achieved.
    Journal of pharmaceutical and biomedical analysis 05/2013; 83C:273-278. DOI:10.1016/j.jpba.2013.05.022 · 2.83 Impact Factor
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    ABSTRACT: In the last decade, an important technical evolution has occurred in pharmaceutical analysis with numerous innovative supports and advanced instruments that have been proposed to achieve fast or ultra-fast separations in LC with an excellent sensitivity and ease of operation. Among the proposed strategies to increase the throughput, the use of short narrow-bore columns packed with sub-3μm core-shell and porous sub-2μm particles have emerged as the gold standards. Nevertheless, to take the full benefits of these modern supports, a suitable chromatographic system has to be employed. This review summarizes the instrumental needs and challenges in terms of extra-column variance, dwell volume, maximum system pressure, detector data acquisition rate, and injection cycle time. In addition, because of their reasonable pressure drop, the use of columns packed with sub-3μm core-shell particles on a conventional LC instrument is discussed in detail. A methodology is proposed to check the compatibility between stationary phase and instrument, and some solutions are proposed to improve the performance of standard instruments. Finally, because the column technology is evolving faster than instrumentation, it is nowadays possible to purchase short, narrow-bore columns packed with 1.3μm core-shell particles. Micro columns (1mm I.D.) packed with 1.7-1.9μm porous particles are also available from several providers, which limit frictional heating effects and reduce solvent and sample consumption. However, it remains difficult to find instruments compatible with such column geometries and a severe loss of performance may be observed due to the system itself.
    Journal of pharmaceutical and biomedical analysis 03/2013; DOI:10.1016/j.jpba.2013.03.012 · 2.83 Impact Factor
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    ABSTRACT: This paper presents new reversed phase liquid chromatographic methods (HPLC-FLD and LC-MS/MS) for the quantification of sulfonamides in spiked and incurred honey samples. The sample preparation was optimized using Oasis HLB (hydrophilic–lipophilic balance) solid-phase extraction (SPE) cartridge. Elutions of sulfonamides were carried out under acidic, neutral, and basic conditions using methanol. Recoveries under acid condition were in the range from 66.8–90%, which were approximately 10% higher than those obtained under other conditions. The sample clean-up was also tested using Strata-XL cartridges. The HPLC-FLD separation was performed using a Varian C18 column and a ternary (methanol-acetonitrile-phosphate buffer, pH 5) mobile phase resulting good selectivity for the determination. The robustness of the ternary gradient method was evaluated by computer simulation (DryLab). LC-MS/MS separation was carried out on a Kinetex XB core-shell type HPLC column that enabled a low limit of detection (0.01–0.5 µg/kg) and faster separation (6 min). The developed methods were validated in accordance with the European Union Commission Decision 2002/657/EC and were applied successfully for more than four hundred honey samples (under a national monitoring program). The concentrations of sulfadimethoxine, sulfachloropyridazine, and trimethoprim residues in samples were found in a concentration range from 0.03 up to 686 µg/kg.
    Journal of Liquid Chromatography &amp Related Technologies 03/2013; 36(8). DOI:10.1080/10826076.2012.685911 · 0.64 Impact Factor
  • Szabolcs Fekete, Katalin Ganzler, Davy Guillarme
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    ABSTRACT: A new size exclusion chromatography column packed with 1.7μm particles and possessing 200Å pore size has been critically evaluated for the determination of proteins and monoclonal antibody aggregates. In a first instance, the kinetic performance of this column was compared with that of a conventional column packed with 5μm particles and with a recently launched 3μm material, also possessing 200Å pore size. In average, 2-5 times lower plate height were achieved on the 1.7μm packing, compared with the conventional 5μm particles. It was also demonstrated that elevated mobile phase temperature (up to 50 or 60°C) allows improving the kinetic efficiency by 20-40% in size exclusion chromatography, compared to 30°C. On the other hand, the new 3μm material performed only slightly lower kinetic efficiency than the 1.7μm one. When considering the upper pressure and temperature limits of these three columns, the 1.7μm column systematically outperforms the 5 and 3μm materials in the "practical" plate number range (N<30,000) and analysis times could be cut by 2-4 times. The column packed with 5μm particles was only beneficial for plate counts beyond 100,000 plates, while the 3μm packing could be considered as a good compromise between speed, efficiency and pressure. Besides the excellent kinetic performance of 1.7μm size exclusion material under high temperature conditions, some artifacts were observed when quantifying protein aggregates. Indeed, both high pressure observed with 1.7μm particles (shear forces, frictional heating) and elevated temperature produce some non negligible amount of on-column additional protein aggregates.
    Journal of pharmaceutical and biomedical analysis 02/2013; 78-79C:141-149. DOI:10.1016/j.jpba.2013.02.013 · 2.83 Impact Factor
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    ABSTRACT: Various recent wide-pore reversed-phase stationary phases were studied for the analysis of intact monoclonal antibodies (mAbs) of 150 kDa and their fragments possessing sizes between 25 and 50 kDa. Different types of column technology were evaluated, namely, a prototype silica-based inorganic monolith containing mesopores of ∼250 Å and macropores of ∼ 1.1 μm, a column packed with 3.6 μm wide-pore core-shell particles possessing a wide pore size distribution with an average around 200 Å and a column packed with fully porous 1.7 μm particles having pore size of ∼300 Å. The performance of these wide-pore materials was compared with that of a poly(styrene-divinyl benzene) organic monolithic column, with a macropore size of approximately 1 μm but without mesopores (stagnant pores). A systematic investigation was carried out using model IgG1 and IgG2 mAbs, namely rituximab, panitumumab, and bevacizumab. Firstly, the recoveries of intact and reduced mAbs were compared on the two monolithic phases, and it appeared that adsorption was less pronounced on the organic monolith, probably due to the difference in chemistry (C18 versus phenyl) and the absence of mesopores (stagnant zones). Secondly, the kinetic performance was investigated in gradient elution mode for all columns. For this purpose, peak capacities per meter as well as peak capacities per time unit and per pressure unit (PPT) were calculated at various flow rates, to compare performance of columns with different dimensions. In terms of peak capacity per meter, the core-shell 3.6 μm and fully porous 1.7 μm columns outperformed the two monolithic phases, at a temperature of 60 °C. However, when considering the PPT values, the core-shell 3.6 μm column remained the best phase while the prototype silica-based monoliths became very interesting, mostly due to a very high permeability compared with the organic monolith. Therefore, these core-shell and silica-based monolith provided the fastest achievable separation. Finally, at the maximal working temperature of each column, the core-shell 3.6 μm column was far better than the other one, because it is the only one stable up to 90 °C. Lastly, the loading capacity was also measured on these four different phases. It appeared that the organic monolith was the less interesting and rapidly overloaded, due to the absence of mesopores. On the other hand, the loading capacity of prototype silica-based monolith was indeed reasonable.
    Analytical and Bioanalytical Chemistry 01/2013; 405(10). DOI:10.1007/s00216-013-6759-7 · 3.58 Impact Factor
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    ABSTRACT: Recombinant monoclonal antibodies (mAbs) have become particularly relevant for the treatment of autoimmune diseases or cancers. Because of their inherent complexity and for safety reasons, there is a need to develop powerful analytical methods to provide detailed characterizations of mAbs. The aim of the present review is to detail the state-of-the-art of analytical strategies for mAb characterization. It focuses on the most important separation techniques used in this field, specifically, the chromatographic and electrophoretic approaches and their combination with mass spectrometry (MS). Thanks to recent improvements in separation science and MS devices, mAbs can be analyzed more easily. However, there is still a need to find new approaches that avoid adsorption issues.
    TrAC Trends in Analytical Chemistry 01/2013; 42:74-83. DOI:10.1016/j.trac.2012.09.012 · 6.61 Impact Factor
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    ABSTRACT: A possible complication of ultra-high pressure liquid chromatography (UHPLC) is related to the effect of pressure and mobile phase velocity on the retention properties of the analytes. In the present work, numerous model compounds have been selected including small molecules, peptides, and proteins (such as monoclonal antibodies). Two instrumental setups were considered to attain elevated pressure drops, firstly the use of a post-column restrictor capillary at low mobile phase flow rate (pure effect of pressure) and secondly the increase of mobile phase flow rate without restrictor (i.e. a combined effect of pressure and frictional heating). In both conditions, the goal was to assess differences in retention behaviour, depending on the type or character of the analyte. An important conclusion is that the effect of pressure and mobile phase velocity on retention varied in proportion with the size of the molecule and in some cases showed very different behaviour. In isocratic mode, the pure effect of pressure (experiments with a post-column restrictor capillary) induces an increase in retention by 25-100% on small molecules (MW<300g/mol), 150% for peptides (∼1.3kDa), 800% for insulin (∼6kDa) and up to >3000% for myoglobin (∼17kDa) for an increase in pressure from 100bar up to 1100bar. The important effect observed for the isocratic elution of proteins is probably related to conformational changes of the protein in addition to the effect of molecular size. Working in gradient elution mode, the pressure related effects on retention were found to be less pronounced but still present (an increase of apparent retention factor between 0.2 and 2.5 was observed).
    Journal of Chromatography A 11/2012; 1270. DOI:10.1016/j.chroma.2012.10.056 · 4.26 Impact Factor
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    ABSTRACT: Recent reversed-phase wide-pore stationary phases were evaluated for the separation of intact monoclonal antibodies and their fragments. Two types of stationary phases were tested: Phenomenex Aeris Widepore, with 3.6 μm core-shell particles and Waters Acquity BEH300 with 1.7 μm fully porous particles. A systematic investigation was carried out using model IgG1 and IgG2 antibodies, namely rituximab, panitumumab, and bevacizumab. It appeared that adsorption of these antibodies on the stationary phase was significantly higher compared to proteins of equivalent size. The adsorption was particularly important for the intact antibodies of 150 kDa and for the largest fragments of 50 to 100 kDa (i.e., heavy chain, -fraction of antigene-binding). The present study demonstrated an obvious relationship between adsorption phenomenon and the unwanted strong secondary interactions (ionic and hydrogen bond) of the stationary phase. Thus, adsorption was more pronounced on the Aeris column because of the stronger ion exchange contribution of this stationary phase. Using C4 phase instead of C18 at 50-70°C, there is a slight reduction (5-20%) in adsorption. Two solutions were proposed to decrease the strength of secondary interactions and thus resolve (or at least diminish) adsorption issue. First, increasing mobile phase temperature up to 80-90°C appeared as a promising solution. However, temperature should be used with caution as it can partially damage large biomolecules. A compromise between residence time and temperature should be found. Second, it is recommended to add a small amount of an ancillary solvent, such as n-butanol to the mobile phase. Indeed, the hydroxyl group of n-butanol probably interacts with water adsorbed on the residual silanol groups "to shield" silanols.
    Journal of Separation Science 11/2012; 35(22). DOI:10.1002/jssc.201200297 · 2.59 Impact Factor
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    ABSTRACT: This paper describes a newly developed method for the simultaneous determination of eight corticosteroid residues in bovine muscle, liver and kidney samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The determination of methylprednisone, the main metabolite of methylprednisolone, in bovine tissues using LC-MS/MS is carried out for the first time. The method development demonstrates that the pH is important in optimizing the sample preparation. Tests performed using different solid-phase extraction (SPE) cartridges were enabled to produce conditions for reducing the matrix effects (ion suppression and enhancement) of analysis. Acidic condition and mixed-mode cation exchange SPE columns resulted in the most suitable clean-up for muscle and liver, and also yielded acceptable results for kidney. The enhanced sample clean-up resulted in excellent clear baselines of ion transitions, and therefore, a higher delta electron multiplier voltage (ΔEMV) could be set in the MS/MS detector. The application of 500V of ΔEMV improved the signal responses, however, the noise level did not change, and consequently, the overall sensitivity and analytical limits (limit of detection, limit of quantification) could be enhanced. In the HPLC separation, the recently introduced Kinetex phenyl-hexyl core-shell type column was used that enabled baseline separation for dexamethasone and its β-epimer, betamethasone. Dexamethasone and betamethasone were eluted within 12min and such reduced retention, obtained with core-shell HPLC type column, further enhanced the sensitivity. The method was validated according to the European Union (EU) 2002/657/EC Decision; the studied parameters met the EU standards. The decision limits and limit of detections were calculated in each matrix for all corticosteroids and varied from 0.01 to 13.3μg/kg and from 0.01 to 0.1μg/kg, respectively.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 09/2012; 906:75-84. DOI:10.1016/j.jchromb.2012.08.033 · 2.69 Impact Factor
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    ABSTRACT: In the present contribution, columns packed with fully porous widepore 1.7μm particles (Acquity BEH300) and widepore core-shell 3.6μm particles (Aeris WP) were evaluated for the separation of model and therapeutic proteins of varying sizes, hydrophobicity and isoelectric points. Two types of bonding were compared, namely C4 and C18 in a systematic way. The kinetic performance of these stationary phases was evaluated in a previous paper hence this new work focuses on their retention behaviour, loading capacity and selectivity. Using the Tanaka tests, model proteins, and other confirmatory experiments, it is highly probable that with proteins, strong interaction mechanisms were predominant on the Aeris WP while the hydrophobic interaction was the driving force of the retention on the Acquity BEH300 material. This explained why, despite the lower pore volume of the Aeris WP material, the apparent retention factors of proteins possessing both hydrophobic and charged amino acids residues were very close on the four investigated columns. In terms of peak widths, values for proteins were similar for all the tested stationary phases, despite the probable strong ion exchange mechanisms of Aeris WP column. This could be explained by the excellent mass transfer characteristics afforded by the thin porous layer (∼0.2μm) at the surface of the particle which probably compensates for the slow secondary ionic interaction kinetics. The loading capacity was also evaluated on all the four widepore columns, using model proteins. On average, approximately 2-4 times higher amount of proteins can be injected on the fully porous BEH300 compared to the core-shell Aeris WP columns when avoiding 10% change in peak width or in tailing. However, this result could be strongly influenced by the nature and shape of the protein, its hydrophobicity, folding, size and number of charges. Finally, all of these columns were employed for the highly efficient separation of a therapeutic protein (interferon-α-2A) and some closely related proteins and showed excellent performance and selectivity. This result confirms that RPLC gained interest in the biopharmaceutical field as it provides significantly better peak widths than size-exclusion or ion-exchange and inherent compatibility with MS.
    Journal of Chromatography A 06/2012; 1252:90-103. DOI:10.1016/j.chroma.2012.06.066 · 4.26 Impact Factor
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    ABSTRACT: Monoclonal antibodies (mAbs) are an emerging class of therapeutic agents that have recently gained importance. To attain acceptable kinetic performance with mAbs in reversed phase liquid chromatography, there is a need to work with the last generation of wide-pore sub-2μm fully porous or core-shell particles stationary phases. In addition, temperature in the range 60-90°C was found to be mandatory to limit adsorption phenomenon of mAbs and their fragments. A generic method development strategy was proposed to account for the selectivity, efficiency, recovery, and the possible thermal degradation. This study also demonstrated that the gradient steepness and temperature cannot be optimized using van't Hoff type linear models. Similarly, the common linear solvent strength model also generated some error in predicting the retention times. In contrast, when quadratic models were employed, the prediction accuracy of retention times was found to be excellent (relative error between 0.5 and 1%) using a reasonable number of experiments (9 or 6 experiments for optimization of gradient time and temperature, which requires between 6 and 8h). Two separations of mAbs fragments were performed to demonstrate the reliability of the quadratic approach.
    Journal of pharmaceutical and biomedical analysis 06/2012; 70:158-68. DOI:10.1016/j.jpba.2012.06.021 · 2.83 Impact Factor
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    Szabolcs Fekete, Jean-Luc Veuthey, Davy Guillarme
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    ABSTRACT: In the pharmaceutical field, there is considerable interest in the use of peptides and proteins for therapeutic purposes. There are various ways to characterize such complex samples, but during the last few years, a significant number of technological developments have been brought to the field of RPLC and RPLC-MS. Thus, the present review focuses first on the basics of RPLC for peptides and proteins, including the inherent problems, some possible solutions and some directions for developing a new RPLC method that is dedicated to biomolecules. Then the latest advances in RPLC, such as wide-pore core-shell particles, fully porous sub-2 μm particles, organic monoliths, porous layer open tubular columns and elevated temperature, are described and critically discussed in terms of both kinetic efficiency and selectivity. Numerous applications with real samples are presented that confirm the relevance of these different strategies. Finally, one of the key advantages of RPLC for peptides and proteins over other historical approaches is its inherent compatibility with MS using both MALDI and ESI sources.
    Journal of pharmaceutical and biomedical analysis 03/2012; 69:9-27. DOI:10.1016/j.jpba.2012.03.024 · 2.83 Impact Factor
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    ABSTRACT: The separation of large biomolecules such as proteins or monoclonal antibodies (mAbs) by RPLC can be drastically enhanced thanks to the use of columns packed with wide-pore porous sub-2 μm particles or shell particles. In this context, a new wide-pore core-shell material has been recently released under the trademark Aeris WIDEPORE. It is made of a 3.2 μm solid inner core surrounded by a 0.2 μm porous layer (total particle size of 3.6 μm). The aim of this study was to evaluate the performance of this new material, compare it to other recently developed and older conventional wide-pore columns and demonstrate its applicability to real-life separations of proteins and mAbs. At first, the traditional h(min) values of the Aeris WIDEPORE column were determined for small model compounds. The h(min) values were equal to 1.7-1.8 and 1.4 for the 2.1 and 4.6 mm I.D. columns, respectively, which are in agreement with the values reported for other core-shell materials. In the case of a small protein Insulin (5.7 kDa), the achievable lowest h value was below 2 and this impressive result confirms that the Aeris WIDEPORE material should be dedicated to protein analysis. This column was then compared with five other commercially available wide-pore and medium-pore stationary phases, in the gradient elution mode, using various flow rates, gradient steepness and model proteins of MW=5.7-66.8 kDa. The Aeris WIDEPORE material often provided the best performance, in terms of peak capacity, peak capacity per time and pressure unit (PPT) and also based on the gradient kinetic plot representation. Finally, real separations of filgrastim (18.8 kDa) and its oxidized and reduced forms were performed on the different columns and the Aeris WIDEPORE material provided the most impressive performance (peak capacity>100 for t(grad)<6 min). Last but not least, this new material was also evaluated on digested and reduced mAb and powerful, high-throughput separations were also attained.
    Journal of Chromatography A 03/2012; 1236:177-88. DOI:10.1016/j.chroma.2012.03.018 · 4.26 Impact Factor

Publication Stats

774 Citations
178.31 Total Impact Points

Institutions

  • 2012–2015
    • University of Lausanne
      • School of Pharmaceutical Sciences (EPGL)
      Lausanne, Vaud, Switzerland
  • 2012–2014
    • University of Geneva
      • Department of Pharmaceutical Analysis Chemistry
      Genève, Geneva, Switzerland
  • 2011–2013
    • Budapest University of Technology and Economics
      • Department of Inorganic and Analytical Chemistry
      Budapeŝto, Budapest, Hungary
  • 2008–2010
    • Gedeon Richter Plc
      Budapeŝto, Budapest, Hungary