TY - JOUR

T1 - Chemical Transformations Can Occur during DMS Separations

T2 - Lessons Learned from Beer’s Bittering Compounds

AU - Ieritano, Christian

AU - Haack, Alexander

AU - Hopkins, W. Scott

N1 - Funding Information: The authors would like to acknowledge Dr. J. C. Yves Le Blanc and Dr. Bradley B. Schneider of SCIEX for helpful discussions and software support as well as the high-performance computing support from Compute Canada. W.S.H. acknowledges financial support provided by the Natural Sciences and Engineering Research Council (NSERC) of Canada in the form of Discovery, Engage, and Alliance grants, the Ontario Centres of Excellence in the form of a VIP-II grant, the InnoHK Initiative, and the Hong Kong Special Administrative Region government. C.I. acknowledges financial support from the Government of Canada for the Vanier Canada Graduate Scholarship. A.H. acknowledges his contribution being funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) 449651261.

PY - 2023/7/5

Y1 - 2023/7/5

N2 - While developing a DMS-based separation method for beer’s bittering compounds, we observed that the argentinated forms of humulone tautomers (i.e., [Hum + Ag]+) were partially resolvable in a N2 environment seeded with 1.5 mol % of isopropyl alcohol (IPA). Attempting to improve the separation by introducing resolving gas unexpectedly caused the peaks for the cis-keto and trans-keto tautomers of [Hum + Ag]+ to coalesce. To understand why resolution loss occurred, we first confirmed that each of the tautomeric forms (i.e., dienol, cis-keto, and trans-keto) responsible for the three peaks in the [Hum + Ag]+ ionogram were assigned to the correct species by employing collision-induced dissociation, UV photodissociation spectroscopy, and hydrogen-deuterium exchange (HDX). The observation of HDX indicated that proton transfer was stimulated by dynamic clustering processes between IPA and [Hum + Ag]+ during DMS transit. Because IPA accretion preferentially occurs at Ag+, which can form pseudocovalent bonds with a suitable electron donor, solvent clustering also facilitated the formation of exceptionally stable microsolvated ions. The exceptional stability of these microsolvated configurations disproportionately impacted the compensation voltage (CV) required to elute each tautomer when the temperature within the DMS cell was varied. The disparity in CV response caused the peaks for the cis- and trans-keto species to merge when a temperature gradient was induced by the resolving gas. Moreover, simulations showed that microsolvation with IPA mediates dienol to trans-keto tautomerization during DMS transit, which, to the best of our knowledge, is the first observation of keto/enol tautomerization occurring within an ion-mobility device.

AB - While developing a DMS-based separation method for beer’s bittering compounds, we observed that the argentinated forms of humulone tautomers (i.e., [Hum + Ag]+) were partially resolvable in a N2 environment seeded with 1.5 mol % of isopropyl alcohol (IPA). Attempting to improve the separation by introducing resolving gas unexpectedly caused the peaks for the cis-keto and trans-keto tautomers of [Hum + Ag]+ to coalesce. To understand why resolution loss occurred, we first confirmed that each of the tautomeric forms (i.e., dienol, cis-keto, and trans-keto) responsible for the three peaks in the [Hum + Ag]+ ionogram were assigned to the correct species by employing collision-induced dissociation, UV photodissociation spectroscopy, and hydrogen-deuterium exchange (HDX). The observation of HDX indicated that proton transfer was stimulated by dynamic clustering processes between IPA and [Hum + Ag]+ during DMS transit. Because IPA accretion preferentially occurs at Ag+, which can form pseudocovalent bonds with a suitable electron donor, solvent clustering also facilitated the formation of exceptionally stable microsolvated ions. The exceptional stability of these microsolvated configurations disproportionately impacted the compensation voltage (CV) required to elute each tautomer when the temperature within the DMS cell was varied. The disparity in CV response caused the peaks for the cis- and trans-keto species to merge when a temperature gradient was induced by the resolving gas. Moreover, simulations showed that microsolvation with IPA mediates dienol to trans-keto tautomerization during DMS transit, which, to the best of our knowledge, is the first observation of keto/enol tautomerization occurring within an ion-mobility device.

KW - differential mobility spectrometry

KW - FAIMS

KW - humulone

KW - microsolvation

KW - tautomerization

UR - http://www.scopus.com/inward/record.url?scp=85163554754&partnerID=8YFLogxK

U2 - 10.1021/jasms.3c00040

DO - 10.1021/jasms.3c00040

M3 - Article

C2 - 37310853

AN - SCOPUS:85163554754

VL - 34

SP - 1315

EP - 1329

JO - Journal of the American Society for Mass Spectrometry

JF - Journal of the American Society for Mass Spectrometry

SN - 1044-0305

IS - 7

ER -