Determination of ultra-trace amounts of nickel in environmental samples by atomic absorption spectrometry with in-situ trapping of volatile species in an iridium–palladium coated graphite furnace

A sensitive and accurate method is described for the determination of ultra-trace nickel in environmental samples with in-situ trapping of volatile species in iridium-palladium coated graphite furnace atomic absorption spectrometry. The effects of the conditions for the generation and collection of volatile nickel species, such as medium acidity, potassium borohydride concentration, enhancement reagent concentration, reaction temperature, as well as graphite tube coating, carrier gas flow rate and trapping time were investigated. Phenanthroline was selected as the enhancement reagent due to its good enhancing effect, and iridium–palladium coating was used for the in-situ trapping of volatile nickel species at 300°C. Under the optimal conditions, the calibration curve was linear from 0.21 up to 30.0 ng mL^?1 with correlation coefficient of 0.9991, the detection limit (S/N = 3) was 0.21 ng mL^?1 for 4 mL sample volumes and the relative standard deviation for 11 determinations of Ni at 10 ng mL^?1 was 3.5%. The results found by the proposed methods are accordant with the certified values of water, soil and tea certified reference materials. The proposed methods have been applied for the determination of ultra-trace Ni in tap, river and wastewater, as well as rice and soil samples, with recoveries ranging from 97.3 to 100.5%.     

Ion mobility spectrometer—field asymmetric ion mobility spectrometer-mass spectrometry

Since the development of electrospray ionization (ESI) for ion mobility spectrometry mass spectrometry (IMMS), IMMS have been extensively applied for characterization of gas-phase bio-molecules. Conventional ion mobility spectrometry (IMS), defined as drift tube IMS (DT-IMS), is typically a stacked ring design that utilizes a low electric field gradient. Field asymmetric ion mobility spectrometry (FAIMS) is a newer version of IMS, however, the geometry of the system is significantly different than DT-IMS and data are collected using a much higher electric field. Here we report construction of a novel ambient pressure dual gate DT-IMS coupled with a FAIMS system and then coupled to a quadrupole ion trap mass spectrometer (QITMS) to form a hybrid three-dimensional separation instrument, DT-IMS-FAIMS-QITMS. The DT-IMS was operated at ~3 Townsend (electric field/number density (E/N) or (Td)) and was coupled in series with a FAIMS, operated at ~80 Td. Ions were mobility-selected by the dual gate DT-IMS into the FAIMS and from the FAIMS the ions were detected by the QITMS for as either MS or MSⁿ. The system was evaluated using cocaine as an analytical standard and tested for the application of separating three isomeric tri-peptides: tyrosine-glycine-tryptophan (YGW), tryptophan-glycine-tyrosine (WGY) and tyrosine-tryptophan-glycine (YWG). All three tri-peptides were separated in the DT-IMS dimension and each had one mobility peak. The samples were partially separated in the FAIMS dimension but two conformation peaks were detected for the YWG sample while YGW and WGY produced only one peak. Ion validation was achieved for all three samples using QITMS.     

大学化学实验教学中构建绿色化学思维的探索与实践

依据绿色化学的基本原理,分析了在大学化学实验教学中构建绿色化学思维的重要性与必要性。结合多年的教学实践,从实验教学理念、教学内容和教学管理三方面,探研了在大学化学实验教学过程中构建绿色化学思维的途径;并从实验教学内容绿色化的角度,重点探讨了如何在大学化学实验教学过程中构建绿色化学思维。     

Simultaneous determination of monoamine and amino acid neurotransmitters in rat endbrain tissues by pre-column derivatization with high-performance liquid chromatographic fluorescence detection and mass spectrometric identification

A sensitive and efficient method for simultaneous determination of glutamic acid (Glu), gamma-amino-butyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in rat endbrains was developed by high-performance liquid chromatography (HPLC) with fluorescence detection and on-line mass spectrometric identification following derivatization with 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC). Different parameters which influenced derivatization and separation were optimized. The complete separation of five neurotransmitter (NT) derivatives was performed on a reversed-phase Hypersil BDS-C(18) column with a gradient elution. The rapid structure identification of five neurotransmitter derivatives was carried out by on-line mass spectrometry with electrospray ionization (ESI) source in positive ion mode, and the BCEOC-labeled derivatives were characterized by easy-to-interpret mass spectra. Stability of derivatives, repeatability, precision and accuracy were evaluated and the results were excellent for efficient HPLC analysis. The quantitative linear range of five neurotransmitters were 2.441-2x10(4) nM, and limits of detection were in the range of 0.398-1.258 nM (S/N=3:1). The changes of their concentrations in endbrains of three rat groups were also studied using this HPLC fluorescence detection method. The results indicated that exhausting exercise could obviously influence the concentrations of neurotransmitters in rat endbrains. The established method exhibited excellent validity, high sensitivity and convenience, and provided a new technique for simultaneous analysis of monoamine and amino acid neurotransmitters in rat brain.     

Effects of preparation conditions of Au/FeOx/Al203 catalysts prepared by a modified two-step method on the stability for CO oxidation

Composite oxide FeO x /Al 2 O 3 -supported gold catalysts were prepared by a modified two-step method. The effects of preparation conditions on the initial catalytic activity and long-time stability were studied for CO oxidation. XRD, XPS and in situ FTIR were employed to investigate the state of FeO x and the species on the catalyst surface. The results showed that Au/FeO x /Al 2 O 3 catalysts prepared by this method exhibited high activity and high stability in a wide pH value range. Calcination pretreatment was proved to be beneficial to improving the activity and stability. The beneficial effects of FeO x acting as a structural promoter could be ascribed to the ability to supply active oxygen species. As the precursor of FeO x , Fe(NO 3 ) 3 is superior to FeCl 3 for obtaining higher stability.     

液晶共聚物与PSF原位复合的界面研究

合成了两种热致性液晶共聚酯ＢＰ—ＬＣＰ和ＳＤＰ—ＬＣＰ，对其熔融指数、取向性作了考察。选用基体聚砜（ＰＳＦ）与液晶共聚酯进行熔融共混，得原位复合材料。ＳＥＭ断口形态显示了两种液晶在基体中不同的成纤性，并显示出两相的不相容性。采用ＦＴ—ＩＲ方法分析了液晶共聚酯与ＰＳＦ界面间的分子相互作用。进一步研究发现在ＰＳＦ／ＢＰ－ＬＣＰ原位复合体系中加入含ＰＳＦ和ＢＰ－ＬＣＰ的嵌段共聚物，其相容性得以改善     

微流控芯片上的红细胞电泳淌度研究

以单细胞成像法分别测量了 3组无农药含水质净化剂、有农药无水质净化剂及其有农药有水质净化剂处理后的杂交鲤鱼红细胞在塑料 ( polymethalmethacrylate ,PMMA)微流控芯片上的电泳淌度。其值分别为 1.138× 10 -4、0 .12 79× 10 -4和 - 0 .85 2 0× 10 -4cm2 v-1s-1。从电泳淌度的差别可以看出功夫菊酯和水质条件恶化均可使鲤鱼红细胞表面的电荷密度发生变化 ,从而引起电泳淌度的变化。同时还初步考察了细胞电泳淌度作为参数进行细胞分类的可行性 ,显示这种淌度差别有可能作为细胞分类的一项依据     

海洛因对别洛索夫-扎鲍京斯基振荡化学反应的影响及其分析应用

研究了海洛因对Belousov Zhabotinsky(B Z)振荡反应的影响 ,结果表明 :海洛因的加入明显地改变了振荡体系的周期和振幅 ,即对振荡体系产生扰动 ,扰动的浓度范围为 1.8× 10 -8～ 2 .1× 10 -3 mol/L ,且海洛因的浓度分别在 3.8× 10 -6～ 2 .8× 10 -5mol/L和 0 .9× 10 -6～ 2 .9× 10 -5mol/L范围内与振荡周期改变值ΔT和振幅改变值ΔA均呈现良好的线性关系 ,相关系数分别为 0 .9931和 0 .974 6。据此 ,建立了测定海洛因的新方法。     

杂化MCM-41固载催化剂的合成、表征及催化研究

用γ-氯丙基三乙氧基硅烷和正硅酸乙酯混合在模板剂引导下共水解合成了有机-无机杂化的介孔分子筛MCM-41,通过与(1R,2R)-1,2-环己二胺和[RuCl2(p-cymene)]2反应,制成了固载化的不对称氢转移反应催化剂,并进行了FT-IR、XRD和N2吸附 脱附的表征.不对称氢转移催化反应结果表明,在催化还原苯乙酮成α-苯乙醇的反应中,平均转化率为6.42％,产物平均ee（对映体过量）值为12.64％,固载化催化剂与其匀相体系的催化性能相比(转化率为3.56％,ee值为33.04％),转化率更高,ee值有一定程度的降低.