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Vargas Medina DA, Maciel EVS, Pereira Dos Santos NG, Lancas FM. The overshadowed role of electron ionization-mass spectrometry in analytical biotechnology. Curr Opin Biotechnol 2023; 82:102965. [PMID: 37393696 DOI: 10.1016/j.copbio.2023.102965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 05/30/2023] [Accepted: 06/05/2023] [Indexed: 07/04/2023]
Abstract
Target and untargeted analysis of several compounds are crucial methods in important areas such as omics sciences. Gas chromatography coupled to mass spectrometry (GC-MS) is widely used for volatile and thermally stable compounds. In this case, the electron ionization technique (EI) is preferable as it produces highly fragmented and reproducible spectra comparable to spectral libraries. However, only a fraction of target compounds is analyzable by GC without chemical derivatization. Therefore, liquid chromatography (LC) coupled with MS is the most used technique. Contrary to EI, electrospray ionization does not produce reproducible spectra. That is why researchers have been working on interfaces between LC and EI-MS to bridge the gap between those techniques. This short review will discuss advancements, applications, and perspectives on biotechnological analysis.
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Affiliation(s)
- Deyber Arley Vargas Medina
- Laboratory of Chromatography, Institute of Chemistry at Sao Carlos, University of Sao Paulo, P.O Box 780, 13566590 Sao Carlos, Brazil; Clemens Schöpf Institute, Department of Chemistry, Technical University of Darmstadt, 64287 Darmstadt, Germany
| | - Edvaldo Vasconcelos Soares Maciel
- Laboratory of Chromatography, Institute of Chemistry at Sao Carlos, University of Sao Paulo, P.O Box 780, 13566590 Sao Carlos, Brazil; Clemens Schöpf Institute, Department of Chemistry, Technical University of Darmstadt, 64287 Darmstadt, Germany
| | - Natalia Gabrielly Pereira Dos Santos
- Laboratory of Chromatography, Institute of Chemistry at Sao Carlos, University of Sao Paulo, P.O Box 780, 13566590 Sao Carlos, Brazil; Clemens Schöpf Institute, Department of Chemistry, Technical University of Darmstadt, 64287 Darmstadt, Germany
| | - Fernando Mauro Lancas
- Laboratory of Chromatography, Institute of Chemistry at Sao Carlos, University of Sao Paulo, P.O Box 780, 13566590 Sao Carlos, Brazil.
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Pereira Dos Santos NG, Maciel EVS, Vargas Medina DA, Lanças FM. NanoLC-EI-MS: Perspectives in Biochemical Analysis. Int J Mol Sci 2023; 24:11746. [PMID: 37511506 PMCID: PMC10380556 DOI: 10.3390/ijms241411746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/14/2023] [Accepted: 07/18/2023] [Indexed: 07/30/2023] Open
Abstract
Although LC-MS with atmospheric pressure ionization (API) sources is the primary technique used in modern bioanalytical studies, electron ionization mass spectrometry (EI-MS) can provide some substantial advantages over it. EI-MS is a matrix effect-free technique that provides reproducible and comparable mass spectra, serving as a compound fingerprint for easy identification through automated comparison with spectral libraries. Leveraging EI-MS in biochemical studies can yield critical analytical benefits for targeted and untargeted analyses. However, to fully utilize EI-MS for heavy and non-volatile molecules, a new technology that enables the coupling of liquid chromatography with EI-MS is needed. Recent advancements in nanoLC have addressed the compatibility issues between LC and EI-MS, and innovative interfacing strategies such as Direct-EI, liquid electron ionization (LEI), and Cold-EI have extended the application of EI-MS beyond the determination of volatile organic molecules. This review provides an overview of the latest developments in nanoLC-EI-MS interfacing technologies, discussing their scope and limitations. Additionally, selected examples of nanoLC-EI-MS applications in the field of biochemical analysis are presented, highlighting the potential prospects and benefits that the establishment of this technique can bring to this field.
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Affiliation(s)
| | | | | | - Fernando Mauro Lanças
- Institute of Chemistry of São Carlos, University of São Paulo, São Carlos 13566-590, Brazil
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Famiglini G, Palma P, Termopoli V, Cappiello A. The history of electron ionization in LC-MS, from the early days to modern technologies: A review. Anal Chim Acta 2021; 1167:338350. [PMID: 34049632 DOI: 10.1016/j.aca.2021.338350] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 02/18/2021] [Accepted: 02/20/2021] [Indexed: 02/06/2023]
Abstract
This review article traces the history of the use of liquid chromatography coupled with mass spectrometry (LC-MS) using electron ionization (EI) from the first attempts up to the present day. At the time of the first efforts to couple LC to MS, 70 eV EI was the most common ionization technique, typically used in gas chromatography-mass spectrometry (GC-MS) and providing highly reproducible mass spectra that could be collated in libraries. Therefore, it was obvious to transport this dominant approach to the early LC-MS coupling attempts. The use of LC coupled to EI-MS is challenging mainly due to restrictions related to high-vacuum and high-temperature conditions required for the operation of EI and the need to remove the eluent carrying the analyte before entering the ion source. The authors will take readers through a journey of about 50 years, showing how through the succession of different attempts it has been possible to successfully couple LC with EI-MS, which in principle appear to be incompatible.
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Affiliation(s)
- Giorgio Famiglini
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino, Urbino, Italy.
| | - Pierangela Palma
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino, Urbino, Italy
| | - Veronica Termopoli
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino, Urbino, Italy
| | - Achille Cappiello
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino, Urbino, Italy.
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Borden SA, Palaty J, Termopoli V, Famiglini G, Cappiello A, Gill CG, Palma P. MASS SPECTROMETRY ANALYSIS OF DRUGS OF ABUSE: CHALLENGES AND EMERGING STRATEGIES. MASS SPECTROMETRY REVIEWS 2020; 39:703-744. [PMID: 32048319 DOI: 10.1002/mas.21624] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 01/22/2020] [Indexed: 06/10/2023]
Abstract
Mass spectrometry has been the "gold standard" for drugs of abuse (DoA) analysis for many decades because of the selectivity and sensitivity it affords. Recent progress in all aspects of mass spectrometry has seen significant developments in the field of DoA analysis. Mass spectrometry is particularly well suited to address the rapidly proliferating number of very high potency, novel psychoactive substances that are causing an alarming number of fatalities worldwide. This review surveys advancements in the areas of sample preparation, gas and liquid chromatography-mass spectrometry, as well as the rapidly emerging field of ambient ionization mass spectrometry. We have predominantly targeted literature progress over the past ten years and present our outlook for the future. © 2020 Periodicals, Inc. Mass Spec Rev.
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Affiliation(s)
- Scott A Borden
- Applied Environmental Research Laboratories (AERL), Department of Chemistry, Vancouver Island University, Nanaimo, BC, V9R 5S5, Canada
- Department of Chemistry, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Jan Palaty
- LifeLabs Medical Laboratories, Burnaby, BC, V3W 1H8, Canada
| | - Veronica Termopoli
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino Carlo Bo, 61029, Urbino, Italy
| | - Giorgio Famiglini
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino Carlo Bo, 61029, Urbino, Italy
| | - Achille Cappiello
- Applied Environmental Research Laboratories (AERL), Department of Chemistry, Vancouver Island University, Nanaimo, BC, V9R 5S5, Canada
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino Carlo Bo, 61029, Urbino, Italy
| | - Chris G Gill
- Applied Environmental Research Laboratories (AERL), Department of Chemistry, Vancouver Island University, Nanaimo, BC, V9R 5S5, Canada
- Department of Chemistry, University of Victoria, Victoria, BC, V8P 5C2, Canada
- Department of Chemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, 98195
| | - Pierangela Palma
- Applied Environmental Research Laboratories (AERL), Department of Chemistry, Vancouver Island University, Nanaimo, BC, V9R 5S5, Canada
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino Carlo Bo, 61029, Urbino, Italy
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Rigano F, Russo M, Arigò A, Dugo P, Mondello L. Combining linear retention index and electron ionization mass spectrometry for a reliable identification in nano liquid chromatography. J Chromatogr A 2019; 1610:460581. [PMID: 31610919 DOI: 10.1016/j.chroma.2019.460581] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 09/27/2019] [Accepted: 09/29/2019] [Indexed: 10/25/2022]
Abstract
The present research is focused on the object to improve identification capability in liquid chromatography (LC), by creating a system as similar as possible to gas chromatography (GC), where the combination/complementarity of Linear Retention Index (LRI) and Electron Ionization Mass Spectrometry (EI-MS) data makes the identification process easy, automatic and reliable. Conversely, in LC the untargeted characterization of real-world samples is still a challenge, due to the not repeatable and poorly informative nature of typical atmospheric pressure ionization mass spectrometry, normally hyphenated to LC. In the last decades the miniaturization of LC instrumentation together with the considerable progresses in MS vacuum pump capability has made the LC-EI-MS hyphenation more feasible. In the present work, a prototypal nanoLC-EI-MS system was used for the determination of typically LC-amenable compunds, such as coumarins, furocoumarins and polymethoxyflavones in citrus essential oils. All the compounds provided high quality EI-MS spectra, evaluated by the comparison with thousands of spectra present in commercial EI-MS libraries. Spectral similarities major than 80% were achieved. Furthermore, an LRI system, based on the use of an alkyl aryl ketone homologue reference series, was proposed as additional filter to achieve a univocal identification. Then, a novel dual-filter LRI/EI-MS library was built and resulted very helpful in the case of isomeric compounds characterized by identical EI-MS spectrum, but different retention behaviour. The very low inter-day variability attained for each LRI value, together with the satisfactory chromatographic resolution of the developed method, led to a 100% reliability of the identification process based on LRI.
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Affiliation(s)
- Francesca Rigano
- Chromaleont s.r.l., c/o Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy
| | - Marina Russo
- Unit of Food Science and Nutrition, Department of Medicine, University Campus Bio-Medico of Rome, Rome, Italy
| | - Adriana Arigò
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy
| | - Paola Dugo
- Chromaleont s.r.l., c/o Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy; Unit of Food Science and Nutrition, Department of Medicine, University Campus Bio-Medico of Rome, Rome, Italy; Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy; BeSep s.r.l., c/o Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy
| | - Luigi Mondello
- Chromaleont s.r.l., c/o Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy; Unit of Food Science and Nutrition, Department of Medicine, University Campus Bio-Medico of Rome, Rome, Italy; Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy; BeSep s.r.l., c/o Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy.
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Rigano F, Tranchida PQ, Dugo P, Mondello L. High-performance liquid chromatography combined with electron ionization mass spectrometry: A review. Trends Analyt Chem 2019. [DOI: 10.1016/j.trac.2019.05.032] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Evaluation of a liquid electron ionization liquid chromatography-mass spectrometry interface. J Chromatogr A 2019; 1591:120-130. [PMID: 30660440 DOI: 10.1016/j.chroma.2019.01.034] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 12/20/2018] [Accepted: 01/11/2019] [Indexed: 11/27/2022]
Abstract
Liquid Electron Ionization (LEI), is an innovative liquid chromatography-mass spectrometry (LC-MS) interface that converts liquid HPLC eluent to the gas-phase in a mass spectrometer equipped with an electron ionization (EI) source. LEI extends the electronic spectra libraries access to liquid chromatography, providing a powerful tool in the untargeted approacssh. Negligible matrix effects allow accurate quantitative information. The purpose of this research was to evaluate the main aspects concerning the interfacing process. These fundamental studies were necessary to understand the mechanism of LEI in details, and improve the interfacing process, especially regarding robustness and sensitivity. Hardware components were installed to prevent analytes precipitation, reduce thermal decomposition of sensitive compounds, and to stabilize the nano-flow delivery with different mobile-phase compositions. Particular attention was devoted to insulating the heated vaporization area from the LC part of the system. Experiments were performed to optimize the interface inner capillary dimensions, and other operative parameters, including temperature, gas and liquid flow rates. Test compounds of environmental interest were selected based on molecular weight, thermal stability, volatility, and polarity. Robustness was evaluated with a set of replicated injections and calibration experiments using a soil matrix as a test sample. MRM detection limits in the low-picogram range were obtained for five pesticides belonging to different classes in a soil sample. High-quality electron ionization mass spectra of a mixture of pesticides were also obtained.
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Electron Ionization LC-MS. ADVANCES IN THE USE OF LIQUID CHROMATOGRAPHY MASS SPECTROMETRY (LC-MS) - INSTRUMENTATION DEVELOPMENTS AND APPLICATIONS 2018. [DOI: 10.1016/bs.coac.2017.06.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Sol-gel coated ion sources for liquid chromatography-direct electron ionization mass spectrometry. Anal Chim Acta 2017; 978:35-41. [DOI: 10.1016/j.aca.2017.04.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/07/2017] [Accepted: 04/09/2017] [Indexed: 11/24/2022]
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Termopoli V, Famiglini G, Palma P, Piergiovanni M, Cappiello A. Atmospheric Pressure Vaporization Mechanism for Coupling a Liquid Phase with Electron Ionization Mass Spectrometry. Anal Chem 2017; 89:2049-2056. [PMID: 28208289 DOI: 10.1021/acs.analchem.6b04646] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A novel liquid chromatography-mass spectrometry (LC-MS) interfacing concept is presented and discussed. The new interface, called liquid-EI (LEI), is based on electron ionization (EI) but, differently from any previous attempt, the vaporization of solutes and mobile phase takes place at atmospheric pressure into a specifically designed region, called "vaporization microchannel", before entering the high-vacuum ion source. The interface is completely independent from the rest of the instrumentation and can be adapted to any gas chromatography/mass spectrometry (GC/MS) system, as an add-on for a rapid LC-MS conversion. Pressure drop and temperature gradient between LC and MS were considered to enhance the analyte response and reduce band broadening and/or solute carryovers. A fused silica liner, placed inside the vaporization microchannel, acts as an inert vaporization surface speeding up the gas-phase conversion of large molecules while lessening possible memory effects. The liner is easily replaceable for a quick and extremely simple interface maintenance. Proof of concept and detailed description of the interface are here presented.
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Affiliation(s)
- Veronica Termopoli
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino , Urbino, Italy
| | - Giorgio Famiglini
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino , Urbino, Italy
| | - Pierangela Palma
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino , Urbino, Italy
| | - Maurizio Piergiovanni
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino , Urbino, Italy
| | - Achille Cappiello
- LC-MS Laboratory, Department of Pure and Applied Sciences, University of Urbino , Urbino, Italy
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Zhao H, Xie Y, Yang Q, Cao Y, Tu H, Cao W, Wang S. Pharmacokinetic study of cinnamaldehyde in rats by GC–MS after oral and intravenous administration. J Pharm Biomed Anal 2014; 89:150-7. [DOI: 10.1016/j.jpba.2013.10.044] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/17/2013] [Accepted: 10/27/2013] [Indexed: 11/25/2022]
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Drutis DM, Hancewicz TM, Pashkovski E, Feng L, Mihalov D, Holtom G, Ananthapadmanabhan KP, Xie XS, Misra M. Three-dimensional chemical imaging of skin using stimulated Raman scattering microscopy. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:111604. [PMID: 24858033 DOI: 10.1117/1.jbo.19.11.111604] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 04/30/2014] [Indexed: 05/20/2023]
Abstract
Stimulated Raman scattering (SRS) microscopy is used to generate structural and chemical three-dimensional images of native skin. We employed SRS microscopy to investigate the microanatomical features of skin and penetration of topically applied materials. Image depth stacks are collected at distinct wavelengths corresponding to vibrational modes of proteins, lipids, and water in the skin. We observed that corneocytes in stratum corneum are grouped together in clusters, 100 to 250 μm in diameter, separated by 10- to 25-μm-wide microanatomical skin-folds called canyons. These canyons occasionally extend down to depths comparable to that of the dermal-epidermal junction below the flat surface regions in porcine and human skin. SRS imaging shows the distribution of chemical species within cell clusters and canyons. Water is predominately located within the cell clusters, and its concentration rapidly increases at the transition from stratum corneum to viable epidermis. Canyons do not contain detectable levels of water and are rich in lipid material. Oleic acid-d34 applied to the skin surface lines the canyons down to a depth of 50 μm below the surface of the skin. This observation could have implications on the evaluation of penetration profiles of bioactive materials measured using traditional methods, such as tape-stripping.
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Affiliation(s)
- Dane M Drutis
- Unilever Research and Development, Trumbull, Connecticut 06611
| | | | - Eugene Pashkovski
- Unilever Research and Development, Trumbull, Connecticut 06611cThe Lubrizol Corporation, Wickliffe, Ohio 44092
| | - Lin Feng
- Unilever Research and Development, Trumbull, Connecticut 06611
| | - Dawn Mihalov
- Unilever Research and Development, Trumbull, Connecticut 06611
| | - Gary Holtom
- Harvard University, Department of Chemistry and Chemical Biology, Cambridge, Massachusetts 02138
| | | | - X Sunney Xie
- Harvard University, Department of Chemistry and Chemical Biology, Cambridge, Massachusetts 02138
| | - Manoj Misra
- Unilever Research and Development, Trumbull, Connecticut 06611
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Rapid determination of hexapeptides by hydrophilic interaction LC–MS/MS for in vitro skin-penetration studies. Bioanalysis 2013; 5:1353-62. [DOI: 10.4155/bio.13.60] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Background: A sensitive analytical method is needed for assessing penetration of topically applied peptides for in vitro skin-penetration studies. Results: A rapid hydrophilic interaction LC (HILIC)–MS/MS method for analyzing the polar peptides Ac-EEMQRR-amide and H2N-EEMQRR-amide in various skin layers and matrices has been developed and evaluated. The matrices included emulsion, receptor fluids, cotton-tipped applicators, stratum corneum tape strips, epidermis and dermis of the skin. Stable isotopically labeled analogues were used as internal standards to correct for recovery and matrix effects. A HILIC-SPE procedure was optimized to minimize significant ion suppression in the more complex matrices. Conclusion: This HILIC–MS/MS method is applicable to the determination of Ac-EEMQRR-amide and H2N-EEMQRR-amide in complex skin samples and other matrices generated during in vitro skin-penetration studies.
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Zedda M, Zwiener C. Is nontarget screening of emerging contaminants by LC-HRMS successful? A plea for compound libraries and computer tools. Anal Bioanal Chem 2012; 403:2493-502. [PMID: 22476785 DOI: 10.1007/s00216-012-5893-y] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 02/17/2012] [Accepted: 02/20/2012] [Indexed: 10/28/2022]
Abstract
This review focuses on the possibilities and limits of nontarget screening of emerging contaminants, with emphasis on recent applications and developments in data evaluation and compound identification by liquid chromatography-high-resolution mass spectrometry (HRMS). The general workflow includes determination of the elemental composition from accurate mass, a further search for the molecular formula in compound libraries or general chemical databases, and a ranking of the proposed structures using further information, e.g., from mass spectrometry (MS) fragmentation and retention times. The success of nontarget screening is in some way limited to the preselection of relevant compounds from a large data set. Recently developed approaches show that statistical analysis in combination with suspect and nontarget screening are useful methods to preselect relevant compounds. Currently, the unequivocal identification of unknowns still requires information from an authentic standard which has to be measured or is already available in user-defined MS/MS reference databases or libraries containing HRMS spectral information and retention times. In this context, we discuss the advantages and future needs of publicly available MS and MS/MS reference databases and libraries which have mostly been created for the metabolomic field. A big step forward has been achieved with computer-based tools when no MS library or MS database entry is found for a compound. The numerous search results from a large chemical database can be condensed to only a few by in silico fragmentation. This has been demonstrated for selected compounds and metabolites in recent publications. Still, only very few compounds have been identified or tentatively identified in environmental samples by nontarget screening. The availability of comprehensive MS libraries with a focus on environmental contaminants would tremendously improve the situation.
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Affiliation(s)
- Marco Zedda
- Environmental Analytical Chemistry, Center for Applied Geoscience (ZAG), Eberhard Karls University Tübingen, Tübingen, Germany
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