Volatile phenols chromatograms

ESI-MS has emerged as a powerful technique for the characterization of biomolecules, and is the most versatile ionization technique in existence today. This highly sensitive and soft ionization technique allows mass spectrometric analysis of thermolabile, non-volatile, and polar compounds and produces intact ions from large and complex species in solution. In addition, it has the ability to introduce liquid samples to a mass detector with minimum manipulation. Volatile acids (such as formic acid and acetic acid) are often added to the mobile phase as well to protonate anthocyanins. A chromatogram with only the base peak for every mass spectrum provides more readily interpretable data because of fewer interference peaks. Cleaner mass spectra are achieved if anthocyanins are isolated from other phenolics by the use of C18 solid phase purification. - ... 

In contrast, both gas and liquid chromatography enable the samples of interest to be separated into individual components prior to introduction into the mass spectrometer ion source. Gas chromatography involves sample introduction with the requisite that the sample components must be volatilized prior to separation, and results in a gas sample being introduced to the mass spectrometer (i.e. El, Cl). Figure 5-2 shows the chromatogram obtained after a mixture of three simple phenolic compounds - phenol,... 

Top complete chromatographic trace of volatile acids from the urine of a patient suffering from Wilson s disease. Middle Trace showing part of the chromatograph ranging from spectra 300 to 400. Bottom Trace showing the chromatograms of m/z 151 and 166 that are typical of TMS-phenol and thus indicate its presence. 

Figure 7.3. Analysis of a 50% ethanol untoasted oak wood extract GC/PICI reconstructed ion chromatogram of benzene compounds [M+H]+ signals. (54) anisaldehyde (m/z 137) (35) eugenol (m/z 165) (37) vinylguaiacol (m/z 151) (45) vanillin (m/z 153) (55) methoxyeugenol (m/z 195) (50) syringaldehyde (m/z 183) (56) trimethoxy-phenol (m/z 185) (53) coniferaldehyde (m/z 179). Internal standard-i.s. 1-heptanol (m/z 55). Analytical conditions PEG fused silica capillary column (30m x 0.25mm i.d. df 0.25 pm) injection port 240°C volume injected lpL (splitless) program oven temperature 3min at 70°C, 2°C/min to 160°C, 3°C/min to 230 °C, 25 min at 230°C transfer line temperature 280 °C carrier gas He at constant flow 1.3mL/min. (Reprinted from Journal of Mass Spectrometry 42, Flamini et al., 2007, GC/MS-Positive Ion Chemical Ionization and MS/MS study of volatile benzene compounds in five different woods used in barrel-making, pp. 641-646, with permission from John Wiley Sons, Ltd.)...

It is recommended that these reactions be conducted in the presence of bases without active hydrogen atoms (pyridine, triethyl amine, etc.). These basic media are necessary for the conversion of acidic by-products into non-volatile salts to protect the acid-sensitive analytes from decomposition and to avoid the appearance of extra peaks of by-products on the chromatograms. Exceptions are indicated by reagent/(H ). Phenols can be converted into Na salts before acylation. A large variety of anhydrides of perfluormated carboxylic acids are recommended for derivatization because of the favorable chromatographic properties of perfluoroacyl derivatives. 

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