1
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Losacco GL, Cohen RD, DaSilva JO, Haidar Ahmad IA, Sherer EC, Mangion I, Regalado EL. Deuterated Modifiers in Sub/Supercritical Fluid Chromatography for Streamlined NMR Structure Elucidation. Anal Chem 2022; 94:12176-12184. [PMID: 36001377 DOI: 10.1021/acs.analchem.2c02623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Isolation and chemical characterization of target components in fast-paced pharmaceutical laboratories can often be challenging, especially when dealing with mixtures of closely related, possibly unstable species. Traditionally, this process involves intense labor and manual intervention including chromatographic method development and optimization, fraction collection, and drying processes prior to NMR analyses for unambiguous structure elucidation. To circumvent these challenges, a foundational framework for the proper utilization of supercritical carbon dioxide (scCO2) and deuterated modifiers (CD3OD) in sub/supercritical fluid chromatography (SFC) is herein introduced. This facilitates a streamlined multicomponent isolation with minimized protic residues, further enabling immediate NMR analysis. In addition to bypassing tedious drying processes and minimizing analyte degradation, this approach (complementary to traditional reversed-phase liquid chromatography, RPLC) delivers highly efficient separations and automated fraction collection using readily available analytical/midscale SFC instrumentation. A series of diverse analytes across a wide spectrum of chemical properties (acid, basic, and neutral), combined with different stationary-phase columns in SFC are investigated using both a protic organic modifier (CH3OH) and its deuterated counterpart (CD3OD). The power of this framework is demonstrated with pharmaceutically relevant applications in the context of target characterization and analysis of complex multicomponent reaction mixtures from modern synthetic chemistry, demonstrating high isolation yields while reducing both the environmental footprint and manual intervention. This workflow enables unambiguous fast-paced structure elucidation on the analytical scale, providing results that are comparable to traditional, but time-consuming, RPLC purification approaches.
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Affiliation(s)
- Gioacchino Luca Losacco
- Analytical Research and Development, MRL, Merck & Co., Inc., 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Ryan D Cohen
- Analytical Research and Development, MRL, Merck & Co., Inc., 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Jimmy O DaSilva
- Analytical Research and Development, MRL, Merck & Co., Inc., 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Imad A Haidar Ahmad
- Analytical Research and Development, MRL, Merck & Co., Inc., 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Edward C Sherer
- Analytical Research and Development, MRL, Merck & Co., Inc., 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Ian Mangion
- Analytical Research and Development, MRL, Merck & Co., Inc., 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Erik L Regalado
- Analytical Research and Development, MRL, Merck & Co., Inc., 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
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2
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Ahmad IAH, Losacco GL, Shchurik V, Wang X, Cohen RD, Herron AN, Aiken S, Fiorito D, Wang H, Reibarkh M, Nowak T, Makarov AA, Stoll DR, Guillarme D, Mangion I, Aggarwal VK, Yu JQ, Regalado EL. Trapping-Enrichment Multi-dimensional Liquid Chromatography with On-Line Deuterated Solvent Exchange for Streamlined Structure Elucidation at the Microgram Scale. Angew Chem Int Ed Engl 2022; 61:e202117655. [PMID: 35139257 DOI: 10.1002/anie.202117655] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Indexed: 11/10/2022]
Abstract
At the forefront of chemistry and biology research, development timelines are fast-paced and large quantities of pure targets are rarely available. Herein, we introduce a new framework, which is built upon an automated, online trapping-enrichment multi-dimensional liquid chromatography platform (TE-Dt-mDLC) that enables: 1) highly efficient separation of complex mixtures in a first dimension (1 D-UV); 2) automated peak trapping-enrichment and buffer removal achieved through a sequence of H2 O and D2 O washes using an independent pump setup; and 3) a second dimension separation (2 D-UV-MS) with fully deuterated mobile phases and fraction collection to minimize protic residues for immediate NMR analysis while bypassing tedious drying processes and minimizing analyte degradation. Diverse examples of target isolation and characterization from organic synthesis and natural product chemistry laboratories are illustrated, demonstrating recoveries above 90 % using as little as a few micrograms of material.
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Affiliation(s)
- Imad A Haidar Ahmad
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | | | - Vladimir Shchurik
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Xiao Wang
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Ryan D Cohen
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Alastair N Herron
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Sheenagh Aiken
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
| | - Daniele Fiorito
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
| | - Heather Wang
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Mikhail Reibarkh
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Timothy Nowak
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Alexey A Makarov
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Dwight R Stoll
- Department of Chemistry, Gustavus Adolphus College, Saint Peter, MN 56082, USA
| | - Davy Guillarme
- School of Pharmaceutical Sciences, University of Geneva, CMU, Rue Michel-Servet 1, 1211, Geneva 4, Switzerland.,Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Rue Michel-Servet 1, 1211, Geneva 4, Switzerland
| | - Ian Mangion
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
| | | | - Jin-Quan Yu
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Erik L Regalado
- Analytical Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USA
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3
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Ahmad IAH, Losacco GL, Shchurik V, Wang X, Cohen RD, Herron AN, Aiken S, Fiorito D, Wang H, Reibarkh M, Nowak T, Makarov AA, Stoll DR, Guillarme D, Mangion I, Aggarwal VK, Yu J, Regalado EL. Trapping‐Enrichment Multi‐dimensional Liquid Chromatography with On‐Line Deuterated Solvent Exchange for Streamlined Structure Elucidation at the Microgram Scale. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202117655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | | | - Vladimir Shchurik
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | - Xiao Wang
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | - Ryan D. Cohen
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | - Alastair N. Herron
- Department of Chemistry The Scripps Research Institute La Jolla CA 92037 USA
| | - Sheenagh Aiken
- School of Chemistry University of Bristol Bristol BS8 1TS UK
| | - Daniele Fiorito
- School of Chemistry University of Bristol Bristol BS8 1TS UK
| | - Heather Wang
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | - Mikhail Reibarkh
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | - Timothy Nowak
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | - Alexey A. Makarov
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | - Dwight R. Stoll
- Department of Chemistry Gustavus Adolphus College Saint Peter MN 56082 USA
| | - Davy Guillarme
- School of Pharmaceutical Sciences University of Geneva, CMU Rue Michel-Servet 1 1211 Geneva 4 Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland University of Geneva, CMU Rue Michel-Servet 1 1211 Geneva 4 Switzerland
| | - Ian Mangion
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
| | | | - Jin‐Quan Yu
- Department of Chemistry The Scripps Research Institute La Jolla CA 92037 USA
| | - Erik L. Regalado
- Analytical Research & Development, MRL, Merck & Co., Inc. Rahway NJ 07065 USA
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4
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Eills J, Hale W, Utz M. Synergies between Hyperpolarized NMR and Microfluidics: A Review. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2022; 128:44-69. [PMID: 35282869 DOI: 10.1016/j.pnmrs.2021.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 09/10/2021] [Accepted: 09/11/2021] [Indexed: 06/14/2023]
Abstract
Hyperpolarized nuclear magnetic resonance and lab-on-a-chip microfluidics are two dynamic, but until recently quite distinct, fields of research. Recent developments in both areas increased their synergistic overlap. By microfluidic integration, many complex experimental steps can be brought together onto a single platform. Microfluidic devices are therefore increasingly finding applications in medical diagnostics, forensic analysis, and biomedical research. In particular, they provide novel and powerful ways to culture cells, cell aggregates, and even functional models of entire organs. Nuclear magnetic resonance is a non-invasive, high-resolution spectroscopic technique which allows real-time process monitoring with chemical specificity. It is ideally suited for observing metabolic and other biological and chemical processes in microfluidic systems. However, its intrinsically low sensitivity has limited its application. Recent advances in nuclear hyperpolarization techniques may change this: under special circumstances, it is possible to enhance NMR signals by up to 5 orders of magnitude, which dramatically extends the utility of NMR in the context of microfluidic systems. Hyperpolarization requires complex chemical and/or physical manipulations, which in turn may benefit from microfluidic implementation. In fact, many hyperpolarization methodologies rely on processes that are more efficient at the micro-scale, such as molecular diffusion, penetration of electromagnetic radiation into a sample, or restricted molecular mobility on a surface. In this review we examine the confluence between the fields of hyperpolarization-enhanced NMR and microfluidics, and assess how these areas of research have mutually benefited one another, and will continue to do so.
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Affiliation(s)
- James Eills
- Institute for Physics, Johannes Gutenberg University, D-55090 Mainz, Germany; GSI Helmholtzzentrum für Schwerionenforschung GmbH, Helmholtz-Institut Mainz, 55128 Mainz, Germany.
| | - William Hale
- Department of Chemistry, University of Florida, 32611, USA
| | - Marcel Utz
- School of Chemistry, University of Southampton, SO17 1BJ, UK.
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5
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Gathungu RM, Kautz R, Kristal BS, Bird SS, Vouros P. The integration of LC-MS and NMR for the analysis of low molecular weight trace analytes in complex matrices. MASS SPECTROMETRY REVIEWS 2020; 39:35-54. [PMID: 30024655 PMCID: PMC6339611 DOI: 10.1002/mas.21575] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 06/28/2018] [Indexed: 05/12/2023]
Abstract
This review discusses the integration of liquid chromatography (LC), mass spectrometry (MS), and nuclear magnetic resonance (NMR) in the comprehensive analysis of small molecules from complex matrices. We first discuss the steps taken toward making the three technologies compatible, so as to create an efficient analytical platform. The development of online LC-MS-NMR, highlighted by successful applications in the profiling of highly concentrated analytes (LODs 10 μg) is discussed next. This is followed by a detailed overview of the alternative approaches that have been developed to overcome the challenges associated with online LC-MS-NMR that primarily stem from the inherently low sensitivity of NMR. These alternative approaches include the use of stop-flow LC-MS-NMR, loop collection of LC peaks, LC-MS-SPE-NMR, and offline NMR. The potential and limitations of all these approaches is discussed in the context of applications in various fields, including metabolomics and natural product discovery.
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Affiliation(s)
- Rose M. Gathungu
- Department of Medicine, Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital and Department of Medicine, Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts
- Barnett Institute of Chemical and Biological Analysis and Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts
| | - Roger Kautz
- Barnett Institute of Chemical and Biological Analysis and Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts
| | - Bruce S. Kristal
- Department of Medicine, Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital and Department of Medicine, Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts
| | | | - Paul Vouros
- Barnett Institute of Chemical and Biological Analysis and Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts
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6
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van Zelst FHM, van Meerten SGJ, van Bentum PJM, Kentgens APM. Hyphenation of Supercritical Fluid Chromatography and NMR with In-Line Sample Concentration. Anal Chem 2018; 90:10457-10464. [PMID: 30080387 PMCID: PMC6127797 DOI: 10.1021/acs.analchem.8b02357] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
![]()
By
coupling supercritical fluid chromatography (SFC) and nuclear
magnetic resonance (NMR) in-line, a powerful analytical method arises
that enables chemically specific analysis of a broad range of complex
mixtures. However, during chromatography, the compounds are diluted
in the mobile phase, in this case supercritical CO2 (scCO2), often resulting in concentrations that are too low to be
detected by NMR spectroscopy or at least requiring excessive signal
averaging. We present a hyphenated SFC-NMR setup with an integrated
approach for concentrating samples in-line, which are diluted in scCO2 during chromatography. This in-line concentration is achieved
by controlled in-line expansion of the scCO2. As a proof
of concept four isomers of vitamin E (tocopherol) were isolated by
SFC, concentrated in-line by expanding CO2 from 120 to
50 bar, and finally shuttled to the NMR spectrometer fitted with a
dedicated probehead for spectroscopic characterization of microfluidic
samples. The abundant isomers were readily detected, supporting the
viability of SFC-NMR as a powerful analytical tool.
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Affiliation(s)
- F H M van Zelst
- Institute for Molecules and Materials (IMM) , Radboud University , Nijmegen 6525 AJ , The Netherlands.,TA-COAST , Science Park 904 , Amsterdam 1098 XH , The Netherlands
| | - S G J van Meerten
- Institute for Molecules and Materials (IMM) , Radboud University , Nijmegen 6525 AJ , The Netherlands.,TA-COAST , Science Park 904 , Amsterdam 1098 XH , The Netherlands
| | - P J M van Bentum
- Institute for Molecules and Materials (IMM) , Radboud University , Nijmegen 6525 AJ , The Netherlands
| | - A P M Kentgens
- Institute for Molecules and Materials (IMM) , Radboud University , Nijmegen 6525 AJ , The Netherlands
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7
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Teisseyre TZ, Urban J, Halpern-Manners NW, Chambers SD, Bajaj VS, Svec F, Pines A. Remotely Detected NMR for the Characterization of Flow and Fast Chromatographic Separations Using Organic Polymer Monoliths. Anal Chem 2011; 83:6004-10. [DOI: 10.1021/ac2010108] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Thomas Z. Teisseyre
- Program in Bioengineering, University of California—Berkeley and University of California—San Francisco, California 94133, United States
| | - Jiri Urban
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720, United States
| | | | - Stuart D. Chambers
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720, United States
| | - Vikram S. Bajaj
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720, United States
| | | | - Alexander Pines
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720, United States
- Program in Bioengineering, University of California—Berkeley and University of California—San Francisco, California 94133, United States
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8
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Gillespie TA, Winger BE. Mass spectrometry for small molecule pharmaceutical product development: a review. MASS SPECTROMETRY REVIEWS 2011; 30:479-490. [PMID: 21500245 DOI: 10.1002/mas.20289] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Developing a pharmaceutical product has become increasingly difficult and expensive. With an emphasis on developing project knowledge at an earlier stage in development, the use of information-rich technologies (particularly MS) has continued to expand throughout product development. Continued improvements in LC/MS technology have widened the scope of utilizing MS methods for performing both qualitative and quantitative applications within product development. This review describes a multi-tiered MS strategy designed to enhance and accelerate the identification and profiling of both process- and degradation-related impurities in either the active pharmaceutical ingredient (API) or formulated product. Such impurities can be formed either during chemical synthesis, formulation, or during storage. This review provides an overview of a variety of orthogonal-mass spectrometric methodologies, namely GC/MS, LC/MS, and ICP-MS, in support of product development. This review is not meant to be all inclusive; however, it has been written to highlight the increasing use of hyphenated MS techniques within the pharmaceutical development area.
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Affiliation(s)
- Todd A Gillespie
- Lilly Research Laboratories, A Division of Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
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9
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Fratila RM, Velders AH. Small-volume nuclear magnetic resonance spectroscopy. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2011; 4:227-249. [PMID: 21391818 DOI: 10.1146/annurev-anchem-061010-114024] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is one of the most information-rich analytical techniques available. However, it is also inherently insensitive, and this drawback precludes the application of NMR spectroscopy to mass- and volume-limited samples. We review a particular approach to increase the sensitivity of NMR experiments, namely the use of miniaturized coils. When the size of the coil is reduced, the sample volume can be brought down to the nanoliter range. We compare the main coil geometries (solenoidal, planar, and microslot/stripline) and discuss their applications to the analysis of mass-limited samples. We also provide an overview of the hyphenation of microcoil NMR spectroscopy to separation techniques and of the integration with lab-on-a-chip devices and microreactors.
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Affiliation(s)
- Raluca M Fratila
- MIRA Institute for Biomedical Engineering and Technical Medicine, Faculty of Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands.
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10
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Gulston MK, Titman CM, Griffin JL. Applications of metabolomics to understanding obesity in mouse and man. Biomark Med 2010; 1:575-82. [PMID: 20477375 DOI: 10.2217/17520363.1.4.575] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The functional genomic approach of metabolomics consists of the application of a global analytical tool to profile metabolism in a cell, tissue or organism. The most popular analytical tools include high-resolution (1)H nuclear magnetic resonance spectroscopy and mass spectrometry. Metabolomics is high throughput and relatively cheap on a per-sample basis and, hence, ideal for collecting large data sets. Biofluids are being used to follow the progression of obesity both in animal models and humans, while tissue extracts can be examined to probe the mechanisms responsible for these biofluid changes. Given these benefits and the results already produced in the field, metabolomics will play an increasing role in understanding the progression of obesity.
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Affiliation(s)
- Melanie K Gulston
- University of Cambridge, The Department of Biochemistry, Tennis Court Road, Cambridge, CB2 1QW, UK.
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Keifer PA. Chemical-shift referencing and resolution stability in gradient LC-NMR (acetonitrile:water). JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 199:75-87. [PMID: 19423372 DOI: 10.1016/j.jmr.2009.04.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 03/14/2009] [Accepted: 04/07/2009] [Indexed: 05/27/2023]
Abstract
Wide ranges of solvent conditions are generated during solvent-gradient LC-NMR. This complicates the referencing of the chemical-shift scale of the resulting NMR data. The problems that arise when performing LC-NMR in acetonitrile:water - particularly when the mobile-phase composition can range anywhere from 0% to 100% - are examined here, and the reliability of the secondary reference signals are evaluated. It is shown that under these conditions the use of the acetonitrile signal is superior to the use of the water signal in any form (either the (1)H or the (2)H signal) as a secondary reference, a lock signal, and a signal for shimming. The limitations of the referencing methods and other experimental parameters, and the limitations on the solvent-gradient ramp parameters, primarily as they affect lineshapes, are all shown. These results are compared to the way some other publications have referenced the (1)H chemical-shift axis (when using acetonitrile:water mixtures to perform reversed-phase chromatography LC-NMR).
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Affiliation(s)
- Paul A Keifer
- Varian Inc., 3120 Hansen Way D-298, Palo Alto, CA 94304-1030, USA.
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13
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Mietchen D, Manz B, Volke F, Storey K. In vivo assessment of cold adaptation in insect larvae by magnetic resonance imaging and magnetic resonance spectroscopy. PLoS One 2008; 3:e3826. [PMID: 19057644 PMCID: PMC2586655 DOI: 10.1371/journal.pone.0003826] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 11/04/2008] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Temperatures below the freezing point of water and the ensuing ice crystal formation pose serious challenges to cell structure and function. Consequently, species living in seasonally cold environments have evolved a multitude of strategies to reorganize their cellular architecture and metabolism, and the underlying mechanisms are crucial to our understanding of life. In multicellular organisms, and poikilotherm animals in particular, our knowledge about these processes is almost exclusively due to invasive studies, thereby limiting the range of conclusions that can be drawn about intact living systems. METHODOLOGY Given that non-destructive techniques like (1)H Magnetic Resonance (MR) imaging and spectroscopy have proven useful for in vivo investigations of a wide range of biological systems, we aimed at evaluating their potential to observe cold adaptations in living insect larvae. Specifically, we chose two cold-hardy insect species that frequently serve as cryobiological model systems--the freeze-avoiding gall moth Epiblema scudderiana and the freeze-tolerant gall fly Eurosta solidaginis. RESULTS In vivo MR images were acquired from autumn-collected larvae at temperatures between 0 degrees C and about -70 degrees C and at spatial resolutions down to 27 microm. These images revealed three-dimensional (3D) larval anatomy at a level of detail currently not in reach of other in vivo techniques. Furthermore, they allowed visualization of the 3D distribution of the remaining liquid water and of the endogenous cryoprotectants at subzero temperatures, and temperature-weighted images of these distributions could be derived. Finally, individual fat body cells and their nuclei could be identified in intact frozen Eurosta larvae. CONCLUSIONS These findings suggest that high resolution MR techniques provide for interesting methodological options in comparative cryobiological investigations, especially in vivo.
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Affiliation(s)
- Daniel Mietchen
- Magnetic Resonance Group, Fraunhofer Institute for Biomedical Engineering, IBMT, St Ingbert, Germany.
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14
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Ibuprofen metabolite profiling using a combination of SPE/column-trapping and HPLC-micro-coil NMR. J Pharm Biomed Anal 2007; 47:328-34. [PMID: 18276099 DOI: 10.1016/j.jpba.2007.12.035] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 12/13/2007] [Accepted: 12/18/2007] [Indexed: 11/22/2022]
Abstract
Solid-phase extraction and column-trapping preconcentration are combined to enhance HPLC-nuclear magnetic resonance (HPLC-NMR) and applied to metabolite profiling in biological samples. Combining the two signal enhancement techniques improved the NMR signal substantially such that we were able to identify 2-hydroxyibuprofen, carboxyibuprofen, and unmetabolized ibuprofen molecules from a small urine sample after a therapeutic dose of ibuprofen. The hyphenated SPE/column-trapping method resulted in an excellent overall signal enhancement of up to 90-fold.
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15
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McDonnell EE, Han S, Hilty C, Pierce KL, Pines A. NMR analysis on microfluidic devices by remote detection. Anal Chem 2007; 77:8109-14. [PMID: 16351162 DOI: 10.1021/ac051320+] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present a novel approach to perform high-sensitivity NMR imaging and spectroscopic analysis on microfluidic devices. The application of NMR, the most information-rich spectroscopic technique, to microfluidic devices remains a challenge because the inherently low sensitivity of NMR is aggravated by small fluid volumes leading to low NMR signal and geometric constraints resulting in poor efficiency for inductive detection. We address the latter by physically separating signal detection from encoding of information with remote detection. Thereby, we use a commercial imaging probe with sufficiently large diameter to encompass the entire device, enabling encoding of NMR information at any location on the chip. Because large-diameter coils are too insensitive for detection, we store the encoded information as longitudinal magnetization and flow it into the outlet capillary. There, we detect the signal with optimal sensitivity, using a solenoidal microcoil, and reconstruct the information encoded in the fluid. We present a generally applicable design for a detection-only microcoil probe that can be inserted into the bore of a commercial imaging probe. Using hyperpolarized 129Xe gas, we show that this probe enables sensitive reconstruction of NMR spectroscopic information encoded by the large imaging probe while keeping the flexibility of a large coil.
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Affiliation(s)
- Erin E McDonnell
- Materials Sciences Division, Lawrence Berkeley National Laboratory, and Department of Chemistry, University of California Berkeley, Berkeley, California 94720, USA.
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Affiliation(s)
- Gabriela Cimpan
- a Consultant , 53 Hastings Road, Pembury, Tunbridge Wells, TN2 4JS, UK
| | - Simion Gocan
- b Analytical Chemistry Department , “Babes-Bolyai” University , 11 A. Janos str., Cluj-Napoca, 3400, Romania
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17
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Djukovic D, Liu S, Henry I, Tobias B, Raftery D. Signal enhancement in HPLC/microcoil NMR using automated column trapping. Anal Chem 2006; 78:7154-60. [PMID: 17037915 PMCID: PMC2577147 DOI: 10.1021/ac0605748] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A new HPLC NMR system is described that performs analytical separation, preconcentration, and NMR spectroscopy in rapid succession. The central component of our method is the online preconcentration sequence that improves the match between postcolumn analyte peak volume and microcoil NMR detection volume. Separated samples are collected on to a C18 guard column with a mobile phase composed of 90% D2O/10% acetonitrile-D3 and back-flushed to the NMR microcoil probe with 90% acetonitrile-D3/10% D2O. To assess the performance of our unit, we separated a standard mixture of 1 mM ibuprofen, naproxen, and phenylbutazone using a commercially available C18 analytical column. The S/N measurements from the NMR acquisitions indicated that we achieved signal enhancement factors up to 10.4 (+/-1.2)-fold. Furthermore, we observed that preconcentration factors increased as the injected amount of analyte decreased. The highest concentration enrichment of 14.7 (+/-2.2)-fold was attained injecting 100 microL of solution of 0.2 mM (approximately 4 microg) ibuprofen.
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Affiliation(s)
- Danijel Djukovic
- Department of Chemistry, Purdue University 560 Oval Drive, West Lafayette, IN 47907
| | - Shuhui Liu
- Department of Chemistry, Purdue University 560 Oval Drive, West Lafayette, IN 47907
| | - Ian Henry
- Department of Chemistry, Purdue University 560 Oval Drive, West Lafayette, IN 47907
| | | | - Daniel Raftery
- Department of Chemistry, Purdue University 560 Oval Drive, West Lafayette, IN 47907
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18
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Korir AK, Almeida VK, Larive CK. Visualizing Ion Electromigration during Isotachophoretic Separations with Capillary Isotachophoresis-NMR. Anal Chem 2006; 78:7078-87. [PMID: 17037906 DOI: 10.1021/ac061431o] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sample stacking techniques in electrophoresis are gaining popularity due to their ability to provide improved sensitivity and separation efficiency. The principles behind sample stacking and electrophoretic migration have been studied extensively. Nevertheless, there are still a number of observations and descriptions of ionic boundaries and migration modes for which the underlying principles are not yet fully understood. For example, the behavior of capillary isotachophoresis (cITP) systems that exhibit self-sharpening effects can be complex, especially when the buffer systems contain many ionic components. In this work, cITP coupled with 1H NMR detection is used to study electrophoretic migration of ions in both anionic and cationic cITP. A significant advantage of 1H NMR over other detection methods is the high specificity of this method, allowing detection of individual buffer and analyte constituents within the migration zones.
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Affiliation(s)
- Albert K Korir
- Department of Chemistry, University of California, Riverside, California 92521, USA
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19
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Webb AG. Nuclear magnetic resonance coupled microseparations. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2005; 43:688-96. [PMID: 16049953 DOI: 10.1002/mrc.1616] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The increased separation efficiency afforded by reducing the size of the separation column has resulted in 'microseparations' becoming an important component in many chemical and biochemical applications. The coupling of microseparations with NMR detection is an area of increasing interest owing to the high structural information of NMR. In order to couple efficiently with the separation, the NMR detector must be reduced in size to correspond to that of the separation peak. This paper summarizes some of the approaches used in coupling NMR detection with pressure-driven and electrophoretic microseparations, the design of small NMR detectors and applications of this technology.
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Affiliation(s)
- A G Webb
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 61801, USA.
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20
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Putzbach K, Krucker M, Grynbaum MD, Hentschel P, Webb AG, Albert K. Hyphenation of capillary high-performance liquid chromatography to microcoil magnetic resonance spectroscopy—determination of various carotenoids in a small-sized spinach sample. J Pharm Biomed Anal 2005; 38:910-7. [PMID: 16087051 DOI: 10.1016/j.jpba.2005.01.049] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Revised: 01/10/2005] [Accepted: 01/22/2005] [Indexed: 11/16/2022]
Abstract
The development of miniaturized hyphenated systems such as capillary high-performance liquid chromatography--and nuclear magnetic resonance spectroscopy (HPLC-NMR) remains challenging in the field of structure elucidation. In combination with a highly specific sample preparation technique, matrix solid-phase dispersion (MSPD), and a highly selective C30 reverse phase HPLC-NMR enables the identification of small amounts of natural compounds. Here, the investigation of five carotenoids in a standard solution and two carotenoids from a spinach sample demonstrate the potential of this new development. The separation of the carotenoids is performed with self-packed fused-silica capillaries with a binary solvent gradient consisting of acetone and water. The miniaturized system allows the use of fully deuterated solvents for on-line HPLC-NMR coupling. The 1H NMR spectra of the various carotenoids obtained in stopped-flow mode gave a high signal-to-noise ratio with a sample amount in the low nanogram range. All necessary parameters for structure elucidation such as multiplet structure, coupling constants and integration values can be detected unambiguously.
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Affiliation(s)
- Karsten Putzbach
- Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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21
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Webb AG. Microcoil nuclear magnetic resonance spectroscopy. J Pharm Biomed Anal 2005; 38:892-903. [PMID: 16087050 DOI: 10.1016/j.jpba.2005.01.048] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 01/15/2005] [Accepted: 01/22/2005] [Indexed: 11/16/2022]
Abstract
In comparison with most analytical chemistry techniques, nuclear magnetic resonance has an intrinsically low sensitivity, and many potential applications are therefore precluded by the limited available quantity of certain types of sample. In recent years, there has been a trend, both commercial and academic, towards miniaturization of the receiver coil in order to increase the mass sensitivity of NMR measurements. These small coils have also proved very useful in coupling NMR detection with commonly used microseparation techniques. A further development enabled by small detectors is parallel data acquisition from many samples simultaneously, made possible by incorporating multiple receiver coils into a single NMR probehead. This review article summarizes recent developments and applications of "microcoil" NMR spectroscopy.
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Affiliation(s)
- A G Webb
- Department of Electrical and Computer Engineering, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 4221 Beckman Institute, 405 N. Mathews, Urbana, IL 61801, USA.
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22
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Xiao HB, Krucker M, Putzbach K, Albert K. Capillary liquid chromatography–microcoil 1H nuclear magnetic resonance spectroscopy and liquid chromatography–ion trap mass spectrometry for on-line structure elucidation of isoflavones in Radix astragali. J Chromatogr A 2005; 1067:135-43. [PMID: 15844518 DOI: 10.1016/j.chroma.2005.01.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Miniaturization and hyphenation of chromatographic separation techniques to nuclear magnetic resonance spectroscopy is being increasingly demanded in the field of biomedical, drug metabolite and natural product analysis. Herein, capillary liquid chromatography was coupled on-line to microcoil 1H nuclear magnetic resonance spectroscopy (capLC-NMR) equipped with a 1.5 microL solenoidal probe for structure elucidation of isoflavones in Radix astragali. The extract was screened by HPLC-UV-MS as the preliminary step and four major peaks were identified tentatively by ion trap mass spectrometry molecular weights and characteristic fragments. Then, stopped-flow capLC-UV-NMR was performed using 33 microg extract injected on-column. The four peaks were parked manually in the micro probe one by one and corresponding 1H NMR spectra were recorded with good resolutions under the applied capLC-NMR conditions (120 and 220 ng injected on-column for peaks 2 and 4, respectively). All aromatic regions of 1H NMR spectra correlated well to the characteristic signals of isoflavone aglycone protons. And the signal corresponding to the anomeric proton of the glucopyranoside of isoflavone glycoside was also obtained for peak 1. Therefore, these four peaks are determined as calycosin-7-O-beta-D-glucopyranoside (1), ononin (2), calycosin (3) and formononetin (4) unambiguously. The capLC-NMR results indicate that this hyphenated technique could be used for the determination of a great variety of natural products from small sample amounts, e.g., only 5 g R. astragali in this study.
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Affiliation(s)
- H B Xiao
- University of Tuebingen, Institute of Organic Chemistry, Auf der Morgenstelle 18, D-72076 Tuebingen, Germany
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23
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Zhang X, Webb AG. Magnetic resonance microimaging and numerical simulations of velocity fields inside enlarged flow cells used for coupled NMR microseparations. Anal Chem 2005; 77:1338-44. [PMID: 15732916 PMCID: PMC2754838 DOI: 10.1021/ac048532b] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The coupling of various chemical microseparation methods with small-scale NMR detection is a growing area in analytical chemistry. The formation of enlarged flow cells within the active volume of the NMR detector can significantly increase the coil filling factor and hence the signal-to-noise ratio of the NMR spectra. However, flow cells can also lead to deterioration of the separation efficiency due to the development of complex flow patterns, the form of which depend on the particular geometry of the flow cell and the flow rate used. In this study, we investigated the flow characteristics in different flow cell geometries relevant to the coupling of capillary liquid chromatography and NMR. Computational fluid dynamics was used to simulate fluid flow inside flow cells with a volume of approximately 1 microL. Magnetic resonance microimaging was used to measure experimentally the velocity fields inside these flow cells. The results showed good agreement between experiment and simulation and demonstrated that a relatively gradual expansion and contraction is necessary to avoid areas of weak recirculation and strong radial velocities, both of which can potentially compromise separation efficiency.
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Affiliation(s)
- Xiaofeng Zhang
- Department of Electrical and Computer Engineering; and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801
| | - Andrew G. Webb
- Department of Electrical and Computer Engineering; and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801
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24
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Wolters AM, Jayawickrama DA, Sweedler JV. Comparative analysis of a neurotoxin from Calliostoma canaliculatum by on-line capillary isotachophoresis/1H NMR and diffusion 1H NMR. JOURNAL OF NATURAL PRODUCTS 2005; 68:162-167. [PMID: 15730236 DOI: 10.1021/np030302p] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
NMR spectroscopy has been coupled on-line to capillary isotachophoresis (cITP) to enhance structural analyses of dilute charged species through separation and sample concentration. Microcoils, the most mass-sensitive NMR probes available, provide optimal detection for cITP/NMR. To evaluate the utility of cITP/NMR for natural product analysis, a homogenate of the hypobranchial gland from the marine snail Calliostoma canaliculatum containing a cationic neurotoxin (1, a disulfide-bonded dimer of 6-bromo-2-mercaptotryptamine) was studied. For comparison, hypobranchial gland homogenate was also examined by diffusion-NMR, an alternative approach for NMR mixture analysis. cITP/NMR concentrated the neurotoxin by almost 20-fold and isolated it from some of the other components present in the matrix. However, a minor component, likely a precursor or degradant, co-migrated with compound 1. Diffusion-NMR also did not resolve the two, indicating that the compounds possessed similar diffusion coefficients and electrophoretic mobilities. The strengths and limitations of the two approaches for NMR mixture analysis are discussed.
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Affiliation(s)
- Andrew M Wolters
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, IL 61801, USA
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25
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Saito Y, Jinno K, Greibrokk T. Capillary columns in liquid chromatography: between conventional columns and microchips. J Sep Sci 2004; 27:1379-90. [PMID: 15638147 DOI: 10.1002/jssc.200401902] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Liquid chromatography on columns with small internal diameters has been reviewed as the intermediate technique between conventional liquid chromatography and microchip separations. The development of micro column separations in the early years has been described, starting with the papers of Horváth and co-workers and Ishii and co-workers, continuing into the first part of the eighties, then making a leap in time to recent innovations with small-bore columns. Based on internal diameters a classification of the different analytical HPLC columns has been suggested. The advantages of small-bore columns have been discussed, with particular emphasis on the advantage of coupling to concentration sensitive detectors when the sample amount is limited. Open tubular columns are treated as a part of the historic background. The recent developments include a brief look into the current status of monolithic columns, the use of packed nano columns and micro columns with electrospray mass spectrometry, and the potential of two-dimensional comprehensive liquid chromatography. Finally, the coupling of sample preparation to analytical columns and the future applications of the novel technological improvements to the microchip separation methods have been discussed.
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Affiliation(s)
- Yoshihiro Saito
- School of Materials Science, Toyohashi University of Technology, Toyohashi 441-8580, Japan
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26
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Krucker M, Lienau A, Putzbach K, Grynbaum MD, Schuler P, Albert K. Hyphenation of Capillary HPLC to Microcoil 1H NMR Spectroscopy for the Determination of Tocopherol Homologues. Anal Chem 2004; 76:2623-8. [PMID: 15117207 DOI: 10.1021/ac030379i] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Highly selective reversed phases (C(30) phases) are self-packed in 250 microm inner diameter fused-silica capillaries and employed for capillary HPLC separation of shape-constrained natural compounds (tocopherol homologues, vitamin E). Miniaturized hyphenated systems such as capillary HPLC-ESI-MS (positive ionization mode) and, with special emphasis, continuous-flow capillary HPLC- NMR are used for structural determination of the separated compounds. Despite the small amount of sample available (1.33 microg of each tocopherol), the authors have been able to monitor the capillary HPLC separation under continuous-flow (1)H NMR conditions, thus allowing an immediate peak identification. Further structural assignment was carried out in the stopped-flow NMR mode as shown, for example, by a 2D (1)H,(1)H COSY NMR spectrum of alpha-tocopherol. We demonstrate in this paper the considerable potential of hyphenated capillary separations coupled to MS and NMR for the investigation of restricted amounts of sample.
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Affiliation(s)
- Manfred Krucker
- Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
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27
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Sandvoss M, Roberts AD, Ismail IM, North SE. Direct on-line hyphenation of capillary liquid chromatography to nuclear magnetic resonance spectroscopy: Practical aspects and application to drug metabolite identification. J Chromatogr A 2004; 1028:259-66. [PMID: 14989479 DOI: 10.1016/j.chroma.2003.11.105] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In combining the high peak concentrations of capillary liquid chromatography (CapLC) with the high mass sensitivity of micro scale nuclear magnetic resonance (NMR) the hyphenation of CapLC to micro NMR offers a substantial gain in overall sensitivity. This paper deals with our experiences gained using a commercial CapLC-NMR system which has very recently become available. The limits of detection (SNR > 3) for a test compound of a molecular weight of M 318 were found to be approximately 100 ng (0.35 nmol) within an hour acquisition time and approximately 25 ng over night (85 pmol). Practical aspects such as the feasibility of stopped-flow experiments and sample handling issues are discussed in detail and first possible drug metabolite applications to hepatocyte incubations and direct analysis of plasma samples are presented.
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Affiliation(s)
- Martin Sandvoss
- DMPK Structural ID Group, GlaxoSmithKline R&D, Park Road, Ware, Herts SG12 0DP, UK.
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28
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Advantages and disadvantages of nuclear magnetic resonance spectroscopy as a hyphenated technique. Anal Chim Acta 2003. [DOI: 10.1016/j.aca.2003.08.048] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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29
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Jayawickrama DA, Sweedler JV. Hyphenation of capillary separations with nuclear magnetic resonance spectroscopy. J Chromatogr A 2003; 1000:819-40. [PMID: 12877202 DOI: 10.1016/s0021-9673(03)00447-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The hyphenation of small-volume separations to information-rich detection offers the promise of unmatched analytical information on the components of complex mixtures. Nuclear magnetic resonance (NMR) spectroscopy provides information about molecular structure, although sensitivity remains an issue for on-line NMR detection. This is especially true when hyphenating NMR to capillary separations as the observation time and analyte mass are decreased to the point where reduced information is obtained from the eluting analytes. Because of these limitations, advances in instrumental performance have a large impact on the overall performance of a separation-NMR system. Instrumental aspects and the capabilities of cLC-NMR, CEC-NMR and CE-NMR are reviewed, and applications that have used this technology highlighted. Recent trends towards small volume capillary scale separations are emphasized, as is the recent success of capillary-isotachophoresis (cITP)-NMR.
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Affiliation(s)
- Dimuthu A Jayawickrama
- Department of Chemistry, Beckman Institute, University of Illinois, Urbana, IL 61801, USA
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Abstract
Flow NMR techniques are now well accepted and widely used in many areas of drug discovery. Although natural-product-, rational-drug-design-, and NMR-screening-programs have begun to use flow NMR more routinely, flow NMR has not yet gained widespread acceptance in combinatorial chemistry, even though it has been shown to be a potentially useful tool. Recent developments in DI-NMR, FIA-NMR, and LC-NMR will help flow NMR eventually gain a wider acceptance within combinatorial chemistry. These developments include LC-NMR-MS instrumentation, flow probe improvements, new pulse sequences, improved automation of NMR data analysis, and the application of flow NMR to related fields in drug discovery.
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Affiliation(s)
- Paul A Keifer
- University of Nebraska Medical Center/Eppley Institute, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA.
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31
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Biomedical applications of directly-coupled chromatography–nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1567-7192(03)80011-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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32
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Abstract
NMR spectroscopy is increasingly being used to characterize microliter and smaller-volume samples. Substances at picomole levels have been identified using NMR spectrometers equipped with microcoil-based probes. NMR probes that incorporate multiple sample chambers enable higher-throughput NMR experiments. Hyphenation of capillary-scale separations and microcoil NMR has also decreased analysis time of mixtures. For example, capillary isotachophoresis/NMR allows the highest mass sensitivity nanoliter-volume flow cells to be used with low microliter volume samples because isotachophoresis concentrates the microliter volume sample into the nanoliter volume NMR detection probe. In addition, the diagnostic capabilities of NMR spectroscopy allow the physico-chemical aspects of a capillary separation process to be characterized on-line. Because of such advances, the application of NMR to smaller samples continues to grow.
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Affiliation(s)
- Andrew M Wolters
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana 61801, USA
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Wolters AM, Jayawickrama DA, Larive CK, Sweedler JV. Insights into the cITP process using on-line NMR spectroscopy. Anal Chem 2002; 74:4191-7. [PMID: 12199592 DOI: 10.1021/ac025585p] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recently, capillary isotachophoresis (cITP) has been coupled on-line with nuclear magnetic resonance (NMR) to enhance analysis of dilute charged analytes through sample concentration and separation. This study focuses on the unique detection capabilities of NMR to noninvasively examine the cITP process and obtain diagnostic information. With their enhanced mass sensitivity, microcoil NMR probes provide optimal detection for cITP/NMR. Whereas previous studies used deuterated buffers, a 1H NMR observable leading electrolyte, tetramethylammonium acetate, is employed here to better track cITP progression. Fortuitously, the 1H chemical shift of the acetate methyl resonance depends on pD. Hence, by using a calibration curve, the solution pD can be determined on-line during cITP. Similarly, intracapillary temperature can be measured in cITP/NMR by observing the HOD chemical shift. To obtain accurate chemical shift measurements, charge-neutral tert-butyl alcohol is added to all cITP electrolyte solutions as an internal reference. As an ancillary benefit, line width measurements of the ubiquitous tert-butyl alcohol enable NMR spectral resolution to be examined throughout the experiment. Capable of providing quantitative results, NMR simultaneously determines the concentrations of the leading ion, sample, and counterion over the course of the cITP experiment.
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Affiliation(s)
- Andrew M Wolters
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana 61801, USA
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Affiliation(s)
- William R LaCourse
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore 21250, USA
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35
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Wolters AM, Jayawickrama DA, Larive CK, Sweedler JV. Capillary isotachophoresis/NMR: extension to trace impurity analysis and improved instrumental coupling. Anal Chem 2002; 74:2306-13. [PMID: 12038755 DOI: 10.1021/ac015744p] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Building upon its promising initial performance, the online coupling of capillary isotachophoresis (cITP) to nuclear magnetic resonance (NMR) is extended to trace impurity analysis. By simultaneously concentrating and separating dilute charged species on the basis of their electrophoretic mobility, cITP greatly facilitates NMR structural elucidation. cITP/NMR appears particularly attractive for identifying trace charged synthetic and natural organic compounds obscured by large excesses of other components. A 9.4 microL injection of 200 microM (1.9 nmol) atenolol in a 1000-fold excess of sucrose (200 mM) is analyzed by cITP/NMR. A microcoil, the most mass sensitive NMR probe, serves as the detector as it provides optimal NMR observation of the capillary-scale separation. cITP successfully isolates the atenolol from the sucrose while concentrating it 200-fold to 40 mM before presentation to the 30 nL observe volume microcoil, thereby enabling rapid 1H NMR spectral acquisition of atenolol (experimental time of 10 s) without obstruction from sucrose. For this particular probe and sample, the stacking efficiency is near the theoretical limit as 67% of the sample occupies the 1 mm long microcoil during peak maximum. A multiple-coil probe with two serial 1 mm long microcoils arranged 1 cm apart has been developed to facilitate peak trapping and sample band positioning during cITP/NMR.
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Affiliation(s)
- Andrew M Wolters
- Department of Chemistry, University of Illinois, Urbana 61801, USA
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36
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Current awareness in phytochemical analysis. PHYTOCHEMICAL ANALYSIS : PCA 2002; 13:55-62. [PMID: 11899608 DOI: 10.1002/pca.617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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37
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