High-performance liquid chromatography/electrospray ionization mass spectrometric characterization of new products formed by the reaction between flavanols and malvidin 3-glucoside in the presence of acetaldehyde

Monomer and polymer flavan-3-ols and anthocyanins are the two major groups of phenolic compounds in red wine and one of the most important reactions during red wine ageing is the condensation reaction, either direct or indirect, between these two classes of compounds. In this work, the reaction of (+)-catechin, (-)-epicatechin and dimer procyanidin B2 with malvidin 3-glucoside, in the presence of acetaldehyde, was carried out in wine model solutions at pH 1.7 and 3.2. Identification of the reaction products was carried out by high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) and MS(n) analysis. Various reaction products were detected. The structures of three condensation products - malvidin-3-glucoside-ethyl-(epi)catechin-1'-hydroxyethyl, malvidin-3-glucoside-ethyl-dimer-vinyl and malvidin-3-glucoside-ethyl-dimer-1'-hydroxyethyl - were identified in a model solution for the first time. Moreover, in the reaction solution containing dimer B2 at pH 3.2, monomer epicatechin, trimer and tetramer procyanidins were also detected indicating that, under these conditions, dimer procyanidins can either be hydrolyzed to monomers or polymerized to higher oligomer or polymers.     

Exactly alternating silarylene–siloxane polymers. II. The condensation polymerization of arylenedisilanols and bisureidosilanes

A new method for the preparation of exactly alternating silarylene–siloxane polymers by the low temperature step-growth condensation polymerization reaction of arylenedisilanols and bisurei-dosilanes in chlorobenzene was investigated. To obtain high molecular weight products ¹H NMR spectroscopy and gel permeation chromatography were used to monitor the polymerization reaction. By using these procedures 12 different polymers were prepared from 1,4-bis(dimethylhydroxysilyl)-benzene, 4,4′-bis(dimethylhydroxysilyl)phenyl ether, bis(1,1-tetramethylene-3-phenylureido)-dimethylsilane, and bis(1,1-tetramethylene-3-phenylureido)-methylvinylsilane monomers. The polymers were obtained in high yields, purities, and molecular weights.     

Synthesis of Novel Symmetric Porphyrin Schiff Base Dimers by Solid–Liquid Reaction Methodology

A new convenient solid–liquid condensation reaction procedure for the synthesis of novel asymmetric and symmetric meso‐tetraarylporphyrin and metalloporphyrin Schiff bases is reported. The condensation reaction between β‐formyl porphyrin or metalloporphyrins and aromatic amines was carried out at solid–liquid interface by using neutral alumina powder as a solid support for β‐formyl porphyrin or metalloporphyrins and absolute ethanol as the carrier solvent for aromatic amines. Six different asymmetric porphyrin/metalloporphyrin Schiff bases were synthesized via solid–liquid interface reaction methodology. The same solid–liquid synthetic methodology was applied for the synthesis of six novel symmetric Schiff base porphyrin/metalloporphyrin dimers. The comparison of UV–visible spectra of porphyrin Schiff base monomers and dimers revealed that some degree of electronic perturbation has occurred upon dimerization as the Soret bands of the monomers underwent peak broadening along with red shifts. Column chromatography and crystallization were used to purify the compounds. Fourier transform infrared, UV–visible, elemental analysis, ¹H NMR, and mass spectrometry were used to characterize the newly synthesized compounds.     

Separation and characterisation of products of the reaction between propionamide and formaldehyde

Summary Propionamide-formaldehyde reaction products have been characterised using micellar electrokinetic chromatography (MEKC), HPLC-electrospray-MS (HPLC-ES-MS) and time-of-flight-MS (TOF-MS). HPLC-MS-MS was used to distinguish between isomeric species. The MEKC separation of all reaction products was obtained with good resolution and efficiency. Comparison of water-micelle distribution constants (P _MEKC) for propionamide-formaldehyde with those for caprolactam-formaldehyde reaction products suggests that the concentration of sodium dodecyl sulfate appropriate for use in MEKC is inversely related toP _MEKC. Quantification of all species containing one or two amide units was achieved using standard calibration, mass balance and the assumption of identical absorption coefficients for the same functional groups in monomers and dimers.     

乳液聚合型品红成色剂的合成

2，4，6-三氯苯肼与β-乙氧基-β-亚氨基-丙酸乙酯在乙醇钠的存在下，经缩 合成环生成1-(2＇，4＇，6＇-三氯苯基)-3-氨基-5-吡唑啉酮(3)．3和它的4-位衍 生物与甲基丙烯酰氯反应生成了三种可聚合的成色剂单体．将这些单体与丙烯酸丁 酯共聚得到了三种乳液聚合型品红成色剂．给出了合成反应中间体及单体的红外光 谱与核磁共振光谱数据，讨论了影响合成反应及乳液聚合反应的一些因素．     

High throughput physical organic chemistry: analytical constructs for monomer reactivity profiling

A polymer-supported analytical construct was used to quantify the reactivity of a range of monomers in the Ugi four-component condensation using positive electrospray ionization mass spectrometry (MS) as a quantitative analytical tool. The construct incorporated a bromo group to act as a peak splitter and a quaternary ammonium to act as a MS sensitizer and ionization leveler, thereby allowing direct quantitation of the cleaved adducts by MS. The relative reactivities of 10 carboxylic acids were quantified by the relative levels of product generated as determined by MS and 10 isonitriles, and 10 aldehydes were investigated in the same way. The effect of concentration variations on monomers reactivity and product profiles were rapidly determined using this approach, and the method opens up the way for studying, in a single pot, multiple reactions with a broad range of monomers under identical and self-consistent reaction conditions.     

Thermal degradation of the polyurethane from 1,4-butanediol and methylene bis(4-phenyl isocyanate)

A polyurethane prepared from 1,4-butanediol (BD) and methylene bis(4-phenyl isocyanate) begins to evolve volatile degradation products at approximately 240°C. By a combination of thermal analysis methods (TVA, TG, and DSC) and examination of the volatile and involatile products by using a combination of GLC and infrared and mass spectrometric analysis, it is shown that the total reaction comprises a primary depoly-condensation process in which the two monomers are formed, followed by the subsequent reaction of these monomers to form the volatile products, tetrahydrofuran, dihydrofuran, carbon dioxide, water, butadiene, hydrogen cyanide, and carbon monoxide and residual carbodiimide and urea structures. A mechanism, which accounts for all these products, has been formulated and tested.     

Determination of proanthocyanidins in fresh grapes and grape products using liquid chromatography with mass spectrometric detection

Fresh grapes and grape products, such as grape wine and grape juice, were analyzed for proanthocyanidins (PACs) using liquid chromatography with electrospray ionization mass spectrometric (MS) detection. PACs were successfully separated and analyzed on the basis of their protonated molecules, allowing the identification of PACs in different degrees of polymerization from monomers to oligomers (up to 7 units), and in various isomeric forms. Using reversed-phase high-performance liquid chromatography (HPLC) combined with MS detection, the PAC monomers, (+)-catechin (C), (-)-epicatechin (EC), (-)-catechin gallate (CG), and (-)-epicatechin gallate (ECG), were successfully quantified using selected ion monitoring (SIM) mode. Standard curves were fitted for each PAC ranging from 43.8 to 5600 ng/mL for C, from 42.2 to 5400 ng/mL for EC, from 36.7 to 4700 ng/mL for CG, and from 39.8 to 5100 ng/mL for ECG. Good linearity (r2>0.999) was achieved for each analyte. The accuracy and precision (RSD) were within 10% (n=8) at the limit of detection. This method allows direct quantification of monomeric PACs in fresh grapes and grape-derived products. Additionally, flow injection analysis (FIA) was applied to estimate the concentration levels of PAC oligomers by comparing their FIA-MS peak areas, which were well correlated (r2=0.936) to the total concentrations of PAC monomers.     

Melt-polymerizable bisimido-bisphthalonitriles containing silicon,fluoro, and ether groups: Synthesis,characterization, and NMR study

Various melt-polymerizable bisimido-bisphthalonitrile polymer precursors were synthesized by the reaction of 4-aminophthalonitrile (4-APN) with bis(3,4-dicarboxyphenyl) dimethylsilane dianhydride (SIDA), 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), bis(3,4-dicarboxyphenyl)ether dianhydride (ODPA), and 3,3′, 4,4′-tetracarboxylichenzophen+ne dianhydride (BTDA) in an aprotic solvent. The synthesized monomers showed crystalline melting at 269 and 271°C. Elemental analysis, differential thermal analysis (DTA), infrared (IR), nuclear magnetic resonance (¹H-NMR) and mass spectral studies were carried out to characterize the synthesized monomers. Thermogravimetric analysis (TGA) of the synthesized monomers showed their thermal stability at 410–400°C. A detailed study and NMR investigation of the first step of condensation reaction was carried out and indicated the formation of a transient charge transfer complex. Thermal cyclization of the formed intermediate, however, gave the required monomers. A preliminary study demonstrated that melt-polymerization of the synthesized monomers gave thermallystable, tough polymers.     

Friedel-crafts copolymerization of thiophene and p-di(chloromethyl)benzene. II. Products of the later stages of the reaction

Products of the copolymerization of thiophene and p-di(coloromethyl)benzene in presence of stannic chloride have been separated by using gel-permeation chromatography (GPC) and identified by using principally mass, infrared, and nuclear magnetic resonance spectroscopy. The GPC separation is not nearly as efficient as the separation of the products of the corresponding benzene–DCMB and diphenylmethane–DCMB reactions which have previously been described. A further complication which makes a kinetic analysis of this reaction more difficult is the occurrence of intramolecular condensation of certain of the earlier products leading to cyclic structures incorporating four aromatic rings. These investigations have made it possible to deduce some of the principal structural differences between the thiophene–DCMB and benzene–DCMB polymers which may have some bearing on the differences which have been found in their thermal stabilities.     

Analytical characterisation of glutardialdehyde cross-linking products in gelatine-gum arabic complex coacervates

Encapsulates having shells of cross-linked mixtures of proteins and polysaccharides are widely used in the food and pharmaceutical industry for controlled release of actives and flavour compounds. In order to be able to predict the behaviour and the release characteristics of the microcapsules, a better understanding of the nature and extent of the cross-linking reaction is needed. Several analytical techniques were applied for the characterisation of glutardialdehyde (GDA) cross-linked encapsulates made of gelatine and gum arabic. To allow the use of sensitive, high-resolution methods such as chromatography and mass spectrometry, the sample first had to be hydrolysed. In this way, a mixture of amino acids, small peptides and the cross-link moieties was obtained. High-resolution liquid chromatography coupled to high-resolution mass spectrometry (HPLC-MS) was applied to detect possible cross-link markers through a comparison of HPLC-MS mass-chromatograms obtained for cross-linked and non-cross-linked coacervates. HPLC-MS/MS was used to identify the species responsible for the differences. Cross-linking occurred between GDA molecules and lysine and hydroxylysine epsilon-amino groups, and up to eight cross-link products of different nature could be identified. They included pyridinium ions and Schiff bases, and also unreacted GDA condensation products. Next, based on the insight gained in the possible chemical structures present in the cross-link markers, methods for selective labelling of these functionalities were employed to allow easier detection of related reaction products. Both liquid chromatography (LC) and gas chromatography (GC) were used in these experiments. Unfortunately, these approaches failed to detect new cross-link markers, most likely as a result of the low levels at which these are present.     

预聚-酶催化缩聚法合成超支化聚酯及其结构表征

以丙三醇、1,6-己二醇和己二酸为共聚单体,以固定化脂肪酶Novozym435为催化剂,尝试先进行共聚单体的预聚后在有机介质中进行酶催化直接缩聚反应合成脂肪族超支化聚酯的新途径,考察了反应介质和反应温度对酶催化缩聚反应的影响,并采用凝胶渗透色谱和核磁共振确定产物的分子量和结构.结果表明,将单体的预聚与酶催化缩聚反应相结...     

One-pot synthesis of [1+1] and 62-membered [2+2] Schiff base macrocycles

New [1+1] and 62-membered [2+2] Schiff base macrocycles containing a 2,6-diamidopyridine subunit have been synthesized by condensation reaction of the precursors pyridine-2,6-dicarboxamide and 1,10-bis(20-formylphenyloxy)decane in the presence of phosphoric acid via a one-pot process. The cyclocondensed products were effectively isolated by gel column chromatography and characterized by ~1H NMR, FTIR, mass spectrometry and X-ray analysis. The two macrocycles have a twisted structure, and not an open ‘circular' conformation in the solid state.     

Monitoring the synthesis of new pitches from coal tar and its fractions by chromatography and related techniques.

The aim of this paper is to study the applications of chromatography and related techniques in the transformation of coal-derived products into pitches for specific uses. Anthracene oil, tar and pitch were thermally treated in the presence of air (and sulfur in the case of anthracene oil) in order to cause the polymerization/condensation of their components. The evolution of the components of the parent materials during the treatments was monitored by gas chromatography-mass spectrometry, gas chromatography-atomic emission detection, probe mass spectrometry and size-exclusion chromatography. From the results obtained, possible mechanisms for the transformation of coal-derived products into new pitches were established.     

One‐step strategy for the synthesis of a derivatized cyclodextrin‐based monolithic column

Derivatized β‐cyclodextrin (β‐CD) functionalized monolithic columns were prepared by a “one‐step” strategy using click chemistry. First, the intended derivatized β‐CD monomers were synthesized by a click reaction between propargyl methacrylate and mono‐6‐azido‐β‐CD and then sulfonation or methylation was carried out. Finally, monolithic columns were prepared through a one‐step in situ copolymerization of the derivatized β‐CD monomer and ethylene glycol dimethacrylate. The sulfated β‐CD‐based monolith was successfully applied to the hydrophilic interaction liquid chromatography separation of nucleosides and small peptides, while the methylated β‐CD‐functionalized monolith was useful for the separation of nonpolar compounds and drug enantiomers in capillary reversed‐phase liquid chromatography. The structures of the monomers were characterized by Fourier transform infrared spectroscopy and mass spectrometry. The physicochemical properties and column performance of monoliths were evaluated by scanning electron microscopy and micro high performance liquid chromatography. This strategy has considerable prospects for the preparation of other derivatized CD‐functionalized methacrylate monoliths.     

Synthesis and Pyrolysis of Soluble Cyclic Hf-Schiff Base Polymers

Soluble Hf-containing polymers are significant processable precursors for the fabrication of ultra-high temperature ceramics. In this work, cyclic Hf-Schiff base polymers were synthesized via direct polymerization of hafnium alkoxide and bis-salen monomers. The defined structure and molecular weight of the polymers were characterized by NMR spectroscopy, gel permeation chromatography and MALDI-TOF mass spectroscopy. The feed ratio of monomers regulated the molecular weight and solubility of the polymers. This synthetic strategy features simple operation under ambient conditions, efficient reaction with high yield and cyclic polymers as the main products. The Hf-Schiff base polymers were converted to HfC/C materials after pyrolysis under argon at 1600 °C, which was identified by XRD measurements, elemental analyses and Raman spectroscopy. This work will inspire more precise and efficient synthesis and applications of metallopolymers.     

Combination of β-elimination and liquid chromatography/quadrupole time-of-flight mass spectrometry for the determination of O-glycosylation sites

Determination of O-glycosylation sites in glycopeptides was developed by using two model compounds designed from mucin2 tandem repeat motif and erythropoietin. β-Elimination/addition reaction using dimethylamine on glycosylated site through a Michael-type condensation produced efficient deglycosylation with appropriate chemical modification. The use of dimethylamine was efficient to release the O-linked glycan in a reaction time period of 2-6 h at 55 °C. Peptide sequencing was then performed using the liquid chromatography/quadrupole time-of-flight mass spectrometry and MS-MS experiments. Interpretation of fragmentation pathways of the β-elimination/addition products enabled straightforward recognition of glycosylation site. Compared to the fragmentation of corresponding native peptides, mass shift of −18 Da or +27 Da was clearly observed for the two kinds of β-elimination/addition products of the glycosylated threonine. Dimethylamine was found to provide higher efficiency of β-elimination/addition than methylamine and ammonia.     

Narrow molecular weight distribution of condensation polymers achieved by adding monomers in many batches

The Z transform method has been used to calculate the molecular weight distribution (MWD) of condensation polymers. The MWD obtained by using Z transform is explicitly discrete. The method is illustrated for two cases: (1) further polycondensation of AB prepolymers with certain initial MWD, and (2) polycondensation of AB and Ar (r is the number of A type functional groups) monomers where AB monomers are added in several batches. In the latter case, it is found that the resulting MWD is much narrower than that of one-batch polycondensation. The trick of producing narrow MWDs of condensation polymers is merely a consequence of keeping AB monomer concentration as low as possible during the reaction in order to suppress the condensation reaction between monomeric AB molecules. The theoretical prediction has been confirmed by Monte Carlo simulation. Therefore, it provides a new possible technique for obtaining narrow MWD polymers through polycondensation reactions.     

Hydrolysis and polycondensation of ethyl silicates. 3. Hydrolysis and polycondensation of ETS40 (ethyl silicate 40) in the presence of water colloidal silica sols

The hydrolysis and condensation of ETS40 (ethyl silicate 40) in the presence of water colloidal silica sols were studied with the aid of gas chromatography, potentiometry and gelation tests. The acids HCl, H₂SO₄, HNO₃, HCOOH, (COOH)₂ and p-toluenesulfonic acid were used as catalysts.

Water—ethanol solutions of the reaction products of the hydrolysis and condensation of ETS40 in the presence of water colloidal silica sols were stable for more than 2 years.

This stability was caused by a low water content in the water—ethanol solutions of the reaction products, a stable pH of about 2.0 and by bonded or non-bonded interactions between ETS40 hydrolysates (ethoxyhydroxysiloxanes) and large particles of water colloidal silica sols.     

Determination of ochratoxin A in meat products by high-performance liquid chromatography coupled to electrospray ionisation sequential mass spectrometry

A method based on liquid chromatography with electrospray ionisation ion trap mass spectrometry, for the determination of ochratoxin A (OTA) in meat products using ochratoxin B (OTB) as an internal standard, is described. Fragmentation patterns of OTA and OTB were studied by sequential mass spectrometry. Trace determination was then accomplished by consecutive reaction monitoring (CRM) of a fragment obtained by MS(3) experiments. This led to a better signal-to-noise ratio and to a higher specificity of the technique. The response to OTA was linear over at least one concentration decade with a limit of detection of 0.6 ng/g. The method was applied to pig tissue samples naturally contaminated by OTA.