气相色谱-质谱联用测定水果和蔬菜中哒螨灵残留量

建立气相色谱-质谱联用测定水果和蔬菜中哒螨灵农药残留量的检测方法.样品经过提取、净化、浓缩后,用气质联用进行检测.方法的检出限0.05 mg/L,样品中哒螨灵的平均添加回收率在79.7%～89.5%之间,变异系数在3.21%～4.78%之间.     

气相色谱-质谱联用法测定漆膜中邻苯二甲酸酯类化合物

建立了漆膜中邻苯二甲酸酯类化合物的气相色谱-质谱（GC-MS）测定方法。以二氯甲烷为萃取溶剂,用溶剂萃取器萃取漆膜中的邻苯二甲酸酯类化合物,采用气相色谱-质谱联用仪（GC-MS）进行检测。邻苯二甲酸酯的线性相关系数r〉0.999,对实际加标样品的回收率在85%～115%之间,相对标准偏差（RSD）0.8%～6.6%,适合于漆膜中邻苯二甲酸酯类化合物的测定。     

气相色谱-质谱联用仪测定土壤中的溴敌隆

介绍了气相色谱-质谱联机法测定土壤中的溴敌隆.样品经粉碎机粉碎,用乙醇萃取后直接进行分析,以溴敌隆的单离子峰(m/z 258)和保留时间(8.915 min)定性,分析结果的相对标准偏差为2.2%～4.6%,回收率为93.9%～106.4%.     

气相色谱——质谱联用法测定水中的环氧氯丙烷方法初探

建立了气相色谱-质谱联用测定水中环氧氯丙烷的方法。用二氯甲烷萃取水样中的环氧氯丙烷,经色谱分离后采用质谱的选择离子检测(SIM)模式进行检测,提取特征离子进行定量。400mL水样中环氧氯丙烷的最低检测浓度可达0.1μg/L,标准曲线的线性相关系数r=0.9996,线性范围为0.05～2mg/L,样品平均加标回收率在85.8%～86.7%之间,相对标准偏差低于5.71%。方法简单、灵敏度高、准确、重现性好,适合水源水和饮用水中环氧氯丙烷的测定。     

染料中痕量多氯联苯的气相色谱-质谱联用分析

本文介绍了染料产品中痕量的多氯联苯(PCBs)的定量测定方法。采用正己烷作提取剂,用DB-5MS毛细管色谱柱进行分离,气相色谱-质谱联用仪进行定性分析,外标法定量。由于采用了灵敏度较高的选择离子检测(SIM)方式定量,本方法对目标化合物的检测限可达到0.01mg/kg,回收率为80%～100%,相对标准偏差≤4.0%。     

气相色谱串接质谱快速检测植物油中邻苯二甲酸酯

建立了气相色谱-串接质谱联用检测植物油中16种邻苯二甲酸酯类塑化剂的方法。采用乙腈直接萃取,固相萃取柱净化、洗脱,洗脱液经浓缩后,直接用气相色谱-串接质谱仪测定,内标法定量。结果显示,16种邻苯二甲酸酯类塑化剂的线性关系较好,方法检测限范围在0.004～0.01 mg/kg。在高、中、低3个水平下进行植物油加标实验,平均回收率为67.5%～117%,相对标准偏差小于15%(n=6)。方法简便快速,整个分析流程可在1 h之内完成,溶剂消耗量小,且应用串接质谱更好地消除了基质效应的干扰,灵敏度高,定性更为准确。     

婴幼儿奶嘴中12种N-亚硝胺类物质迁移量检测的研究

建立了婴幼儿奶嘴中12种N-亚硝基胺类物质迁移量的气相色谱-质谱联用检测方法。 样品经人工唾液盐浸提后,以二氯甲烷为溶剂萃取浸提液中的N-亚硝胺,去水浓缩后,用气相色谱-质谱联用仪进行测定,外标法定量。结果表明,方法的定量限为0.027mg/L～0.031mg/L,回收率为86.9%～120%,相对标准偏差为4.25%～8.31%,应用本方法对21 个国内外品牌的婴幼儿奶嘴进行了测试,其中16 个样品中检出了N-亚硝胺。     

气相色谱-质谱联用法测定染料中苯胺类化合物

本文采用气相色谱-质谱联用仪测定染料中的19种苯胺类化合物。用二氯甲烷作为溶剂,提取出染料中的苯胺类化合物,在气相色谱上进行分离,使用质谱检测器检测,用特征离子峰面积外标法进行定量。19种苯胺类化合物的测定结果相对标准偏差小于2%,检测回收率为65%～120%,定量限为0. 02～0. 5 mg/kg。     

气相色谱-质谱联用检测环境水体中的三嗪类除草剂

研究了用气相色谱-质谱联用技术检测环境水中三嗪类除草剂的分析方法,被测物质包括阿特拉津、西玛津、氰草津及阿特拉津的两种代谢产物去乙基阿特拉津和去异丙基阿特拉津。外标法定量,液–液萃取分析500mL水样,加标浓度分别为0.2,0.5,1.0μg/L时,回收率在51.75%～125.05%之间,两种代谢物的回收率相对较低。理论方法检出限为0.01～0.06μg/L,线性范围为0.01μg/mL～1.0μg/mL。用该方法可实现对环境水体中痕量三嗪类除草剂的检测。     

气相色谱-质谱联用法测定食品中丙烯酰胺

采用气相色谱-质谱联用法测定食品中丙烯酰胺。本次研究提取食品样品中丙烯酰胺经水与醇类等极性溶剂,经高速冷冻离心过滤以及固相萃取柱进行净化,溴化衍生后采用气相色谱进行分离并以质谱联用法来测定食品中的丙烯酰胺含量。丙烯酰胺在浓度为5~500μg/L范围内具有良好的线性关系,相关线性系数为r=0.998 92;定性检出限为1.7μg/kg,定量检出限5μg/kg,回收率在96%以上;相对标准偏差在6.7%以下。采用气相色谱-质谱联用法测定食品中丙烯酰胺能够满足分析要求,在实验的过程中具有操作简单、准确可靠、干扰少以及快速等特点,值得大力推广使用。     

空气中有害物质冬季污染情况的调查和分析

监测了2007年1月27号到2007年2月2号惠州市冬季主要交通干道空气污染情况,并采用气相色谱分析,结果显示在监测期间苯的含量为2μg／m^3-35μg／m^3,甲苯的含量为3μg／m^3-26μg／m^3,二甲苯的含量为0μg／m^3-95μg／m^3,乙酸正丁酯的含量为1μg／m^3-29μg／m^3,乙苯的含量为0μg／m^3-17μg／m^3,苯乙烯的含量为0μg／m^3-12μg／m^3,正十一烷的含量为0μg／m^3-22μg／m^3,CO的含量的为1．4ppm-4．1ppm,CO2的浓度为0．030％-0．060％,通过和国内其他城市的调查情况相比,其污染的程度较低,且监测结果表明,污染的情况受风速的影响较大,同时,还提出了改善城市污染状况的一些建议。     

The influence of porosity and surface oxygen groups of peat-based activated carbons on benzene adsorption from dry and humid air

Activated carbons (ACs) prepared from peat were used for benzene adsorption (5 ppmv) from dry and humid (relative humidity (RH) 70%) air streams. Benzene uptake by the ACs was lower in the presence of water vapor due to competition between benzene and water molecules for the adsorption sites. Adsorption of benzene from dry and humid air on the ACs with low content of surface oxygen groups was attributed to the presence of narrow micropores (size <0.7 nm). A linear correlation between the amount of adsorbed benzene and micropore volume calculated from CO₂ adsorption isotherms was found. The coefficients of determination R² were 0.87 for benzene adsorption in the absence of water vapor and 0.83 for adsorption at relative humidity 70%. It was shown that the presence of surface groups in the ACs reduces benzene uptake more profoundly in the presence of moisture than in the dry conditions.     

Direct synthesis of phenol from benzene over hydroxyapatite catalysts

The direct synthesis of phenol from benzene in the gas phase was studied over hydroxyapatite catalysts. The reaction was carried out in a fixed-bed reactor at atmospheric pressure and reaction temperature of 450°C in the presence of ammonia. A high selectivity (about 97%) of phenol formation at about 3.5% conversion of benzene was achieved over catalysts containing Ca and Cu ions in the cation part of hydroxyapatite. Besides phenol as the main reaction product, aniline is also formed. The reaction mechanism involves formation of N₂O from NH₃ in the first step of reaction. Benzene is oxidized by active oxygen species which are formed on the catalyst by decomposition of N₂O.     

液相法苯选择加氢制环己烯反应条件的探讨

采用化学还原法制备负载型钌催化剂,进行了苯选择加氢制环己烯。研究了反应温度、氢气压力、搅拌速率、反应时间对苯转化率、环己烯选择性及收率的影响。结果表明:在最佳反应条件下,反应温度为140℃、氢气压力为6.0MPa、搅拌速率为900r/min、反应时间为20min时,苯转化率为76.27%,环己烯选择性为68.33%,环己烯收率为52.12%。     

Efficient conversion of benzene and syngas to toluene and xylene over ZnO-ZrO2&H-ZSM-5 bifunctional catalysts

A series of ZnO-ZrO₂ solid solutions with different Zn contents were synthesized by the urea co-precipitation method, which were coupled with H-ZSM-5 zeolite to form bifunctional catalysts. As a new benzene alkylation reagent, syngas was used instead of methanol to realize the efficient conversion of syngas and benzene into toluene and xylene. A suitable ratio of ZnO-ZrO₂ led to the significant improvement in the catalytic performance, and a suitable amount of acid helped to increase the selectivity of toluene/xylene and reduce the selectivity of the by-products ethylbenzene and C₉⁺ aromatics. The highest benzene conversion of 89.2% and toluene/xylene selectivity of 88.7% were achieved over 10% ZnO-ZrO₂&H-ZSM-5 (Si/Al = 23) at a pressure of 3 MPa and a temperature of 450 ℃. In addition, the effect of the zeolite framework structure on product distribution was examined. Similar to the molecular dynamics of aromatic hydrocarbons, H-ZSM-5 zeolites comprise 10-membered-ring pores, which are beneficial to the activation of benzene; hence, the conversion of benzene is higher. H-ZSM-35 and H-MOR zeolites exhibited small eight-membered-ring channels, which were not conducive to the passage of benzene; hence, the by-product ethylbenzene exhibits a higher selectivity. The distance between the active centers of the bifunctional catalysts was the main factor affecting the catalytic performance, and the powder mixing method was more conducive to the conversion of syngas and benzene.     

The effect of feedstock and process conditions on the synthesis of high purity CNTs from aromatic hydrocarbons

High purity multi-walled carbon nanotubes were synthesized from aromatic hydrocarbons (benzene, toluene, xylene and trimethyl benzene) using ferrocene as the source of Fe catalyst. Screening studies of aromatic feeds at 675 °C, residence time of 14 s and Fe/C atom ratio of 1.07%, resulted in feedstock carbon conversion of 20-31%, CNT yield of 19.8-30.5%, and catalyst yield of 5.3-8.3 (g CNT/g catalyst). While the quality of the CNTs as determined by TGA, SEM, TEM and Raman spectroscopy, were high and comparable for different feedstocks; their carbon conversion, CNT yield and catalyst yield differed noticeably. A process optimization study for toluene feed showed that carbon conversion of more than 39%, CNT yield of 38.7% and catalyst yield of 18.3 can be achieved at temperature of 800 °C, Fe/C atom ratio of 0.47%, and residence time of 10-20 s.     

接枝改性腈纶织物亲水性能的研究

采用酰胺类亲水性单体对腈纶织物接枝改性,利用正交试验法对溶胀剂、乳化剂、引发剂的种类和用量进行了选择。结果表明,选择溶胀剂NaSCN 0．8 g／L,乳化剂十二烷基苯磺酸钠0．4g／L,引发剂BPO 0．4 g／L,接枝改性效果较好。腈纶织物的吸湿率由0．2％提高至5．0％,保水率由3％提高至13％。     

Rhodium nanoparticles intercalated into montmorillonite for hydrogenation of aromatic compounds in the presence of thiophene

Rhodium metal nanoparticles intercalated into montmorillonite (Rh-MMT) have been prepared and used for the hydrogenation of benzene and other aromatic compounds. Rh-MMT was characterized by PXRD, TEM and ICP-AES. The crystallite size of the rhodium particles was 6.9 nm using PXRD and the particle size by TEM was 25.6 ± 2.5 nm. Benzene hydrogenation was carried out at different substrate/catalyst mass ratios, temperature and pressure to optimize the reaction conditions. The benzene is completely hydrogenated with 100% selectivity to cyclohexane at 453 K and 6.2 MPa. The catalyst was poisoned by thiophene, and benzene hydrogenation decreased with increasing thiophene concentration. Hydrogenation of toluene, o,m,p-xylenes, naphthalene and anthracene were also carried out at the optimized reaction conditions.     

KINETICS AND MODELING OF BENZENE OXIDATION

The gas phase oxidation of benzene over a V₂O₅ + P₂O₅ + MoO₃ + Sb₂O₃ catalyst supported on kieselguhr carrier is studied at the temperature range 344-393^°C. 14 different kinetic models are tried to determine the mechanism of benzene oxidation. It is shown that benzene oxidation takes place via a two step redox mechanism which is first order with respect to benzene and 1/2 or 1st order with respect to oxygen. Rate constants for both models are presented.     

Synergistic Effect in the Dehydrogenation of Cyclohexene on C/W(111) Surfaces Modified by Submonolayer Coverage Pt

The dehydrogenation and decomposition of cyclohexene on the Pt-modified C/W(111) surfaces have been studied by temperature-programmed desorption (TPD), Auger electron spectroscopy (AES) and high-resolution electron energy loss spectroscopy (HREELS). The objective of the current study is to investigate how the surface reactivity of tungsten carbide is modified by the presence of submonolayer Pt. Similar to that observed on Pt(111), Pt(100) and C/W(111) surfaces, the characteristic reaction pathway on Pt/C/W(111) is the selective dehydrogenation of cyclohexene to benzene. At a Pt coverage of 0.52 monolayer, the selectivity to the gas-phase benzene product is 86±7%, which is slightly higher than that on Pt(111) (75%) and on C/W(111) (67±7%). More importantly, the desorption of benzene on Pt/C/W(111) is a reaction-limited process that occurs at 290 K, which is much lower than the benzene desorption temperature of 400 K from Pt(111).