Identification of Epoxide Functionalities in Protonated Monofunctional Analytes by Using Ion/Molecule Reactions and Collision-Activated Dissociation in Different Ion Trap Tandem Mass Spectrometers

Abstract

A mass spectrometric method has been delineated for the identification of the epoxide functionalities in unknown monofunctional analytes. This method utilizes gas-phase ion/ molecule reactions of protonated analytes with neutral trimethyl borate (TMB) followed by collision-activated dissociation (CAD) in an ion trapping mass spectrometer (tested for a Fouriertransform ion cyclotron resonance and a linear quadrupole ion trap). The ion/molecule reaction involves proton transfer from the protonated analyte to TMB, followed by addition of the analyte to TMB and elimination of methanol. Based on literature, this reaction allows the general identification of oxygen-containing analytes. Vinyl and phenyl epoxides can be differentiated from other oxygen-containing analytes, including other epoxides, based on the loss of a second methanol molecule upon CAD of the addition/methanol elimination product. The only other analytes found to undergo this elimination are some amides but they also lose O=B-R (R=group bound to carbonyl), which allows their identification. On the other hand, other epoxides can be differentiated from vinyl and phenyl epoxides and from other monofunctional analytes based on the loss of (CH 3 O) 2 BOH or formation of protonated (CH 3 O) 2 BOH upon CAD of the addition/ methanol elimination product. For propylene oxide and 2,3-dimethyloxirane, the (CH 3 O) 2 BOH fragment is more basic than the hydrocarbon fragment, and the diagnostic ion (CH 3 O) 2 BOH 2 + is formed. These reactions involve opening of the epoxide ring. The only other analytes found to undergo (CH 3 O) 2 BOH elimination are carboxylic acids, but they can be differentiated from the rest based on several published ion/molecule reaction methods. Similar results were obtained in the Fourier-transform ion cyclotron resonance and linear quadrupole ion trap mass spectrometer.

Mass spectrometric identification of the N‐monosubstituted N‐hydroxylamino functionality in protonated analytes via ion/molecule reactions in tandem mass spectrometry

“…Moreover, no characteristic fragmentation behavior has been found for ionized hydroxylamine metabolites in tandem mass spectrometry (MS/MS) experiments based on collision‐induced dissociation (CID) . MS/MS methods based on ion/molecule reactions of ionized analytes hold great promise for being able to provide information useful in the identification of specific functional groups . Our group has successfully developed such methods for the identification of many different functionalities in protonated analytes .…”

“…[2,10] MS/MS methods based on ion/molecule reactions of ionized analytes hold great promise for being able to provide information useful in the identification of specific functional groups. [11][12][13][14][15] Our group has successfully developed such methods for the identification of many different functionalities in protonated analytes. [12][13][14][15][16][17][18][19][20] In the work presented here, gas-phase ion/molecule reactions of 2-methoxypropene (MOP) are demonstrated to allow the identification of the protonated N-monosubstituted hydroxylamine functionality in a liner quadrupole ion trap.…”

Gas-phase ion-molecule reactions for the identification of the sulfone functionality in protonated analytes in a linear quadrupole ion trap mass spectrometer

“…This should allow the TMP to deprotonate protonated sulfoxides and sulfones, which is usually the first step in functional‐group‐selective ion–molecule reactions. As shown in Table , proton transfer was the major reaction for both protonated sulfones and protonated sulfoxides. However, protonated sulfones showed characteristic [TMP adduct–MeOH] product ions.…”

“…When the functionalities of ionized analytes cannot be definitively determined by CID alone, an alternative MS n technique based on ion–molecule reactions can be utilized to obtain structural information . We have successfully developed methods based on ion–molecule reactions to identify various functional groups in ionized analytes . Several neutral reagents have been investigated extensively, including boron‐ and oxygen‐containing organic reagents with good leaving groups .…”

A membrane introduction mass spectrometer utilizing ion-molecule reactions for the on-line speciation and quantitation of volatile organic molecules

“…The principal advantage of CI is that analyte ions are generated with a minimum of excess internal energy, which results in little or no fragmentation of molecular ions. A variety of reagent ions have been used with CI for the identification of hydrocarbons and epoxide functionalities, and it has even been employed for the differentiation of isomers …”