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| In ], '''inlet ionization''' is a soft ] technique which involves the transfer of particles of the analyte/matrix sample from ] (AP) to the heated inlet tube connecting the AP region to the vacuum of the ]. Initial ionization occurs as the pressure drops within the inlet tube.<ref>Solvent Assisted Inlet Ionization: An Ultrasensitive New Liquid Introduction Ionization Method for Mass Spectrometry | |||
| Vincent S. Pagnotti, Nicholas D. Chubatyi, and Charles N. McEwen | |||
| Analytical Chemistry 2011 83 (11), 3981-3985 | |||
| DOI: 10.1021/ac200556z</ref><ref>High-Throughput Solvent Assisted Ionization Inlet for Use in Mass Spectrometry | |||
| Beixi Wang and Sarah Trimpin | |||
| Analytical Chemistry 2014 86 (2), 1000-1006 | |||
| DOI: 10.1021/ac400867b</ref> | |||
| Inlet ionization is similar to ] in that a reverse phase solvent system is used and the ions produced are highly charged, however a voltage or a laser is not always needed.<ref>Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules | |||
| Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin | |||
| Analytical Chemistry 2011 83 (20), 7591-7594 | |||
| DOI: 10.1021/ac201982r | |||
| </ref> It is a highly sensitive process for small and large molecules like ], ]<ref>Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules | |||
| Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin | |||
| Analytical Chemistry 2011 83 (20), 7591-7594 | |||
| DOI: 10.1021/ac201982r | |||
| </ref> and lipids<ref>Matrix Assisted Ionization: New Aromatic | |||
| and Nonaromatic Matrix Compounds Producing | |||
| Multiply Charged Lipid, Peptide, and Protein Ions | |||
| in the Positive and Negative Mode Observed | |||
| Directly from Surfaces | |||
| Jing Li, Ellen D. Inutan, Beixi Wang, Christopher B. Lietz, Daniel R. Green, | |||
| Cory D. Manly, Alicia L. Richards, Darrell D. Marshall, Steven Lingenfelter, Yue Ren, | |||
| Sarah Trimpin</ref> that can be coupled to a ]. | |||
| Inlet ionization techniques can be used with an ] mass analyzer, Orbitrap ], ] and ] | |||
| ==Types of inlet ionization== | |||
| ===Matrix-assisted inlet ionization (MAII)=== | |||
| A ] which can be a solvent is used at ambient temperature with the analyte of interest as a mixture. The matrix/analyte mixture is inserted into the heated inlet tube through tapping the mixture at the opening end of the tube. For the highly charged ions of the analyte to be produced from ionization ] of the matrix molecules needs to occur. | |||
| Matrices that can be used include<ref>Matrix Assisted Ionization: New Aromatic and Nonaromatic Matrix Compounds Producing Multiply Charged Lipid, Peptide, and Protein Ions in the Positive and Negative Mode Observed Directly from Surfaces Jing Li, Ellen D. Inutan, Beixi Wang, Christopher B. Lietz, Daniel R. Green, Cory D. Manly, Alicia L. Richards, Darrell D. Marshall, Steven Lingenfelter, Yue Ren, Sarah Trimpin</ref>: | |||
| * 2,5-dihydroxybenzoic acid | |||
| * 2,5-dihydroxyacetophenone | |||
| * 2-aminobenzyl alcohol | |||
| * ] | |||
| * 2-hydroxyacetophenone | |||
| ] | |||
| ==== Laserspray inlet ionization (LSII) ==== | |||
| Laserspray ionization is a subset of MAII and uses a matrix-assisted laser desorption/ionization (]) method. It was originally called atmospheric pressure matrix-assisted laser desorption/ionization however was renamed as LSII to avoid confusion with MALDI and as it was found to be a type of inlet ionization. <ref>Trimpin S, Inutan ED, Herath TN, McEwen CN. Laserspray Ionization, a New Atmospheric Pressure MALDI Method for Producing Highly Charged Gas-phase Ions of Peptides and Proteins Directly from Solid Solutions. Molecular & Cellular Proteomics : MCP. 2010;9(2):362-367. doi:10.1074/mcp.M900527-MCP200.</ref><ref>Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules | |||
| Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin | |||
| Analytical Chemistry 2011 83 (20), 7591-7594 | |||
| DOI: 10.1021/ac201982r</ref> As all inlet ionization techniques, highly multiply charged ions are produced. A nitrogen laser is used to ] the solid matrix/analyte into the heated inlet tube, the observed ions are generated at the surface of the matrix/analyte and so the laser is not directly involved in the ionization as was originally thought. (pg 5) LSII can determine protein molecular weights and has been found to detect masses of proteins up to 20,000 ]. LSII is more than an order or magnitude more sensitive to proteins than ]. <ref>Inutan ED, Richards AL, Wager-Miller J, Mackie K, McEwen CN, Trimpin S. Laserspray Ionization, a New Method for Protein Analysis Directly from Tissue at Atmospheric Pressure with Ultrahigh Mass Resolution and Electron Transfer Dissociation. Molecular & Cellular Proteomics : MCP. 2011;10(2):M110.000760. doi:10.1074/mcp.M110.000760.</ref> | |||
| ===Solvent assisted inlet ionization (SAII)=== | |||
| SAII is very similar to matrix-assisted inlet ionization however the matrix is a solvent such as water, ] and ].<ref>Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules | |||
| Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin | |||
| Analytical Chemistry 2011 83 (20), 7591-7594 | |||
| DOI: 10.1021/ac201982r</ref> This ionization technique is highly sensitive to small molecules, peptides and proteins.<ref>Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules | |||
| Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin | |||
| Analytical Chemistry 2011 83 (20), 7591-7594 | |||
| DOI: 10.1021/ac201982r | |||
| </ref> | |||
| The analyte is dissolved in the solvent and can either be introduced to the heated inlet tube by a capillary column or directly injected into the inlet tube with a syringe or by pipetting. The capillary column is comprised of fused silica particles with one end submerged in the sample solvent and the other in the end of the heated inlet tube. The solvent flows through the capillary column without the use of a pump due to the pressure difference between ambient pressure and the vacuum. (reference pg 3) | |||
| The temperature can vary in the inlet tube from 50°C to 450°C, with the lower temperature being used if the results obtained from a higher temperature are of good resolution.<ref>Matrix Assisted Ionization: New Aromatic and Nonaromatic Matrix Compounds Producing Multiply Charged Lipid, Peptide, and Protein Ions in the Positive and Negative Mode Observed Directly from Surfaces Jing Li, Ellen D. Inutan, Beixi Wang, Christopher B. Lietz, Daniel R. Green, Cory D. Manly, Alicia L. Richards, Darrell D. Marshall, Steven Lingenfelter, Yue Ren, Sarah Trimpin</ref> Solvent assisted inlet ionization can be coupled not only to ] (LC) but also to nano LC. | |||
| == Advantages of inlet ionization == | |||
| * Ionization at atmospheric pressure often leads to a loss of ions during the transfer of the ions from the ] region to the vacuum of the mass analyzer.<ref>Sheehan EW, Willoughby RC. June 13, 2006. U.S. Patent 7,060,976.</ref> Ions are lost due to dispersion of analyte spray and 'rim loss' causing fewer ions to reach the vacuum for ] to occur. Initial ionization occurs in the sub-atmospheric pressure region of the heated inlet tube which is directly attached to the vacuum of the mass analyzer and so ion loss is reduced as transfer of the ions does not occur. | |||
| * In LSII the use of the laser increases the image quality of the results by producing better ]. This is where more ] are created and so a clearer image is obtained. | |||
| * High-speed imaging | |||
| * Multiply charged ions are produced | |||
| ** further extending mass range | |||
| ** producing ] for structural information | |||
| * multiple methods can be used to fragment molecules | |||
| ** ] | |||
| ** ] | |||
| ** ] | |||
| *when using a laser ablation only small volumes are needed (6) | |||
| == References == | |||
| {{reflist}} | |||
| ] | |||
Revision as of 01:49, 15 April 2015
In mass spectrometry, inlet ionization is a soft ionization technique which involves the transfer of particles of the analyte/matrix sample from atmospheric pressure (AP) to the heated inlet tube connecting the AP region to the vacuum of the mass analyser. Initial ionization occurs as the pressure drops within the inlet tube.
Inlet ionization is similar to electrospray ionization in that a reverse phase solvent system is used and the ions produced are highly charged, however a voltage or a laser is not always needed. It is a highly sensitive process for small and large molecules like peptides, proteins and lipids that can be coupled to a liquid chromatograph.
Inlet ionization techniques can be used with an Orbitrap mass analyzer, Orbitrap fourier transform mass spectrometer, linear trap quadrupole and MALDI-TOF
Types of inlet ionization
Matrix-assisted inlet ionization (MAII)
A matrix which can be a solvent is used at ambient temperature with the analyte of interest as a mixture. The matrix/analyte mixture is inserted into the heated inlet tube through tapping the mixture at the opening end of the tube. For the highly charged ions of the analyte to be produced from ionization desolvation of the matrix molecules needs to occur. Matrices that can be used include:
- 2,5-dihydroxybenzoic acid
- 2,5-dihydroxyacetophenone
- 2-aminobenzyl alcohol
- anthranilic acid
- 2-hydroxyacetophenone
Laserspray inlet ionization (LSII)
Laserspray ionization is a subset of MAII and uses a matrix-assisted laser desorption/ionization (MALDI) method. It was originally called atmospheric pressure matrix-assisted laser desorption/ionization however was renamed as LSII to avoid confusion with MALDI and as it was found to be a type of inlet ionization. As all inlet ionization techniques, highly multiply charged ions are produced. A nitrogen laser is used to ablate the solid matrix/analyte into the heated inlet tube, the observed ions are generated at the surface of the matrix/analyte and so the laser is not directly involved in the ionization as was originally thought. (pg 5) LSII can determine protein molecular weights and has been found to detect masses of proteins up to 20,000 Da. LSII is more than an order or magnitude more sensitive to proteins than ESI.
Solvent assisted inlet ionization (SAII)
SAII is very similar to matrix-assisted inlet ionization however the matrix is a solvent such as water, acetonitrile and methanol. This ionization technique is highly sensitive to small molecules, peptides and proteins. The analyte is dissolved in the solvent and can either be introduced to the heated inlet tube by a capillary column or directly injected into the inlet tube with a syringe or by pipetting. The capillary column is comprised of fused silica particles with one end submerged in the sample solvent and the other in the end of the heated inlet tube. The solvent flows through the capillary column without the use of a pump due to the pressure difference between ambient pressure and the vacuum. (reference pg 3)
The temperature can vary in the inlet tube from 50°C to 450°C, with the lower temperature being used if the results obtained from a higher temperature are of good resolution. Solvent assisted inlet ionization can be coupled not only to liquid chromatography (LC) but also to nano LC.
Advantages of inlet ionization
- Ionization at atmospheric pressure often leads to a loss of ions during the transfer of the ions from the ambient pressure region to the vacuum of the mass analyzer. Ions are lost due to dispersion of analyte spray and 'rim loss' causing fewer ions to reach the vacuum for m/z separation to occur. Initial ionization occurs in the sub-atmospheric pressure region of the heated inlet tube which is directly attached to the vacuum of the mass analyzer and so ion loss is reduced as transfer of the ions does not occur.
- In LSII the use of the laser increases the image quality of the results by producing better spacial resolution. This is where more pixels are created and so a clearer image is obtained.
- High-speed imaging
- Multiply charged ions are produced
- further extending mass range
- producing fragmentation for structural information
- multiple methods can be used to fragment molecules
- when using a laser ablation only small volumes are needed (6)
References
- Solvent Assisted Inlet Ionization: An Ultrasensitive New Liquid Introduction Ionization Method for Mass Spectrometry Vincent S. Pagnotti, Nicholas D. Chubatyi, and Charles N. McEwen Analytical Chemistry 2011 83 (11), 3981-3985 DOI: 10.1021/ac200556z
- High-Throughput Solvent Assisted Ionization Inlet for Use in Mass Spectrometry Beixi Wang and Sarah Trimpin Analytical Chemistry 2014 86 (2), 1000-1006 DOI: 10.1021/ac400867b
- Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin Analytical Chemistry 2011 83 (20), 7591-7594 DOI: 10.1021/ac201982r
- Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin Analytical Chemistry 2011 83 (20), 7591-7594 DOI: 10.1021/ac201982r
- Matrix Assisted Ionization: New Aromatic and Nonaromatic Matrix Compounds Producing Multiply Charged Lipid, Peptide, and Protein Ions in the Positive and Negative Mode Observed Directly from Surfaces Jing Li, Ellen D. Inutan, Beixi Wang, Christopher B. Lietz, Daniel R. Green, Cory D. Manly, Alicia L. Richards, Darrell D. Marshall, Steven Lingenfelter, Yue Ren, Sarah Trimpin
- Matrix Assisted Ionization: New Aromatic and Nonaromatic Matrix Compounds Producing Multiply Charged Lipid, Peptide, and Protein Ions in the Positive and Negative Mode Observed Directly from Surfaces Jing Li, Ellen D. Inutan, Beixi Wang, Christopher B. Lietz, Daniel R. Green, Cory D. Manly, Alicia L. Richards, Darrell D. Marshall, Steven Lingenfelter, Yue Ren, Sarah Trimpin
- Trimpin S, Inutan ED, Herath TN, McEwen CN. Laserspray Ionization, a New Atmospheric Pressure MALDI Method for Producing Highly Charged Gas-phase Ions of Peptides and Proteins Directly from Solid Solutions. Molecular & Cellular Proteomics : MCP. 2010;9(2):362-367. doi:10.1074/mcp.M900527-MCP200.
- Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin Analytical Chemistry 2011 83 (20), 7591-7594 DOI: 10.1021/ac201982r
- Inutan ED, Richards AL, Wager-Miller J, Mackie K, McEwen CN, Trimpin S. Laserspray Ionization, a New Method for Protein Analysis Directly from Tissue at Atmospheric Pressure with Ultrahigh Mass Resolution and Electron Transfer Dissociation. Molecular & Cellular Proteomics : MCP. 2011;10(2):M110.000760. doi:10.1074/mcp.M110.000760.
- Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin Analytical Chemistry 2011 83 (20), 7591-7594 DOI: 10.1021/ac201982r
- Inlet Ionization: A New Highly Sensitive Approach for Liquid Chromatography/Mass Spectrometry of Small and Large Molecules Vincent S. Pagnotti, Ellen D. Inutan, Darrell D. Marshall, Charles N. McEwen, and Sarah Trimpin Analytical Chemistry 2011 83 (20), 7591-7594 DOI: 10.1021/ac201982r
- Matrix Assisted Ionization: New Aromatic and Nonaromatic Matrix Compounds Producing Multiply Charged Lipid, Peptide, and Protein Ions in the Positive and Negative Mode Observed Directly from Surfaces Jing Li, Ellen D. Inutan, Beixi Wang, Christopher B. Lietz, Daniel R. Green, Cory D. Manly, Alicia L. Richards, Darrell D. Marshall, Steven Lingenfelter, Yue Ren, Sarah Trimpin
- Sheehan EW, Willoughby RC. June 13, 2006. U.S. Patent 7,060,976.