多壁碳纳米管作为气相色谱固定相的性能研究

将甲烷催化裂解法生产的经过纯化的多壁碳纳米管(PMWCNTs)、活性炭、石墨 化碳黑(Carbopack B)分别填装成气相色谱填充柱,比较它们分离烷烃、芳香烃、 卤代烃、醇、酮、醚、酯类的性能。分别在PMWCNTs和Carbopack B上涂清5%(w/w) 的Carbowax 20M,填装成气相色谱填充柱后,比较它们分离醇、酮、醚、酯、有机 酸类的性能。结果表明,PMWCNTs是一种性能优异的气相色谱固定相。与相同比表 面积的Carbopack B石墨化碳黑相比较,它有更强的保留能力,适合于分析沸点相 对较低的化合物;具有更均匀的表面,表现为极性化合物亦可得到对称的峰形;理 论塔板数较小。此外,和Carbopack B一样,PMWCNTs涂清5% (w/w) Carbowax 20M 后可用来分离极性化合物,甚至是强极性的小分子有机酸。     

动物源食品中呋喃苯烯酸钠残留的液相色谱串联质谱法检测

建立了液相色谱串联质谱法测定动物源食品(猪肝、猪肾、猪肉、鳗鱼、蜂蜜、鸡蛋)中呋喃苯烯酸钠残留的检测方法.样品采用乙腈提取,正己烷萃取净化,并对液相色谱串联质谱分离条件以及样品前处理条件进行了优化.呋喃苯烯酸钠的线性范围为2.0 ～50.0 μg/L,线性良好,相关系数均大于0.999 0,回收率为82% ～90%,日内相对标准偏差为0.9% ～5.8%,方法的定量下限为5.0 μg/kg.方法可满足进出口动物源食品中呋喃苯烯酸钠残留的确证与测定.     

顶空采样-毛细管气相色谱法分析格列美脲原料药中的溶剂残留

建立了顶空采样-毛细管气相色谱检测格列美脲原料药中溶剂残留的分析方法。对产自国内8个生产厂家的格列美脲样品中有机溶剂的残留状况进行了系统评价,结合药品生产工艺信息,确定了丙酮、乙酸乙酯、甲醇、异丙醇、乙醇、氯仿、甲苯、1,4-二氧六环、吡啶、氯苯、乙醚、二氯甲烷、正己烷和苯等14种有机溶剂为残留检测对象。根据被测组分在色谱柱上的保留性质将其分为两类,以实现基线分离。用Supelco-Wax极性色谱柱,以乙腈为内标物,分离检测了丙酮、乙酸乙酯、甲醇、异丙醇、乙醇、氯仿、甲苯、1,4-二氧六环、吡啶和氯苯的残留量;用Supelco OVI-G43弱极性色谱柱,以丁酮为内标,分离检测了乙醚、二氯甲烷、正己烷和苯的残留量。14种残留组分在各自的浓度范围内呈良好的线性关系(r=0.99167～0.99997,n=8),最低检出限范围为0.2～13.5 μg/g;14种残留组分检测的日间重复性(以相对标准偏差(RSD)计)为0.6%～9.2%(n=3),3种加标浓度的平均添加回收率为86.3%～104.1%(RSD为0.2%～5.3%,n=16)。实验结果表明,该方法简单、灵敏、可靠,适用于格列美脲中残留溶剂的分析确证。     

气相色谱-负化学离子源质谱联用法测定植物性产品中多组分农药残留量

通过气相色谱-负化学离子源质谱技术建立了同时检测18种农药残留的分析方法. 样品经正己烷和丙酮混合溶剂及正己烷提取后, 用活性炭-中性氧化铝混合小柱净化, 再由气相色谱-负化学离子源质谱分时段选择离子监测技术进行测定. 一次进样就能得到18种农药残留结果;各农药在0.005、 0.01和0.02 mg/kg 3个添加水平的平均回收率在70.2%～115.3%之间, RSD<12%, 检出限为0.01～6 μg/kg, 方法可应用于8种植物性产品中的农残检测.     

固相流体热萃取-GC/MS分析土壤中氯苯类有机污染物

选用不同配比的正己烷与丙酮混合液、乙腈作为提取溶剂，应用固相流体热萃取仪对土壤中的氯苯类有机物进行提取分离，用气相色谱-质谱进行测定。结果表明：仪器工作条件为提取温度120℃，冷却温度为30℃时，正己烷与丙酮混合提取效果明显优于乙腈。方法线性关系良好，相关系数高于0．99，回收率大于80％，相对标准偏差小于5％，氯苯类物质检测限为2ng／g。     

超高效液相色谱-串联质谱联用法对水产品中亚甲基蓝及其代谢物残留的检测

建立了超高效液相色谱-串联质谱同时检测水产品中亚甲基蓝及其代谢物天青A、天青B、天青C残留的方法.试样中的残留药物采用离子对试剂提取,正己烷脱脂净化,超高效液相色谱-串联质谱法测定.对前处理及液相色谱分离条件进行了探讨与优化.4种分析物在0.25 ～50 μg/L范围内线性关系良好,相关系数均大于0.999,方法定量下限可达0.5 μg/kg.在0.5、1.0、5.0 μg/kg范围内,平均加标回收率为80% ～91%;相对标准偏差为6.38% ～9.41%.方法灵敏、稳定,可满足水产品中亚甲基蓝及其代谢物残留的检测与确证及对药物动力学研究的需要.     

氢气在碳纳米管基材料上的吸附-脱附特性

利用高压容积法测定多壁碳纳米管(MWCNTs)及钾盐修饰的相应体系(K＋-MWCNTs)的储氢容量,并用程序升温脱附(TPD)方法表征研究氢气在MWCNTs基材料上的吸附-脱附特性.结果表明,在经纯化MWCNTs上,室温、9.0 MPa实验条件下氢的储量可达1.51％（质量分数）;K＋盐对MWCNTs的修饰对增加其储氢容量并无促进效应,但相应化学吸附氢物种的脱附温度有所升高;K＋的修饰也改变了MWCNTs表面原有的疏水性质.在低于723 K的温度下,H2/MWCNTs体系的脱附产物几乎全为氢气;773 K以上高温脱附产物不仅含H2,也含有CH4、C2H4、C2H2等C1/C2烃混合物;H2/K＋-MWCNTs储氢试样的脱附产物除占主体量的H2及少量C1/C2烃混合物外,还含水汽,其量与吸附质H2源水汽含量密切相关.H2在碳纳米管基材料上吸附兼具非解离 (即分子态) 和解离(即原子态)两种形式.     

扩散采集-气相色谱法测定空气中7种挥发性有机物

用扩散采集方法采集空气中环氧丙烷、正己烷、苯、甲苯、乙苯、二甲苯、苯乙烯7种挥发性有机物,建立了气相色谱同时测定这些化合物的分析方法.考察并确定了采集、萃取和气相色谱仪器分析的参数.分析方法的线性回归系数为0.9997～0.9999,检出限为0.037～0.16 μg/mL,回收率为89.1％～105％,测定方法的精密...     

介孔Ni/MgO催化剂催化水蒸气重整生物质油制氢

采用水热法制备了介孔MgO作为催化剂的载体,并制备了介孔Ni/MgO催化剂。利用N_2吸附-脱附、XRD、H_2-TPR等对样品进行表征,并考察了介孔Ni/MgO催化水蒸气重整糠醛、生物质油模型物和两种商用生物质油制氢的活性。结果表明,在介孔Ni/MgO催化剂催化水蒸气重整糠醛制氢反应中,随着反应温度的提高,水蒸气重整糠醛中糠醛的转化率、氢气的产率和氢气的选择性,都呈现递增的趋势。在反应温度提高到600℃时,糠醛的转化率和氢气的产率分别达到94.9%和83.2%。Ni/MgO催化水蒸气重整二组分模拟生物质油,糠醛/乙酸、糠醛/羟基丙酮制氢的反应中,氢气的产率分别达到87.3%和86.8%,均高于水蒸气重整糠醛反应中氢气的产率。由此表明,乙酸或羟基丙酮的存在,提高了模拟生物质油中主要有机物组分糠醛的转化率,并相应地提高了氢气的产率。在水蒸气重整商用生物质油制氢反应中,随着反应物水碳比(S/C(molar ratio)=5、10、15、20、25)的提高,主要有机物的转化率、氢气的产率和选择性呈现出增加的趋势。在水碳比为20时,两种生物质油的主要有机物组分(糠醛、乙酸和羟基丙酮)的转化率均可达90%以上,氢气的产率也达到81.0%以上。由此可知,Ni催化剂对于水蒸气重整商用生物质油也具有较高的催化活性。     

载体对负载型NiSn催化剂丙烷脱氢性能的影响

研究了载体对负载型Ni Sn催化剂丙烷脱氢性能的影响,主要对比考察了以Si O2、Mg O、Al2O3、Mg Al2O4为载体的Ni Sn催化剂的丙烷脱氢性能。采用X射线衍射技术(XRD)、氮气吸附-脱附技术、氨气程序升温脱附技术(NH3-TPD)以及氢气程序升温还原技术(H2-TPR)对催化剂样品进行表征。结果表明,Si O2因具有较大的比表面积、大孔径、酸性较弱等特点,以其为载体制备所得催化剂中Ni2.67Sn2组分含量高,催化剂性能较高。     

Doping effects of manganese on the catalytic performance and structure of NiMgO catalysts for controllabe synthesis of multi-walled carbon nanotubes

Doping effects of manganese （Mn） on catalytic performance and structure evolution of NiMgO catalysts for synthesis of multi-walled carbon nanotubes （MWCNTs） from methane were investigated for the first time. Addition of Mn in NiMgO catalyst can greatly improve the MWCNTs yield. Mno.2NiMgO catalyst among the tested ones gives the highest MWCNTs yield as 2244%, which is two times higher than that of the catalyst without Mn. The structure evolution, reduction behaviors and surface chemical properties of MnNiMgO catalysts with various Mn contents were studied in detail. It was found that the stable solid solution of NiMgO2 formed in NiMgO catalyst was disturbed by the addition of Mn. Instead, another solid solution of MnMg608 is formed. More amount of Ni can be reduced and dispersed on the catalyst surface to be acted as active sites. Importantly, the changes of Ni content on the surface are correlated with the Ni particle size and the outer diameter of MWCNTs, suggesting the controllable synthesis of MWCNTs over MnNiMgO catalysts.     

Mg1.8La0.2Ni-xNi nanocomposites for electrochemical hydrogen storage

Mg1.8La0.2Ni hydrogen storage alloy was ball-milled with Ni powder, leading to the formation of a nanocrystalline and amorphous microstructure with particle sizes less than 50 nm in diameter. Each sample was examined by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). This structure was beneficial for the reduction of electrochemical impedance, as well as significant improvement of its discharge capacity, cycle life, and rate capability for electrochemical hydrogen storage in an alkaline solution. When the molar ratio (x) of Ni over Mg1.8La0.2Ni was equal to 2, the dehydriding capacity reached 2.55 wt % from electrochemical pressure-temperature isotherms (P-C-T). It was in good agreement with its initial discharge capacity, 716 mA*h/[g of (Mg1.8La0.2Ni)], observed from the electrochemical charge and discharge process. After 50 cycles, its discharge capacity still reached 381 mA*h/[g of (Mg1.8La0.2Ni)]. Further results showed that this composite had a promising high rate capability. At the current density of 1200 mA/g its discharge capacity reached 48% of its initial capacity.     

Effect of Different Purification Techniques on the Characteristics of Heteropolysaccharide-Protein Biopolymer from Durian (<em>Durio zibethinus</em>) Seed

Natural biopolymers from plant sources contain many impurities (e.g., fat, protein, fiber, natural pigment and endogenous enzymes), therefore, an efficient purification process is recommended to minimize these impurities and consequently improve the functional properties of the biopolymer. The main objective of the present study was to investigate the effect of different purification techniques on the yield, protein content, solubility, water- and oil-holding capacity of a heteropolysaccharide-protein biopolymer obtained from durian seed. Four different purification methods using different chemicals and solvents (i.e., A (isopropanol and ethanol), B (isopropanol and acetone), C (saturated barium hydroxide), and D (Fehling solution)] to liberate the purified biopolymer from its crude form were compared. In most cases, the purification process significantly (p < 0.05) improved the physicochemical properties of heteropolysaccharide-protein biopolymer from durian fruit seed. The present work showed that the precipitation using isopropanol and acetone (Method B) resulted in the highest purification yield among all the tested purification techniques. The precipitation using saturated barium hydroxide (Method C) led to induce the highest solubility and relatively high capacity of water absorption. The current study reveals that the precipitation using Fehling solution (Method D) most efficiently eliminates the protein fraction, thus providing more pure biopolymer suitable for biological applications.     

Hydrogen storage in ni nanoparticle-dispersed multiwalled carbon nanotubes

Hydrogen storage properties of mutiwalled carbon nanotubes (MWCNTs) with Ni nanoparticles were investigated. The metal nanoparticles were dispersed on MWCNTs surfaces using an incipient wetness impregnation procedure. Ni catalysts have been known to effectively dissociate hydrogen molecules in gas phase, providing atomic hydrogen possible to form chemical bonding with the surfaces of MWCNTs. Hydrogen desorption spectra of MWCNTs with 6 wt % of Ni nanoparticles showed that approximately 2.8 wt % hydrogen was released in the range of 340-520 K. In Kissinger's plot to evaluate the nature of interaction between hydrogen and MWCNTs with Ni nanoparticles, the hydrogen desorption activation energy was measured to be as high as approximately 31 kJ/mol.H(2), which is much higher than the estimates of pristine SWNTs. C-H(n)() stretching vibrations after hydrogenation in FTIR further supported that hydrogen molecules were dissociated when bound to the surfaces of MWCNTs. During cyclic hydrogen absorption/desorption, there was observed no significant decay in hydrogen desorption amount. The hydrogen chemisorption process facilitated by Ni nanopaticles could be suggested as an effective reversible hydrogen storage method.     

镁含量对RE-Mg-Ni系A2B7型储氢合金结构与性能的影响

采用感应熔炼方法制备了La0.8-xGd0.2MgxNi3.1Co0.3Al0.1(x=0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4)储氢合金, 并在氩气气氛和1173 K下进行退火处理. 合金相结构分析结果表明, 镁含量(x)较低时合金以Ce2Ni7型为主相结构, A2B7型相丰度(Ce2Ni7+Gd2Co7)达到98.8%; 镁含量较高时合金相由A2B7型、 CaCu5型和PuNi3型物相构成, 随着镁含量的增加, PuNi3型和CaCu5型相组成逐渐增多, 其晶胞参数随Mg含量的增加而减小, 同时合金的吸氢平台也随之升高. 电化学测试结果表明, 随着合金中Mg含量增加, 合金电极的最大放电容量和循环稳定性均呈先增大后减小的规律, 其中x=0.15时合金电极具有最高的电化学放电容量(393 mA·h/g)和最佳的循环寿命(S100=92.82%). 合金电极的高倍率放电性能(HRD)随Mg含量的增加先减小再增大然后又减小, 适量的Mg元素改善了合金电极的动力学性能.     

工业色谱法分离制备7-木糖基-10-去乙酰紫杉醇酶解产物10-去乙酰紫杉醇

基于工业色谱法分离制备抗癌药物紫杉醇的半合成前体10-去乙酰紫杉醇(10-DAP)。7-木糖基-10-去乙酰紫杉醇(10-DAXP)在我国特有红豆杉品系(中华红豆杉)枝叶中含量丰富,以其为原料可制备紫杉醇最理想的半合成前体——10-DAP。本研究以部分纯化后的7-木糖基-10-去乙酰紫杉烷为原料,通过β-木糖苷酶水解该粗提物中的主要成分10-DAXP及其两个微量类似物7-木糖基-10-去乙酰三尖杉宁碱(10-DAXC)和7-木糖基-10-去乙酰紫杉醇C(10-DAXP C),脱去其C-7位上的木糖基,水解产物采用大孔吸附树脂吸附,正相快速柱分离和反相制备色谱分离,可获得高纯度的目标物10-DAP,产物纯度为96%,整个工艺的收率大于75%。该方法适合以10-DAXP为原料大规模制备紫杉醇的半合成前体化合物10-DAP,为工业化生产紫杉醇开辟了一条新途径。     

The effect of cold trap adsorbents on the gas chromatographic analysis of ambient VOCs under Peltier cooling conditions

In this work, the relative analytical performance of the GC-based detection method was investigated with a major focus on cold trap (CT) adsorbent materials against four aromatic volatile organic compounds (VOCs) (e. g., benzene, toluene, xylene, and styrene). A series of calibration experiments were hence conducted under cryofocusing conditions formed by the Peltier cooling system in a thermal desorber (TD) unit. During the course of this study, comparative calibration datasets were acquired for each of the three CT types: (i) CT (I) = Carbopack B + Carbopack C, (ii) CT (II) = Carbopack B + Carboxen 1000, and (iii) CT (III) = Tenax TA. All calibration datasets were obtained under subambient temperature (-10 degrees C) conditions controlled by the Peltier cooling system. The reliability of the calibration data was also assessed in an ancillary experiment with the aid of the modified injection through a thermal desorber (MITD) method. The results demonstrated that the GC detection properties of different VOCs were not altered significantly between different CT applications under Peltier conditions, although relative sensitivity could be distinguished moderately depending on the CT type.     

LaMg8.40Ni2.34合金的相结构和储氢性能

利用真空感应熔炼和退火方法制备了LaMg_8.40Ni_2.34合金. 采用X射线衍射(XRD)分析、扫描电镜(SEM)和压力-组成-温度(PCT)测试仪测试了合金的相组成、微观形貌和储氢性能. LaMg_8.40Ni_2.34合金由La₂Mg₁₇、LaMg₂Ni和Mg₂Ni组成,且在第一次吸放氢循环中就可以完全活化. 在558 K下的可逆储氢量为3.01%(质量分数), 合金的PCT曲线表现出双吸氢平台, 分别对应着形成的MgH₂和Mg₂NiH₄. 但是放氢曲线却只有一个平台出现, 这是由MgH2和Mg2NiH4之间的协同脱氢作用产生的. LaMg_8.40Ni_2.34合金在吸放氢时的活化能分别为(52.4±0.4)和(59.2±0.1) kJ·mol^-1, 均低于Mg₂Ni合金. 与纯Mg和Mg₂Ni合金相比, LaMg_8.40Ni_2.34合金具有良好的活化性能、较高的储氢性能和优良的动力学性能.     

Hydrogen Peroxide Sensor Based on Carbon Nanotubes/β‐Ni(OH)2 Nanocomposites

Ni(OH)₂ nanoflowers were synthesized by a simple and energy‐efficient wet chemistry method. The product was characterized by scanning electron microscopy (SEM) and X‐ray powder diffraction (XRD). Then Ni(OH)₂ nanoflowers attached multi‐walled carbon nanotubes (MWCNTs) modified glassy carbon electrodes (GCE) were proposed (MWCNTs/Ni(OH)₂/GCE) to use as electrochemical sensor to detect hydrogen peroxide. The results showed that the synergistic effect was obtained on the MWCNTs/Ni(OH)₂/GCE whose sensitivity was better than that of Ni(OH)₂/GCE. The linear range is from 0.2 to 22 mmol/L, the detection limit is 0.066 mmol/L, and the response time is <5 s. Satisfyingly, the MWCNTs/Ni(OH)₂/GCE was not only successfully employed to eliminate the interferences from uric acid (UA), acid ascorbic (AA), dopamine (DA), glucose (GO) but also NO₂^? during the detection. The MWCNTs/Ni(OH)₂/GCE allows highly sensitive, excellently selective and fast amperometric sensing of hydrogen peroxide and thus is promising for the future development of hydrogen peroxide sensors.