1
|
Mallik AK, Montero L, Rösler J, Meckelmann SW, Schmitz OJ. Surface Modification of Silica with β-Alanine Derivatives for Unique Applications in Liquid Chromatography. ACS APPLIED MATERIALS & INTERFACES 2023; 15:54176-54184. [PMID: 37949437 PMCID: PMC10685355 DOI: 10.1021/acsami.3c11932] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 10/11/2023] [Accepted: 10/18/2023] [Indexed: 11/12/2023]
Abstract
Column purchasing cost is an important issue for an analyst to analyze complex sample matrices. Here, we report the development of an amino acid (β-alanine)-derived stationary phase (Sil-Ala-C12) with strategic and effective interaction sites (amide and urea as embedded polar groups with C12 alkyl chain) able to separate various kinds of analytes. Owing to the balanced hydrophobicity and hydrophilicity of the phase, it showed exceptional separation abilities in both reversed-phase high-performance liquid chromatography (RP-HPLC) as a hydrophobic phase and hydrophilic interaction chromatography (HILIC) as a hydrophilic phase. Remarkably, the baseline separation was achieved for the challenging β- and γ-isomers of tocopherol. Usually, three columns such as pentafluorophenyl or C30, C18, and sulfobetaine HILIC are required for the analysis of vitamin E, capsaicinoids, and vitamin C in chili peppers (Capsicum spp.), respectively. However, only Sil-Ala-C12 was able to separate these analytes. A single column can serve 3-4 purposes, which suggests that Sil-Ala-C12 had the potential to reduce column purchasing costs.
Collapse
Affiliation(s)
- Abul K. Mallik
- Applied
Analytical Chemistry, University of Duisburg-Essen, Universitaetsstr. 5, 45141 Essen, Germany
- Department
of Applied Chemistry and Chemical Engineering, University of Dhaka, Dhaka 1000, Bangladesh
| | - Lidia Montero
- Applied
Analytical Chemistry, University of Duisburg-Essen, Universitaetsstr. 5, 45141 Essen, Germany
- Institute
of Food Science Research - CIAL (CSIC-UAM), Calle Nicolas Cabrera 9, 28049 Madrid, Spain
| | - Jonas Rösler
- Applied
Analytical Chemistry, University of Duisburg-Essen, Universitaetsstr. 5, 45141 Essen, Germany
| | - Sven W. Meckelmann
- Applied
Analytical Chemistry, University of Duisburg-Essen, Universitaetsstr. 5, 45141 Essen, Germany
| | - Oliver J. Schmitz
- Applied
Analytical Chemistry, University of Duisburg-Essen, Universitaetsstr. 5, 45141 Essen, Germany
| |
Collapse
|
2
|
Gmeiner J, Seibicke M, Lang C, Gärtner U, Trapp O. An Immobilised Grubbs 2ndGeneration Catalyst for Application in Flow-Through Devices. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201301182] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
3
|
|
4
|
Mallik AK, Qiu H, Sawada T, Takafuji M, Ihara H. Molecular shape recognition through self-assembled molecular ordering: evaluation with determining architecture and dynamics. Anal Chem 2012; 84:6577-85. [PMID: 22788678 DOI: 10.1021/ac300791x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The relationship between molecular gel-forming compound-based double-alkylated L-glutamide-derived functional group-integrated organic phase (Sil-FIP) structure and chromatographic performance is investigated and compared with widely used alkyl phases (C(30), polymeric and monomeric C(18)) as references. The functional group-integrated molecular gel on silica is chemically designed newly in a way that the weak interaction sites are integrated with high orientation and high selectivity can be realized by multiple interactions with the solutes. Its functions can be emphasized by being immobilizable with a terminal carboxyl group and the fact that five amide bonds including β-alanine subunit are integrated per molecule. Furthermore, its self-assembling function can be detected by monitoring of the chiroptical property. Temperature-dependent circular dichroism (CD) intensity was determined as an indicator of chirality for the gel forming compounds. (13)C cross-polarization magic angle spinning (CP/MAS) NMR spectra of the Sil-FIP phase indicate that predominance of gauche conformations exists at higher temperature (above 30 °C). (29)Si CP/MAS NMR were carried out to investigate the degree of cross-linking of the silane and silane functionality of the modified silica. Temperature-dependent (13)C CP/MAS NMR and suspended-state (1)H NMR measurements of the Sil-FIP phase exhibit the dynamic behavior of the alkyl chains. To correlate the NMR and CD results with temperature-dependent chromatographic studies, standard reference materials (SRM 869b and SRM 1647e), column selectivity test mixture for liquid chromatography was employed. Additional shape selectivity text mixtures were also used to clarify the mechanism of shape selectivity performance of Sil-FIP compared with commercially available columns. The evaluation with the spectroscopic and chromatographic analyses presents very important information on the surface morphology of the new organic phase and the molecular recognition process. Integrated and ordered functional groups were investigated to be the main driving force for very high molecular shape selectivity of the Sil-FIP phase.
Collapse
Affiliation(s)
- Abul K Mallik
- Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan
| | | | | | | | | |
Collapse
|
5
|
Warad I, Omar Abd-Elkader H, Al-Resayes S, Husein A, Al-Nuri M, Boshaala A, Al-Zaqri N, Ben Hadda T. Synthesis and characterization of hybrid materials consisting of n-octadecyltriethoxysilane by using n-hexadecylamine as surfactant and Q(0) and T(0) cross-linkers. Int J Mol Sci 2012; 13:6279-6291. [PMID: 22754364 PMCID: PMC3382804 DOI: 10.3390/ijms13056279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 05/03/2012] [Accepted: 05/10/2012] [Indexed: 11/16/2022] Open
Abstract
Novel hybrid xerogel materials were synthesized by a sol-gel procedure. n-octadecyltriethoxysilane was co-condensed with and without different cross-linkers using Q(0) and T(0) mono-functionalized organosilanes in the presence of n-hexadecylamine with different hydroxyl silica functional groups at the surface. These polymer networks have shown new properties, for example, a high degree of cross-linking and hydrolysis. Two different synthesis steps were carried out: simple self-assembly followed by sol-gel transition and precipitation of homogenous sols. Due to the lack of solubility of these materials, the compositions of the new materials were determined by infrared spectroscopy, (13)C and (29)Si CP/MAS NMR spectroscopy and scanning electron microscopy.
Collapse
Affiliation(s)
- Ismail Warad
- Department of Chemistry, Science College, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia; E-Mails: (S.A.-R.); (N.A.-Z.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +96-61-4675992; Fax: +96-61-4675992
| | - H Omar Abd-Elkader
- Electron Microscope Unit, Zoology Department, College of Science, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia; E-Mail:
- Electron Microscope & Thin Films Department, Physics Division, National Research Center, Dokki 12622, Cairo, Egypt
| | - Saud Al-Resayes
- Department of Chemistry, Science College, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia; E-Mails: (S.A.-R.); (N.A.-Z.)
| | - Ahmad Husein
- Department of Chemistry, Science College, AN-Najah National University, P.O. Box 7, Nablus 00972, Palestine Territories; E-Mails: (A.H.); (M.A.-N.)
| | - Mohammed Al-Nuri
- Department of Chemistry, Science College, AN-Najah National University, P.O. Box 7, Nablus 00972, Palestine Territories; E-Mails: (A.H.); (M.A.-N.)
| | - Ahmed Boshaala
- Chemistry Department, Faculty of Science, Benghazi University, P. O. Box 1308, Benghazi, 22385, Libya; E-Mail:
| | - Nabil Al-Zaqri
- Department of Chemistry, Science College, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia; E-Mails: (S.A.-R.); (N.A.-Z.)
| | - Taibi Ben Hadda
- Materials Chemistry Laboratory, Faculty of Sciences, University of Mohammed Premier, Oujda-60000, Morocco; E-Mail:
| |
Collapse
|
6
|
Vogt FG, Williams GR. Analysis of a Nanocrystalline Polymer Dispersion of Ebselen Using Solid-State NMR, Raman Microscopy, and Powder X-ray Diffraction. Pharm Res 2012; 29:1866-81. [DOI: 10.1007/s11095-012-0713-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Accepted: 02/15/2012] [Indexed: 11/29/2022]
|
7
|
Maier F, Trapp O. Quantifizierung der Stationärphasen- und Lösungsmitteleinflüsse auf die Stereodynamik von biphep-Liganden durch dynamische Drei-Säulen-HPLC. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201107907] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
8
|
Maier F, Trapp O. Effects of the Stationary Phase and the Solvent on the Stereodynamics of biphep Ligands Quantified by Dynamic Three-Column HPLC. Angew Chem Int Ed Engl 2012; 51:2985-8. [DOI: 10.1002/anie.201107907] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 01/03/2012] [Indexed: 11/06/2022]
|
9
|
Lang C, Gärtner U, Trapp O. Catalysts by the meter: rapid screening approach of N-heterocyclic carbeneligand based catalysts. Chem Commun (Camb) 2011; 47:391-3. [DOI: 10.1039/c0cc02306j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
10
|
Williams-Harry M, Bhaskar A, Ramakrishna G, Goodson T, Imamura M, Mawatari A, Nakao K, Enozawa H, Nishinaga T, Iyoda M. Giant Thienylene-Acetylene-Ethylene Macrocycles with Large Two-Photon Absorption Cross Section and Semishape-Persistence. J Am Chem Soc 2008; 130:3252-3. [DOI: 10.1021/ja078246s] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Michele Williams-Harry
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Ajit Bhaskar
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Guda Ramakrishna
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Theodore Goodson
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Mika Imamura
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Akane Mawatari
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Kazumi Nakao
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Hideo Enozawa
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Tohru Nishinaga
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Masahiko Iyoda
- Department of Chemistry and Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| |
Collapse
|
11
|
Cheng X, Ver Heyen A, Mamdouh W, Uji-i H, De Schryver F, Höger S, De Feyter S. Synthesis and adsorption of shape-persistent macrocycles containing polycyclic aromatic hydrocarbons in the rigid framework. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:1281-6. [PMID: 17241046 DOI: 10.1021/la062360r] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Shape-persistent macrocycles with interiors in the nanometer regime were prepared by the oxidative cyclization of the appropriate bisacetylene precursors under high-dilution conditions. These compounds contain polycyclic aromatic hydrocarbons in the ring backbone and are decorated with extra annular oligoalkyl or silyl side groups. Interestingly, after depositing them on different surfaces and investigating the self-assembled structures by means of scanning tunneling microscopy (STM) and atomic force microscopy (AFM), various nanostructures were observed. STM showed that these macrocycles are organized in two-dimensional (2D) layers, whereas AFM showed, in addition, the formation of 2D crystallites and one-dimensional fibrils. These results reveal the importance of the extra annular substitution of the macrocycles in creating patterned surfaces and nanoscale objects.
Collapse
Affiliation(s)
- Xiaohong Cheng
- Institut für Technische Chemie und Polymerchemie, Engesserstrasse 18, 76131 Karlsruhe, Germany
| | | | | | | | | | | | | |
Collapse
|
12
|
Nakao K, Nishimura M, Tamachi T, Kuwatani Y, Miyasaka H, Nishinaga T, Iyoda M. Giant Macrocycles Composed of Thiophene, Acetylene, and Ethylene Building Blocks. J Am Chem Soc 2006; 128:16740-7. [PMID: 17177424 DOI: 10.1021/ja067077t] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fully conjugated giant macrocyclic oligothiophenes with 60pi, 90pi,120pi, 150pi, and 180pi frames (1, 2, 3, 4 and 5) have been designed, and their butyl-substituted derivatives (1a, 2a, 3a, 4a, and 5a) have been synthesized using modified Sonogashira and McMurry coupling reactions as key steps. The 60-180pi systems 1-5 are circular with 1.8-6 nm inner cavities and 3.3-7.5 nm outside molecular diameters. Compound 1a containing ten 3,4-dibutyl-2,5-thienylene, eight ethynylene, and two vinylene units has been converted into macrocyclic oligo(3,4-dibutyl-2,5-thienylene-ethynylene) 6a using bromination/dehydrobromination procedure. Giant macrocycles 1a-6a exhibit a red shift of their absorption spectra and a fairly strong fluorescence with a large Stokes shift as compared to a linear conjugated counterpart having five thiophene rings. Compounds 1a-6a exhibit multistep reversible redox behaviors with fairly low first oxidation potentials, reflecting their cyclic conjugation. Furthermore, chemical oxidation of 1a-6a with FeCl3 shows drastic changes of spectroscopic properties due to intramolecular and intermolecular pi-pi interactions. Doping of 1a-3a with iodine forms semiconductor due to its pi-donor properties and pi-pi stacking ability. X-ray analysis of 1a confirmed a round, planar structure with nanoscale inner cavity, and revealed host ability for alkanes and unique packing structure. Interestingly, 2a and 3a self-aggregate in the solid state to form "molecular wires," which are about 200 nm thick and more than 1 mm long. The internal structures of fibrous aggregates have been investigated by optical microscope, scanning electron microscopy, atomic force microscopy, and X-ray diffraction analyses.
Collapse
Affiliation(s)
- Kazumi Nakao
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | | | | | | | | | | | | |
Collapse
|
13
|
Zhao T, Liu Z, Song Y, Xu W, Zhang D, Zhu D. Novel Diethynylcarbazole Macrocycles: Synthesis and Optoelectronic Properties. J Org Chem 2006; 71:7422-32. [PMID: 16958538 DOI: 10.1021/jo0611869] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Diethynylcarbazole macrocycles 1b and 2b have been synthesized by oxidative coupling of appropriate precursors. In particular, macrocycle 2b was prepared by bimolecular Pd-catalyzed oxidative coupling in 35% isolated yield. The spectroscopic properties of these macrocycles and their precursors were measured in detail. The films of these macrocycles by the dipping method and the Langmuir-Blodgett technique were fabricated to study their photoinduced charge-transfer properties. A rapid and steady cathodic photocurrent of these films was produced in a three-electrode cell when irradiated with white light. A possible mechanism of the photoinduced electron-transfer pathway was suggested.
Collapse
Affiliation(s)
- Tianyue Zhao
- Beijing National Laboratory for Molecular Science, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, and Graduate School of Chinese Academy of Sciences, Beijing 100080, PRC
| | | | | | | | | | | |
Collapse
|
14
|
Abdel-Mottaleb MMS, Götz G, Kilickiran P, Bäuerle P, Mena-Osteritz E. Influence of halogen substituents on the self-assembly of oligothiophenes--a combined STM and theoretical approach. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:1443-8. [PMID: 16460059 DOI: 10.1021/la052566c] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Iodinated quaterthiophenes 2-3 have been synthesized and their self-assembling behavior investigated at the liquid-solid interface by means of high-resolution scanning tunneling microscopy in comparison to parent oligothiophene 1. All three compounds spontaneously give well-ordered 2D crystalline monolayers at the graphite surface and order in a lamella-type arrangement of the conjugated backbones concomitant with an interlocking of the alkyl side chains. Symmetrically substituted oligothiophenes 1 and 3 without a relevant dipole moment self-assemble in a similar fashion, exhibiting comparable unit cells, whereas monoiodo derivative 2 arranges as pairs along the lamella axis due to the presence of a permanent dipole moment induced by the polarizable halogen group. Corroborated by quantum chemical calculations, novel head-to-head (iodo-iodo) intermolecular interactions were found to take place for this unsymmetrical derivative. The investigation of mixed solutions clearly reveals that at the solid-liquid interface a homogeneous layer of this compound is formed, which comprises the highest packing density leading to a separation process at the interface.
Collapse
|
15
|
Gritti F, Guiochon G. A chromatographic estimate of the degree of heterogeneity of RPLC packing materials. J Chromatogr A 2006; 1103:43-56. [PMID: 16337638 DOI: 10.1016/j.chroma.2005.10.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Revised: 09/23/2005] [Accepted: 10/03/2005] [Indexed: 10/25/2022]
Abstract
A new chromatographic method estimating the degree of heterogeneity of RPLC packing materials is based on the results of systematic measurements of the adsorption data in a wide concentration range for selected probe compounds. These data are acquired by frontal analysis (FA), modeled, and used for the calculation of the adsorption energy distribution (AED). Four compounds were used, two neutral compounds of different molecular sizes (caffeine and phenol) and two ionizable compounds of opposite charges, 2-naphthalene sulfonate, an anion, and propranololium, a cation. This work was done on a C30-bonded silica stationary phase (Prontosil-C30), using the same aqueous mobile phase (30% methanol, v/v) for all compounds, except that sodium chloride (25 mM) was added to elute the ionizable compounds. All four adsorption isotherms have Langmuirian behavior. The AEDs are tri-modal for phenol, quadri-modal for caffeine. The total saturation capacity of the stationary phase is four-fold lower for caffeine than for phenol, due in part to its larger molecular size. The equilibrium constants on the low-energy sites of types 1 and 2 are eight-fold larger. These two types of sites characterize the heterogeneity of the bonded layer itself. The density of the high-energy sites of types 3 and 4 is higher for caffeine, suggesting that caffeine molecules can be accommodated in some hydrophobic cages into which smaller molecules like phenol cannot. These high-energy types of sites characterize the heterogeneity of the whole stationary phase (silica support included). The ionizable compounds have larger molecules than the neutral ones and, accordingly, a lower relative density of sites of type 2 to sites of type 1. A tri-modal and a quadri-modal energy distributions were observed for the 2-naphthalene sulfonate anion and the propranololium cation, respectively. The fourth types of sites measured and its unusually high equilibrium constant are most probably due to ion-exchange interactions between the non-endcapped ionized silanols and the propranololium ion. No such strong interactions are observed with the anionic compound.
Collapse
Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA
| | | |
Collapse
|
16
|
Gritti F, Guiochon G. Critical contribution of nonlinear chromatography to the understanding of retention mechanism in reversed-phase liquid chromatography. J Chromatogr A 2005; 1099:1-42. [PMID: 16271269 DOI: 10.1016/j.chroma.2005.09.082] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Revised: 09/23/2005] [Accepted: 09/27/2005] [Indexed: 11/25/2022]
Abstract
The retention of most compounds in RPLC proceeds through a combination of several independent mechanisms. We review a series of recent studies made on the behavior of several commercial C18-bonded stationary phases and of the complex, mixed retention mechanisms that were observed in RPLC. These studies are essentially based on the acquisition of adsorption isotherm data, on the modeling, and on the interpretation of these data. Because linear chromatography deals only with the initial slope of the global, overall, or apparent isotherm, it is unable fully to describe the complete adsorption mechanism. It cannot even afford clues as to the existence of several overlaid retention mechanisms. More specifically, it cannot account for the consequences of the surface heterogeneity of the packing material. The acquisition of equilibrium data in a wide concentration range is required for this purpose. Frontal analysis (FA) of selected probes gives data that can be modeled into equilibrium isotherms of these probes and that can also be used to calculate their adsorption or affinity energy distribution (AED). The combination of these data, the detailed study of the best constants of the isotherm model, the determination of the influence of experimental parameters (e.g., buffer pH and pI, temperature) on the isotherm constants provide important clues regarding the heterogeneity of the adsorbent surface and the main properties of the adsorption mechanisms. The comparison of similar data obtained for the adsorption of neutral and ionizable compounds, treated with the same approach, and the investigation of the influence on the thermodynamics of phase equilibrium of the experimental conditions (temperature, average pressure, mobile phase composition, nature of the organic modifier, and, for ionizable compounds, of the ionic strength, the nature, the concentration of the buffer, and its pH) brings further information. This review provides original conclusions regarding retention mechanisms in RPLC.
Collapse
Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA
| | | |
Collapse
|
17
|
Zhang W, Moore JS. Reaction Pathways Leading to Arylene Ethynylene Macrocycles via Alkyne Metathesis. J Am Chem Soc 2005; 127:11863-70. [PMID: 16104765 DOI: 10.1021/ja053466w] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mechanistic studies on the direct formation of arylene ethynylene macrocycles via alkyne metathesis catalyzed by a molybdenum complex are reported. Gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry on the products from metathesis of monomer 1 show the initial formation of linear oligomers and large macrocycles (n > 6), followed by their transformation into the thermodynamically most stable product distribution-mainly the cyclic hexamer. Variable temperature and scrambling experiments reveal the reversibility of macrocycle formation. Nearly identical product distributions are observed from the cross metathesis of hexacycle 2 with diphenylacetylene and from the metathesis of bis(phenylethynyl) substituted monomer 4, demonstrating that macrocycle formation is thermodynamically rather than kinetically controlled. The metathesis byproduct, 3-hexyne, is shown to inhibit the catalyst. It is suggested that the relative metathesis rates of dialkylalkynes versus diarylalkynes trap the catalyst in a nonproductive manifold, rendering it unavailable for the productive metathesis of aryl alkylalkyne substrates. This finding indicates that dialkyl-substituted alkyne byproducts should be avoided (or efficiently removed) if the metatheses of aryl substrates, especially those with electron-withdrawing groups, are to proceed to high conversion.
Collapse
Affiliation(s)
- Wei Zhang
- Roger Adams Laboratory, Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | | |
Collapse
|
18
|
Meyer C, Busche S, Welsch N, Wegmann J, Gauglitz G, Albert K. Contact-angle, ellipsometric, and spin-diffusion solid-state nuclear magnetic resonance spectroscopic investigations of copolymeric stationary phases immobilized on SiO2 surfaces. Anal Bioanal Chem 2005; 382:1465-71. [PMID: 16001236 DOI: 10.1007/s00216-005-3363-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Revised: 05/20/2005] [Accepted: 05/23/2005] [Indexed: 10/25/2022]
Abstract
SiO2 surfaces-silica gel particles and silica wafers-were modified by covalently immobilizing three poly(ethylene-co-acrylic acid) copolymers, (-CH2CH2-)x[CH2CH/(CO2H)-]y, with different chain lengths and mass fractions of acrylic acid. 13C solid-state NMR spectroscopy on the modified silica gel particles revealed both mobile gauche and rigid trans aligned alkyl chains in the copolymers. For copolymers attached to silica wafers via a 3-aminopropyltriethoxysilane spacer molecule, ellipsometric measurements revealed a mean value of the layer thickness distribution of 6.5 and 4.3 nm, respectively, for the more acidic and the shorter copolymers with mobile alkyl chains mostly in the gauche conformation. For the longest and least acidic copolymer with more rigid trans ordered alkyl chains, however, a mean phase thickness of 10.6 nm was found. When this copolymer was immobilized via a 3-glycidoxypropyltrimethoxysilane spacer molecule we measured a mean layer thickness of 9.9 nm. A model of the surface morphology of this immobilization strategy was derived using spin-diffusion 13C NMR measurements on the corresponding modified silica. It was thereby proven that the trans and gauche-aligned alkyl chains occur in distinct domains of certain sizes on the silica surface. The surface polarity of all modified silica wafers was also investigated by measurement of contact-angle.
Collapse
Affiliation(s)
- Christoph Meyer
- Institute of Organic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, 72076, Tuebingen, Germany.
| | | | | | | | | | | |
Collapse
|
19
|
Rajca A, Miyasaka M, Pink M, Wang H, Rajca S. Helically Annelated and Cross-Conjugated Oligothiophenes: Asymmetric Synthesis, Resolution, and Characterization of a Carbon−Sulfur [7]Helicene. J Am Chem Soc 2004; 126:15211-22. [PMID: 15548018 DOI: 10.1021/ja0462530] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis and characterization of a novel oligothiophene, in which the thiophene rings are annelated into a [7]helicene with cross-conjugated pi-system, are described. Such [7]helicenes may be viewed as fragments of the unprecedented carbon-sulfur (C(2)S)(n)() helix, possessing sulfur-rich molecular periphery. Racemic synthesis of [7]helicene is based upon iterative alternation of two steps: C-C bond homocouplings between the beta-positions of thiophenes and annelation between the alpha-positions of thiophenes. Asymmetric synthesis is carried out using (-)-sparteine-mediated annelation of the axially chiral bis(aryllithium) with electrophilic sulfur equivalent. Alternatively, enantiomers of the [7]helicene are obtained via resolution using menthol-based chiral siloxanes. Racemic [7]helicene and four other macrocyclic products of the annelation are characterized by X-ray crystallography. One of the solvent polymorphs of the [7]helicene possesses pi-stacked columns of opposite enantiomers and multiple short intermolecular contacts, including both homochiral and heterochiral short S...S contacts, suggesting an effective intermolecular electronic coupling in two-dimensions. The [7]helicene is configurationally stable at room temperature and racemizes at 199 degrees C with a half-time of about 11 h. Selected physicochemical studies (UV-vis absorption, CD, optical rotation, and cyclic voltammetry) of the [7]helicene are described.
Collapse
Affiliation(s)
- Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA.
| | | | | | | | | |
Collapse
|
20
|
Meyer C, Skogsberg U, Welsch N, Albert K. Nuclear magnetic resonance and high-performance liquid chromatographic evaluation of polymer-based stationary phases immobilized on silica. Anal Bioanal Chem 2004; 382:679-90. [PMID: 15289980 DOI: 10.1007/s00216-004-2752-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Accepted: 06/14/2004] [Indexed: 10/26/2022]
Abstract
Three poly(ethylene-co-acrylic) acid copolymers (-CH(2)CH(2)-)(x)[CH(2)CH(CO(2)H)-](y) with different chain lengths and mass fractions of acrylic acid were covalently immobilized as stationary phases on silica via two variants of spacer molecules (3-aminopropyltriethoxysilane and 3-glycidoxypropyltrimethoxysilane). Different mobilities of the alkyl chains in the stationary phases were observed using (13)C solid-state NMR spectroscopy. The stationary phases with more rigid trans-ordered alkyl chains had better selectivity for geometric beta-carotene and xanthophyll isomers (provitamin A derivatives). Also, all the separations of the analytes were affected by polar interactions with the chromatographic sorbent. This was further proved by separating more polar cis/trans retinoic acid isomers (vitamin A derivatives). (13)C high-resolution/magic-angle spinning (HR/MAS) NMR measurements of the chromatographic sorbents suspended in the mobile phase confirmed a dependence of molecular shape recognition ability on alkyl chain conformation.
Collapse
Affiliation(s)
- Christoph Meyer
- Institute of Organic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, 72076 Tuebingen, Germany
| | | | | | | |
Collapse
|
21
|
Xia C, Fan X, Locklin J, Advincula RC, Gies A, Nonidez W. Characterization, Supramolecular Assembly, and Nanostructures of Thiophene Dendrimers. J Am Chem Soc 2004; 126:8735-43. [PMID: 15250726 DOI: 10.1021/ja0484404] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the synthesis and characterization of dendritic thiophene derivatives with their unique supramolecular assembly into 2-D crystals, nanowires, and nanoparticle aggregates. The structure and size of the dendrons and dendrimers have been confirmed with various techniques, such as NMR, SEC, and MALDI-TOF-MS. The mass values were consistent with the mass observed by MALDI-TOF-MS, whereas SEC measurements also gave useful information on the hydrodynamic volume of the individual dendrimers. The interesting electrooptical properties were highlighted by very broad absorption spectra and narrower fluorescence consistent with their electrochemical behavior. The self-organization of the dendrimers on the solid substrate is dependent on the nature of the substrate, preparation methods, and the molecule-molecule and molecule-substrate interactions. Thus, 14T-1 and 30T both formed globular aggregates on mica surface, while 14T-1 also formed nanowires on graphite surface. On the other hand, the larger 30T was observed to form 2-D crystalline structures. By varying the alkyl chain length attached to 14T-1, we were also able to obtain 2-D crystals on graphite. This showed that the different symmetry of packing for 30T and 14T-1 is also dependent on several factors, such as the molecular shape, size, and the presence of noncovalent intermolecular interactions. The results demonstrated the unique ability of thiophene dendrimers to form nanostructures on surfaces.
Collapse
Affiliation(s)
- Chuanjun Xia
- Department of Chemistry, University of Houston, Houston, Texas 77204, USA
| | | | | | | | | | | |
Collapse
|
22
|
Tyrpień K, Schefer R, Bachmann S, Albert K. Development and application of new C30-modified TLC plates. JPC-J PLANAR CHROMAT 2003. [DOI: 10.1556/jpc.16.2003.4.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
23
|
Reichert D. Solid-state NMR spectroscopy and its application in analytical chemistry. Anal Bioanal Chem 2003; 376:308-10. [PMID: 12734631 DOI: 10.1007/s00216-003-1929-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- D Reichert
- Fachbereich Physik, Fachgruppe NMR & Biophysik, Universität Halle, Friedemann-Bach-Platz 6, Germany.
| |
Collapse
|
24
|
Qualitative and quantitative determination of carotenoid stereoisomers in a variety of spinach samples by use of MSPD before HPLC-UV, HPLC-APCI-MS, and HPLC-NMR on-line coupling. Chromatographia 2003. [DOI: 10.1007/bf02492079] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
25
|
Campbell K, McDonald R, Branda NR, Tykwinski RR. Rigid, cross-conjugated macrocycles: a cyclic alternative to 4,4'-bipyridines in supramolecular chemistry. Org Lett 2001; 3:1045-8. [PMID: 11277791 DOI: 10.1021/ol0156087] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[structure: see text]. The synthesis of two fully conjugated, rigid macrocyclic analogues to 4,4'-bipyridine is described. The use of these macrocycles in self-assembly processes is demonstrated by axial coordination to metalloporphyrins, and one system (R = Me) has been characterized by single-crystal X-ray crystallography.
Collapse
Affiliation(s)
- K Campbell
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | | | | | | |
Collapse
|