Fractionation chemical ionization mass

This system was studied by Schwartz. Toluene at 10 ppm, nitric oxide at 1 ppm, and nitrogen dioxide at 1.2 ppm were irradiated with ultraviolet lamps in a 17-m batch reactor for 270 min. Collected aerosols were successively extracted with methylene chloride and then methanol. The methylene chloride extract was fractionated into water-soluble and water-insoluble material, and the latter fraction was further divided into acidic, neutral, and basic fractions. The acidic and neutral fractions were analyzed by gas chromatography and chemical-ionization mass spectrometry the compounds identified are shown in Figure 3-7. The two analyzed fractions represented only about 5.5% of the total aerosol mass. It is noteworthy that classical nitration of an aromatic ring appears to... 

Gr0nneberg, T. 0. (1978-79). Analysis of a wax ester fraction from anal gland secretion of beaver [Castorfiber) by chemical ionization mass spectrometiy. Chemical Scripta 13, 56-58. 

A. Nonalkaloidal, 0.35, 198°C, m/z 265(50), 264(100), 222(58), 180(72). This proved to be octadecenoic acid methyl ester with a true parent ion of m/z 296. Fatty acid methyl esters do not afford a major protonated parent ion with NH3 chemical ionization-mass spectrometry. Such fatty acid methyl esters frequently represent trace contaminants of alkaloid fractions. 

The fatty acid composition of lipids is usually analyzed by gas chromatography following transesterification into methyl esters. Unmodified lipids can be analyzed by HPLC or by soft chemical ionization mass spectrometry. In the course of sample preparation it is often necessary to separate the various membrane fractions (plasma membrane, thylakoid, microsomal, mitochondrial, etc.) by sophisticated gradient centrifugations, as well as the individual lipid classes within a membrane fraction, usually by thin-layer chromatography (TLC). 

Subsequent work revealed that chelate formation with Group IA and IIA metal salts could successfully separate N-permethylated TEPA samples. As mentioned, TEPA is the notation given to the commercial polyamine fraction containing mainly the isomeric tetraethylenepenta-mines (6). The N-permethylated pentamine components, characterized by NMR and chemical-ionization mass spectrometry (19), include the two acyclic isomers—Compound 7 and 8—and three derivatives of piperazine—Compounds 9 through 11. Of these, only three of the pentamines—n-HMTP (Compound 7), iso-HMTP (Compound 8), and N,N -c-PMPP (Compound 10)—are present in amounts greater than 10% in a typical N-permethylated sample of TEPA. The amounts of these components found in one such sample are listed in Table V. 

McCarry et al. [19-25] performed a similar series of HPLC fractionations to determine the PAHs in sediment samples. They observed C24H14 LPAHs similar to those found by Wise and co-workers in a coal-tar SRM. In later work, LPAHs of 26, 28, 30, and 32 carbons were found. Both a DAD and direct atmospheric-pressure chemical-ionization mass spectrometry were used for detection. To make the DAD less specific and more universal, the average response from 250 nm to 370 nm was collected as a total-absorbance chromatogram. 

The i-butane chemical ionization mass spectra of a number of saturated mono-hydroxylic alcohols have been determined to establish the general patterns of the spectra of this class of compounds. The spectrum of 2-hexanol is given as a typical example in Table X, and it may be seen that the following ion types comprise large fractions of the spectra of alcohols the alkyl ion formed from the hydrocarbon portion of the molecule R ) the ion formed by abstraction of the hydride from the molecule, (M l)" the protonated molecule, (M + 1) the association complex of the molecule with the mje = 39 ion of the i-butane plasma, (M -h 39) the association complex of the molecule with the mje = 57 ion of the /-butane plasma, (M -h 57) and the protonated dimer of the molecule, (2M -h 1). The intensity of this ion in the spectrum of 2-hexanol is so small that it is not included in Table X. 

Stereochemical studies based on C-nuclear magnetic resonance spectroscopy ( C-NMR) showed the presence of eight cis and trans allylic hydroperoxides (Table 2.1). To determine the isomeric distribution of allylic hydroxyooctadecenoate derivatives, cis and trans fractions were separated by silver nitrate-thin layer chromatography (TLC), a procedure that separates according to the number, position and geometry of double bonds, and they were hydrogenated prior to GC-MS analyses of the TMS ether derivatives. More recently, the six major hydroperoxide isomers of methyl oleate were partially separated by silica HPLC, and identified by chemical-ionization mass spectrometry and IH NMR (Table 2.1). These hydroperoxide isomers were better separated as the hydroxy octadecenoate derivatives by the same silica HPLC method and re-analysed by GC-MS. 

Several methods have been developed specifically for naphthenic acids, a class which includes the surface active carboxylate surfactants. Naphthenic acids are present as a complex mixture of a number of homologues with only a small range in molar mass (166-450 mol/g), little change in solubility character, and have been difficult to assay using conventional analytical methods. Methods such as negative ion-mode mass spectrometry using fast atom bombardment (FABMS), have been successfully applied to the analysis of naphthenic acid mixtures [93, 94], Other promising techniques include fluoride ion chemical ionization mass spectrometry (FI-MS) [95], and electrospray ionization mass spectrometry (ESIMS), which may allow for the quantification of the various naphthenic acid fractions [96]. 

Chen X, Hu L, Su X, Kong L, Ye M, Zou H. Separation and detection of compotmds in honeysuckle by integration of ion-exchange chromatography fractionation with reversed-phase liquid chromatography—atmospheric pressure chemical ionization mass spectrometer and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis. J Pharm Biomed Anal 2006 40 559-70. 

The following discussion will be concerned primarily with applications of the ms/ms technique in the synfuel area. Attempts will be made to illustrate the unique capabilities of the ms/ms analysis with examples taken from our work on coal liquefaction products. Figure 5 shows the positive ion chemical ionization (PCI) mass spectrum of the coal liquid in question (SRC II mid heavy distillate, total bottoms). This spectrum is actually the normalized sum of approximately 500 individual mass spectra taken while the SRC II was thermally vaporized from a solids probe into the source of a mass spectrometer, and represents the molecular weight profile of this distillate fraction. Since isobutane Cl gives to a first approximation only protonated molecular ions (and no fragment ions), the peaks represent the individual components in the SRC II arranged incrementally by molecular weight. 

The volatile concentrate from the commercial condensate was first separated into 2 main fractions by micro distillation under reduced pressure (0.1mm Hg). The distillation fractions were then resolved into their components by packed column GLC separation first with a 10 m Silicone SF96 packed column with further GLC resolution of the Silicone GLC fractions using a 3 m Carbowax 20-M column. Infrared absorption spectra were measured with the separated components. In some cases HNMR spectra and chemical ionization (C.I.) mass spectra were obtained. This additional... 

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