1
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Agrawal R, Belemkar S, Bonde C. A Stepwise Strategy Employing Automated Screening for Reversed-Phase Chromatographic Separation of Itraconazole and Its Impurities. Chromatographia 2019. [DOI: 10.1007/s10337-019-03802-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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2
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Sedov IA, Salikov TM, Solomonov BN. Contrasting the solvation properties of protic ionic liquids with different nanoscale structure. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111361] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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3
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Žuvela P, Skoczylas M, Jay Liu J, Ba Czek T, Kaliszan R, Wong MW, Buszewski B, Héberger K. Column Characterization and Selection Systems in Reversed-Phase High-Performance Liquid Chromatography. Chem Rev 2019; 119:3674-3729. [PMID: 30604951 DOI: 10.1021/acs.chemrev.8b00246] [Citation(s) in RCA: 143] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Reversed-phase high-performance liquid chromatography (RP-HPLC) is the most popular chromatographic mode, accounting for more than 90% of all separations. HPLC itself owes its immense popularity to it being relatively simple and inexpensive, with the equipment being reliable and easy to operate. Due to extensive automation, it can be run virtually unattended with multiple samples at various separation conditions, even by relatively low-skilled personnel. Currently, there are >600 RP-HPLC columns available to end users for purchase, some of which exhibit very large differences in selectivity and production quality. Often, two similar RP-HPLC columns are not equally suitable for the requisite separation, and to date, there is no universal RP-HPLC column covering a variety of analytes. This forces analytical laboratories to keep a multitude of diverse columns. Therefore, column selection is a crucial segment of RP-HPLC method development, especially since sample complexity is constantly increasing. Rationally choosing an appropriate column is complicated. In addition to the differences in the primary intermolecular interactions with analytes of the dispersive (London) type, individual columns can also exhibit a unique character owing to specific polar, hydrogen bond, and electron pair donor-acceptor interactions. They can also vary depending on the type of packing, amount and type of residual silanols, "end-capping", bonding density of ligands, and pore size, among others. Consequently, the chromatographic performance of RP-HPLC systems is often considerably altered depending on the selected column. Although a wide spectrum of knowledge is available on this important subject, there is still a lack of a comprehensive review for an objective comparison and/or selection of chromatographic columns. We aim for this review to be a comprehensive, authoritative, critical, and easily readable monograph of the most relevant publications regarding column selection and characterization in RP-HPLC covering the past four decades. Future perspectives, which involve the integration of state-of-the-art molecular simulations (molecular dynamics or Monte Carlo) with minimal experiments, aimed at nearly "experiment-free" column selection methodology, are proposed.
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Affiliation(s)
- Petar Žuvela
- Department of Chemistry , National University of Singapore , Singapore 117543 , Singapore
| | - Magdalena Skoczylas
- Department of Environmental Chemistry and Bioanalytics, Center for Modern Interdisciplinary Technologies , Nicolaus Copernicus University , Wileńska 4 , 87-100 Toruń , Poland
| | - J Jay Liu
- Department of Chemical Engineering , Pukyong National University , 365 Sinseon-ro , Nam-gu, 48-513 Busan , Korea
| | | | | | - Ming Wah Wong
- Department of Chemistry , National University of Singapore , Singapore 117543 , Singapore
| | - Bogusław Buszewski
- Department of Environmental Chemistry and Bioanalytics, Center for Modern Interdisciplinary Technologies , Nicolaus Copernicus University , Wileńska 4 , 87-100 Toruń , Poland
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4
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Moldoveanu SC, Caiali E, David V. Results from solvophobic theory applied to methylene selectivity in reversed-phase HPLC. J LIQ CHROMATOGR R T 2018. [DOI: 10.1080/10826076.2017.1410708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
| | - Edvin Caiali
- Department of Analytical Chemistry, Faculty of Chemistry, University of Bucharest, Bucharest, Romania
| | - Victor David
- Department of Analytical Chemistry, Faculty of Chemistry, University of Bucharest, Bucharest, Romania
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5
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Cavazzini A, Marchetti N, Guzzinati R, Pasti L, Ciogli A, Gasparrini F, Laganà A. Understanding Mixed-Mode Retention Mechanisms in Liquid Chromatography with Hydrophobic Stationary Phases. Anal Chem 2014; 86:4919-26. [DOI: 10.1021/ac500248b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Alberto Cavazzini
- Department
of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari, 46, 44121 Ferrara, Italy
| | - Nicola Marchetti
- Department
of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari, 46, 44121 Ferrara, Italy
| | - Roberta Guzzinati
- Department
of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari, 46, 44121 Ferrara, Italy
| | - Luisa Pasti
- Department
of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari, 46, 44121 Ferrara, Italy
| | - Alessia Ciogli
- Dipartimento
di Chimica e Tecnologia del Farmaco, University “La Sapienza”, 00185 Rome, Italy
| | - Francesco Gasparrini
- Dipartimento
di Chimica e Tecnologia del Farmaco, University “La Sapienza”, 00185 Rome, Italy
| | - Aldo Laganà
- Department
of Chemistry, University of Rome, “La Sapienza”, Piazzale
Aldo Moro 5, 00185 Rome, Italy
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6
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Sedov IA, Solomonov BN. Solvophobic effects: Qualitative determination and quantitative description. J STRUCT CHEM+ 2014. [DOI: 10.1134/s0022476613080076] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Lindsey RK, Rafferty JL, Eggimann BL, Siepmann JI, Schure MR. Molecular simulation studies of reversed-phase liquid chromatography. J Chromatogr A 2013; 1287:60-82. [PMID: 23489490 DOI: 10.1016/j.chroma.2013.02.040] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 02/10/2013] [Accepted: 02/11/2013] [Indexed: 11/28/2022]
Abstract
Over the past 20 years, molecular simulation methods have been applied to the modeling of reversed-phase liquid chromatography (RPLC). The purpose of these simulations was to provide a molecular-level understanding of: (i) the structure and dynamics of the bonded phase and its interface with the mobile phase, (ii) the interactions of analytes with the bonded phase, and (iii) the retention mechanism for different analytes. However, the investigation of chromatographic systems poses significant challenges for simulations with respect to the accuracy of the molecular mechanics force fields and the efficiency of the sampling algorithms. This review discusses a number of aspects concerning molecular simulation studies of RPLC systems including the historical development of the subject, the background needed to understand the two prevalent techniques, molecular dynamics (MD) and Monte Carlo (MC) methods, and the wealth of insight provided by these simulations. Examples from the literature employing MD approaches and from the authors' laboratory using MC methods are discussed. The former can provide information on chain dynamics and transport properties, whereas the latter techniques are uniquely suited for the investigation of phase and sorption equilibria that underly RPLC retention, and both can be used to elucidate the bonded-chain conformations and solvent distributions.
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Affiliation(s)
- Rebecca K Lindsey
- Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431, USA
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8
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Johnson AR, Johnson CM, Stoll DR, Vitha MF. Identifying orthogonal and similar reversed phase liquid chromatography stationary phases using the system selectivity cube and the hydrophobic subtraction model. J Chromatogr A 2012; 1249:62-82. [DOI: 10.1016/j.chroma.2012.05.049] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 05/09/2012] [Accepted: 05/14/2012] [Indexed: 11/28/2022]
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9
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Dashtbozorgi Z, Golmohammadi H, Konoz E. Simultaneous Prediction of the Logarithmic Capacity Factor of Some Aliphatic and Aromatic Compounds on Five Different Stationary Phases in RP-LC Using Artificial Neural Network. Chromatographia 2012. [DOI: 10.1007/s10337-012-2257-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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10
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Quast AD, Curtis AD, Horn BA, Goates SR, Patterson JE. Role of Nonresonant Sum-Frequency Generation in the Investigation of Model Liquid Chromatography Systems. Anal Chem 2012; 84:1862-70. [DOI: 10.1021/ac2032035] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Arthur D. Quast
- Department of Chemistry and
Biochemistry, Brigham Young University,
Provo, Utah 84602, United States
| | - Alexander D. Curtis
- Department of Chemistry and
Biochemistry, Brigham Young University,
Provo, Utah 84602, United States
| | - Brent A. Horn
- Department of Criminal Justice, Weber State University, Ogden, Utah 84408, United States
| | - Steven R. Goates
- Department of Chemistry and
Biochemistry, Brigham Young University,
Provo, Utah 84602, United States
| | - James E. Patterson
- Department of Chemistry and
Biochemistry, Brigham Young University,
Provo, Utah 84602, United States
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11
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Rafferty JL, Siepmann JI, Schure MR. A molecular simulation study of the effects of stationary phase and solute chain length in reversed-phase liquid chromatography. J Chromatogr A 2012; 1223:24-34. [DOI: 10.1016/j.chroma.2011.11.039] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 11/17/2011] [Accepted: 11/20/2011] [Indexed: 10/15/2022]
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12
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Rafferty JL, Siepmann JI, Schure MR. Molecular simulations of retention in chromatographic systems: use of biased Monte Carlo techniques to access multiple time and length scales. Top Curr Chem (Cham) 2012; 307:181-200. [PMID: 21898207 DOI: 10.1007/128_2011_210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The use of configurational-bias Monte Carlo simulations in the Gibbs ensemble allows for the sampling of phenomena that occur on vastly different time and length scales. In this review, applications of this simulation approach to probe retention in gas and reversed-phase liquid chromatographic systems are discussed. These simulations provide an unprecedented view of the retention processes at the molecular-level and show excellent agreement with experimental retention data.
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Affiliation(s)
- Jake L Rafferty
- Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431, USA
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13
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Debrus B, Lebrun P, Kindenge JM, Lecomte F, Ceccato A, Caliaro G, Mbay JMT, Boulanger B, Marini R, Rozet E, Hubert P. Innovative high-performance liquid chromatography method development for the screening of 19 antimalarial drugs based on a generic approach, using design of experiments, independent component analysis and design space. J Chromatogr A 2011; 1218:5205-15. [DOI: 10.1016/j.chroma.2011.05.102] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 05/30/2011] [Accepted: 05/30/2011] [Indexed: 11/15/2022]
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14
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Rafferty JL, Siepmann JI, Schure MR. Mobile phase effects in reversed-phase liquid chromatography: A comparison of acetonitrile/water and methanol/water solvents as studied by molecular simulation. J Chromatogr A 2011; 1218:2203-13. [DOI: 10.1016/j.chroma.2011.02.012] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 01/28/2011] [Accepted: 02/05/2011] [Indexed: 11/16/2022]
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15
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Guiochon G, Tarafder A. Fundamental challenges and opportunities for preparative supercritical fluid chromatography. J Chromatogr A 2011; 1218:1037-114. [DOI: 10.1016/j.chroma.2010.12.047] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 12/08/2010] [Accepted: 12/13/2010] [Indexed: 10/18/2022]
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16
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Kwietniewski L. THE EFFECT OF THE CHAIN LENGTH OF BONDED PHASE ON RETENTION OF AROMATIC SOLUTES IN RP LC WITH PURE WATER AS MOBILE PHASE. J LIQ CHROMATOGR R T 2010. [DOI: 10.1080/10826076.2010.503744] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- L. Kwietniewski
- a Faculty of Mathematics and Natural Science, Institute of Biotechnology, Chair of Bioanomaterials, John Paul II Catholic University of Lublin , Lublin, Poland
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17
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Description of retention characteristics of calixarene-bonded stationary phases in dependence of the methanol content in the mobile phase. J Chromatogr A 2009; 1216:6285-94. [DOI: 10.1016/j.chroma.2009.07.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 06/29/2009] [Accepted: 07/01/2009] [Indexed: 11/19/2022]
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18
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Andrzejewska A, Gritti F, Guiochon G. Investigation of the adsorption mechanism of a peptide in reversed phase liquid chromatography, from pH controlled and uncontrolled solutions. J Chromatogr A 2009; 1216:3992-4004. [DOI: 10.1016/j.chroma.2009.03.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 03/02/2009] [Accepted: 03/06/2009] [Indexed: 10/21/2022]
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19
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Retention models for isocratic and gradient elution in reversed-phase liquid chromatography. J Chromatogr A 2009; 1216:1737-55. [DOI: 10.1016/j.chroma.2008.09.051] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Revised: 09/11/2008] [Accepted: 09/12/2008] [Indexed: 11/20/2022]
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20
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Rafferty JL, Siepmann JI, Schure MR. Influence of bonded-phase coverage in reversed-phase liquid chromatography via molecular simulation. J Chromatogr A 2008; 1204:20-7. [DOI: 10.1016/j.chroma.2008.07.038] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Revised: 06/24/2008] [Accepted: 07/04/2008] [Indexed: 11/16/2022]
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21
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Luo H, Ma L, Paek C, Carr PW. Application of silica-based hyper-crosslinked sulfonate-modified reversed stationary phases for separating highly hydrophilic basic compounds. J Chromatogr A 2008; 1202:8-18. [PMID: 18617181 DOI: 10.1016/j.chroma.2008.06.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 06/10/2008] [Accepted: 06/12/2008] [Indexed: 10/21/2022]
Abstract
The separation and determination of hydrophilic basic compounds are of great importance in many fields including clinical and biological research, pharmaceutical development and forensic analysis. However, the most widely used analytical separation technique in these disciplines, reversed-phase liquid chromatography (RPLC), usually does not provide sufficient retention for several important classes of highly hydrophilic basic compounds including catecholamines, many drug metabolites and many drugs of abuse. Commonly eluents having little or no organic modifier and/or strong ion pairing agents must be used to achieve sufficient retention and separation. Use of highly aqueous eluents can lead to column failure by dewetting, resulting in poor retention, low selectivity and irreproducibility and slow recovery of performance. The use of a strong ion pairing agent to increase retention renders the separation incompatible with mass spectrometric detection and complicates preparative separations. This paper describes the successful applications of a novel type of silica-based, hyper-crosslinked, sulfonate-modified reversed stationary phase, denoted as (-)SO(3)-HC-C(8)-L, for the separation of highly hydrophilic cations and related compounds by a hydrophobically assisted cation-exchange mechanism. Compared to conventional reversed-phases, the (-)SO(3)-HC-C(8)-L phase showed significantly improved retention and separation selectivity for hydrophilic amines. Concurrently, due to the presence of both cation-exchange and reversed-phase retention mechanisms and the high acid stability of hyper-crosslinked phases, the separation can be optimized by changing the type or concentration of ionic additive or organic modifier, and by varying the column temperature. In addition, gradients generated by programming the concentration of either the ionic additive or the organic modifier can be applied to reduce the analysis time without compromising resolution. Furthermore, remarkably different chromatographic selectivities, especially toward cationic solutes, were observed upon comparing the (-)SO(3)-HC-C(8)-L phase with conventional reversed-phases. We believe that the combination of these two types of stationary phases will be very useful in two-dimensional liquid chromatography.
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Affiliation(s)
- Hao Luo
- Department of Chemistry, University of Minnesota, Smith and Kolthoff Hall, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
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22
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Wang M, Mallette J, Parcher JF. Strategies for the determination of the volume and composition of the stationary phase in reversed-phase liquid chromatography. J Chromatogr A 2008; 1190:1-7. [DOI: 10.1016/j.chroma.2008.02.099] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 02/25/2008] [Accepted: 02/28/2008] [Indexed: 10/22/2022]
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23
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Stoll DR, Li X, Wang X, Carr PW, Porter SEG, Rutan SC. Fast, comprehensive two-dimensional liquid chromatography. J Chromatogr A 2007; 1168:3-43; discussion 2. [PMID: 17888443 PMCID: PMC3205947 DOI: 10.1016/j.chroma.2007.08.054] [Citation(s) in RCA: 307] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2007] [Revised: 07/09/2007] [Accepted: 08/10/2007] [Indexed: 11/21/2022]
Abstract
The absolute need to improve the separating power of liquid chromatography, especially for multi-constituent biological samples, is becoming increasingly evident. In response, over the past few years, there has been a great deal of interest in the development of two-dimensional liquid chromatography (2DLC). Just as 1DLC is preferred to 1DGC based on its compatibility with biological materials we believe that ultimately 2DLC will be preferred to the much more highly developed 2DGC for such samples. The huge advantage of 2D chromatographic techniques over 1D methods is inherent in the tremendous potential increase in peak capacity (resolving power). This is especially true of comprehensive 2D chromatography wherein it is possible, under ideal conditions, to obtain a total peak capacity equal to the product of the peak capacities of the first and second dimension separations. However, the very long timescale (typically several hours to tens of hours) of comprehensive 2DLC is clearly its chief drawback. Recent advances in the use of higher temperatures to speed up isocratic and gradient elution liquid chromatography have been used to decrease the time needed to do the second dimension LC separation of 2DLC to about 20s for a full gradient elution run. Thus, fast, high temperature LC is becoming a very promising technique. Peak capacities of over 2000 and rates of peak capacity production of nearly 1 peak/s have been achieved. In consequence, many real samples showing more than 200 peaks with signal to noise ratios of better than 10:1 have been run in total times of under 30 min. This report is not intended to be a comprehensive review of 2DLC, but is deliberately focused on the issues involved in doing fast 2DLC by means of elevating the column temperature; however, many issues of broader applicability will be discussed.
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Affiliation(s)
- Dwight R. Stoll
- University of Minnesota, Department of Chemistry, Smith and Kolthoff Halls, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | - Xiaoping Li
- University of Minnesota, Department of Chemistry, Smith and Kolthoff Halls, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | - Xiaoli Wang
- University of Minnesota, Department of Chemistry, Smith and Kolthoff Halls, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | - Peter W. Carr
- University of Minnesota, Department of Chemistry, Smith and Kolthoff Halls, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | - Sarah E. G. Porter
- Department of Chemistry, Virginia Commonwealth University, 1001 West Main Street, Richmond, VA 23284-2006, USA
| | - Sarah C. Rutan
- Department of Chemistry, Virginia Commonwealth University, 1001 West Main Street, Richmond, VA 23284-2006, USA
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24
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Huai QY, Zuo YM. Study of the Retention Characteristics of Calix[4]arene‐bonded Silica Stationary Phase and Comparison with Common Phases for HPLC Using Linear Solvation Energy Relationships. J LIQ CHROMATOGR R T 2007. [DOI: 10.1080/10826070500530252] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Q. Y. Huai
- a Department of Chemistry , Shandong University , Jinan , P.R. China
- b Department of Chemistry , Qufu Normal University , Qufu , P.R. China
| | - Y. M. Zuo
- c Department of Chemistry , Nankai University , Tianjin , P.R. China
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25
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Vailaya A. Fundamentals of Reversed Phase Chromatography: Thermodynamic and Exothermodynamic Treatment. J LIQ CHROMATOGR R T 2007. [DOI: 10.1081/jlc-200052969] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Anant Vailaya
- a Merck Research Laboratories , Rahway, New Jersey, USA
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26
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Zhang L, Rafferty JL, Siepmann JI, Chen B, Schure MR. Chain conformation and solvent partitioning in reversed-phase liquid chromatography: Monte Carlo simulations for various water/methanol concentrations. J Chromatogr A 2006; 1126:219-31. [PMID: 16820151 DOI: 10.1016/j.chroma.2006.06.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 05/24/2006] [Accepted: 06/01/2006] [Indexed: 11/25/2022]
Abstract
Many structural models for the stationary phase in reversed-phase liquid chromatography (RPLC) systems have been suggested from thermodynamic and spectroscopic measurements and theoretical considerations. To provide a molecular picture of chain conformation and solvent partitioning in a typical RPLC system, a particle-based Monte Carlo simulation study is undertaken for a dimethyl octadecyl (C(18)) bonded stationary phase on a model siliceous substrate in contact with mobile phases having different methanol/water concentrations. Following upon previous simulations for gas-liquid chromatography and liquid-liquid phase equilibria, the simulations are conducted using the configurational-bias Monte Carlo method in the Gibbs ensemble and the transferable potentials for phase equilibria force field. The simulations are performed for a chain surface density of 2.9 micromol/m(2), which is a typical bonded-phase coverage for mono-functional alkyl silanes. The solvent concentrations used here are pure water, approximately 33 and 67% mole fraction of methanol and pure methanol. The simulations show that the chain conformation depends only weakly on the solvent composition. Most chains are conformationally disordered and tilt away from the substrate normal. The interfacial width increases with increasing methanol content and, for mixtures, the solvent shows an enhancement of the methanol concentration in a 10 Angstrom region outside the Gibbs dividing surface. Residual surface silanol groups are found to provide hydrogen bonding sites that lead to the formation of substrate bound water and methanol clusters, including bridging clusters that penetrate from the solvent/chain interfacial region all the way to the silica surface.
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Affiliation(s)
- Ling Zhang
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431, USA
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27
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Sun Y, Stalcup AM. Mobile phase effects on retention on a new butylimidazolium-based high-performance liquid chromatographic stationary phase. J Chromatogr A 2006; 1126:276-82. [PMID: 16854426 DOI: 10.1016/j.chroma.2006.06.092] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2006] [Revised: 06/14/2006] [Accepted: 06/19/2006] [Indexed: 11/22/2022]
Abstract
A new HPLC stationary phase based on n-butylimidazolium bromide has been characterized by a linear solvation energy relationship (LSER) approach in the binary acetonitrile/water mobile phases. The retention properties of the stationary phase were systematically evaluated in terms of intermolecular interactions between 28 test solutes and the stationary phase. The results and further comparisons with conventional reversed phase system confirm that retention properties are similar to phenyl phases in acetonitrile/water mixtures. The results obtained with acetonitrile/water mixtures are also compared with results obtained using methanol/water mixtures.
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Affiliation(s)
- Yaqin Sun
- Department of Chemistry, University of Cincinnati, Cincinnati, OH, USA
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28
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Bhagwat V, Bereznitski Y, Buszewski B, Jaroniec M. Comparative Characterization of Octyl Bonded Phases using Methylene Selectivity Data. J LIQ CHROMATOGR R T 2006. [DOI: 10.1080/10826079808005859] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- V. Bhagwat
- a Separation and Surface Science Center Chemistry Department , Kent State University , Kent, OH, 44242, USA
| | - Y. Bereznitski
- a Separation and Surface Science Center Chemistry Department , Kent State University , Kent, OH, 44242, USA
| | - B. Buszewski
- b Department of Environmental Chemistry , Copernicus University , TOIWI, 87-100, Poland
| | - M. Jaroniec
- a Separation and Surface Science Center Chemistry Department , Kent State University , Kent, OH, 44242, USA
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Czajkowska T, Tittelbach V, Bereznitski Y, Jaroniec M. Adsorption, Thermogravimetric, and Chromatographic Studies of Bare Silicas and Silica-Based Octyl Bonded Phases. J LIQ CHROMATOGR R T 2006. [DOI: 10.1080/10826079808006601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- T. Czajkowska
- a American Cyanamid Company , Agricultural Research Center , Princeton, NJ 08543
| | - V. Tittelbach
- a American Cyanamid Company , Agricultural Research Center , Princeton, NJ 08543
| | - Y. Bereznitski
- b Separation and Surface Science CenterChemistry Department , Kent State University , Kent, OH 44242
| | - M. Jaroniec
- b Separation and Surface Science CenterChemistry Department , Kent State University , Kent, OH 44242
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30
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Pappa-Louisi A, Rofalikou E, Michaelidis B. Determination of Biogenic Amines and Related Compounds in the Ganglia and the Auricle and Ventricle of the Heart of the Snail Helix Lucorum L. by HPLC with Amperometric Detection. J LIQ CHROMATOGR R T 2006. [DOI: 10.1080/10826079708002713] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- A. Pappa-Louisi
- a Laboratory of Physical Chemistry Department of Chemistry , Aristotle University of Thessaloniki , 54006, Thessaloniki, Greece
| | - E. Rofalikou
- b Laboratory of Animal Physiology Department of Biology , Aristotle University of Thessaloniki , 54006, Thessaloniki, Greece
| | - B. Michaelidis
- b Laboratory of Animal Physiology Department of Biology , Aristotle University of Thessaloniki , 54006, Thessaloniki, Greece
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31
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West C, Lesellier E. Characterisation of stationary phases in subcritical fluid chromatography with the solvation parameter model IV. J Chromatogr A 2006; 1115:233-45. [PMID: 16529759 DOI: 10.1016/j.chroma.2006.02.050] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Revised: 02/15/2006] [Accepted: 02/17/2006] [Indexed: 11/30/2022]
Abstract
The purpose of the present work was to systematically study the chromatographic behaviour of different aromatic stationary phases in a subcritical fluid mobile phase. We attempted to assess the chemical origin of the differences in retention characteristics between the different columns. Various types of aromatic stationary phases, all commercially available, were investigated. The effect of the nature of the aromatic bonding on interactions between solute and stationary phases and between solute and carbon dioxide-methanol mobile phase was studied by the use of a linear solvation energy relationship (LSER): the solvation parameter model. This study was performed to provide a greater knowledge of the properties of these phases in subcritical fluid chromatography, and to allow a more rapid and efficient choice of aromatic stationary phase in regard of the chemical nature of the solutes to be separated. Charge transfer interactions naturally contribute to the retention on all these stationary phases but are completed by various other types of interactions, depending on the nature of the aromatic group. The solvation vectors were used to compare the different phase properties. In particular, the similarities in the chromatographic behaviour of porous graphitic carbon (PGC), polystyrene-divinylbenzene (PS-DVB) and aromatic-bonded silica stationary phases are evidenced.
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Affiliation(s)
- C West
- LETIAM, Groupe de Chimie Analytique de Paris Sud (EA 3343), IUT d'Orsay, Plateau du Moulon, 91400 Orsay, France
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32
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Pistos C, Tsantili-Kakoulidou A, Koupparis M. Investigation of the retention/pH profile of zwitterionic fluoroquinolones in reversed-phase and ion-interaction high performance liquid chromatography. J Pharm Biomed Anal 2005; 39:438-43. [PMID: 15894451 DOI: 10.1016/j.jpba.2005.03.032] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 03/02/2005] [Accepted: 03/15/2005] [Indexed: 10/25/2022]
Abstract
The retention/pH profiles of three fluoroquinolones, ofloxacin, norfloxacin and ciprofloxacin, was investigated by means of reversed-phase high performance liquid chromatography (RP-HPLC) and reversed-phase ion-interaction chromatography (RP-IIC), using an octadecylsilane stationary phase and acetonitrile as organic modifier. Sodium hexanesulphonate and tetrabutylammonium hydroxide were used as sources of counter ions in ion-interaction chromatography. The retention/pH profiles under in RP-HPLC were compared to the corresponding lipophilicity/pH profiles. Despite the rather hydrophilic nature of the three fluoroquinolones positive retention factors were obtained while there was a shift of the retention maximum towards more acidic pH values. This behavior was attributed mainly to non-hydrophobic silanophilic interactions with the silanized silica gel material of the stationary phase. In ion-interaction chromatography the effect of counter ions over a broad pH range was found to be ruled rather by the ion pair formation in the mobile phase which led to a drastic decrease in retention as a consequence of the disruption of the zwitterionic structure and thereupon the deliberation of a net charge in the molecules. At pH values at which zwitterionic structure was not favored both the ion-exchange and ion pair formation mechanisms were assumed to contribute to the retention.
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Affiliation(s)
- C Pistos
- Division of Pharmaceutical Chemistry, Department of Pharmacy, University of Athens, Panepistimiopolis, Zografou 15771, Greece
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33
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West C, Lesellier E. Effects of modifiers in subcritical fluid chromatography on retention with porous graphitic carbon. J Chromatogr A 2005; 1087:64-76. [PMID: 16130699 DOI: 10.1016/j.chroma.2005.03.104] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The effect of different modifiers in subcritical fluid chromatography (SubFC) on interactions between solute and porous graphitic carbon (PGC) and between solute and carbon dioxide-modifier mobile phases was studied by the use of linear solvation energy relationships (LSERs). This study was performed to allow efficient optimization of the composition of the carbon dioxide-modifier mobile phase in regard of the chemical nature of the solutes to be separated. With all modifiers tested (methanol, ethanol, n-propanol, isopropanol, acetonitrile, tetrahydrofuran and hexane), the solute/stationary phase interactions are greater than the solute/mobile phase ones. Dispersion interactions and charge transfer between electron donor solute and electron acceptor PGC mainly explain the retention on this surface, whatever the modifier. These interactions are quite constant over the range of modifier percentage studied (5-40%). For acidic compounds, the retention variation is mainly related to the change in the basic character of mobile and stationary phase due to the variation of modifier percentage. Changes in eluting strength are mostly related to adsorption of mobile phase onto the PGC with methanol and acetonitrile, and to the increase of dispersion interactions between the solute and the mobile phase for other modifiers. Relationships between varied selectivities and solvation parameter values have been studied and are discussed in this paper.
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Affiliation(s)
- C West
- LETIAM, Groupe de Chimie Analytique de Paris Sud (EA 3343), IUT d'Orsay, Plateau du Moulon, 91400 Orsay, France
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Sun Y, Cabovska B, Evans CE, Ridgway TH, Stalcup AM. Retention characteristics of a new butylimidazolium-based stationary phase. Anal Bioanal Chem 2005; 382:728-34. [PMID: 15883788 DOI: 10.1007/s00216-004-3051-x] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Revised: 12/10/2004] [Accepted: 12/21/2004] [Indexed: 10/25/2022]
Abstract
A new HPLC stationary phase has been synthesized based on the ionic liquid n-butylimidazolium bromide. Imidazolium was covalently immobilized on a silica substrate through an n-alkyl tether and the retention characteristics of the resulting stationary phase were evaluated systematically. Using 28 small aromatic test solutes and reversed phase conditions, the linear solvation energy relationship approach was successfully used to characterize this new phase. The retention characteristics of the test solutes show remarkable similarity with phenyl stationary phases, despite the presence of a positive charge on the new imidazolium phase. Operated in the reversed phase mode, this new stationary phase shows considerable promise for the separation of neutral solutes and points to the potential for a truly multi-modal stationary phase.
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Affiliation(s)
- Y Sun
- Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221-0172, USA
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35
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Effect of adsorption of organic solvents on the band profiles in reversed-phase non-linear chromatography. Chem Eng Sci 2005. [DOI: 10.1016/j.ces.2004.10.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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36
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Wick CD, Siepmann JI, Schure MR. Simulation Studies on the Effects of Mobile-Phase Modification on Partitioning in Liquid Chromatography. Anal Chem 2004; 76:2886-92. [PMID: 15144201 DOI: 10.1021/ac0352225] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Various driving forces have been suggested to explain retention and selectivity in reversed-phase liquid chromatography (RPLC). To provide molecular-level information on the retention mechanism in RPLC, configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out for model systems consisting of three phases: an n-hexadecane retentive phase, a mobile phase with varying water-methanol composition, and a helium vapor phase as reference state. Liquid n-hexadecane functions as a model of a hydrophobic stationary phase, and a wealth of experimental data exists for this system. Gibbs free energies for solute transfers from gas to retentive phase, from gas to mobile phase, and from mobile to retentive phase were determined for a series of short linear alkanes and primary alcohols. Although the magnitude of the incremental Gibbs free energy of transfer for a methylene segment is always larger for the gas- to retentive-phase transfer than the gas- to mobile-phase transfer, it is found that the partitioning of alkanes and alkyl tail groups is mostly affected by the changes in the aqueous mobile phase that occur when methanol modifiers are added. In contrast, the partitioning of the alcohol headgroup is sensitive to changes in both the n-hexadecane and the mobile phases. In particular, it is found that hydrogen-bonded aggregates of methanol are present in the n-hexadecane phase for higher methanol concentrations in the mobile phase. These aggregates strongly increase alcohol partitioning into the retentive phase. The simulation data clearly demonstrate that due to modification of the retentive-phase hydrocarbons by solvent components, neither the solvophobic theory of RPLC, advocated by Horvath and co-workers, nor the lipophilic theory of RPLC, advocated by Carr and co-workers, can adequately describe the separation mechanism of the hexadecane model system of a retentive phase studied here nor the more complex situation present in actual RPLC systems.
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Affiliation(s)
- Collin D Wick
- Department of Chemistry and of Chemical Engineering and Materials Science, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, USA
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37
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Nikitas P, Pappa-Louisi A, Agrafiotou P. New insights on the retention mechanism of non-polar solutes in reversed-phase liquid chromatographic columns. J Chromatogr A 2004; 1034:41-54. [PMID: 15116913 DOI: 10.1016/j.chroma.2004.02.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A clarification of the retention mechanism of non-polar solutes in octadecyl reversed-phase chromatographic columns is attempted based on a systematic comparison of the retention in C18 and C2 columns under the assumption that the retention in C2 columns is due to adsorption. The comparison involves curve fitting procedures and tests based on the properties of special functions suggested in the present paper. For the application of this approach the retention behaviour of six non-polar solutes, benzene, toluene, ethylbenzene, propylbenzene, isopropylbenzene and tert-butylbenzene, is studied from aqueous mobile phases modified with methanol, isopropanol, acetonitrile and tetrahydrofuran using C18 and C2 reversed-phase columns. It was found that the retention mechanism in C18 columns is not the same in the four modifiers. In particular, our results show that the adsorption mechanism has a significant contribution in mobile phases modified by acetonitrile and tetrahydrofuran, the partition mechanism is likely to predominate in isopropanol-water mobile phases provided that the mole fraction of isopropanol is higher than 0.2, whereas the case of MeOH is rather obscure, since the various tests did not give a clear picture about the retention mechanism in methanol-water mobile phases.
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Affiliation(s)
- P Nikitas
- Laboratory of Physical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
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38
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Nawrocki J, Dunlap C, Li J, Zhao J, McNeffe CV, McCormick A, Carr PW. Part II. Chromatography using ultra-stable metal oxide-based stationary phases for HPLC. J Chromatogr A 2004; 1028:31-62. [PMID: 14969281 DOI: 10.1016/j.chroma.2003.11.050] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In this part of the review authors discuss methods used for modification of metal oxide surfaces. On the basis of literature data it is shown, that silanization of the surfaces do not form stable supports for chromatography. On the other hand, the success of polymer modified surfaces such as polybutadiene (PBD) and polystyrene (PS) is emphasized. Permanent modification of metal oxide surfaces with Lewis bases is also widely discussed. Chromatographic properties of polymer modified surfaces of zirconia are discussed in details. The perspectives of carbon-coated metal oxide surfaces in HPLC and high temperature separations are described.
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Affiliation(s)
- J Nawrocki
- Department of Water Treatment Technology, Faculty of Chemistry, A. Mickiewicz University, Drzymały 24, 60-613 Poznań, Poland.
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39
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Walles M, Mullett WM, Pawliszyn J. Monitoring of drugs and metabolites in whole blood by restricted-access solid-phase microextraction coupled to liquid chromatography–mass spectrometry. J Chromatogr A 2004; 1025:85-92. [PMID: 14753675 DOI: 10.1016/j.chroma.2003.08.068] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Robust biocompatible solid-phase microextraction (SPME) devices were prepared using various alkyldiol-silica (ADS) restricted-access materials (RAM) as the SPME coating. The ADS-SPME approach was able to simultaneously fractionate the protein component from a biological sample, while directly extracting diazepam and the major metabolites N-desmethyldiazepam, oxazepam and temazepam, and overcame the present disadvantages of direct sampling in biological matrices by SPME. The devices were interfaced with an LC-MS system and an isocratic mobile phase was used to desorb, separate, and quantify the analytes. The calculated diazepam, nordiazepam, temazepam, and oxazepam detection limits were 20, 20, 30, and 35 ng/ml in heparinized blood, respectively. The method was confirmed to be linear over the range of 50-1000 ng/ml with an average linear coefficient (R2) value of 0.996. The injection repeatability and intra-assay precision of the method were evaluated over ten injections at concentrations of 50, 200, and 500 ng/ml, resulting in a R.S.D. of ca. 10%. The robustness of the ADS-SPME device was evaluated for future use in in vivo studies, providing many direct extractions and subsequent determination of benzodiazepines in blood. For the extraction of the peptides angiotensin I, II, and III from blood, a novel restricted access material with cation exchange properties was evaluated. The ion-exchange diol silica improved the extraction efficiency of peptides relative to the conventional ADS material with reversed phase extraction centers.
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Affiliation(s)
- M Walles
- Department of Chemistry, University of Waterloo, Waterloo, Ont., N2L 3G1 Canada
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40
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Evaluation of the retention characteristics of ferrocene-bonded silica stationary phase and other silica-based reversed phases for HPLC using linear solvation energy relationships. Chromatographia 2003. [DOI: 10.1007/bf02491755] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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41
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Park JH, Jung, Vitha MF, Carr PW. Solvent Strength Parameters and Retention Factors in Pure Water Using UNIFAC-Predicted Activity Coefficients. Ind Eng Chem Res 2003. [DOI: 10.1021/ie0209125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jung Hag Park
- Department of Chemistry, Yeungnam University, Kyongsan 712-749, South Korea, Department of Chemistry, Drake University, Des Moines, Iowa 50311, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Jung
- Department of Chemistry, Yeungnam University, Kyongsan 712-749, South Korea, Department of Chemistry, Drake University, Des Moines, Iowa 50311, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Mark F. Vitha
- Department of Chemistry, Yeungnam University, Kyongsan 712-749, South Korea, Department of Chemistry, Drake University, Des Moines, Iowa 50311, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Peter W. Carr
- Department of Chemistry, Yeungnam University, Kyongsan 712-749, South Korea, Department of Chemistry, Drake University, Des Moines, Iowa 50311, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
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42
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Beltrán J, Sanli N, Fonrodona G, Barrón D, Özkan G, Barbosa J. Spectrophotometric, potentiometric and chromatographic pKa values of polyphenolic acids in water and acetonitrile–water media. Anal Chim Acta 2003. [DOI: 10.1016/s0003-2670(03)00334-9] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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43
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Szepesy L. Evaluation of column characteristics in RPLC using linear solvation energy relationships (LSERs). J Sep Sci 2003. [DOI: 10.1002/jssc.200390027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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44
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Yamagami C, Kawase K, Iwaki K. Hydrophobicity parameters determined by reversed-phase liquid chromatography. XV: optimal conditions for prediction of log P(oct) by using RP-HPLC procedures. Chem Pharm Bull (Tokyo) 2002; 50:1578-83. [PMID: 12499594 DOI: 10.1248/cpb.50.1578] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The use of log k derived from reversed phase (RP)-HPLC retention times provides a convenient method for estimating log P(oct) values (P(oct): 1-octanol/water partition coefficient). In order to establish optimal HPLC conditions, the difference between chromatographic (C18 modified column and aqueous methanol eluents) and bulk solvent systems was examined by use of a batch-like equilibration with octane/aqueous methanol. Comparison of values for log P(O/M-W) (log P for the Octane/MeOH-Water partitioning system) and log k measured for monosubstituted pyrazines at different methanol concentrations, showed closest correlation (r, 0.94) with 50% aqueous methanol; and importantly, under these conditions, log k shows even better correlation (r, 0.99) with log P(oct). Effects of residual silanols on HPLC retention with C18 stationary phases were examined. The results show that, in the presence of a small quantity of accessible silanols, the use of 50% aqueous methanol (M50) as eluent yields values of log k directly proportional to log P(oct) in accord with our earlier proposal that use of log k(M50) provides a convenient means for rapid estimation and prediction of log P(oct).
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45
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Lesellier E, Gurdale K, Tchapla A. Interaction mechanisms on octadecyl packed columns in subcritical fluid chromatography with CO2-modifier mobile phases. J Chromatogr A 2002; 975:335-47. [PMID: 12456087 DOI: 10.1016/s0021-9673(02)01091-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
An experimental design was carried out for describing the interaction mechanisms between solutes and octadecyl bonded silicas in subcritical fluid chromatography (SubFC), with CO2-methanol and CO2-acetonitrile mobile phases. The effects of modifier amount, temperature and outlet pressure were studied. The homologous series of alkylbenzenes was mainly used as probe, and results were in part assessed with other series. Curves between the methylene selectivity (alphaCH2) and the alkyl chain carbon number (Cn) were plotted, because changes of slope or discontinuity in these curves are yielded by interaction mechanism modifications. Moreover, the linearity of the Van 't Hoff curves with CO2-acetonitrile mobile phases has enabled one to calculate the transfer enthalpy (deltaH) for each homologue. The curves log k = f(-deltaH) allow a discrimination of the retention behaviors between the short and the long homologues for CO2-acetonitrile mobile phases. Depending on the analytical conditions, different oriented partition mechanisms occur for the long homologues, when the short ones seem to be fully embedded into the grafted chains near the silica surface. With methanol-CO2 mobile phases the discrimination between the homologues disappears and the methylene selectivity curves correspond to a bulk partition mechanism. The differences in the interaction mechanisms following the modifier nature are related to the adsorption the mobile phase onto the stationary phase, because the amount of adsorbed mobile phase modifies the bonded chain mobility. With methanol, an important adsorption of the mobile phase occurs, when this adsorption is reduced with acetonitrile. In this latter case, an anisotropy in the stationary phase mobility can explain the observed difference in the interaction mechanisms of homologues. Finally, effects of stationary phase chain length (from C18 to C22) and bonding density (from 2.5 to 3.4 micromol m(-2)) were also reported.
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Affiliation(s)
- E Lesellier
- LETIAM, IUT ORSAY, Plateau du Moulon, 91400 Orsay, France.
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46
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Nikitas P, Pappa-Louisi A, Agrafiotou P. Effect of the organic modifier concentration on the retention in reversed-phase liquid chromatography I. General semi-thermodynamic treatment for adsorption and partition mechanisms. J Chromatogr A 2002; 946:9-32. [PMID: 11873986 DOI: 10.1016/s0021-9673(01)01535-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A semi-thermodynamic treatment is adopted to account for adsorption or partition of solute molecules from aqueous mobile phases on/in reversed-phase liquid chromatography stationary phases. The theoretical expressions of ln k' versus organic modifier content are tested against 10 data sets covering a variety of solute molecules. It is shown that the mean field approximation, adopted widely in ptevious studies, is marginally valid in aqueous mobile phases, especially in the presence of solute molecules, and the lattice model approximation, which is also used in relevant studies, is a poor approximation. Clear conclusions about the validity of either the adsorption or the partition model for the retention mechanism could not be drawn. The equations of the adsorption model describe all data sets absolutely satisfactorily and yield a physically reasonable picture about the behavior of modifier and solvent at the adsorbed layer. However, the high applicability of the adsorption model may not safely entail the validity of the adsorption mechanism at a molecular level, especially in the case of solutes with small and non-polar molecules, where our analysis gives strong indications about the validity of the partition mechanism. The next steps needed for the final elucidation of the retention mechanism in reversed-phase chromatographic columns are indicated.
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Affiliation(s)
- P Nikitas
- Department of Chemistry, Aristotle University of Thessaloniki, Greece.
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47
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Taillardat-Bertschinger A, Barbato F, Quercia M, Carrupt PA, Reist M, La Rotonda M, Testa B. Structural Properties Governing Retention Mechanisms on Immobilized Artificial Membrane (IAM) HPLC Columns. Helv Chim Acta 2002. [DOI: 10.1002/1522-2675(200202)85:2<519::aid-hlca519>3.0.co;2-q] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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48
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Sanz-Nebot V, Toro I, Barbosa J. Prediction of retention behaviour and evaluation of pka values of peptides and quinolones in liquid chromatography. J Chromatogr A 2001; 933:45-56. [PMID: 11758746 DOI: 10.1016/s0021-9673(01)01255-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The present paper examines the effect of the solute ionisation on the retention behaviour in liquid chromatography of a series of peptide and quinolone compounds of biological interest, using acetonitrile-water media as mobile phases and a polymeric-based stationary phase. Polymeric columns with polystyrene-divinylbenzene (PS-DVB) polymer show advantages over silica-based reversed-phase packings since the former are stable in a wide pH range. (s)(s)pKa values have been evaluated using chromatographic data in acetonitrile-water mixtures with acetonitrile percentages of 30, 35, 40 and 50% (v/v) for quinolones and 12.5 and 20% (v/v) for peptides. The quinolones show great retention on PS-DVB phase stationary. It was thus necessary to work with a higher acetonitrile content in the mobile phase than for the less retained peptides. The pH values were measured in the hydroorganic mixtures, used as mobile phases, instead of in water and account was taken of the effect of activity coefficients. The derived equations permit the chromatographic determination of (s)(s)pKa. values of the peptides and quinolones in acetonitrile-water mixtures by fitting it to the experimental data in a nonlinear least-square procedure and also permit the prediction of the effect of (s)(s)pH on their chromatographic behaviour. We have also compared the obtained (s)(s)pKa values with those previously obtained in acetonitrile-water mixtures from potentiometric measurements.
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Affiliation(s)
- V Sanz-Nebot
- University of Barcelona, Department of Analytical Chemistry, Av. Diagonal, 647. E-08028, Barcelona, Spain.
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49
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Valkó K, Espinosa S, Du CM, Bosch E, Rosés M, Bevan C, Abraham MH. Unique selectivity of perfluorinated stationary phases with 2,2,2-trifluoroethanol as organic mobile phase modifier. J Chromatogr A 2001; 933:73-81. [PMID: 11758748 DOI: 10.1016/s0021-9673(01)01254-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The selectivity of Luna C18 Xterra C18 and Fluophase (perfluorinated C6) stationary phases has been investigated with aqueous acetonitrile, methanol and 2,2,2-trifluoroethanol mobile phases using linear solvation equations. The gradient retention times of a set of 60 compounds with known molecular descriptors have been determined. Linear solvation equations have been set up to describe the relationship between the gradient retention times and the molecular properties. The selectivity of the stationary phase/mobile phase systems was characterised by the regression coefficients of the molecular descriptors. The perfluorinated stationary phase showed very different selectivity using 2,2,2-trifluoroethanol (TFE) as co-solvent. Compounds with H-bond donor functionality were retained much less than in the other investigated high-performance liquid chromatography (HPLC) systems. This unique selectivity can be explained by the stronger adsorption of trifluoroethanol on the perfluorinated stationary phase surface, than on the hydrocarbon surface. It suggests the importance of the adsorbed organic modifiers in the separation mechanism during reversed-phase HPLC.
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Affiliation(s)
- K Valkó
- Computational, Analytical and Structural Sciences, GlaxoSmithKline, Stevenage, UK. .
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50
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