Fixed-Charge Generation Derivatization for the Analysis of Carbonyl Compounds by Electrospray Ionization Mass Spectromet
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Fixed-Charge Generation Derivatization for the Analysis of Carbonyl Compounds by Electrospray Ionization Mass Spectrometry V. V. Ilyushenkovaa, D. I. Zhilyaeva, L. N. Kulikovab, S. V. Goryainova, b, and R. S. Borisova, b, * a
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia bРeoples Friendship University of Russia (RUDN University), Moscow, 117198 Russia *e-mail: [email protected] Received February 12, 2019; revised June 5, 2019
Abstract—The fixed-charge generation derivatization approach based on a reaction with ω-N,N-dimethylaminoalkylamines followed by quaternization with alkyl halides was applied to the analysis of aliphatic aldehydes and ketones, as well as ketosteroids by electrospray ionization (ESI) mass spectrometry. Both stages of reaction proceed quantitatively, and the registered ESI mass spectra of the products contain abundant peaks of the corresponding ammonium cations. In most cases, the dissociation of the last named compounds under collision activation results only in the loss of the terminal trialkylamino group as a neutral species. Such predictable fragmentation can be used for developing of highly sensitive methods of analysis based on selected reaction monitoring. Keywords: ω-N,N-dimethylaminoalkylamines/alkyl halides, electrospray/ionization, mass spectrometry, fixed-charge derivatization, carbonyl compounds DOI: 10.1134/S1061934820130055
INTRODUCTION Electrospray ionization (ESI) is currently the most popular “soft” low-energy ionization method in mass spectrometry, which is used to analyze the widest range of organic and bioorganic compounds [1–3]. One of the main problems in using this method was revealed in the analysis of nonpolar and weakly polar compounds, molecules of which cannot participate in ionization processes characteristic of ESI, namely protonation, cationization, or deprotonation [4]. The preliminary chemical modification of such compounds is one of the most effective approaches to improving the detection, identification, and quantification of analytes [5–7]. Compounds bearing a carbonyl group in their composition are used in industry and synthetic organic chemistry and participate in the processes of the vital activity of organisms as endogenous metabolites. The direct analysis of a large part of such analytes by “soft” mass spectrometric methods, including ESI, is limited by their low polarity and, consequently, low ionization efficiency, and rather high limits of detection. To eliminate these drawbacks of ESI mass spectrometry, the target chemical modification of the carbonyl group is quite often used. The published works describe a significant number of derivatization methods used for this purpose. Most of them rely on the interaction of carbonyl compounds with amines [8, 9] and hydrazines [9, 10], which is accompanied by the
formation of Schiff bases, which can be studied by ESI mass spectrometry. In particular, the reaction products of carbonyl compounds with the very common reagent 2,4-dinitrophenylhydrazine can
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