羟基自由基检测方法的研究进展

羟基自由基氧化是高级氧化技术重要的机理之一,也是研究的难点之一。本文归纳总结了测定羟基自由基的几种方法,并探讨了各种方法存在的问题,提出了新的检测方法所应具备的特点。     

对羟基苯甲酸乙酯印迹聚合物固相微萃取制备及条件优化

采用分子印迹技术,以对羟基苯甲酸乙酯(模板分子):α-甲基丙烯酸(功能单体):乙二醇二甲基丙烯酸酯(交联剂)摩尔比为1∶4∶20,反应温度为80℃,反应时间为15h,本体聚合的方法合成印迹聚合物。利用微量进样器和玻璃毛细管自制分子印迹固相微萃取装置。将自制固相微萃取与气相色谱联用,并对萃取头的萃取条件如萃取温度、萃取时间、解析时间、溶液离子强度等进行优化。通过选择性吸附实验测得,分子印迹固相微萃取对对羟基苯甲酸甲酯、对羟基苯甲酸乙酯和对羟基苯甲酸丙酯的萃取量分别为103.54、134.26和114.68μg,均大于非分子印迹固相微萃取的萃取量47.88、49.24和41.41μg,印迹萃取头表现出了良好的吸附性和选择性。     

气相色谱法测定食品中对羟基苯甲酸酯类防腐剂含量

通过试验建立了一种采用气相色谱法检测食品中对羟基苯甲酸酯类(乙酯和丙酯)含量的方法。样品在酸性条件下用混合萃取剂(正乙烷+乙醚,体积比1∶9)萃取后,经碳酸氢钠溶液洗涤净化,浓缩定容,用HP-5熔融石英毛细管柱分离并用氢火焰检测器检测。采用保留时间定性和外标法定量的分析方法进行测定。对羟基苯甲酸乙酯在50～800μg/mL的浓度范围内,线性相关系数R为0.9992,加标回收率在89.95%～98.35%之间,相对标准偏差为3.29%;对羟基苯甲酸丙酯在50～800μg/mL的浓度范围内,线性相关系数R为0.9997,加标回收率在94.30%～102.11%之间,相对标准偏差为2.83%。该方法测定结果准确可靠,且稳定性好,灵敏度高。     

食品中对羟基苯甲酸酯类的检测方法研究进展

对羟基苯甲酸酯类由于其颇具争议的雌激素活性和在食品中的广泛使用使其在检测方面受到极大的关注。目前主要的检测方法有毛细管电泳法、气相色谱法、液相色谱法、质谱法。主要综述了食品中对羟基苯甲酸酯类检测方法的研究状况。并对样品前处理方法和检测技术进行了分析和比较,包括这些检测方法的原理、适用范围、技术参数和优缺点等,旨在为建立简单高效且经济准确的检测技术提供参考。     

化妆品中对羟基苯甲酸酯的检测

主要介绍了采用层析法，气相色谱，高效液相色谱和毛细管电泳法对化妆品对羟基苯甲酸酯的检测，并提出了检测方法的最新进展和趋势。     

羟基自由基的特性及检测方法比较

文章对水体中羟基自由基检测进行了概述,介绍了羟基自由基的特性,并对羟基自由基的各种检测方法如电子自旋共振波谱法(ESR)等进行了分析。通过比较各种方法,发现无论是间接测定还是直接测定,干扰因素都较多,影响了测定的准确度。对此,文章最终提出了羟基自由基检测比较好的方法:利用不同分析手段相结合来提高分析效果的方法。     

羟基自由基活性氧用于中水处理

羟基自由基在液相中的氧化电势为2.8 V,能够破坏微生物通透性屏障,破坏病原微生物的蛋白质、酶和核酸,导致病原微生物的死亡.在现场进行的中水灭菌实验中,当药剂质量浓度为38.2 g/L,投加量为O.14 kg/t时,大肠杆菌杀灭率可达到99.9%以上.同时,水体中的COD降低50%、NH3-N降低35%.羟基自由基制备原料为空气、水和电解质溶液,在常温常压条件下进行,无三废排放,兼具安全性和环境友好性.实践证明:它是替代氯气消毒的优选消毒品种.     

Fenton法中的羟基自由基的测定技术简介

Fenton法是一种高级氧化技术(Advanced Oxidation Technologies,AOTs),它是由过氧化氢与催化剂Fe2 所构成的氧化体系产生两种活泼的氢氧自由基(HO2.和.OH),从而引发和传播自由基链反应,加快有机物和还原性物质的氧化。本文简要介绍了羟基自由基(.OH)的形成及反应机理,并着重介绍了测定羟基自由基的方法及其进展趋势。     

葵花壳中绿原酸微波协助萃取工艺及清除羟基自由基的研究

以葵花壳为原料,以乙醇为萃取剂,在单因素实验基础上,研究了葵花壳中绿原酸的微波协助萃取工艺。采用正交试验法优化工艺条件,结果表明,最佳工艺条件为:乙醇浓度60%,料液比(原料质量与萃取剂体积之比)1:20(g/mL),微波温度60℃,微波功率300 W,pH值6,在此最佳工艺条件下,葵花壳中绿原酸提取率为5.862 mg/g。对葵花壳绿原酸粗提取物进行清除羟基自由基实验,研究表明,葵花壳中的绿原酸有较强的抗氧化性,且随着浓度的升高,对羟基自由基的清除效果更好,清除能力更强,其最大清除率为60.42%。     

对-羟基苯甲酸苄酯合成方法的改进

用对 羟基苯甲酸和氯化苄为原料 ,以二甲基亚砜 (DMSO)为溶剂 ,采用改进工艺合成对 羟基苯甲酸苄酯。结果表明 ,n(酸 )∶n(氯化苄 ) =1 0 0∶1 6 0 ,反应温度 134℃ ,反应时间 3 5h ,产率达 96 4 % ,产品质量分数 99%     

植物添加剂降低卷烟烟气自由基研究进展

卷烟烟气自由基是一种典型有害物质,对人体有很大的毒害作用。本文介绍了烟气中有毒成分自由基的形成、性质及对人体的危害,并介绍了对植物添加剂降低清除烟气自由基的研究进展。     

微纳米气泡形成羟基自由基的研究进展

从微纳米气泡溶液中是否可以产生·OH、·OH的鉴别方法、·OH的生成机理以及强化·OH的生成等几个方面论述了微纳米气泡溶液中生成·OH的研究进展.电子自旋共振技术和荧光分光光度法作为检测·OH的2种技术,均存在一定的误导性,对于荧光分光光度法,最重要的就是排除H2 O2的干扰.此外,目前要获得含有高浓度·OH的微纳米气...     

卷烟主流烟气中烟草特有亚硝胺的测定

建立了一种高效液相色谱-串联质谱联用法测定卷烟主流烟气中烟草特有亚硝胺的方法。采用含10ng.mL-1内标的0.1mol.L-1乙酸铵溶液直接对收集了主流烟气的剑桥滤片进行超声萃取30min,过膜后的萃取液用带电喷雾装置的LC-MS/MS仪进行分析。该方法数据可靠、操作简单、重复性好。     

Particle-Gas Equilibria of Ammonia and Nicotine in Mainstream Cigarette Smoke

The particle-gas equilibria of ammonia and nicotine in mainstream cigarette smoke have been studied by diffusion denuder collection. The surface deposition rate of nicotine is observed to decrease as the smoke traverses the denuder, and this effect is attributed to a changing particle nicotine vapor pressure driven by the measured rapid loss of volatile ammonia from the particles, an interpretation that differs from that of prior studies. The rapid ammonia deposition is observed to be complete at a length-to-flow rate ratio of 28 s/cm 2 for an American blended cigarette, and ～38% of the total ammonia analyzed in the collected smoke appears to be nonvolatile in the aerosol, possibly bound in the particles by reaction with acids. Fitting of a theoretical model that predicts the rapid ammonia loss and changing nicotine vapor pressure to the measurements predicts that the nicotine vapor pressure over the particles in fresh smoke is about 6% of the pure component nicotine value, and the ammonia vapor pressure over the smoke particulate is considerably less than that predicted by its aqueous Henry's law coefficient. Dilution of mainstream smoke enhanced the fractional deposition of both ammonia and nicotine in the denuder tubes and provided a means to estimate the nonvolatile ammonia fraction, which varied considerably in cigarettes made with different tobacco types. Among the different tobacco type cigarettes, smoke ammonia concentration, "smoke pH," and smoke nicotine-to-particulate ratio varied with ammonia and nicotine deposition from diluted smoke when extreme values for an all burley tobacco cigarette were included in the analysis, but no trends were apparent when only the more typical range of the other cigarettes was considered.     

电化学处理废水过程中羟基自由基的测定

采用三维电极-电Fenton耦合法降解模拟苯酚废水,验证模拟苯酚废水降解过程中羟基自由基的存在,考察不同电压、起始p H值、铁粉加入量、曝气等因素对羟基自由基生成量的影响,实验结果表明:当溶液的p H为6.86(原溶液),加入3.0 g/300 m L Fe粉,5 V电压下1.5 L·min-1的曝气下电解30 min后,苯酚降解过程中羟基自由基的生成量最大。     

Physical Characterization of Cigarette Smoke Aerosol Generated from a Walton Smoke Machine

Mainstream cigarette smoke generated using a Walton smoking machine and Kentucky 2R1 research cigarettes was studied. Results showed that puff volume and total particulate matter were consistent after the first puff, with average values of 35.6 cm³ and 3.37 mg, respectively. The particle size distribution, measured with a multijet cascade impactor, was not related to butt length or relative humidity (≤95%), but was strongly dependent on the aging time. Based on simple monodisperse coagulation, the mass median aerodynamic diameter was calculated to be 0.45 μm at a dilution ratio of 21.7. Using a technique based on the dimensional change of collected droplet particles at various viewing angles of a scanning electron microscope, the count median diameter was estimated to be 0.22 μm. These values were in good agreement with those reported by others. The results suggest that there is a dilution value critical to the rapid evaporation and final particle size of the cigarette smoke aerosol. Once reaching this value, further dilution has little effect on the final particle size. By using the derived mass concentration and size distribution, the particle density, number concentration, and coagulation coefficient of the cigarette smoke aerosol were estimated to be 1.12 g/cm³, 7.20 × 109 particles/cm³, and 6.64 × 10 ^?10 cm³/s respectively. Solid particles > 1 μm were found in the first few puffs. These were considered to consist of tobacco debris.     

Kinetic Analysis of Heterogeneous Photocatalysis: Role of Hydroxyl Radicals

This article provides the current research activities that concentrate on the role of hydroxyl radicals in heterogeneous photocatalysis by transition metal oxides for different nanostructures. We devote most attention to Al-based Fe₂O₃ nanostructures that have been synthesized using chemical methods. The visible light photocatalytic activity of nanocrystalline pure and Al-based Fe₂O₃ photocatalysts for degradation of Salicylic acid, 4-Cholorphenol, and Acid orange 7 (Azo dye) is reported. The catalytic activity and selectivity for organic species are remarkably influenced by the size of the different photocatalyst. Utilization of various structures, advanced oxidation processes, heterojunction between Al-based Fe₂O₃ and TiO₂, and application of solar energy for heterogeneous photocatalysis of water impurities were discussed. Extent of complete mineralization of such compounds by measuring COD and TOC was discussed. We conclude this review with personal perspectives on the directions towards which future research on this new class of nanostructured materials for photocatalysis might be directed.     

卷烟纸特性对卷烟燃烧及主流烟气中CO释放量的影响

为考察卷烟纸特性对卷烟燃烧及主流烟气中CO释放量的影响,采用不同特性(透气度、定量、助燃剂含量)的卷烟纸卷制卷烟,测定卷烟燃烧温度和主流烟气中的CO释放量,并分析主流烟气中CO释放量与温度积分和最高抽吸温度的相关性,结果表明:主流烟气CO释放量与温度积分显著相关,与卷烟最高抽吸温度有一定相关或不相关。     

Size and Generation Rate of Sidestream Cigarette Smoke Particles

Sidestream cigarette smoke generated using an automatic smoking machine (SEM-II) and Kentucky 2R1 reference cigarettes was analyzed for particle generation rate and size distribution. Part of the sidestream smoke was sampled with an Andersen Cascade Impactor, following dilution with about 29 to 54 liters/min of laboratory air. The remaining sidestream smoke was further diluted 1,000-fold with vapor phase from filtered sidestream smoke before analysis with an Electrical Aerosol Analyzer and Condensation Nuclei Counter. The smoking parameters of primary dilution ratio and puff pressure were varied in the experiments. The number median diameter of sidestream cigarette smoke was about 0.10 μm, and the mass median diameter was typically 0.16 μm, about half the size of fresh mainstream smoke. Additionally, the size distribution of sidestream smoke was significantly broader than that of mainstream smoke. The particle generation rate of sidestream smoke depended on smoking conditions and varied from 1.4 × 10⁹ to 3.9 × 10⁹ particles/s. The equivalent total particulate matter of sidestream smoke based on the Electrical Aerosol Analyzer measurements varied from 1.3 to 2.3 mg/cigarette, whereas it was 6.0 to 9.6 mg/cigarette based on the Andersen Cascade determinations. Reasons for these differences are not definitive at this time.