Investigating effect of pH values on CeSiW catalyst for the selective catalytic reduction of NO by NH3

Research on Chemical Intermediates - The effect of different pH values (8, 9, 10 and 11) on the catalytic activity over CeSiW catalysts was investigated for the selective catalytic reduction of NO...     

全自动QuEChERS样品制备系统结合高效液相色谱-串联质谱法检测植物源性食品中34种农药残留

建立了全自动QuEChERS样品制备系统结合高效液相色谱-串联质谱（HPLC-MS/MS）同时检测植物源性食品中34种农药残留的分析方法。方法利用全自动QuEChERS样品制备系统涡旋振动和离心功能，将手动QuEChERS方法中样品提取和分散固相萃取相结合；优化了操作参数及前处理步骤，在多反应监测（MRM）模式下检测，基质匹配外标法定量。从方法学验证角度对全自动QuEChERS法与手动QuEChERS法进行了比较。结果表明：该方法中大多数农药在一定范围内呈现良好的线性关系，相关系数（R²）均大于0.99，检出限为0.76~3.60 μg/kg，定量限为2.28~10.80 μg/kg，加标回收率为53.0%~125.2%，相对标准偏差（RSD）<15.9%（n=5）。该方法与手动QuEChERS法的方法验证比对结果显示差异不明显，用于植物源性食品中多农药残留检测可有效降低劳动强度和出错概率。     

方波伏安法测定酚酞片含量

研究了酚酞在0.5 mol/L氨水-氯化铵缓冲溶液(pH 10)介质中汞膜电极上的电化学行为,并依此建立了酚酞含量的方波伏安法测定.酚酞于-0.98 V(VS.Ag/AgCl)处出现一灵敏的阴极还原峰,峰高与酚酞的浓度在3.0×10-7-5.0×10-5mol/L范围内有良好的线性关系.方法的最低检出限为1.0×10-7mol/L,方法用于酚酞片中酚酞含量的测定,结果满意.     

计时电流法研究4-(N-亚硝基甲氨基)-1-(3-吡啶基)-1-丁酮对谷氨酸脱氢酶活性的影响

用计时电流法研究了烟草特有亚硝胺之一4 (N 亚硝基甲氨基) 1 (3 吡啶基) 1 丁酮(NNK)对谷氨酸脱氢酶(GLDH)催化活性的影响,测定了NNK存在与否时GLDH酶促反应的最大反应速率及米氏常数或表观米氏常数。实验结果表明,NNK对GLDH的催化活性有明显抑制作用,而且属于可逆竞争性抑制,测得在25℃,pH 8.0时抑制常数Ki为176μmol·L-1。     

碳糊电极阳极吸附伏安法测定大黄酸

在pH4.2的HAc-NaAc底液中,大黄酸在碳糊电极(CPE)上有一灵敏的吸附氧化峰,峰电位为1.14V(vs.SCE)。该氧化峰的二阶导数峰电流与大黄酸的浓度在8.0×10-9~8.0×10-7mol/L(富集120s)范围内呈良好的线性关系(r=0.998),检出限为2×10-9mol/L(S/N=3,富集180s)。探讨了大黄酸在CPE上的伏安性质和电极反应机理,并将本法应用于中药大黄中的大黄酸的测定,结果良好。     

FTIR study of hydrogen bonding of stearic acid with ethanol, dimethyl sulfoxide,and acetonitrile in supercritical CO_2

FTIR spectroscopy was used to study the hydrogen bonding of stearic acid with ethanol, dimethyl sulfoxide (DMSO),and acetonitrile in supercritical CO_2 at 318.15 K, and 12.5 and 16.5 MPa. The concentrations of the cosolvents range from 0—0.6 mol·L~(-1). The area percentage of absorption bands for hydrogen-bonded and nonhydrogen-bonded species was obtained from the IR spectra. The acid and the cosolvents can form hydrogen bond even when their concentrations are very low. At fixed solute concentration, the extent of hydrogenbonding increases with cosolvent concentration. At higher ethanol concentrations, it seems that one stearic acid molecule can hydrogen bond with more than one ethanol molecules simultaneously. It is seen that the strength of the hydrogen bond formed by the acid and the cosolvents is in the order: DMSO>ethanol>acetonitrile.     

Solubility of stearic acid in supercritical CO_2-acetonitrile mixtures

The solubility of stearic acid in supercritical CO2 with acetonitrile (CH3CN) cosolvent was measured at 318.15 K in the pressure range from 9.5 to 16.5 MPa, and the cosolvent concentration ranges from 0. 0 to 5.5 mol% . The solubility increases with acetonitrile concentration and pressure, and it also increases with the apparent density of CO2 d1(moles of CO2 in per liter of fluid) at higher cosolvent concentrations. At lower d1, however, the solubility of the acid at lower acetonitrile concentrations is lower than that in pure CO2 provided that d1 is fixed, which is discussed qualitatively based on the clustering of the components in the system.     

络合吸附波极谱法测定稀土钢中微量稀土

研究了在ｐＨ９．２－ｐＨ９．５的ＮＨ３０Ｎａ２Ｂ４Ｏ７介质中,稀土与百里香酚酞的络合物极谱波,波高与镧量在４．０×１０＾－７－３．６×１０＾－６ｍｏｌ／Ｌ范围内成线性关系。方法已用于稀土钢中微量稀土的测定。     

用1H NMR相对化学位移计算CyDTA金属配合物乙羧基键合几率的方法

用~１ＨＮＭＲ相对化学位移计算ＣｙＤＴＡ金属配合物乙羧基键合几率的方法宋瑞方,李菲,刘广民,毛友钢（吉林大学理论化学研究所分子光谱与分子结构开放实验室,长春,１３００２３）关键词ＭＣｙＤＴＡ,乙羧基键合分布几率,标准自由能胺羧金属配合物一般为正八面体?..     

均聚物/共聚物共混体系的相行为研究进展

通过控制均聚物与共聚物共混过程中的相行为,能够得到许多性能优异的材料。本文从理论和实验两方面总结了影响均聚物／共聚物共混体系相容性和形态结构的因素,主要包括均聚物的分子量、浓度,共聚物的组成、结构、浓度,与均聚物相应的共聚物组分的分子量,共聚物分子内的相互作用,均聚物与共聚物分子间的相互作用等。