Separate quantitative determination of hexoses and pentoses employing o-toluidine reagent

Conclusions A spectrophotometric method was proposed for the separate determination of hexoses and pentoses when jointly present, which is based on the difference in the absorption spectra of the reaction products of these sugars with o-toluidine reagent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 877–880, April, 1974.     

Structural characterization of hexoses and pentoses using lead cationization. An electrospray ionization and tandem mass spectrometric study

The analytical potential of the complexation of isomeric underivatized hexoses (D-glucose, D-galactose, D-mannose, D-talose, D-fructose), methylglycosides (1-O-methyl-alpha-D-glucose and 1-O-methyl-beta-D-glucose) and pentoses (D-ribose, D-xylose, D-arabinose and D-lyxose) by Pb(2+) ions, was investigated by electrospray ionization and tandem mass spectrometry (MS/MS). Pb(2+) ions react mainly with monosaccharides by proton abstraction to generate [Pb(monosaccharide)(m) - H](+) ions (m = 1-3). At low cone voltage, a less abundant series of doubly charged ions of general formula [Pb(monosaccharide)(n)](2+) is also observed. The maximum number n of monosaccharides surrounding a single Pb(2+) ion depends on the metal : monosaccharide ratio. Our study shows that MS/MS experiments have to be performed to differentiate Pb(2+)-coordinated monosaccharides. Upon collision, [Pb(monosaccharide) - H](+) species mainly dissociate according to cross-ring cleavages, leading to the elimination of C(n)H(2n)O(n) neutrals. The various fragmentation processes observed allow the C(1), C(2) and C(4) stereocenters of aldohexoses to be characterized, and also a clear distinction aldoses and fructose. Furthermore, careful analysis of tandem mass spectra also leads to successful aldopentose distinction. Lead cationization combined with MS/MS therefore appears particularly useful to identify underivatized monosaccharides.     

Direct identification of pentoses and hexoses by pyrolysis/capillary gas chromatography

The combination of rapid pyrolysis and capillary-column gas chromatography (pyrolysis/capillary g.c.) was used to identify the stereoisomers of pentoses and hexoses. Analytical pyrolysis is shown to be a viable alternative to the formation of volatile derivatives of carbohydrates for chromatographic separation. The individual stereoisomers (glucose, galactose, arabinose, xylose etc.) were positively identified by the retention times of their distinctive anhydrosugar products. The aldohexoses formed both 1,6-anhydrohexopyranose and 1,6-anhydrohexofuranose products; the aldopentoses formed 1,4-anhydropentopyranose products; and the ketohexoses, to a lesser extent, formed 2,6-anhydrohexofuranose products. The anhydrosugars were identified by mass spectrometry and many were authenticated with standard samples. Pyrolysis/capillary g.c. is rapid and direct and is useful for solids and solutions and for microscale samples. Sample preparation or prior derivatization is not required. Experimental parameters that are important for structural characterization and reproducibility include samples size, pyrolysis temperature, transfer zones and the type and film thickness of the capillary column.     

Electrospray ionization mass spectra of pentoses,hexoses, and 2-deoxy-2-fluoro-<Emphasis Type="SmallCaps">d</Emphasis>-glucose

Electrospray ionization (ESI) mass spectra of hexoses, pentoses, and 2-deoxy-2-fluoro-d-glucose (FDG) were investigated and compared using liquid chromatography/mass spectroscopy (LC/MS). ¹⁸F-FDG is one of the most widely used radiopharmaceuticals. This work is aimed at the possible interpretations of ESI mass spectra and at the comparison of various pentoses (arabinose, ribose, xylose), and hexoses (glucose, fructose, galactose, mannose) which can be formed during the ¹⁸F-FDG’s synthesis or decomposition. As a result, nine major associates were found in the positive and four in the negative mass spectra of all examined saccharides of which intensities and mass can be used with their retention times to determine the saccharide. M · NH₄⁺ and M · COOH⁻ were identified as the most stable associates.     

Investigation of the tris(trimethoxyphenyl)phosphonium acetyl charged derivatives of peptides by electrospray ionization mass spectrometry and tandem mass spectrometry

Charged derivatives of peptides are useful in obtaining simpler collision-activated dissociation (CAD) mass spectra. An N-terminal charge-derivatizing reagent capable of reacting with picomole levels of peptide has been recently reported (Huang et al. Anal. Chem. 1997, 69, 137-144) in the contexts of analyses by fast atom bombardment (FAB) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Electrospray ionization (ESI) mass spectrometric investigation of these tris(trimethoxyphenylphosphonium) acetyl derivatives are described in this article, including studies by in-source fragmentation (ISF) and tandem mass spectrometry (MS/MS). Results from ISF are compared with those from MS/MS. Similarities and differences between ESI-ISF, MALDI-post-source decay (PSD), and FAB-CAD data are presented. Differences in fragmentation of these charged derivatives in the triple quadrupole and ion trap mass spectrometers also are discussed. Application of this derivatizing procedure to tryptic digests and subsequent analysis by liquid chromatography-mass spectrometry is also shown.     

缩氨基脲类和缩氨基硫脲类衍生物的质谱研究

用高、低分辨质谱,重氢标记和亚稳跃迁研究了代缩氨脲和缩氨基硫脲类衍生物的质谱碎行为。结果表明,分子离子的丰度、基峰离子的生成方式以及碎非离子的种类、丰度和数量主要取于取代基R的诱导效应和共轭效应的综合影响。质谱的碎裂特征是:(1)当R为N(CH2)2,OH分子的电子云分布均匀,共轭性好,基峰为分子离子峰。(2)当R为H,F时缩氨基脲8-N位缺子最甚,导致9-N和10-C之间键的断裂,生成的高稳定离子ρ-RC6H4CH=N[+]=NH为墓峰。缩氨基硫脲类衍生物,因电子云分布均匀,基峰仍为分子离子峰。(3)当R为Br,NO2时,由于诱效应强烈,分子的电子云分布不均匀,12-O(或12-S)成为缺电子最甚的原子,8-N和9-N之间键裂、重排而生成的离子-HNC(NH2)=XH]:(X=O,S)为基峰。(4)H-NH2基团重排到苯环5位上,生成离子(O-RC6H4NH2).+[1]。只有当R为H时,反应最易反生。R为强电子基或强极电基,对反应都不利。     

The study of mass spectrometry on semicarbazone and thiosemicarbazone derivatives

The MS fragmentation behaviors of semicarbazone and thiosemicarbazone with different polar substituents R (R=N (CH₃)₂, OH, H, F, Br, NO₂) under electron impact were investigated in detail with the aid of exact mass measurements, metastable transition and their corresponding deuterium labelling compounds. The results showed the abundance of molecular ions, the formming way of base ions, the kinds and abundance as well as numbers of fragments are mainly dependent upon the inductive and conjugative effects of substituents R. These observation has not previously been reported in the literature. Data concerning them are presented and discussed in the paper.     

Monosaccharides as silicon chelators: pentacoordinate bis(diolato)(phenyl)silicates with the cis-furanose isomers of common pentoses and hexoses

Five-coordinate phenylsilicates are formed from the reaction of trimethoxy(phenyl)silane with monosaccharides in methanol in the presence of a stoichiometric amount of base. Five complexes have been isolated and characterized with two ketoses and three aldopentoses. The silicon central atom in [K([18]crown-6)][PhSi(beta-D-Fruf 2,3H-2)2].MeOH (1, Fru=fructose) is part of two chelate rings, with the ligands being beta-D-fructofuranose-O2,O3 dianions. The beta-furanose isomer is best suited for silicon ligation because it exhibits a torsion angle close to 0 degrees for the most acidic diol function, thus assuring a flat chelate ring. The same structural principles are also found in [K([18]crown-6)][PhSi(beta-D-Araf1,2H-2)2].2 MeOH (2, Ara=arabinose), [K([18]crown-6)][PhSi(alpha-D-Ribf1,2H-2)2] (3, Rib=ribose), [K([18]crown-6)][PhSi(alpha-D-Xylf1,2H-2)2]. acetone (4, Xyl=xylose), and [K([18]crown-6)][PhSi(alpha-D-Rulf2,3H-2)2] (5, Rul=ribulose).     

Synthesis,spectral characterization and electrochemical properties of (2-alkylthiobenzoyl)ferrocenes. Crystal structures of 2-methylthio, 2-ethylthio and 2-isopropylthio derivatives

The one-pot synthesis of seven new (2-alkylthiobenzoyl)ferrocenes has been achieved by Friedel–Crafts acylation of ferrocene with acid chlorides generated in situ from the corresponding carboxylic acids and phosphorous trichloride. The obtained compounds were characterized by spectroscopic data (UV, IR, ¹H and ¹³C NMR), whereas their electrochemical properties have been investigated by cyclic voltammetry. The single-crystal X-ray structure determinations for three of them are also reported. Each of the three derivatives exhibits the intramolecular C–H…O interaction which involves the donor from the cyclopentadienyl (Cp) ring and the carbonyl oxygen as acceptor. This interaction favors the coplanar arrangement of the two moieties. The angles between the vectors coinciding the C–O bonds and the corresponding Cp planes are all below 6.4°. Conventional hydrogen bonds do not exist in any of the three crystal structures but some weak intermolecular interactions of the C–H…O, C–H…S and C–H…π types have been found and analyzed in detail. Different geometrical parameters for these crystal structures as well as for 22 similar ones extracted from Cambridge Structural Database (CSD) have been compared and analyzed.     

Membrane-introduction mass spectrometry (MIMS)

Membrane-introduction mass spectrometry (MIMS) for chemical analysis involves directly sampling analytes in gaseous, liquid and solid samples through a semi-permeable membrane coupled to a mass spectrometer, yielding selective and sensitive quantitation. Because MIMS is an on-line technique, in which samples can be continuously flowed over a membrane interface, it can yield analytical results in real time without the need for sample clean-up and chromatographic separation. This review highlights trends and developments in MIMS over the past decade and describes recent studies that pertain to its use for on-site, in-situ and in-vivo chemical analysis. We report on advancements in instrumentation, including membrane materials, interface configurations and ionization techniques that have extended the range of analytes amenable to MIMS.We summarize the progress made in the miniaturization of mass spectrometers that have resulted in field-portable systems and review recent applications of continuous mobile monitoring and on-site environmental monitoring to yield both temporally and spatially resolved quantitative and semi-quantitative data. Finally, we describe recent work involving the use of MIMS for in-vivo chemical analysis.     

Fast atom bombardment mass spectrometry of neutral methanide and ionic carbene platinum(II) derivatives

The fast atom bombardment mass spectra of a series of neutral methanide and ionic carbene platinum(II) complexes of formula dPePtL₂ and [dPePt(LH)₂](BF₄)₂ (dPe = (C₆H₅)₂PCH₂CH₂P(C₆H₅)₂; L = ? C(OCH₃)-NCH₃, ? C(OCH₃) ? NC₆H₁₁, ? C(OCH₃) ? NC₆H₄p ? CH₃), respectively are reported. Glycerol, 3-mercapto-1,2-propanediol, bis (2-hydroxyethyl)sulphide, 3-nitrobenzyl alcohol, and 2,4-di-tert-pentylphenol have been used as matrices. Neutral and ionic derivatives containing the same ligand behave similarly and give the same quasi-molecular [dPePtL(L + H)]⁺ ion by different primary processes. Stepwise breakdown of the ligands L with retention or further loss of atoms or molecules of hydrogen is observed for all these complexes, followed by ejection of radicals from the dPe ligand. Elimination of CH₃OH from [dPePtL(L + H)]⁺ also occurs. The highest ionic yields of both neutral methanide and ionic carbene complexes are observed in 3-mercapto-1,2-propanediol, in bis(2-hydroxyethyl)sulphide, and in 3-nitrobenzyl alcohol with respect to glycerol. The [dPePt(LH)₂]²⁺ doubly charged ions are present in the spectra obtained with 3-nitrobenzyl alcohol and are rather strong when L is ? C(OCH₃) ? NCH₃ and ? C(OCH₃) ? NC₆H₄p ? CH₃. Substitution of ligands L with a molecule or with a fragment of a sulphur containing matrix takes place very seldom with this series of complexes.     

Electron impact mass spectrometry of praziquantel derivatives

The electron impact mass spectra of a series of compounds related to the anthelmintic substance praziquantel are described in sufficient detail to permit their assay in biological samples by selected ion monitoring.     

Electron-induced mass spectrometry of 1,2-dihydropyridine derivatives

The electron-induced mass spectrometry of 1-substituted-4-phenyl-1,2-dihydropyridines is characterized by a [M-1] peak that accounts for the base peak, and a fragment corresponding to the loss of the N-substituent in every example examined.     

Electrolytic electrospray ionization mass spectrometry of C(60)-TTF-C(60) derivatives: high-resolution mass measurement and molecular ion gas-phase reactivity

The electrochemical process involved in electrospray ionization is used to obtain odd-electron molecular ions from C(60)-TTF-C(60) and its methano derivatives. Exact mass measurements obtained using high-resolution mass spectrometry are reported, and the gas-phase behavior of the radical cation (retro-Diels-Alder reaction and [M/2 + H](+) ion formation) is described.     

Tandem mass spectrometry of aminated fullerene derivatives

The products of the reaction between fullerenes (C₆₀/C₇₀) and dimethylamine were investigated by fast atom bombardment (FAB) mass spectrometry and tandem mass spectrometry (MS/MS). The FAB mass spectrum shows peaks corresponding to the addition of up to eight dimethylamine species, exclusively to C₇₀. MS/MS reveals an unusual fragmentation pattern. The mass spectrum of the reaction products, together with a number of tandem mass spectra, are shown.     

Molecular weight determination of high molecular mass (glyco)proteins using CGE-on-a-chip, planar SDS-PAGE and MALDI-TOF-MS

The molecular weights (MW) of seven (glyco)proteins, of which five were plasma-derived, with MWs higher than 200 kDa were determined with three techniques: CGE-on-a-chip, SDS-PAGE and MALDI-TOF-MS. While the analysis of medium to high MW proteins with SDS-PAGE was an already well-established technique, the usefulness of MALDI-TOF-MS for the exact MW determination of high mass proteins was only partly described in literature so far. CGE-on-a-chip is the newest of all three applied techniques and was so far not applicable. Therefore, it was not evaluated for high MW (glyco)proteins. All proteins were analyzed under nonreducing as well as reducing conditions. In this work, it was demonstrated that all three described techniques were capable of determining the MW of all high molecular weight (glyco)proteins. The noncommercial CGE-on-a-chip assay allowed for the first time the electrophoretic separation of proteins in the MW range from 14 to 1000 kDa. MW assignment was limited to 500 kDa in the case of SDS-PAGE and 660 kDa in the case of the high MW CGE-on-a-chip assay. With the proper matrix and sample preparation, analysis with a standard MALDI-TOF-MS provided accurate MWs for all high MW proteins up to 1?MDa.     

Binding sites of [Ru(bpy)2(H2O)2](BF4)2 with sulfur- and histidine-containing peptides studied by electrospray ionization mass spectrometry and tandem mass spectrometry

The composition and binding sites of cis-[Ru(II)(bpy)2]2+-bound sulfur-containing peptides of Met-Arg-Phe-Ala, glutathione and oxidized glutathione, and also histidine-containing peptide of oxidized insulin B chain, were investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The composition of Ru(II)-containing peptides was precisely determined by ESI-MS, zoom scan and simulation of isotope distribution patterns. MS/MS analysis shows that, in sulfur-containing peptides, the Ru(II) complex prefers to anchor to a carboxyl group, although some other potential binding sites of thiol, thioether and N-terminal amino groups present in these peptides, and in oxidized insulin B chain, Ru(II) first anchors to His10, then either to the hydroxyl group of Thr27 or to the carboxyl group of Ala30. Its secondary structure and microenvironment surrounding the potential binding sites may affect the binding ability of cis-[Ru(II)(bpy)2]2+ to oxidized insulin B chain.     

Laserspray ionization (LSI) ion mobility spectrometry (IMS) mass spectrometry

A simple device is described for desolvation of highly charged matrix/analyte clusters produced by laser ablation leading to multiply charged ions that are analyzed by ion mobility spectrometry-mass spectrometry. Thus, for example, highly charged ions of ubiquitin and lysozyme are cleanly separated in the gas phase according to size and mass (shape and molecular weight) as well as charge using Tri-Wave ion mobility technology coupled to mass spectrometry. This contribution confirms the mechanistic argument that desolvation is necessary to produce multiply charged matrix-assisted laser desorption/ionization (MALDI) ions and points to how these ions can be routinely formed on any atmospheric pressure mass spectrometer.