Pyrolytic Methylation/Gas Chromatography: A Short Review

Kossa, Walter C.; MacGee, Joseph; Ramachandran, S.; Webber, Alfred J.

doi:10.1093/chromsci/17.4.177

Cited by 116 publications

(44 citation statements)

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“…The method is based on the high temperature reaction of the quaternary alkylammonium hydroxide with molecules containing functional groups, carboxylic acids, ethers and esters especially, which are susceptible to hydrolysis and methylation. According to the reaction scheme proposed by Kossa et al [45] the thermally assisted methylation of acidic groups involves deprotonation of the acids by the reagent and formation of the quaternary ammonium salts of the acidic groups that immediately thermally decompose into the corresponding methyl esters and tertiary amines. With esters or ethers high-temperature hydrolysis by reaction of the basic TMAH precedes the formation of tetra-alkylammonium salts that then undergo thermal fragmentation to methyl derivatives [46].…”

Section: On-line Derivatization Methods and Reagents For Py-gc/msmentioning

confidence: 99%

Py‐GC/MS of Natural and Synthetic Resins

Scalarone

Chiantore

2009

Organic Mass Spectrometry in Art and Archaeology

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Section: On-line Derivatization Methods and Reagents For Py-gc/msmentioning

confidence: 99%

Py‐GC/MS of Natural and Synthetic Resins

Scalarone

Chiantore

2009

Organic Mass Spectrometry in Art and Archaeology

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“…For mass spectral analysis, 15 L of the bacterial suspension was coinjected with 5 L of 1 M tetramethylammonium hydroxide (TMAH) in water immediately prior to pyrolysis [11,21]. TMAH and similar derivatization reagents have been used on bacteria to chemically lyse the biopolymers and increase the volatility of analytes, allowing analysis by gas chromatography and mass spectrometry [22,23]. This reagent also enhances membrane permeability, as the methylation process forms products that are less polar than the underivatized species [21].…”

Section: Reagents and Instrumentationmentioning

confidence: 99%

Validation using sensitivity and target transform factor analyses of neural network models for classifying bacteria from mass spectra

Harrington

Voorhees

Basile

et al. 2002

J. Am. Soc. Mass Spectrom.

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Temperature constrained cascade correlation networks (TCCCNs) are computational neural networks that configure their own architecture, train rapidly, and give reproducible prediction results. TCCCN classification models were built using the Latin-partition method for five classes of pathogenic bacteria. Neural networks are problematic in that the relationships among the inputs (i.e., mass spectra) and the outputs (i.e., the bacterial identities) are not apparent. In this study, neural network models were constructed that successfully classified the targeted bacteria and the classification model was validated using sensitivity and target transformation factor analysis (TTFA). Without validation of the classification model, it is impossible to ascertain whether the bacteria are classified by peaks in the mass spectrum that have no causal relationships with the bacteria, but instead randomly correlate with the bacterial classes. Multiple single output network models did not offer any benefits when compared to single network models that had multiple outputs. A multiple output TCCCN model achieved classification accuracies of 96 Ϯ 2% and exhibited improved performance over multiple single output TCCCN models. Chemical ionization mass spectra were obtained from in situ thermal hydrolysis methylation of freeze-dried bacteria. Mass spectral peaks that pertain to the neural network classification model of the pathogenic bacterial classes were obtained by sensitivity analysis. A significant number of mass spectral peaks that had high sensitivity corresponded to known biomarkers, which is the first time that the significant peaks used by a neural network model to classify mass spectra have been divulged. Furthermore, TTFA furnishes a useful visual target as to which peaks in the mass spectrum correlate with the bacterial identities. (J Am Soc Mass Spectrom 2002, 13, 10 -21)

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“…It is claimed to be superior to the more widely used tetramethylammonium hydroxide (TMAH) because it accepts a lower reaction/inlet temperature (2408C) and does not cause degradation of unsaturated or substituted fatty acids. TFTMAH reagent permits rapid and simple analysis of fatty acid composition of lipids and free fatty acids present in the sample which are converted into (m-trifluoromethylphenyl)trimethylammonium salts; these react upon injection into the gas chromatograph to yield fatty acid methyl esters [27].…”

Section: Introductionmentioning

confidence: 99%

Direct chemolysis–gas chromatography–mass spectrometry for analysis of paint materials

Pitthard

Finch

Bayerová

2004

J of Separation Science

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A novel direct method using (m-trifluoromethylphenyl)trimethylammonium hydroxide (TFTMAH) has been developed for on-line (trans)esterification of lipidic materials (drying oils, egg) prior to GC-MS analysis. The method was first optimised by comparing three N-methylammonium hydroxide reagents (TMAH, PhTMAH, TFTMAH) and triolein as a lipid standard. Secondly, the procedure was tested on a series of fresh and naturally aged (up to 40 years) (un)pigmented drying oils and egg yolk reference film standards. Thirdly, the method was applied to the analysis of a sample from an altar painting "Resurrection of Christ" by Francesco Solimena (1723) from the Chapel of Upper Belvedere in Vienna. The relative proportions of the fatty acids from the translucent size layer confirm the presence of partially degraded oil, probably prepolymerised walnut oil.

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Pyrolytic Methylation/Gas Chromatography: A Short Review

Cited by 116 publications

References 0 publications

Py‐GC/MS of Natural and Synthetic Resins

Py‐GC/MS of Natural and Synthetic Resins

Validation using sensitivity and target transform factor analyses of neural network models for classifying bacteria from mass spectra

Direct chemolysis–gas chromatography–mass spectrometry for analysis of paint materials

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