The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected Pharmaceuticals
This study investigates the effects of common additives, which provide distinct proton sources—ammonium (NH<sub>4</sub><sup>+</sup>) and hydronium (H<sub>3</sub>O<sup>+</sup>)—along with their corresponding conjugate base species, on signal intensity i...
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2025-04-01
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| author | Pieter Venter |
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| description | This study investigates the effects of common additives, which provide distinct proton sources—ammonium (NH<sub>4</sub><sup>+</sup>) and hydronium (H<sub>3</sub>O<sup>+</sup>)—along with their corresponding conjugate base species, on signal intensity in positive ionization mode. The findings reveal that signal intensity is influenced by factors such as solvation enthalpy, surface tension, and conductivity. At lower additive concentrations (<10 mM), based on fold changes, no clear distinction could be made between formic acid, acetic acid, and their corresponding salts. At higher additive concentrations, NH<sub>4</sub><sup>+</sup> appears to be a more efficient proton source than H<sup>+</sup> (H<sub>3</sub>O<sup>+</sup>), likely due to its more positive solvation enthalpy, which promotes greater enrichment of NH<sub>4</sub><sup>+</sup> on the droplet surface, as well as the reduced surface tension of ammonium salts compared to their acid counterparts. Additionally, ammonium hydroxide proves to be the most effective ammonium-based modifier, likely due to its anionic conjugate base, hydroxide, which has a more negative solvation enthalpy compared to acetate and formate. This characteristic is hypothesized to reduce charge neutralization of cations on the droplet surface and/or in the gas phase. Furthermore, ammonium hydroxide exhibits lower conductivity compared to the other ammonium additives, which is believed to enhance signal intensity. Ammonium bicarbonate, the second most effective additive, uniquely prevents metal adduct formation, leading to enhanced [M + H]<sup>+</sup> ion signals. |
| format | Article |
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| language | English |
| publishDate | 2025-04-01 |
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| spelling | doaj-art-57048fbfb8e64982a5f036db5cc859bc2025-08-20T01:49:50ZengMDPI AGMolecules1420-30492025-04-01309188510.3390/molecules30091885The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected PharmaceuticalsPieter Venter0Biomedical Research and Innovation Platform, South African Medical Research Council, P.O. Box 19070, Tygerberg, Cape Town 7505, South AfricaThis study investigates the effects of common additives, which provide distinct proton sources—ammonium (NH<sub>4</sub><sup>+</sup>) and hydronium (H<sub>3</sub>O<sup>+</sup>)—along with their corresponding conjugate base species, on signal intensity in positive ionization mode. The findings reveal that signal intensity is influenced by factors such as solvation enthalpy, surface tension, and conductivity. At lower additive concentrations (<10 mM), based on fold changes, no clear distinction could be made between formic acid, acetic acid, and their corresponding salts. At higher additive concentrations, NH<sub>4</sub><sup>+</sup> appears to be a more efficient proton source than H<sup>+</sup> (H<sub>3</sub>O<sup>+</sup>), likely due to its more positive solvation enthalpy, which promotes greater enrichment of NH<sub>4</sub><sup>+</sup> on the droplet surface, as well as the reduced surface tension of ammonium salts compared to their acid counterparts. Additionally, ammonium hydroxide proves to be the most effective ammonium-based modifier, likely due to its anionic conjugate base, hydroxide, which has a more negative solvation enthalpy compared to acetate and formate. This characteristic is hypothesized to reduce charge neutralization of cations on the droplet surface and/or in the gas phase. Furthermore, ammonium hydroxide exhibits lower conductivity compared to the other ammonium additives, which is believed to enhance signal intensity. Ammonium bicarbonate, the second most effective additive, uniquely prevents metal adduct formation, leading to enhanced [M + H]<sup>+</sup> ion signals.https://www.mdpi.com/1420-3049/30/9/1885positive electrospray ionizationmobile phase additiveshydration enthalpysurface tensionelectrical conductivity |
| spellingShingle | Pieter Venter The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected Pharmaceuticals Molecules positive electrospray ionization mobile phase additives hydration enthalpy surface tension electrical conductivity |
| title | The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected Pharmaceuticals |
| title_full | The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected Pharmaceuticals |
| title_fullStr | The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected Pharmaceuticals |
| title_full_unstemmed | The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected Pharmaceuticals |
| title_short | The Effects of Solvation Enthalpy, Surface Tension, and Conductivity of Common Additives on Positive Electrospray Ionization in Selected Pharmaceuticals |
| title_sort | effects of solvation enthalpy surface tension and conductivity of common additives on positive electrospray ionization in selected pharmaceuticals |
| topic | positive electrospray ionization mobile phase additives hydration enthalpy surface tension electrical conductivity |
| url | https://www.mdpi.com/1420-3049/30/9/1885 |
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