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An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.
Electrospray ionization (ESI) is a technique used in mass spectrometry to produce ions using an electrospray in which a high voltage is applied to a liquid to create an aerosol. It is especially useful in producing ions from macromolecules because it overcomes the propensity of these molecules to fragment when ionized. ESI is different from other ionization processes since it may produce multiple-charged ions, effectively extending the mass range of the analyser to accommodate the kDa-MDa orders of magnitude observed in proteins and their associated polypeptide fragments.
In mass spectrometry, matrix-assisted laser desorption/ionization (MALDI) is an ionization technique that uses a laser energy-absorbing matrix to create ions from large molecules with minimal fragmentation. It has been applied to the analysis of biomolecules and various organic molecules, which tend to be fragile and fragment when ionized by more conventional ionization methods. It is similar in character to electrospray ionization (ESI) in that both techniques are relatively soft ways of obtaining ions of large molecules in the gas phase, though MALDI typically produces far fewer multi-charged ions.
Electron-capture dissociation (ECD) is a method of fragmenting gas-phase ions for structure elucidation of peptides and proteins in tandem mass spectrometry. It is one of the most widely used techniques for activation and dissociation of mass selected precursor ion in MS/MS. It involves the direct introduction of low-energy electrons to trapped gas-phase ions.
Atmospheric pressure chemical ionization (APCI) is an ionization method used in mass spectrometry which utilizes gas-phase ion-molecule reactions at atmospheric pressure (105 Pa), commonly coupled with high-performance liquid chromatography (HPLC). APCI is a soft ionization method similar to chemical ionization where primary ions are produced on a solvent spray. The main usage of APCI is for polar and relatively less polar thermally stable compounds with molecular weight less than 1500 Da. The application of APCI with HPLC has gained a large popularity in trace analysis detection such as steroids, pesticides and also in pharmacology for drug metabolites.
Electron-transfer dissociation (ETD) is a method of fragmenting multiply-charged gaseous macromolecules in a mass spectrometer between the stages of tandem mass spectrometry (MS/MS). Similar to electron-capture dissociation, ETD induces fragmentation of large, multiply-charged cations by transferring electrons to them. ETD is used extensively with polymers and biological molecules such as proteins and peptides for sequence analysis. Transferring an electron causes peptide backbone cleavage into c- and z-ions while leaving labile post translational modifications (PTM) intact. The technique only works well for higher charge state peptide or polymer ions (z>2). However, relative to collision-induced dissociation (CID), ETD is advantageous for the fragmentation of longer peptides or even entire proteins. This makes the technique important for top-down proteomics. The method was developed by Hunt and coworkers at the University of Virginia.
Desorption electrospray ionization (DESI) is an ambient ionization technique that can be coupled to mass spectrometry (MS) for chemical analysis of samples at atmospheric conditions. Coupled ionization sources-MS systems are popular in chemical analysis because the individual capabilities of various sources combined with different MS systems allow for chemical determinations of samples. DESI employs a fast-moving charged solvent stream, at an angle relative to the sample surface, to extract analytes from the surfaces and propel the secondary ions toward the mass analyzer. This tandem technique can be used to analyze forensics analyses, pharmaceuticals, plant tissues, fruits, intact biological tissues, enzyme-substrate complexes, metabolites and polymers. Therefore, DESI-MS may be applied in a wide variety of sectors including food and drug administration, pharmaceuticals, environmental monitoring, and biotechnology.
Sample preparation for mass spectrometry is used for the optimization of a sample for analysis in a mass spectrometer (MS). Each ionization method has certain factors that must be considered for that method to be successful, such as volume, concentration, sample phase, and composition of the analyte solution. Quite possibly the most important consideration in sample preparation is knowing what phase the sample must be in for analysis to be successful. In some cases the analyte itself must be purified before entering the ion source. In other situations, the matrix, or everything in the solution surrounding the analyte, is the most important factor to consider and adjust. Often, sample preparation itself for mass spectrometry can be avoided by coupling mass spectrometry to a chromatography method, or some other form of separation before entering the mass spectrometer. In some cases, the analyte itself must be adjusted so that analysis is possible, such as in protein mass spectrometry, where usually the protein of interest is cleaved into peptides before analysis, either by in-gel digestion or by proteolysis in solution.
Christie G. Enke is a United States academic chemist who made pioneering contributions to the field of analytical chemistry.
Laser spray ionization refers to one of several methods for creating ions using a laser interacting with a spray of neutral particles or ablating material to create a plume of charged particles. The ions thus formed can be separated by m/z with mass spectrometry. Laser spray is one of several ion sources that can be coupled with liquid chromatography-mass spectrometry for the detection of larger molecules.
Matrix-assisted laser desorption electrospray ionization (MALDESI) was first introduced in 2006 as a novel ambient ionization technique which combines the benefits of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). An infrared (IR) or ultraviolet (UV) laser can be utilized in MALDESI to resonantly excite an endogenous or exogenous matrix. The term 'matrix' refers to any molecule that is present in large excess and absorbs the energy of the laser, thus facilitating desorption of analyte molecules. The original MALDESI design was implemented using common organic matrices, similar to those used in MALDI, along with a UV laser. The current MALDESI source employs endogenous water or a thin layer of exogenously deposited ice as the energy-absorbing matrix where O-H symmetric and asymmetric stretching bonds are resonantly excited by a mid-IR laser.
Desorption atmospheric pressure photoionization (DAPPI) is an ambient ionization technique for mass spectrometry that uses hot solvent vapor for desorption in conjunction with photoionization. Ambient Ionization techniques allow for direct analysis of samples without pretreatment. The direct analysis technique, such as DAPPI, eliminates the extraction steps seen in most nontraditional samples. DAPPI can be used to analyze bulkier samples, such as, tablets, powders, resins, plants, and tissues. The first step of this technique utilizes a jet of hot solvent vapor. The hot jet thermally desorbs the sample from a surface. The vaporized sample is then ionized by the vacuum ultraviolet light and consequently sampled into a mass spectrometer. DAPPI can detect a range of both polar and non-polar compounds, but is most sensitive when analyzing neutral or non-polar compounds. This technique also offers a selective and soft ionization for highly conjugated compounds.
Ambient ionization is a form of ionization in which ions are formed in an ion source outside the mass spectrometer without sample preparation or separation. Ions can be formed by extraction into charged electrospray droplets, thermally desorbed and ionized by chemical ionization, or laser desorbed or ablated and post-ionized before they enter the mass spectrometer.
Atmospheric pressure photoionization (APPI) is a soft ionization method used in mass spectrometry (MS) usually coupled to liquid chromatography (LC). Molecules are ionized using a vacuum ultraviolet (VUV) light source operating at atmospheric pressure, either by direct absorption followed by electron ejection or through ionization of a dopant molecule that leads to chemical ionization of target molecules. The sample is usually a solvent spray that is vaporized by nebulization and heat. The benefit of APPI is that it ionizes molecules across a broad range of polarity and is particularly useful for ionization of low polarity molecules for which other popular ionization methods such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) are less suitable. It is also less prone to ion suppression and matrix effects compared to ESI and APCI and typically has a wide linear dynamic range. The application of APPI with LC/MS is commonly used for analysis of petroleum compounds, pesticides, steroids, and drug metabolites lacking polar functional groups and is being extensively deployed for ambient ionization particularly for explosives detection in security applications.
In mass spectrometry, matrix-assisted ionization is a low fragmentation (soft) ionization technique which involves the transfer of particles of the analyte and matrix sample from atmospheric pressure (AP) to the heated inlet tube connecting the AP region to the vacuum of the mass analyzer.
In mass spectrometry, an ion funnel is a device used to focus a beam of ions using a series of stacked ring electrodes with decreasing inner diameter. A combined radio frequency and fixed electrical potential is applied to the grids. In electrospray ionization-mass spectrometry (ESI-MS), ions are created at atmospheric pressure, but are analyzed at subsequently lower pressures. Ions can be lost while they are shuttled from areas of higher to lower pressure due to the transmission process caused by a phenomenon called joule expansion or “free-jet expansion.” These ion clouds expand outward, which limits the amount of ions that reach the detector, so fewer ions are analyzed. The ion funnel refocuses and transmits ions efficiently from those areas of high to low pressure.
In mass spectrometry, a matrix is a compound that promotes the formation of ions. Matrix compounds are used in matrix-assisted laser desorption/ionization (MALDI), matrix-assisted ionization (MAI), and fast atom bombardment (FAB).
Secondary electro-spray ionization (SESI) is an ambient ionization technique for the analysis of trace concentrations of vapors, where a nano-electrospray produces charging agents that collide with the analyte molecules directly in gas-phase. In the subsequent reaction, the charge is transferred and vapors get ionized, most molecules get protonated and deprotonated. SESI works in combination with mass spectrometry or ion-mobility spectrometry.
Probe electrospray ionization (PESI) is an electrospray-based ambient ionization technique which is coupled with mass spectrometry for sample analysis. Unlike traditional mass spectrometry ion sources which must be maintained in a vacuum, ambient ionization techniques permit sample ionization under ambient conditions, allowing for the high-throughput analysis of samples in their native state, often with minimal or no sample pre-treatment. The PESI ion source simply consists of a needle to which a high voltage is applied following sample pick-up, initiating electrospray directly from the solid needle.
Julia Laskin is the William F. and Patty J. Miller Professor of Analytical Chemistry at Purdue University. Her research is focused on the fundamental understanding of ion-surface collisions, understanding of phenomena underlying chemical analysis of large molecules in complex heterogeneous environments, and the development of new instrumentation and methods in preparative and imaging mass spectrometry.
References
- 1 2 Brenner, Anne; Simpson, Hayes (2021-09-01). "Faces of Mass Spectrometry/Barbara Larsen". Journal of the American Society for Mass Spectrometry. 32 (9): 2281–2283. doi: 10.1021/jasms.1c00229 . ISSN 1044-0305. PMID 34375110. S2CID 236978779.
- 1 2 Mass spectrometry of biological materials. Barbara Seliger Larsen, Charles N. McEwen (2nd ed., rev. and expanded ed.). New York: Marcel Dekker. 1998. ISBN 0-585-11050-6. OCLC 44959064.
{{cite book}}: CS1 maint: others (link) - ↑ "Barbara Larsen Receives EAS Award for Outstanding Achievements in Mass Spectrometry". Spectroscopy Online. 30 September 2020. Retrieved 2022-06-08.
- ↑ Larsen, Barbara S.; McEwen, Charles N. (1991-05-01). "An electrospray ion source for magnetic sector mass spectrometers". Journal of the American Society for Mass Spectrometry. 2 (3): 205–211. Bibcode:1991JASMS...2..205L. doi:10.1016/1044-0305(91)80045-9. ISSN 1044-0305. PMID 24242274. S2CID 40950182.
- ↑ McEwen, Charles N.; Simonsick, William J.; Larsen, Barbara S.; Ute, Kaichi; Hatada, Koichi (1995-10-01). "The fundamentals of applying electrospray ionization mass spectrometry to low mass poly(methyl methacrylate) polymers". Journal of the American Society for Mass Spectrometry. 6 (10): 906–911. Bibcode:1995JASMS...6..906M. doi:10.1016/1044-0305(95)00476-T. ISSN 1044-0305. PMID 24214034. S2CID 21026081.
- ↑ McEwen, Charles N.; Jackson, Christian; Larsen, Barbara S. (1997). "Instrumental effects in the analysis of polymers of wide polydispersity by MALDI mass spectrometry". International Journal of Mass Spectrometry and Ion Processes. 160 (1–3): 387–394. Bibcode:1997IJMSI.160..387M. doi:10.1016/S0168-1176(96)04501-6.
- ↑ McEwen, Charles N.; McKay, Richard G.; Larsen, Barbara S. (2005-12-01). "Analysis of Solids, Liquids, and Biological Tissues Using Solids Probe Introduction at Atmospheric Pressure on Commercial LC/MS Instruments". Analytical Chemistry. 77 (23): 7826–7831. doi:10.1021/ac051470k. ISSN 0003-2700. PMID 16316194.
- ↑ McEwen, Charles N.; Larsen, Barbara S.; Trimpin, Sarah (2010-06-15). "Laserspray Ionization on a Commercial Atmospheric Pressure-MALDI Mass Spectrometer Ion Source: Selecting Singly or Multiply Charged Ions". Analytical Chemistry. 82 (12): 4998–5001. doi:10.1021/ac1006624. ISSN 0003-2700. PMID 20469839.
- ↑ Larsen, Barbara S.; Kaiser, Mary A.; Botelho, Miguel; Wooler, Gilbert R.; Buxton, L. William (2005). "Comparison of pressurized solvent and reflux extraction methods for the determination of perfluorooctanoic acid in polytetrafluoroethylene polymers using LC-MS-MS". The Analyst. 130 (1): 59–62. Bibcode:2005Ana...130...59L. doi:10.1039/b412609b. ISSN 0003-2654. PMID 15614354.
- ↑ Larsen, Barbara S.; Kaiser, Mary A.; Botelho, Miguel A.; Bachmura, Stanley F.; Buxton, L. William (2006). "Efficient "total" extraction of perfluorooctanoate from polytetrafluoroethylene fluoropolymer". The Analyst. 131 (10): 1105–1108. Bibcode:2006Ana...131.1105L. doi:10.1039/B606801D. ISSN 0003-2654. PMID 17003857.
- ↑ "News and Views" (PDF). American Society for Mass Spectrometry. 2017. Retrieved 2022-06-08.
- 1 2 "Spectroscopy Editorial Advisory Board". Spectroscopy Online. January 2019. Retrieved 2022-06-08.
- ↑ "Journal of The American Society for Mass Spectrometry". Springer. December 2019. Retrieved 2022-06-08.
- ↑ "Past Presidents". www.asms.org. Retrieved 2022-06-08.
- ↑ "ASMS Board of Directors History" (PDF). American Society for Mass Spectrometry. Retrieved 2022-06-07.
- ↑ "Seven Division Members Elected as American Chemical Society Fellows". ACS Division of Analytical Chemistry. 2017-06-22. Retrieved 2022-06-08.
- ↑ "Awards | ACS | Delaware Section". delawareacs.org. Retrieved 2022-06-08.
- ↑ "Barbara S. Larsen Awarded DuPont Pederson Medal". www.asms.org. Retrieved 2022-06-08.
- ↑ "The Power List 2016". The Analytical Scientist. Retrieved 2022-06-08.
- ↑ "59th Eastern Analytical Symposium November 16–19, 2020". Spectroscopy Online. 7 September 2020. Retrieved 2022-06-08.
- ↑ Kitson, Fulton G. (1996). Gas chromatography and mass spectrometry : a practical guide. Barbara Seliger Larsen, Charles N. McEwen. San Diego, Calif.: Academic Press. ISBN 978-0-08-053232-5. OCLC 173649318.
- ↑ Electrospray ionization mass spectrometry : fundamentals, instrumentation, and applications. Richard B. Cole. New York: Wiley. 1997. ISBN 0-471-14564-5. OCLC 35637508.
{{cite book}}: CS1 maint: others (link) - ↑ Wilkins, Charles L.; Trimpin, Sarah, eds. (2011), "Snapshot, Conformation, and Bulk Fragmentation Characterization of Polymeric Architectures Using ESI-IMS-MS", Ion Mobility Spectrometry - Mass Spectrometry, CRC Press, doi:10.1201/b10460-17, ISBN 978-0-429-13427-2 , retrieved 2022-06-08
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