[Show abstract][Hide abstract] 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 Fourier-transform 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.
Journal of the American Society for Mass Spectrometry 01/2012; 23(1):12-22. · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Identification and counting of different oxygen-containing functional groups in 40 small aromatic analytes, including a lignin monomer, was explored using a linear quadrupole ion trap (LQIT) mass spectrometer. The analytes were evaporated and ionized by negative-mode electrospray ionization (ESI). In an effort to cleave off all of the functionalities, one at a time, the deprotonated analytes were then subjected to multiple consecutive collision-activated dissociation (CAD) events until no more fragmentation was observed (up to MS5). In most cases, the number and types of functionalities could be determined. This approach was demonstrated to be feasible on the high-performance liquid chromatographic (HPLC) time scale. Hence, valuable structural information can be obtained for previously unknown aromatic analytes directly in complex mixtures, such as lignin degradation products.
[Show abstract][Hide abstract] ABSTRACT: A mass spectrometric method is presented for the identification of analytes with two basic functionalities and PA between 222 and 245 kcal/mol, including diamines. This method utilizes gas-phase ion-molecule reactions of protonated analytes with neutral 1,1-diethoxyethene (DEE) in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR). A variety of protonated mono-, bi-, and trifunctional analytes containing different functional groups, namely, amido, amino, N-oxide, hydroxy, carboxylic acid, keto, thio, thioether, alkene, phosphite, and phosphonate, were tested in the FT-ICR. The results demonstrate that basic protonated bifunctional compounds (PA between 222 and 245 kcal/mol) react selectively with DEE by forming a specific addition/elimination product ion (adduct - EtOH) (this product was also observed for lysine with three functionalities). The diagnostic reaction sequence involves proton transfer from the protonated analyte to the basic vinyl group in DEE, followed by addition of one of the functional groups of the analyte to the electrophilic alpha-carbon in protonated DEE. The next step involves proton transfer from this functionality to the other analyte functionality, followed by proton transfer to DEE and elimination of ethanol. Since the mechanism involves proton transfer between two functional groups of the analyte, the reaction does not occur for analytes where the two functionalities cannot be in close proximity (i.e., meta-phenylenediamine), and where no proton is available (i.e., dimethylaminoketone).
Journal of the American Society for Mass Spectrometry 03/2009; 20(7):1251-62. · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A mass spectrometric method is presented that facilitates the identification and differentiation of primary, secondary and tertiary amino functionalities in protonated monofunctional analytes. This method utilizes gas-phase ion–molecule reactions of protonated analytes with neutral hexamethylphosphoramide (HMPA) and diethylmethylphosphonate (DEMP) in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR). A variety of protonated analytes containing different functional groups, namely, amino, amido, N-oxide and various oxygen-containing functional groups, were examined to demonstrate that protonated primary and secondary amines can be identified and differentiated by reactions with HMPA and DEMP. However, differentiation of tertiary amines from some N-oxides requires additional experiments. First, protonated secondary and tertiary amines can be differentiated from protonated primary amines, amides and oxygen-containing functionalities, as well as from each other (but not from protonated N-oxides), by using HMPA. Protonated primary amines, amides, some N-oxides and oxygen-containing analytes, most with a proton affinity (PA)
International Journal of Mass Spectrometry. 01/2009; 282(3):77-84.