Effects of fullerenes on thermal behaviors of polyethylene glycol

Effects of fullerenes including FS, EFS and pure C₆₀ on thermal behaviors of polyethylene glycol (PEG) have been studied by employing thermogravimetry-differential thermogravimetry (TG-DTG), differential scanning calorimeter (DSC) and off-line furnace-type pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The products were collected by Cambridge filter pad which was widely used in analyzing the combustion products of cigarette. The results showed that the addition of fullerenes obviously restrained the thermal decomposition of PEG. The initial decomposition temperatures (IDT) and maximum decomposition peak temperatures (MDT) were evidently postponed by the addition of fullerenes. Pyrolysis products with one or two hydroxyl end groups obviously increased with the addition of 10% C60. The reasons of the changes were discussed from the aspects of reaction mechanisms.     

GC/MS法测定室内空气中邻苯二甲酸酯类物质

针对室内空气中日益严重的邻苯二甲酸酯类污染,建立了固相萃取柱采样,GC/MS测定室内空气中16种邻苯二甲酸酯类物质的测试方法,可用于评价室内空气质量。     

Synthesis,thermal property and antifungal evaluation of pyrazine esters

Synthesis, thermal properties, as well as antifungal assessment of pyrazine esters were handed in this work. The metal-free esterification of pyrazinyl methanol and acid chloride derivatives in a stoichiometric ratio yielded the following compounds: pyrazin-2-ylmethyl benzoate (3a), (5-methylpyrazin-2-yl) methyl benzoate (3b), 1-(pyrazin-2-yl) ethyl benzoate (3c), 2-(pyrazin-2-yl) ethyl benzoate (3d), pyrazin-2-ylmethyl pivalate (3e). The spectral results totally showed that the synthesis conditions used permitted the compounds to be produced with great yield. The characterization included ¹H NMR, ¹³C NMR, IR, HRMS and organoleptic tests. Their thermal degradation process was examined by using the TG (thermogravimetry) and DSC (differential scanning calorimeter) methods. The pyrolysis products of the pyrazine esters in inert and oxidative atmospheres were analyzed by the Py-GC/MS (pyrolysis–gas chromatography/mass spectrometry) method. It revealed that 3a–3e were totally evaporated throughout the pyrolysis experiments at low temperatures. And they evaporated with high relative contents in pure nitrogen (86.12%–94.17%) and oxidative (75.01%–88.85%) atmospheres, with only a small amount decomposing into a series of substances. Additionally, the in vitro antifungal effects of compounds 3a–3e against R. solani, P. nicotianae, F. oxysporum, F. graminearum, and F. moniliforme were further investigated using the mycelial growth rate methodology. The findings shown that compound 3c has 94% and 80% inhibitor rates at 0.5 mg/ml against R. solani and P. nicotianae, respectively, with an EC₅₀ value (half maximum effective concentration) of 0.0191 mg/ml and 0.1870 mg/ml, respectively. Similarly, that of compounds 3a and 3b exhibited 82% and 91% at 0.5 mg/ml against R. solani, with an EC₅₀ value of 0.0209 mg/ml and 0.0218 mg/ml, respectively. The molecular docking of compound 3c with SDH (Succinate dehydrogenase) was preliminarily performed to reveal the binding modes in active pocket and analyze the interactions between the molecules and the protein.     

Study on pyrolysis behaviors of L-tyrosine-based phthalonitrile resin

The pyrolysis behaviors of l-tyrosine-based phthalonitrile(TPN) resin were investigated by thermogravimetric-Fourier transform infrared spectrometry-mass spectrometry (TG-FTIR-MS) and Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The small molecules produced during pyrolysis process of TPN resin were tracked in real time by TG-FTIR-MS. The larger molecules (m/z > 40) from fast pyrolysis at 900 °C of the TPN resin using Py-GC/MS were identified. From TG-FTIR-MS and Py-GC/MS results, the production pathways of pyrolysis products such as CO₂, CO, NH₃, benzonitrile and phenol were analyzed. The possible pyrolysis mechanism of TPN resin under non-oxidizing gaseous environment was proposed. The results of this study provide the useful information for designing the molecular structure of l-tyrosine-based polymers which possessing high thermal stability.     

Synthesis and thermal degradation kinetics of cellulose esters

Polymers that are biodegradable currently achieve high interest in material science since they offer reductions of landfill space during waste management as well as new end-user benefits in various fields of applications. In this work, cellulose esters such as cellulose benzoate, cellulose succinate and cellulose cinnamate were prepared using dimethylaminopyridine along with dimethylaminopyridine-p-toluene sulfonic acid catalyst. Films of cellulose esters were cast from solution. Cellulose esters were characterized by spectral methods such as infrared, nuclear magnetic resonance, thermal method such as thermogravimetric analysis. Various methods of kinetic analysis were compared in the case of thermal degradation of the cellulose and cellulose esters. Copyright­© 2003 John Wiley & Sons, Ltd.     

气相色谱-串联质谱法测定土壤中的邻苯二甲酸酯

建立了土壤中6种邻苯二甲酸酯的气相色谱-串联质谱(GC-MS/MS)分析方法。土壤样品用超声提取,以二氯甲烷-丙酮(1:1, v/v)混合溶液为提取溶剂,提取液经Florisil小柱净化后,经HP-5MS色谱柱(30 m×0.25 mm×0.25 μm)分离,利用MS/MS的多反应监测(MRM)模式进行定性和定量。结果表明本方法可对样品中的邻苯二甲酸酯进行分析,在10～1000 μg/L质量浓度范围内,线性关系良好,相关系数为0.9973～0.9976;6种邻苯二甲酸酯的相对标准偏差(RSD)不大于14.3%, 2 μg/kg和10 μg/kg两个加标水平的回收率为72.9%～106.2%; 6种目标化合物的检出限为0.1～0.5 μg/kg。该方法快速准确、背景干扰较少、分析灵敏度较高,适用于土壤样品中邻苯二甲酸酯的分析。     

Pyrolysis-GC/MS of Menthyl Esters of N-Benzoxycarbonyl Amino Acid

With the aid of a Pyrolysis-GC/TOF MS technique,the pyrolysis behaviour of two menthyl esters of N-benzoxycarbonyl amino acid was investigated.A clear pattern emerges involving the cleavage of the bond linking the menthyl ring to the carboxy group,followed by further degradation of the fragments.The major pyroproducts were p-menth-1-ene pyrolysed at a higher temperature or p-menth-2-ene pyrolysed at a lower temperature,and va-rious derivatives of cyclohexene pyrolyzed from the menthyl ring.In addition,some ...     

Preparation of unsymmetrical dialkyl acetylenedicarboxylates and related esters by enzymatic transesterification

An unexpected highly selective mono-transesterification of symmetrical acetylenedicarboxylates with various alcohols occurred in the presence of Candida rugosa lipase. This reaction allows an efficient preparation of unsymmetrical acetylenedicarboxylates and related α,β-acetylenic esters.     

Studies on thermal degradation of benzylidene malononitriles

Thermal decomposition studies have been carried out using flash vacuum thermolysis (FVT) to find out the decomposition temperature for benzylidene malononitriles (BMNs) including 2-chlorobenzylidene malononitrile (cs), a widely used riot control agent. The FVT studies have been carried out in a specially designed all glass assembly at various temperatures ranging from 300 to 600°C. A number of rearranged products along with hydrogen cyanide were obtained as major decomposition products. The products were analysed and the structures were confirmed by GC/MS. the thermal behaviour of BMNs has also been investigated by TG under nitrogen atmosphere. These studies show that the pyrotechnic mixture for tear gas munitions should not have burst temperature above 300°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

生物质主要组分低温热解研究

利用热重分析仪和裂解气质联用仪进行生物质主要组分低温热解特性研究。热重实验结果表明,生物质主要组分的热稳定性为：纤维素>木质素>半纤维素。半纤维素主要热解温度在210℃～320℃,而纤维素和木质素的主要热解温度分别在310℃～390℃和200℃～550℃。裂解气质联用实验考察不同温度对生物质主要组分低温热解产物的影响。半纤维素热解产物主要有乙酸、1-羟基-丙酮和1-羟基-2-丁酮,纤维素热解产物主要包括左旋葡聚糖和脱水纤维二糖,而木质素热解产物主要是邻甲氧基苯酚。     

A GC/MS Method of Determining Airborne DI-n-Butyl- and DL(2-Ethyl Hexyl) Phthalates

An analytical technique is presented that determines the amount of airborne phthalates in a glass fiber filter. The methodology makes use of a GC/MS system that has been integrated with a dedicated mini-computer.     

溴化环氧树脂印刷线路板热分解机理实验研究

印刷线路板广泛应用于电子电器产品中,随着大量电子废弃物的产生,印刷线路板的回收处理得到了广泛关注.     

豆类秸秆两级热解特性研究

利用热裂解仪-气相色谱/质谱联用仪(Py-GC/MS)对黄豆秆进行了两级热解。结果表明,随着第一级热解温度(t1)的升高,第一级热解产物总峰面积逐渐增大,第二级热解产物总峰面积逐渐减小;在第一级热解产物中,酸类、酮类和呋喃类等源于纤维素和半纤维素的产物含量在t1为400和450℃时较高;在t1为450和500℃的条件下,第二级热解产物中烃类产物的含量高达20%以上。两级热解可以在第一级和第二级热解中分别获取不同的高含量产物,如乙酸、糠醛、愈创木酚、甲苯和苯等,实现生物质的选择性热解。     

Synthesis and thermal decomposition of mixed Gd-Nd oxalates

Several (Gd_1−xNd_x)₂[C₂O₄]₃·nH₂O samples (0≤x≤1) were prepared by a coprecipitation method: the precipitation is quantitative and all the samples are homogeneous in stoichiometry. XRD analyses have shown that a complete solid solution is formed over the whole range of compositions. The dried Gd rich oxalates have initially a low water content which gradually increases with the Nd content. All the oxalates decompose in O₂ around 700°C either into a single mixed oxide or in a mixture of oxides through several steps, which can be ascribed to the loss of water and CO₂.     

Simultaneous separation and determination of 16 testosterone and nandrolone esters in equine plasma using ultra high performance liquid chromatography-tandem mass spectrometry for doping control

The potential for using testosterone and nandrolone esters in racehorses to boost the biological concentrations of these steroids and enhance athletic performance is very compelling and should be seriously considered in formulating regulatory policies for doping control. In order to regulate the use of these esters in racehorses, a sensitive and validated method is needed. In this paper, we report such a method for simultaneous separation, screening, quantification and confirmation of 16 testosterone and nandrolone esters in equine plasma by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Analytes were extracted from equine plasma by liquid-liquid extraction using a mixture of methyl tert-butyl ether and ethyl acetate (50:50, v/v) and separated on a sub-2 micron C(18) column. Detection of analytes was achieved on a triple-quadrupole mass spectrometer by positive electrospray ionization mode with selected reaction monitoring (SRM). Mobile phase comprised 2 mM ammonium formate and methanol. Deuterium-labeled testosterone enanthate and testosterone undecanoate were used as dual-internal standards for quantification. Limits of detection (LOD) and quantification (LOQ) were 25-100 pg/mL and 100-200 pg/mL, respectively. The linear dynamic range of quantification was 100-10,000 pg/mL. For confirmation of the presence of these analytes in equine plasma, matching of the retention time with mass spectrometric ion ratios from MS/MS product ions was used. The limit of confirmation (LOC) was 100-500 pg/mL. The method is sensitive, robust, selective and reliably reproducible.     

Characterization of fatty acid methyl esters by thermal analysis

The thermal stability of selected straight-chain (C₆-C₁₄) esters of fatty acids has been studied by TG-DTG and DTA analysis. In DTG, a peak is detected between 84° and 125° C followed by a main effect in the range 105°–215°C, whereas in DTA only an exothermic peak appears in the range of 126.5° to 187°C (onset temperatures). The temperatures of these effects have been related with ignition points, molecular weights and boiling points. The characteristics of melting and recrystallization of the above fatty acid methyl esters and those with carbon numbers between C₁₄ and C₂₄ have been established by DSC along the melting range between ?83° and 50°C. Polymorphism appears in caproic, heptanoic, palmitic and stearic acid methyl esters.     

湖泊沉积物中邻苯二甲酸酯类的GC／MS分析

东湖沉积物阴干后用二氯甲烷溶剂萃取，用ＤＢ－５弹性石英毛细管柱ＧＣ／ＭＳ分离鉴定，并结合ｍ／ｚ１４９质量色谱图，确证东湖沉积物中含有９种邻苯二甲酸酯类化合物，它们是邻苯二甲酸二乙酯、二异丁酯、二正丁酯、二己酯、己基辛基酯、二－（２－乙基己基）酯、二辛酯、己基癸基酯和辛基癸基酯，其特征离子及峰度见表１。     

Primary reactions of sucrose thermal degradation

Thermal degradation of sucrose at 185 °C in a closed glassware and presence of air was studied with the help of GC/MS after acetylation of reaction products. Also model compounds were used to support the mechanism of thermolysis. Goal was to identify all the primary reactions of the process. It was observed that already after 5 min of treatment, two glucopyranose isomers were formed as products of sucrose glycosidic bond splitting. The furanose structure is probably transformed to anhydrofructoses, as 2,6-anhydrofructose was identified among the degradation products in much smaller amount than -glucose. At longer thermolysis times some diastereoisomers of sucrose, anhydrosucroses, and anhydroderivatives of monosaccharides were identified as minor products of parallel primary and secondary reaction. After 30 min at 185 °C there was no sucrose present in the reaction mixture, but some new products with longer retention times (RT) occurred. Also isomers of levoglucosan were observed after 1 h of treatment. This indicates that splitting of glycosidic bond is the most prominent primary reaction. The dehydration towards anhydrosucroses seams to be a minor primary reaction and might proceed via configuration changes on the pyranose ring.     

The pharmacokinetic characteristics and excretion studies of fucosterol from Sargasssum fusiforme in rats

Fucosterol is the main phytosterol in brown algae with various pharmacological effects such as cholesterol-lowering, anticancer, hepatoprotection and neuroprotection. Little is known about the pharmacokinetics and excretion characteristics of fucosterol. In this study, a GC–MS method was developed and validated for the determination of fucosterol in rat plasma, urine and feces. The method effectively avoids the interference of Δ⁵-avenasterol, a cis–trans-isomer of fucosterol derived from feed, by using a TG-5 capillary column (a nonpolar column with 5% phenyl-methylpolysilicone as stationary phase material). The linearity ranges were fucosterol 0.300–18.0 μg/ml (R² = 0.9960) for plasma, 0.0500–2.50 μg/ml for the urine sample (R² = 0.9963) and 0.100–8.00 μg/mg (R² = 0.9923) for the feces sample. With good extraction recoveries and stability, this rapid and sensitive method was successfully applied to the pharmacokinetic and excretion studies of fucosterol in Sprague–Dawley rats. Fucosterol from Sargassum fusiforme had poor absorption and slow elimination with an absolute oral bioavailability of 0.74%, and was mainly eliminated through fecal excretion.     

Polymer bound pyrrole compounds,VII: Xanthobilirubinic acid esters and amides from an insoluble,polystyrene-supported precursor

Summary A series of xanthobilirubinic acid (XBR) esters (i.e.,1c to1p) and amides (2a–2c) have been prepared by a procedure involving detachment of the chromophore previously ester-bound to a functionalized, insoluble polystyrene (1b). Detachment is achieved by treatment with the respective alcohol in aqueous alkali or with the amines, yielding directly the corresponding esters or amides. With primary, short-chained alcohols the ester yields are high (60% forn-C₄H₉-OH to 99% for C₂H₅-OH), but decrease rapidly with chain length (40% forn-C₁₀H₂₁-OH and 0% forn-C₁₆H₃₃-OH). The same trends are observed with the amines. These results are interpreted in terms of an (increasingly) unfavourable entropic interaction between the polymer matrix to which the chromophore is bound and the (growing) alcohol chain. The impairment by the long chained nucleophile to reach the transesterification center could also contribute, and, for the most lipophylic alcohols, their low solubility in aqueous alkali is an additional drawback. With secondary and tertiary alcohols, no ester is obtained, in agreement with a B_AC2 mechanism involving a tetrahedral intermediate.

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Polymergebundene Pyrrolverbindungen, 7. Mitt.: Darstellung von Xanthobilirubinsäureestern und-amiden, ausgehend von einer unlöslichen polystyrolgebundenen Vorstufe

Zusammenfassung Unlösliche, durch eine Estergruppe an Polystyrol gebundene Xanthobilirubinsäurederivate liefern mit Alkoholen die monomeren Ester (1c–1p), mit Aminen die monomeren Amide (2a–2c). Die Ausbeuten für primäre kurzkettige Alkohole sind hoch (n-C₄H₉-OH: 60%, C₂H₅-OH: 99%), mit steigender Kettenlänge sinken sie rasch (n-C₁₀H₂₁-OH: 40%,n-C₁₆H₃₃-OH: 0%). Denselben Trend beobachtet man bei Aminen. Die Ergebnisse werden durch eine zunehmend ungünstige entropische Wechselwirkung zwischen Chromophor an der Matrix und Alkohol interpretiert. Durch die steigende Kettenlänge des Alkohols könnte auch aus räumlichen Gründen die Annäherung des Nucleophils an das Reaktionszentrum erschwert werden. Die geringe Löslichkeit der höheren lipophilen Alkohole in wäßrigem Alkali wirkt sich ebenfalls ungünstig auf den Reaktionsverlauf aus. Für sek. und tert. Alkohole wird keine Reaktion erhalten, wie es für einen B_AC2-Mechanismus mit tetraedrischem Zwischenprodukt zu erwarten ist.