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Sciascera L.,University of Rome La Sapienza | Ismail O.,University of Rome La Sapienza | Ciogli A.,University of Rome La Sapienza | Kotoni D.,University of Rome La Sapienza | And 7 more authors.
Journal of Chromatography A | Year: 2015

With the aim of exploring the potential of ultra-fast chiral chromatography for high-throughput analysis, the new sub-2 micron Whelk-O 1 chiral stationary phase (CSP) has been employed in supercritical fluid conditions to screen 129 racemates, mainly of pharmaceutical interest. By using a 5-cm long column (0.46cm internal diameter), a single co-solvent (MeOH) and a 7-min gradient elution, 85% of acidic and neutral analytes considered in this work have been successfully resolved, with resolution (Rs) larger than 2 in more than 65% of cases. Moreover, almost a half of basic samples that, for their own characteristics, are known to be difficult to separate on Whelk-O 1 CSP, have shown Rs greater than 0.3. The screening of the entire library could be accomplished in less than 24h (single run) with 63% of positive score. For well-resolved enantiomers (Rs roughly included between 1 and 3), we show that method transfer from gradient to isocratic conditions is straightforward. In many cases, isocratic ultra-fast separations (with analysis time smaller than 60s) have been achieved by simply employing, as isocratic mobile phase, the eluent composition at which the second enantiomer was eluted in gradient mode. By considering the extension and variety of the library in terms of chemico-physical and structural properties of compounds and numerousness, we believe that this work demonstrates the real potential of the technique for high-throughput enantioselective screening. © 2015 Elsevier B.V.


Ciogli A.,University of Rome La Sapienza | Pierri G.,University of Rome La Sapienza | Kotoni D.,University of Rome La Sapienza | Kotoni D.,Novartis | And 5 more authors.
Electrophoresis | Year: 2014

In this study, a Whelk-O1 chiral stationary phase immobilized on 2.5 mμ silica particles was employed in nanoLC. Two nanocolumns (180 and 250 mm long, 75 mμ id) with a single polymeric organic monolithic outlet frit were packed under high-pressure ultrasonic-assisted packing procedure. The monolithic outlet frit was prepared by thermal polymerization of methacrylate-based monomers affording high-mechanical stability and high-pressure resistance.Very efficient enantioseparations with more than 70 000 plates/m were achieved in normal phase mode by eluting (+/-) acenaphthenol. Nanocolumns were also tested in RP mode by using on-line MS detection with nano-spray ESI ion source. Kinetic performances of columns in RPmode were comparable to those in normal phase-conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


PubMed | University of Rome La Sapienza, Regis Technologies Inc., University of Ferrara and University of Naples Federico II
Type: | Journal: Journal of chromatography. A | Year: 2015

With the aim of exploring the potential of ultra-fast chiral chromatography for high-throughput analysis, the new sub-2 micron Whelk-O 1 chiral stationary phase (CSP) has been employed in supercritical fluid conditions to screen 129 racemates, mainly of pharmaceutical interest. By using a 5-cm long column (0.46cm internal diameter), a single co-solvent (MeOH) and a 7-min gradient elution, 85% of acidic and neutral analytes considered in this work have been successfully resolved, with resolution (Rs) larger than 2 in more than 65% of cases. Moreover, almost a half of basic samples that, for their own characteristics, are known to be difficult to separate on Whelk-O 1 CSP, have shown Rs greater than 0.3. The screening of the entire library could be accomplished in less than 24h (single run) with 63% of positive score. For well-resolved enantiomers (Rs roughly included between 1 and 3), we show that method transfer from gradient to isocratic conditions is straightforward. In many cases, isocratic ultra-fast separations (with analysis time smaller than 60s) have been achieved by simply employing, as isocratic mobile phase, the eluent composition at which the second enantiomer was eluted in gradient mode. By considering the extension and variety of the library in terms of chemico-physical and structural properties of compounds and numerousness, we believe that this work demonstrates the real potential of the technique for high-throughput enantioselective screening.


Kotoni D.,University of Rome La Sapienza | Ciogli A.,University of Rome La Sapienza | Molinaro C.,University of Rome La Sapienza | D'Acquarica I.,University of Rome La Sapienza | And 5 more authors.
Analytical Chemistry | Year: 2012

A new chiral stationary phase for ultrahigh-pressure liquid chromatography (UHPLC) applications was prepared by covalent attachment of the Whelk-O1 selector to spherical, high-surface-area 1.7-μm porous silica particles. Columns of varying dimensions (lengths of 50, 75, 100, and 150 mm and internal diameters of 3.0 or 4.6 mm) were packed and characterized in terms of permeability, efficiency, retention, and enantioselectivity, using both organic and water-rich mobile phases. A conventional HPLC Whelk-O1 column based on 5.0-μm porous silica particles and packed in a 250 mm × 4.6 mm column was used as a reference. Van Deemter curves, generated with low-molecular-weight solutes on a 100 mm × 4.6 mm column packed with the 1.7-μm particles, showed Hmin (μm) and μopt (mm/s) values of 4.10 and 5.22 under normal-phase and 3.74 and 4.34 under reversed-phase elution conditions. The flat C term of the van Deemter curves observed with the 1.7-μm particles allowed the use of higher-than-optimal flow rates without significant efficiency loss. Kinetic plots constructed from van Deemter data confirmed the ability of the column packed with the 1.7-μm particles to afford subminute separations with good efficiency and its superior performances in the high-speed regime, compared to the column packed with 5.0-μm particles. Resolutions in the time scale of seconds were obtained using a 50-mm-long column in the normal phase or polar organic mode. The intrinsic kinetic performances of 1.7-μm silica particles are retained in the Whelk-O1 chiral stationary phase, clearly demonstrating the potentials of enantioselective UHPLC in terms of high speed, throughput, and resolution. © 2012 American Chemical Society.


Kotoni D.,University of Rome La Sapienza | Ciogli A.,University of Rome La Sapienza | D'Acquarica I.,University of Rome La Sapienza | Kocergin J.,University of Rome La Sapienza | And 4 more authors.
Journal of Chromatography A | Year: 2012

This paper reports on the thermodynamic and kinetic evaluation of a new ultra-high performance liquid chromatography broad-spectrum Pirkle-type chiral stationary phase (CSP) for enantioselective applications (eUHPLC). The well-known Whelk-O1 selector was covalently immobilized onto 1.7-μm high-surface-area, porous spherical silica particles to produce a totally synthetic, covalently bonded CSP that was packed into 150mm, 100mm, 75mm and 50mm columns, either 4.6 or 3.0mm ID. A 100mm×4.6mm ID column was fully characterized from a kinetic and thermodynamic point of view, using as reference a conventional HPLC Whelk-O1 column, 250mm×4.6mm ID, based on 5-μm porous silica particles. On the eUHPLC column, van Deemter plots generated Hmin values of 3.53μm for 1,3-dinitrobenzene, at an interstitial mobile phase linear velocity (μinter) of 5.07mm/s, and Hmin of 4.26 and 4.17μm for the two enantiomers of acenaphthenol, at μinter of 4.85mm/s and 4.24mm/s, respectively. Resolution of 21 enantiomeric pairs including alcohols, epoxides, sulfoxides, phosphine oxides, benzodiazepines and 2-aryloxyproprionic esters used as herbicides, were obtained with significant advantages in terms of efficiency and analysis time. Speed gain factors were calculated for the different column geometries (150mm, 100mm, 75mm and 50mm, either 4.6 or 3.0mm ID), with respect to the standard HPLC column (250mm×4.6mm ID), and were as high as 13, in the case of the 50-mm-long column, affording sub-minute separations of enantiomers with excellent resolution factors. In particular, trans-stilbene oxide was resolved in only 10s, while a 50mm×3.0mm ID column was used as a compromise between reduced mobile phase consumption (less than 1mL per analysis) and smaller extra-column band-broadening effect. Given the relatively low viscosity in NP mode, and the excellent permeability of these eUHPLC columns, with backpressure values under 600bar for a wide range of flow rates, the use of standard HPLC hardware is possible. In this case, however, a significant loss in resolution is observed, compared to the UHPLC instrumentation, if no modifications are introduced in the HPLC apparatus to reduce extra-column variance. The excellent efficiency and selectivity, conjugated with the very high-throughput and the ultra-fast analysis time, prove the potentials of the eUHPLC Whelk-O1 columns in the development of enantioselective UHPLC methods. © 2012 Elsevier B.V.


Sarsah S.R.S.,Loyola University Chicago | Sarsah S.R.S.,Star Thermoplastic Alloys and Rubbers Inc. | Lutz M.R.,Loyola University Chicago | Lutz M.R.,Regis Technologies Inc. | And 2 more authors.
Tetrahedron Letters | Year: 2015

A cascade reaction sequence involving a Beckmann rearrangement on benzophenone oxime followed by an electrophilic aromatic substitution (EAS) on the intermediate nitrilium ion affords N-phenyl diaryl imines that may then be hydrolyzed to ketones, or reduced to the corresponding amines. Reaction with benzonitrile afforded 2,4-diphenylquinazoline through a Beckmann-Ritter-EAS cascade. © 2015 Elsevier Ltd. All rights reserved.


Ismail O.H.,University of Rome La Sapienza | Pasti L.,University of Ferrara | Ciogli A.,University of Rome La Sapienza | Villani C.,University of Rome La Sapienza | And 5 more authors.
Journal of Chromatography A | Year: 2016

Pirkle-type Whelk-O1 chiral stationary phase (CSP) was prepared on 2.6 μm superficially porous particles (SPPs). The chromatographic behavior of columns packed with this new CSP was compared with that of columns packed respectively with 1.8 and 2.5 μm Whelk-O1 fully porous particles (FPPs). In the comparison, both thermodynamic and kinetic aspects were considered. Contrary to initial expectations, chiral columns packed with 2.6 μm SPPs were quasi-comparable to those packed with 2.5 μm FPPs, apparently due to larger contributions to band broadening from both eddy dispersion and, especially for the second eluted enantiomer, adsorption–desorption kinetics. These findings raise the question if SPPs, in spite of the undeniable advantages of their morphology to speed up mass transfer, are always the best choice for high-efficient ultrafast chiral separations. The last part of the work focuses on the use of short columns (10 mm long) and very high flow rates to realize the separation of the enantiomers of trans-stilbene oxide (TSO) in normal phase mode in less than 1 s. © 2016 Elsevier B.V.


Cancelliere G.,University of Rome La Sapienza | Ciogli A.,University of Rome La Sapienza | D'Acquarica I.,University of Rome La Sapienza | Gasparrini F.,University of Rome La Sapienza | And 6 more authors.
Journal of Chromatography A | Year: 2010

Three brush-type chiral stationary phases (CSPs) differing in the particle size of the starting silica particles have been prepared by covalent grafting of the π-acidic bis-(3,5-dinitrobenzoyl)-derivative of trans-1,2-diaminocyclohexane (DACH-DNB). Starting silica particles of 4.3, 2.6 and 1.9 micron were used to generate the final CSPs using an improved, highly reproducible synthetic methodology, that allowed to assemble and surface-graft the whole chiral selector in only two steps. The different CSPs have been packed in columns of various length and diameters, and fully characterized in terms of flow permeability, kinetic performances and enantioselectivity using a set of test solutes. Very high speed and high resolution applications together with stereodynamic HPLC examples are demonstrated on the columns with reduced particle diameters, on which separations of several enantiomeric pairs are routinely obtained with analysis times in the 15-40 s range. © 2009 Elsevier B.V. All rights reserved.


PubMed | University of Rome La Sapienza, Regis Technologies Inc. and University of Ferrara
Type: | Journal: Journal of chromatography. A | Year: 2016

Pirkle-type Whelk-O1 chiral stationary phase (CSP) was prepared on 2.6m superficially porous particles (SPPs). The chromatographic behavior of columns packed with this new CSP was compared with that of columns packed respectively with 1.8 and 2.5m Whelk-O1 fully porous particles (FPPs). In the comparison, both thermodynamic and kinetic aspects were considered. Contrary to initial expectations, chiral columns packed with 2.6m SPPs were quasi-comparable to those packed with 2.5m FPPs, apparently due to larger contributions to band broadening from both eddy dispersion and, especially for the second eluted enantiomer, adsorption-desorption kinetics. These findings raise the question if SPPs, in spite of the undeniable advantages of their morphology to speed up mass transfer, are always the best choice for high-efficient ultrafast chiral separations. The last part of the work focuses on the use of short columns (10mm long) and very high flow rates to realize the separation of the enantiomers of trans-stilbene oxide (TSO) in normal phase mode in less than 1s.

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