脂二胺在颜料分散体中光化学反应活泼自由基的ESR研究

用自旋捕捉技术与ESR相结合的方法研究了脂二胺在ZnO、TiO_2的庚烷或苯的分散体系中光诱导的电子转移过程。观察到DMPO与氮中心自由基加合物的ESR信号,表明捕捉到的自由基是脂二胺与光生空穴作用而产生的胺的阳离子自由基。     

有机锡聚合物的研究概况

<正> 有机锡聚合物是一类重要的金属有机聚合物。在大分子链中引进有机锡基团而得到的有机锡聚合物,在有机合成催化剂、生物高分子、防污涂料、水处理剂、涂料固化剂、抗细菌剂和光敏剂等方面,应用相当广泛。有机锡聚合物可分为两类:一类是锡原子在大分子主链上的有机锡缩聚物;另一类是锡原子在大分子主链侧基上的有机锡加聚物。一、有机锡缩聚物二烷(芳)基锡和三烷(芳)基锡化合物与单烷(芳)基锡和四烷(芳)基锡化合物比较,具有更独特的性能,因而得到较多     

酞花菁及金属酞菁化物紫外光解的ESR研究

在较强的紫外辐射作用下,即使较为稳定的酞菁化合物也可能发生光解。水文用自旋捕捉与ESR技术相结合的方法检出了在光解中生成的氮中心自由基。     

粉末涂料领域有机锡限制及检测方法综述

有机锡化合物常被用作催化剂应用于粉末涂料用聚酯树脂合成过程。文中简述了有机锡的毒性及粉末涂料领域对有机锡的限制,主要限制法规为欧盟玩具安全新指令及参照其制定的相关标准。介绍了针对各法规限制来检测有机锡或锡元素的几种检测方法及其优缺点。按法规推荐可选气相色谱-质谱联用法(GC-MS)检测有机锡,而作为内部质量控制则可选电感耦合等离子体-质谱法(ICP-MS)及电感耦合等离子体发射光谱法(ICP-OES),生产厂家可配备X射线荧光光谱仪(XRF)快速低成本测试产品与原材料中锡元素。     

气相色谱-质谱联用法测定PVC塑料制品中的微量有机锡

建立了一种可同时测定聚氯乙烯(PVC)塑料制品中一丁基锡、二丁基锡、三丁基锡、四丁基锡、一辛基锡、二苯基锡和三苯基锡等7种有机锡化合物的气相色谱-质谱(GC-MS)检测方法。利用三水合二乙基二硫代氨基甲酸钠(NaDDTC)与有机锡的螯合作用,以甲醇-NaDDTC水溶液(2%,m/v)的混合溶液浸取PVC样品中的有机锡,经四乙基硼酸钠(NaBEt4)水溶液衍生化后,用正己烷萃取分离,再进行GC-MS的定性定量分析。对样品前处理过程、衍生化条件、色谱条件等进行了优化,并考察了方法的线性关系、检出限、回收率和精密度等。方法的线性范围为0.1～50.0 mg/L,线性相关系数为0.999 0～0.999 8。有机锡化合物的检出限为0.005～0.025 mg/L,样品加标回收率为87.64%～110.16%,相对标准偏差皆小于10%。结果表明,该法简便、灵敏,能很好地应用于PVC制品中微量有机锡的测定。     

活泼中间体的自旋捕捉技术——高压液相色谱-电子自旋共振研究方法

本文尝试用自由基捕捉技术——高压液相色谱-电子自旋共振相结合的方法,对反应体系中同时存在的几种自由基先进行捕捉,再对其自由基加合物进行分离,尔后逐一加以鉴定,并以Ph_3M(M=P、As、Sb、Bi)的光解实例说明这种方法是可取的。     

含杂原子羧酸类有机锡化合物的结构研究

有机锡羧酸酯是有机锡化合物中较为常见的一种,对其研究也最为深入。而含有氮、氧、硫等杂原子的羧酸配体由于含有多个供电中心,与锡反应能够生成结构更加复杂有趣的化合物。研究和探讨这些有机锡化合物的结构特点,既能对有机锡化合物结构的复杂性有更加充分的认识,也对以后探索实际应用有一定的启发意义。     

有机锡化合物及聚合物

一、有机锡化合物有机锡化合物(RnSnX_4-n)是Tisdale在1943年申请的专利中提出的,但当时未能引起重视,直到1950年锡研究所在UtrechtT.N.O发起研究后,有机锡化合物的应用才被公认具有现实意义。今天,有机锡已在全世界得到广泛应用。据1975年的有关资料统计,全世界消耗的有机锡至少达25000吨,而作为杀虫、防污目的用的有机锡约占10000吨。有机锡化合物种类很多,通常有以下四     

Irganox(R) HP-136的稳定机理及在PP稳定过程中的作用

Irganox(R) HP-136(3-芳基-苯并呋喃酮)是一种高效的自由基捕捉剂,它能有效地捕获以碳为中心的自由基,许多实验表明它在聚合物稳定过程中起到了重要的作用.本文比较了Irganox(R) HP-136与传统抗氧剂的抗氧机理,并分析了其在PP稳定过程中的作用.     

PVC塑料制品中有机锡分析的气相色谱-质谱法

建立了1种高效测定聚氯乙烯(PVC)塑料制品中一丁基锡、二丁基锡、三丁基锡、四丁基锡、一辛基锡、二苯基锡和三苯基锡等7种有机锡化合物的气相色谱-质谱(GC-MS)检测方法。以四氢呋喃盐酸溶液溶解PVC样品,超声提取其中的微量有机锡,经四乙基硼酸钠(NaBEt4)水溶液衍生化后,用正己烷萃取分离,再进行GC-MS的定性定量分析。对样品前处理、衍生化条件等进行优化,并考察了方法的线性关系、检出限和精密度等。对实际PVC样品进行测定,检出3种丁基锡,样品加标回收率为84.14%～111.71%,相对标准偏差皆小于10%。结果表明:该法简便、灵敏,能很好地应用于PVC制品中有机锡的测定。     

Carbon radicals generated by solid polymers: Electron spin resonance spectroscopy for detection of species in water

Radicals generated in plastic medical devices (solid phase) by γ-rays or electron-beam irradiation during sterilization are known to cause oxidation of protein drugs, resulting in a loss or reduction in drug efficacy. The generation of radical species in water by the radical species in solid polymers has not been proved. Using electron spin resonance (ESR) spectroscopy, we confirm the generation of new radicals in water by γ-ray irradiated cyclic olefin polymers (COP). ESR measurements are obtained using 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) as a spin probe and 5-(2,2-dimethyl-1,3-propoxycyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO) as a spin trap, in which the irradiated COP was immersed. The ESR signals indicate the TEMPOL radicals decline over time, suggesting the generation of new radicals. Conversely, the characteristic ESR signals of the adduct formed by the reaction between CYPMPO and the hydroxyl radical are observed. Thus, hydroxyl radicals are generated because of the migration of the radicals from COP to water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48604.     

Kinetic Study of Hydroperoxide Degradation in Edible Oils Using Electron Spin Resonance Spectroscopy

Lipid oxidation is a complex phenomenon involving free radicals which are highly reactive molecular species. The life-time of these radical species is extremely short and their detection is therefore difficult. Several electron spin resonance (ESR) spectroscopy methodologies make it possible to identify, quantify and measure the reactivity of radical species formed during oxidation–reduction reactions. In this study we took advantage of the specificity of ESR spectroscopy to detect radical compounds in order to determine the rate constants of hydroperoxide degradation, a key reaction involved in lipid oxidation. The interaction of 5-doxyl stearic acid and lipid-derived radicals was studied by following the intensity of ESR spectra. A kinetic model was developed to simulate data analysis obtained by ESR and values of rate constants for hydroperoxide degradation were determined at 100 and 110 °C. This quantitative approach of ESR spectroscopy has produced useful information about new rate estimates for hydroperoxide degradation in edible oils.     

对二嗪N,N`—二氧化物光还原的电子自旋共振研究

报道了利用原位电子自旋共振(ESR)技术研究对二嗪N,N′-二氧化物光解的结果。研究结果表明,化合物5,6,7和8通过光还原过程从溶剂分子夺取氢原子分别生成稳定的自由基,记录出它们分辨良好的ESR谱。文中还讨论了对二嗪N,N′-二氧化物的光化学反应的自由基机理。     

ESR study of vulcanizates under the deformed state

Electron spin resonance (ESR) measurements under the tensile deformation of cross‐linked polyisoprene were examined by the combination of home‐built stretching machine with commercially available ESR spectrometer. The changes of radical concentration during tensile deformation were successfully determined by this technique. It was found that the number of radicals produced by the stretching process decreased during the retraction of stretched sample. In addition, at a given strain, the decrease of radical concentration with time was accompanied by the increase of stress. Such changes were more prominent in the cross‐linked sample by sulfur PS sample (PS) than by dicumyl peroxide (PCP), PD sample (PD). The tensile modulus of the samples after the one cyclic deformation increased with increasing the keeping time at room temperature after the cyclic deformation. The increase was larger for the PS than for the PD. These results suggest that the broken cross‐linking structure induced by the stretching process was partly reconstructed during and after the retraction with this tendency more prominent in the PS than in the PD. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermally induced homolytic scissions of interunitary bonds in a softwood lignin solution: A spin‐trapping study

Unstable chemical species, that is, radicals generated by the thermal treatment of a dimethyl sulfoxide (DMSO) solution of the lignin of a softwood, Yezo spruce (Picea jezoensis Carr.), were studied in detail with an electron spin resonance (ESR) method combined with a spin‐trapping technique. An unstable secondary carbon radical (～CH ·) in the solution was trapped as a stable nitroxide spin adduct [R? (N? O ·)? CH～ (R = tert‐butyl benzene)] when the DMSO solution was heat‐treated in the presence of a spin‐trapping reagent [2,4,6‐tri‐tert‐butylnitrosobenzene (BNB)] at about 40°C. This meant that alkyl phenyl ether bonds (～CH? O‐phenyl), known as interunitary lignin bonds, were homolytically scissioned by the thermal treatment in the lignin solution. A detailed analysis of the ESR spectrum revealed that three kinds of radicals—primary (～CH₂ ·), secondary (～CH ·), and tertiary (～C ·) carbon radicals—were trapped as stable spin adducts at about 60°C, although the phenoxy radical (Ph? O ·) was not trapped by the BNB spin trap as the counter radical of the secondary carbon radical. This suggested that a fairly large steric hindrance existed between the so‐called guaiacoxy radical with a methoxy group in the ortho position and the BNB molecule bearing two butyl groups as bulky moieties in the ortho positions. However, the phenoxy radicals in the lignin solution were stable up to about 60°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2136–2141, 2004     

利用ESR技术研究α—蒎烯β—蒎烯光敏氧化反应机理

本文主要利用电子顺磁共振自旋捕获技术研究９,１０－二氰基蒽敏化α－蒎烯,β－蒎烯光氧化反应,提供了在乙腈中α－蒎烯和β－蒎烯的光氧化反应过程中存在超氧负离子基和单重 氧的直接证据;在四氯化碳溶剂中只捕获到＾１Ｏ２;在正己烷中没有捕获到Ｏ＾－２或＾１Ｏ２．ＥＳＲ实验结果进一步证明在乙腈中光敏氧化反应的＾１Ｏ２可能来自Ｏ＾－２和反应底物α－β,蒎烯正离子自由基之间的电荷复合。     

Spin-Polarised (by CIDEP) Silicon-Containing Radicals

Polarised ESR signals, observed from silicon-centred radicals produced by irradiation of either di-tert butyl peroxide or acetone in the presence of a silicon hydride, are presented and analysed. The novel feature that radical pair mechanism CIDEP can be used to accentuate weak sidebands due to radicals containing rare isotopes (here ²⁹Si) is demonstrated. Adduct radicals formed by reaction with maleic anhydride and vinyltrimethylsilane were also studied. With the former, the adduct produced and observed in early-time experiments remains the same at room temperature and above; in steady-state studies this has been reported not to be so.     

Formation of Polar Compounds During Deep‐frying—Determination by 1H NMR and ESR

The present study aims to elucidate the factors influencing the generation of polar compounds in oils during deep‐frying. Oils with different fatty acid compositions, including palm oil (PO), refined palm kernel oil (RPKO), and refined coconut oil (RCO), are applied in successive frying processes. ¹H NMR spectra reveal that heated PO has a higher percentage of allyl acyl group and is more prone to formation of non‐polar dimeric triglycerides as compared to other types of oils. In addition, electron spin resonance (ESR) spectra indicate that alkyl radicals are more predominant than alkoxy radicals in heated PO. In contrast, RPKO and RCO are inclined to generation of alkoxy radicals during the thermal treatment. The results reveal that oils with high unsaturated fatty acid content are more prone to generation and oxidation of non‐polar dimeric triglycerides. Practical Applications: The change in free radical profile and concentration is one of the indicators of lipid oxidation and polymerization. Alterations in the levels of alkyl and alkoxyl radicals, revealed by ESR, can be used to illustrate the formation of polar compounds in deep‐fried oils with different fatty acid compositions. The percentage of allyl acyl group, revealed by ¹H NMR, can be used to predict the generation of polar compounds. Therefore, this study provides useful information for the development of different methods to reduce polar compound formation in oils during thermal processing depending on the fatty acid composition of different deep‐fried oils.