Gas phase reaction between chromones and solvent in an electrospray ionization source

Abstract

Chromones were measured by using electrospray ionization mass spectrometry in negative mode. Interestingly, in addition to the deprotonated ion ([M − H]−), unexpected [M + 17]− and [M + 31]− ions were observed in high intensity when water and methanol were used as the solvent. Chromones with different substitutes were tested. Compared with the deprotonated ion, [M + 17]− and [M + 31]− ions were observed with higher abundances when the C‐3 site of chromones was substituted by electron withdrawing groups. Based on high performance liquid chromatography‐mass spectrometry (LC‐MS), deuterium‐labeling and collisional‐induced dissociation experiments, a covalent gas‐phase nucleophilic addition reaction between chromone and water, and the formation of a noncovalent complex between chromone and methanol were proposed as the mechanism for the observed [M + 17]− and [M + 31]− ions, respectively. Understanding and using these unique gas phase reactions can avoid misannotation when analyzing chromones and their metabolites.

Fortuitous Ion–Molecule Reaction Enables Enumeration of Metal–Hydrogen Bonds Present in Gaseous Ions

“…To support the reaction mechanisms proposed for the water interaction, we conducted a computational study on the following system (Scheme 3). The calculated Gibbs free energies of reactants and products predicted that the water interaction, [H-Mg(η 2…”

“…Unwarranted ion–molecule reactions that occur under tandem mass-spectrometric conditions are often a nuisance because they complicate spectral interpretations . Occasionally, such reactions take place in the ion source under electrospray ionization (ESI) conditions. − Ion–molecule reactions are more common in mass spectrometric investigations conducted in tandem-in-time devices, such as ion traps, because the ions are stored in a confined space for a relatively longer period of time prior to ion activation. − Although less common, ion-neutral adduct peaks have also been observed in the spectra recorded on tandem-in-space instruments when reactants such as water, − methanol, ethanol, nitrogen, , oxygen, and carbon dioxide are either present as impurities, or added intentionally as reagents to the collision gas. , …”

SESIUM KLORIDA (CsCl) : TRANSPORT ION DALAM LARUTAN

“…Ie ' = fs (31) f = 6 a (32) Kedua gaya (237)(238)(239)(240) itu bekerja dalam arah yang berlawanan,dan ion mencapai kecepatan akhir yaitu kecepatan hanyut, jika gaya mempercepat Ie di imbangi oleh penahan kental Ie ' maka gaya neto menjadi nol (Ie = Ie ' ) jika : s= (33) karena kecepatan hanyut mengatur laju transportasi ion, maka dapat mengharapkan konduktivitas akan berkurang dengan bertambahnya viskositas pelarut (192)(193)(194)(195)(196) akan ukuran ion.contohnya, konduktivitas molar ion logam (231)(232)(233)(234)(235) alkali bertambah dari Li + ke Cs + ,walaupun radius ionnya bertambah .paradoks ini terpecahkan jika kita menyadari bahwa radius a dalam rumus stokes adalah radius hidrodinamik ion, yaitu radius efektifnya dalam larutan dengan memperhitungkan molekul H2O yang dibawa dalam bola hidrasinya (226)(227)(228)(229)(230) ion kecil menimbulkan medan listrik lebih kuat dari pada ion besar sehingga ion kecil lebih terlarut secara ekstensif dari ion besar.jadi,ion dengan radius kecil dapat mempunyai radius hidrodinamik besar,karena ion itu menyeret banyak molekul pelarut melalui larutan itu saat bermigrasi.…”