Formation of macrocyclic oligoferrocenes: a matrix-assisted laser desorption/ionization mass spectrometric study

Oligomeric ferrocenes were investigated simultaneously by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOFMS). The oligomers were obtained by the reaction of tetrahydro-4,4,8,8-tetramethyl-4,8-disila-s-indacene-3a,7a-diyldilithium (Li(2)L) with FeCl(2).1.5 THF (THF = tetrahydrofuran). Depending on the reaction conditions up to ten linear-chain and eleven cyclic ferrocene oligomers with masses between 1139 and 5071 Da could be detected unambiguously. The most abundant macrocycles contained ten and seven iron atoms when the reactions were carried out at -20 and 25 degrees C, respectively. The chains had cyclopentadienes as end groups and formally resulted from replacing one iron of a cycle by two hydrogens, which corresponds to a mass difference of 54 Da. Copyright 1999 John Wiley & Sons, Ltd.     

Fragmentation Study of Globularin Through Positive and Negative ESI/MS,CID/MS,and Tandem MS/MS

Abstract

The structure of globularin was studied by a mass spectrometric methodology based on the combined use of positive and negative electrospray ionization, collision‐induced dissociation (CID), and tandem mass spectrometry. The mass spectrometry investigation was achieved through in‐source fragmentation of the deprotonated [M?H]^?, protonated [M+H]⁺, lithiated [M+Li]⁺, sodiated [M+Na]⁺, and potassium‐cationized [M+K]⁺ ions. This allowed collision‐induced dissociation spectra of the ionized molecular ions to be obtained to give valuable structural information regarding the nature of both the glycoside and the aglycone moieties and the effect of metal cationization on the CID spectra. Glycosidic fission and ring cleavages of both aglycone and sugar moieties were the major fragmentation pathways observed during collision‐induced dissociation, where the losses of small molecules, the cinnamoyl and the cinnamate parts were also observed. Alkali metal cationization offers additional fragmentation pathways involving cross rings cleavage under CID conditions. Unlike the dissociation of protonated molecular ions, that of metal‐cationized molecules also provides sugar fragments where the C₀ ⁺ fragment corresponding with the glucose ion was obtained as a major daughter peak for all the studied compounds. Even with low abundance, fragment ions coordinated to K⁺ were also observed from [M+K]⁺.     

Analysis of sonolytic degradation products of azo dye Orange G using liquid chromatography-diode array detection-mass spectrometry

In this paper, seven new sonolytic degradation products of Orange G were found and identified using powerful analytical techniques such as liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS), tandem mass spectrometry (MS/MS), and liquid chromatography with diode-array detection (LC-DAD). Each technique provided complementary information for the degradation products identification. In order to resolve the MS and MS/MS spectra obtained, the separation conditions were optimized. Among them, Orange G was unambiguously identified based on its abundant [M-H](-) ion, [M+H](+) ion, ultra-violet and visible spectra, retention time, and tandem mass spectrometric analysis compared with an authentic standard. The seven new degradation products were tentatively identified based on ultra-violet and visible spectra, [M-H](-) ions, and tandem mass spectrometry. The neutral losses of SO(2), SO(3), N(2) and H(2)O for MS/MS spectra which appear to be characteristic of the negative ion mode were observed. Based on this by-product identification, a possible multi-step degradation scheme is proposed. The analysis results of degradation products reveal that the degradation mechanism proceeds via reductive cleavage of the azo linkage, as well as intermolecular dehydration and desulfonation due to the powerful oxidizing hydroxyl radicals as well as hydrogen radical.     

Identification of wheat varieties using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and an artificial neural network

A novel tool for variety identification of wheat (Triticum aestivum L.) has been developed: an artificial neural network (ANN) is used to classify the gliadin fraction analysed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS). The robustness of this novel method with respect to various experimental parameters has been tested. The results can be summarised: (i) With this approach 97% of the wheat varieties can be classified correctly with a corresponding correlation coefficient of 1.0, (ii) The method is fast since the time of extracting gliadins from flour can be reduced to 20 min without significant decrease in overall performance, (iii) The storage of flour or extracts under standard conditions does not influence the classification ability (i. e. the generalisation ability) of the method, and (iv) The classification obtained is not influenced by the identity of the operator making the analysis. This study demonstrates that a combination of an ANN and MALDI-TOFMS analysis of the gliadin fraction provides a fast and reliable tool for the variety identification of wheat. Copyright 1999 John Wiley & Sons, Ltd.     

TOF-SIMS study of cystine and cholesterol stones

Two different human stones, cystine and cholesterol from the kidney and gall bladder, were examined by time-of-flight secondary ion mass spectrometry using Ga(+) primary ions as bombarding particles. The mass spectra of kidney stone were compared with those measured for the standard compounds, cystine and cysteine. Similar spectra were obtained for the stone and cystine. The most important identification was based on the existence of the protonated molecules [M + H](+) and deprotonated molecules [M-H](-). The presence of cystine salt was also revealed in the stone through the sodiated cystine [M + Na](+) and the associated fragments, which might be due to the patient treatment history. In the gallstone, the deprotonated molecules [M-H](+) of cholesterol along with relatively intense characteristic fragments [M-OH](+) were detected.     

ICP-OES分析低钙粉煤灰在NaOH溶液中离子浸出规律

低钙粉煤灰潜在的火山灰活性释放缓慢限制了其大规模利用,通过碱激发提高粉煤灰中Si4+,Al3+和Ca2+等离子浸出率对于加快低钙粉煤灰活性释放具有积极作用。采用电感耦合等离子体发射光谱、傅里叶变换红外光谱、X射线衍射和扫描电子显微镜分别测试和分析了5种浓度NaOH溶液对低钙粉煤灰激发过程中Si4+,Al3+和Ca2+的浸出规律、化学基团变化、水化产物生成及微观形貌演化。结果表明：碱激发作用显著提高了低钙粉煤灰中Si4+,Al3+和Ca2+浸出率,三种离子浸出率大小为：Si4+＞Al3+＞Ca2+,其中Si4+和Al3+浸出率随NaOH浓度增加而增加,随浸出时间延长呈对数规律升高;Ca2+由于在NaOH溶液中生成Ca(OH)₂沉淀,其浸出率大小表现为在水中高,在NaOH溶液中低。红外光谱清晰地表征出低钙粉煤灰受碱激发作用后化学基团在指纹区(波数1 300 cm-1以下)的变化,且随碱激发时间的延长和碱浓度的增加变化愈加明显。水化产物和微观形貌的结果显示出粉煤灰颗粒表面受到碱侵蚀发生解聚,在OH-催化下,硅铝单体分子重新排列形成硅酸盐和铝酸盐低聚络合物,通过亲核取代反应形成铝硅酸盐的低聚态溶胶,并进一步与碱金属阳离子通过配位键或静电键的作用缩聚形成水化凝胶类产物。采用ICP-OES测试粉煤灰中离子浸出率可作为评价粉煤灰火山灰活性的一种快速和准确的方法。     

A single pulse shock tube study of pentene isomer pyrolysis

A single-pulse shock tube study of the four pentene isomers is carried out at 2 ± 0.16 bar and 900–1600 K. C₁ to C₆ species profiles were recorded using gas chromatography mass spectrometry analyses. The species are identified using mass spectrometry and quantified by flame ionization detection. High-pressure limiting and pressure-dependent rate constants for 2M1B, 2M2B and 3M1B + ? were calculated using RRKM theory with a Master Equation (ME) analysis using the Master Equation System Solver, MESS. A mechanism was formulated based on rate rules and theoretical calculations. Comparisons between experimental results and model simulations are provided for all of the five pentene isomers investigated with satisfactory agreement. Furthermore, an insight is provided into the influence of molecular structure on the reactivity of pyrolysis chemistry. Interestingly, it is found that the HACA mechanism is much less prominent for benzene formation compared to the role of cyclopentadienyl radical recombination with methyl radicals and also the recombination of propargyl radicals.     

Endogenous lipase catalyzed transesterification of olive oil fats. The formation of isomeric and oligomeric triacyleglycerols

The role of lipase to catalyze hydrolysis and transesterification of triacylglycerols (TAGs) was evaluated in model systems as well as in virgin olive oil. Tandem mass spectrometry was applied in the identification of modified TAGs, ionized by electrospray, formed during the incubation of selected TAGs with mono and di carboxylic acids. The oligomerization of TAGs was observed in authentic olive oil samples and verified in model systems under catalysis exerted by lipase, whose presence in olive oil was already documented. The hydrolytic pathways taken under enzymatic treatment is balanced by the formation of TAG oligomers that should not alter the nutritional value of the aliment. Copyright ? 2012 John Wiley & Sons, Ltd.     

Electrospray ionization multiple-stage tandem mass spectrometric analysis of diglycosyldiacylglycerol glycolipids from the bacteria Bacillus pumilus

Electrospray ionization (ESI) combined with multiple-stage tandem mass spectrometry (MS(n)) was used to directly analyze the glycolipid mixture from bacteria Bacillus pumilus without preliminary separation. Full scan ESI-MS revealed the composition of picomole quantities of glycerolglycolipid species containing C(14)-C(19) fatty acids, some of which were monounsaturated. Two main components were identified from their molecular masses and fragmentation pathways. The fragmentation pathway of the known compound compared with the investigated compound verified the proposed structure as 1(3)-acyl-2-pentadecanoyl-3(1)-O-[beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl]-sn-glycerols. A comparison of the multiple tandem mass spectra of the different alkali-metal cation adducts indicates that the intensity of fragments and the dissociation pathways are dependent on the alkali-metal type. The basic structures of glycerolglycolipids were reflected clearly from the fragmentation patterns of the sodium cations. The intense fragments of the sugar residue from the precursor ions were obtained from the lithiated adduct ions. ESI-MS(n) spectra of [M + K](+) ions did not provide as much fragmentation as [M + Na](+) and [M + Li](+) adducts, but their spectra allow the position of glycerol acylation to be determined. On the basis of MS(2) spectra of [M + K](+) ions, it was established that all components have a C(15:0) fatty acid at the sn-2 position of the glycerol backbone and C(14)-C(19) acids at the sn-1 position of the glycerol backbone. Copyright 1999 John Wiley & Sons, Ltd.     

MALDI-TOF MS对难溶聚芳酰胺PA6T的分析表征

选用五种样品试剂三氟乙酸、四氢呋喃、甲酸、乙腈、60%乙腈/5%三氟乙酸和两种不同的制样方法,采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)表征难溶性聚合物聚对苯二甲酸己二酰胺(PA6T)的结构和分子量。发现以60%乙腈/5%三氟乙酸为样品试剂所得谱图的分子质量范围和信噪比最大,且溶剂法一步点样优于无溶剂法制样。获得了离子液体中合成产物PA6T的链结构,表明其主链为线性,未发现环状聚合物的存在,存在三种端基结构聚合体： 两端均为氨基或羧基、或一端为氨基另一端为羧基。采用MALDI-TOF MS和SEC两种方法对比测量了PA6T的平均分子量和分子量分布指数,表明MALDI-OF MS测得的平均分子量低于SEC法,分子量分布指数也低于SEC法,这是由于MS处理数据时忽略了低分子量部分,且高分子量部分因难以离子化而无法得到引起的。对于难溶的聚芳酰胺类聚合物的结构和分子量及其分布表征,MALDI-TOF MS仍不失为一个好方法。     

Mass Spectrometry of Oligosaccharides(I)—Formation of the [M+Nh4]+ Ion of Oligosaccharides in Fast Atom Bombardment Mass Spectrometry

In positive-ion fast atom bombardment (FAB) mass spectrometry, when oligosaccharides are mixed with an appropriate amount of NH₄Cl, a highly abundant [M+NH₄]⁺ peak appears in FAB mass spectra. From the adduct ion [M+NH₄]⁺, the molecular weights of oligosaccharides can be determined definitively. This technique may especially be applied to analyze the mixture of oligosaccharides.     

Electrodeposition of polythiophene assisted by sonochemistry and incorporation of fluorophores in the polymeric matrix

This work studies the effect of an ultrasonic field of 530 kHz frequency on the electrodeposition of polythiophene in an acetonitrile solution using lithium perchlorate as background electrolyte. The results obtained show an increase in the polymer mass transfer produced and a more compact and homogenous morphology of the films yielded by sonoelectrochemistry. Electrodeposition of the polymer was also carried out in the presence of the fluorophores Harmane (1-methyl-9H-pyrido[3,4-b]indole) or BCCM (9H-pyrido[3,4-b]indole-3-carboxylic acid methyl ester). Confocal microscopy measurements performed on the films synthesised in the presence of these compounds showed that the latter are embedded in the polymer when it is sonoelectrogenerated at a potential of 2.2, 2.5 or 2.8 V. Films generated in the absence of ultrasound showed no fluorescence.     

Dereplication of known pregnane glycosides and structural characterization of novel pregnanes in Marsdenia tenacissima by high-performance liquid chromatography and electrospray ionization-tandem mass spectrometry

In the search for novel natural products in plants, particularly those with potential bioactivity, it is important to efficiently distinguish novel compounds from previously isolated, known compounds, a process known as dereplication. In this study, electrospray ionization-multiple stage tandem mass spectrometry (ESI-MS(n)) was used to study the behaviour of 12 pregnane glycosides and genins previously isolated from Marsdenia tenacissima, a traditional Chinese medicinal plant, as a basis for dereplication of compounds in a plant extract. In addition to [M + Na](+) and [M + NH(4)](+) ions, a characteristic [M-glycosyl + H](+) ion was observed in full-scan mode with in-source fragmentation. Sequential in-trap collision-induced dissociation of [M + Na](+) ions from 11,12-diesters revealed consistent preferred losses of substituents first from C-12, then from C-11, followed by losses of monosaccharide fragments from the C-3 tri- and tetrasaccharide substituents. A crude methanol extract of M. tenacissima stems was analysed using high-performance liquid chromatography coupled to ESI-MS. Several previously isolated pregnane glycosides were dereplicated, and the presence of an additional nine novel pregnane glycosides is predicted on the basis of the primary and fragment ions observed, including two with a previously unreported C(4)H(7)O C-11/C-12 substituent of pregnane glycosides. This study is the first report of prediction of the structures of novel pregnane glycosides in a crude plant extract by a combination of in-source fragmentation and in-trap collision-induced dissociation and supports the usefulness of LC-ESI-MS(n) not only for dereplication of active compounds in extracts of medicinal plants but also for detecting the presence of novel related compounds.     

一种生物柴油代用品在HZSM-5分子筛催化剂上的催化热解

为了深入了解生物柴油在ZSM-5沸石上的催化反应机理,在常压的流动反应器中进行了生物柴油代用品丁酸甲酯在氢型ZSM-5(HZSM-5)催化剂上的热解和催化热解. 热解产物使用气相色谱-质谱法定性和定量测量. 动力学模型和实验表明,气相中氢提取反应是热解过程中丁酸甲酯分解的主要途径,但在HZSM-5上,丁酸甲酯则主要通过解离生成烯酮和甲醇消耗;与无催化反应相比,丁酸甲酯在HZSM-5上的初始分解温度降低了约300 K. 并且通过Arrhenius方程获得了在催化热解和均相热解条件下丁酸甲酯消耗的表观活化能. 明显降低的表观活化能证实了HZSM-5对丁酸甲酯热解的催化性能. 此外催化剂的活化温度对HZSM-5的某些催化性能具有一定的影响. 该研究对进一步的实际生物柴油燃料的催化燃烧具有一定的指导意义.     

Analysis of cyclic boronated and trimethylsilylated phenolalkylamines by gas chromatography and electron impact mass spectrometry

The side chain of phenolalkylamines containing a bifunctional group was derivatized as the cyclic boronate, and then the residual phenolic group was trimethylsilylated. The resulting derivatives were single reaction products in each case, with good gas chromatographic properties and informative mass spectra to afford prominent molecular ions by gas chromatography with electron impact mass spectrometry (GC/EI-MS). The cyclic boronated-trimethylsilylated derivatives yielded the isotope pattern for boron ((10)B:(11)B =-1:4.2) and characteristic ions [M](+), [M - H](+), [M - CH(3)](+), [M - RBO](+), [M - TMSO](+), and [M - TMSO - C(6)H(5)](+) ions in the mass spectra. In order to distinguish between m- and p-phenolalkylamines, the mass spectra of the cyclic phenylboronated-trimethylsilylated (PBA-TMS) derivatives were compared with those of the trimethylsilylated (TMS) derivatives. The TMS derivatives of octopamine (p-) and norfenefrine (m-) showed identical mass spectra, while the PBA-TMS derivatives had mass spectra sufficiently different from one other to distinguish between the isomers. The most prominent ion of the PBA-TMS derivative is the [M - H](+) ion (m/z 310) for octopamine and the [M](+) ion (m/z 311) for norfenefrine. Copyright 1999 John Wiley & Sons, Ltd.     

Liquid chromatography/mass spectrometric determination of trans-resveratrol in wine using a tandem solid-phase extraction method

Liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization has been successfully applied to the determination of trans-resveratrol (3,5,4'-trihydroxystilbene) in wine. Of a range of analytical conditions that were tested, optimum results were obtained by the use of reversed-phase high performance liquid chromatography (HPLC) using a mixture of methanol and ammonium acetate as the mobile phase. The negative-ion spectrum of trans-resveratrol showed pseudo-molecular ion, [M - H](-), which was the most abundant ion, and low fragment ions corresponding to the losses of hydroxyl groups of the phenol nucleus. Enhanced selectivity for the separation between trans-resveratrol and endogenous wine constituents was afforded by sample purification with a tandem solid-phase extraction method. The approach permits detection at low concentration of trans-resveratrol. The combination of improved sample pretreatment and an isocratic chromatographic system in conjunction with internal standardization forms the basis of a new assay for the quantitation of trans-resveratrol in wine. Full-scan mass spectra were readily obtained from 8 ng of trans-resveratrol, while a limit of detection of 200 pg (signal-to-noise ratio 3) was attained in the selected ion monitoring mode. The application of LC/MS to the determination of trans-resveratrol in wines is demonstrated by the analysis of red wines. Copyright 1999 John Wiley & Sons, Ltd.     

环丙烷衍生物在D2O离子体系中的H/D交换反应

在Ｄ２Ｏ化学反应气条件下环丙烷衍生物的Ｈ／Ｄ交换反应特性,发现了三种新的产物离子（Ｍ＋１）＾＋、（Ｍ＋２）＾＋和（Ｍ＋３）＾＋。应用碰撞诱导碎裂（ＣＩＤ）技术研究了这些离子的碎裂反应特性。实验结果表明三种新的产物离子是由反应物与试剂离子间发生Ｈ／Ｄ交换反应生成的。并获得了环丙烷衍生物结构中活泼氢位置及其数量的信息。     

POLY(3-HYDROXYBUTYRATE)-BASED COPOLYMERS AND BLENDS: INFLUENCE OF A SECOND COMPONENT ON CRYSTALLIZATION AND THERMAL BEHAVIOR*

Isotactic poly(3-hydroxybutyrate) (P3HB) is an aliphatic polyester obtained by bacterial fermentation. This truly biodegradable polymer has been widely investigated, mainly with the aim to replace conventional plastics, which cause environmental pollution. To improve its properties, extensive studies have been conducted to modify it properly by copolymerization or blending with other polymers. Macroscopic properties of polymers, particularly of polymer blends, are strongly affected by their microstructure, especially by the allocation of different phases and their level of dispersion and adhesion. In nonreactive blends, the adhesion level is mainly determined by the similarity between the chemical structure of the components, and the arrangement of the phases is remarkably controlled by the crystallization conditions. The superstructure of the crystalline phases accounts for the mechanical resistance of the blend, but the composition and the distribution of the amorphous phases also play an important role, especially with respect to toughness properties. This article reviews data on thermal properties and the crystallization process of P3HB and its copolymers, both alone and in the presence of other polymers. In particular, copolymers of 3-hydroxybutyrate with 3-hydroxyvalerate and with 4-hydroxybutyrate and blends of P3HB and the copolymers with atactic poly(3-hydroxybutyrate), poly(vinyl acetate), poly(vinyl alcohol), poly(ethylene oxide), poly(methylene oxide), poly(epichlorohydrin), and poly(methyl methacrylate) are considered. Major attention is directed toward the influence of miscibility and composition on solidification kinetics and crystal structure with the objective to provide an overview of the current state of the art.

     

Evidence of simple intramolecular rearrangement at polymer end groups in secondary ion mass spectrometry

Polystyrenes with various end groups were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). These end groups were obtained by termination of the active anionic group by sulfonate or chlorosilane derivatives. Characteristic end group fragments for each sulfonate derivative were observed. On the one hand, for PS capped by methyl sulfonate, or -(CH(2))(4)-O-SO(2)-CH(3), almost complete end group fragment is observed at m/z 95 and a [O-SO(2)-CH(3)](-) molecular structure. On the other hand, when PS is terminated by silyl methyl sulfonate, or -Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3), the most characteristic fragment in the fingerprint secondary ion mass spectrum is located at m/z 153 with [Si(CH(3))(2)-O-SO(2)-CH(3)](+) and the complete end group peak, [Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3)](+), at m/z 201, is absent. According to the molecular structure, characteristic end group secondary ions can be emitted as complete or rearranged fragments. Various silylalkyl alcohol or sulfonate functionalities are analyzed and fragmentation pathways are discussed. To our knowledge, this is the first time that such rearrangement at silyl functions has been observed and demonstrated in fingerprint secondary ion mass spectra. Copyright 1999 John Wiley & Sons, Ltd.