Derivatization in Mass Spectrometry—7. On-Line Derivatization/Degradation

Abstract

The review describes on-line derivatization/degradation methods employed in mass spectrometry to solve some structural and analytical problems. Advantages and applications of various positions of reaction systems connected mainly to a mass spectrometer or a gas chromatograph/mass spectrometer are considered. Among these are reaction systems connected directly to the mass spectrometer (reaction mass spectrometry, pyrolysis-mass spectrometry or direct pyrolysis-mass spectrometry); flash-heaters as reactors in gas chromatography/mass spectrometry (GC/MS); in-line chemical reactors located before the chromatographic column [pre-column derivatization/degradation with the use of catalytic reactions, pyrolysis (pyrolysis-GC/MS), degradation in elemental analyzers-isotope ratio mass pectrometry (EA-IRMS)]; on-column derivatization and deuteration; reactor located between the chromatographic column and a mass spectrometer [post-column catalytic derivatization, gas chromatograph-combustion-isotope ratio mass spectrometer (GC-c-IRMS)]. Post-column derivatization in high performance liquid chromatography/mass spectro-metry is briefly mentioned. Application of such on-line methodology to structure elucidation of low molecular mass compounds and polymers, to the determination of isotope ratios of the most common elements, to the investigation of catalytic reactions is discussed..

Methods for determining the efficacy of radical-trapping antioxidants

“…GC/FID and/or GC/MS analyses are also possible, but must be preceded by reduction of the hydroperoxide to the corresponding alcohol using, e.g., sodium borohydride or triphenylphosphine, 39,40 and sometimes bolstered by silylation of the alcohols for better chromatographic separation. 41 Unfortunately, these methods are generally time-consuming. Unlike the continuous measurements involved in the oxygen consumption experiments, monitoring hydroperoxide production requires regular sampling of the reaction mixture, and subsequent analysis.…”

Evaluation of sequential solvent and thermal extraction followed by analytical pyrolysis for chemical characterization of carbonaceous particulate matter

“…Sample manipulation employed in ex situ derivatization methods (e.g., controlled evaporation used to re-concentrate the sample) may result in analyte losses [16]. Yet, modern methods of online derivatization, particularly its temperature-assisted version, may eliminate this problem [17][18][19][20]. A significant advantage of GC is that it can be readily interfaced with the electron ionization (EI) MS, an efficient ionization/detection method allowing for analyte identification based on the use of extensive MS libraries [21].…”

The influence of nanopowder metal oxides on the methylating activity of dimethyl carbonate in analytical pyrolysis

“…Pyrolysis in combination with chemical reagents is among the techniques employed for on-line degradation/derivatisation in GC-MS analysis of organic materials [1]. Common reagents utilised to this purpose are organic salts formed by an alkylating cation and a basic anion which exhibit concurrent degradative and derivatising properties at high temperatures [2].…”

“…Organic alkali, such as TMAH (tetramethylammonium hydroxide), TMSH (trimethylsulfonium hydroxide), and TMTFTH ((trifluoromethylphenyl)trimethylammonium hydroxide), at high temperatures hydrolyse ester groups and methylate the resulting carboxylate ions to give the corresponding methyl esters amenable to GC analysis. TMAH, TMSH and TMTFTH have been used for investigating the distribution of fatty acids in lipid materials by on-line Py-GC-MS [1][2][3][4][5][6], and TMAH for the characterisation of high molecular weight esters, such as natural waxes [7], poly(3-hydroxybutyrate) [8] and poly(ecaprolactone) [9]. For its ability to cleave hydrolysable ether bonds and methylate hydroxyl groups, TMAH has become a popular reagent in analytical pyrolysis for the structural elucidation of complex phenolic biomacromolecules, such as lignins and tannins [10][11][12][13].…”