A mass spectrometric method has been developed for the identification of the carboxylic acid functional group in analytes evaporated and ionized by electrospray ionization (ESI). This method is based on gas-phase ion-molecule reactions of ammoniated ([M + NH4]+) and sodiated ([M + Na]+) analyte molecules with trimethyl borate (TMB) in a modified linear quadrupole ion trap mass spectrometer. The diagnostic reaction involves addition of the deprotonated analyte to TMB followed by the elimination of methanol. A variety of analytes with different func-tionalities were examined, and this reaction was only observed for molecules containing the carboxylic acid functionality. The selectivity of the reaction is attributed to the acidic hydrogen present in the carboxylic acid group, which provides the proton necessary for the elimination of methanol. The diagnostic products are easily identified based on the m/z value of the product ion, which is 72 Th (thomson) greater than the m/z value of the charged analyte, and also by the character-istic isotope pattern of boron. The applicability of this method for pharmaceutical analysis was demonstrated for three nonsteroidal anti-inflammatory drugs: ibuprofen, naproxen, and ketoprofen.

The 2,4,6-tridehydropyridine radical cation, an analogue of the elusive 1,2,3,5-tetradehydrobenzene, was generated in the gas phase and its reactivity examined. Surprisingly, the tetraradical was found not to undergo radical reactions. This behavior is rationalized by resonance structures hindering fast radical reactions. This makes the cation highly electrophilic, and it rapidly reacts with many nucleophiles by quenching the N-C ortho-benzyne moiety, thereby generating a relatively unreactive meta-benzyne analogue.

Tri‐, bi‐, and monoradicals: The reactivity of a σ,σ,σ‐triradical, 2,4,6‐tridehydropyridinium cation, was compared with that of related mono‐ and biradicals in a Fourier transform ion cyclotron resonance mass spectrometer. The triradical has a doublet ground state and contains three interacting radical sites. The reactivity of the triradical more closely resembles that of related monoradicals than related biradicals.

Mass spectrometric methodology was developed for the determination and manipulation of the primary products of fast pyrolysis of carbohydrates. To determine the true primary pyrolysis products, a very fast heating pyroprobe was coupled to a linear quadrupole ion trap mass spectrometer through a custom-built adaptor. A home-built flow tube that simulates pyrolysis reactor conditions was used to examine the secondary reactions of the primary products. Depending on the experiment, the pyrolysis products were either evaporated and quenched or allowed to react for a period of time. The quenched products were ionized in an atmospheric pressure chemical ionization (APCI) source infused with one of two ionization reagents, chloroform or ammonium hydroxide, to aid in ionization. During APCI in negative ion mode, chloroform produces chloride anions that are known to readily add to carbohydrates with little bias and little to no fragmentation. On the other hand, in positive ion mode APCI, ammonium hydroxide forms ammonium adducts with carbohydrates with little to no fragmentation. The latter method ionizes compounds that are not readily ionized upon negative ion mode APCI, such as furan derivatives. Six model compounds were studied to verify the ability of the ionization methods to ionize known pyrolysis products: glycolaldehyde, hydroxyacetone, furfural, 5-hydroxymethylfurfural, levoglucosan, and cellobiosan. The method was then used to examine fast pyrolysis of cellobiose. The primary fast pyrolysis products were determined to consist of only a handful of compounds that quickly polymerize to form anhydro-oligosaccharides when allowed to react at high temperatures for an extended period of time.

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