Determination of short-chain carbonyl compounds in drinking water matrices by bar adsorptive micro-extraction (BAμE) with in situ derivatization

In this contribution, bar adsorptive micro-extraction using polystyrene-divinylbenzene sorbent phase and in situ derivatization with pentafluorophenyl hydrazine, followed by liquid desorption and high-performance liquid chromatography-diode array detection (BAμE(PS-DVB)(PFPH in situ)-LD/HPLC-DAD), was developed for the determination of six short-chain carbonyl compounds (formaldehyde, acetaldehyde, propanal, acetone, butanone, and 2-hexenal) in drinking water matrices. PFPH presented very good specificity as an in situ derivatization agent for short-chain ketones and aldehydes in aqueous media, allowing the formation of adducts with remarkable sensitivity, selectivity and the absence of photodegradation. Assays performed on 30-mL water samples spiked at the 25.0 μg L(-1) levels, under optimized experimental conditions, yielded recoveries ranging from 47.4 ± 3.8% to 85.2 ± 3.8%, in which the PS-DVB proved to be a convenient sorbent phase. The analytical performance showed good accuracy, suitable precision (RSD < 13.0%), detection limits in between 47 and 132 ng L(-1) and remarkable linear dynamic ranges (r(2) > 0.9907) from 1.0 to 80.0 μg L(-1). By using the standard addition methodology, the application of the present method to drinking water samples treated with different disinfectants, namely, chloride, ozone and both, allowed very good performances to monitor these priority compounds at the trace level. The proposed methodology proved to be a feasible alternative for polar compound analysis, showing to be easy to implement, reliable, sensitive and requiring a low sample volume to monitor short-chain aldehydes and ketones in drinking water matrices.     

氮掺杂手性碳纳米管的电子结构和输运特性的理论研究

运用第一性原理的密度泛函理论,结合非平衡格林函数,研究了氮原子取代掺杂手性单壁(6,3)碳纳米管的电子结构和输运特性.计算结果表明:不同构形和不同数目的氮原子取代掺杂对手性碳管的输运性质有很复杂的影响.研究发现,氮原子掺杂明显改变了碳管的电子结构,使金属型手性碳管的输运性能降低,电流-电压曲线呈非线性变化,而且输运性能随着杂质原子间间距的变化而发生显著改变.在一定条件下,金属型碳管向半导体型转变. 关键词： 手性单壁碳纳米管 氮掺杂 电子结构 输运性能     

基于空间经济视角的大学知识创新效率的区域差异与趋同

为了评价处于相同前沿面的决策单元效率,本文采用超效率DEA方法对我国大学知识创新效率进行评价,考察和总结我国各地区大学知识创新的特点和运行模式;运用Bernard时间序列收敛模型刻画我国大学知识创新效率的时空演变特征;利用我国省际空间面板数据,基于空间溢出的视角考察我国大学知识创新效率空间差异的成因.结果表明,我国大学知识创新效率具有明显的空间外部正效应,且空间内部呈现"俱乐部收敛"特征.大学知识创新效率差距的影响因素往往交织融合在一起,发挥合力的影响作用.各地区大学知识创新差距的主要原因在于研发人员投入、科技创新平台建设、产业化水平、政府扶持以及创新文化等初始条件的诸多差异。     

New Dopamine Derivative from Lycium Barbarum

Incontinuationofourworkoncyclicpeptidesandamides'-',wetestedextractsofthefruitsofLyciumbarbarumwhichwasusedasatonicandsedativeintraditionalChinesemedicineandfoundtheextractscontainedconstituentwhichshowedpositivereactionwithninhydrinafterhydrolysis.ThusweinvestigatedtheplantandanewdopaminederivativeInamedlyciumideAwasisolated.Figure1.ThestructureoflyciumideAIJLyciumideAIwasobtainedascolorlessgum.Itcouldbededucedasanamidesincethecompoundshowednegativereactionwithninhydrinbutpositiveafterhyd…     

Probing phosphate ion via the europium(III)-modulated fluorescence of gold nanoclusters

Fluorescent gold nanoclusters (Au-NCs) were synthesized by a one-pot method using 11-mercaptoundecanoic acid as a reducing and capping reagent. It is found that the red fluorescence of the Au-NCs is quenched by the introduction of Eu(III) at pH 7.0, but that fluorescence is restored on addition of phosphate. The Au-NCs were investigated by transmission electron microscopy and fluorescence photographs. The effect of pH on fluorescence was studied in the range from pH 6 to 10 and is found to be strong. Based on these findings, we have developed an assay for phosphate. Ions such as citrate, Fe(CN)₆ ^3?, SO₄ ^2?, S₂O₈ ^2?, Cl^?, HS^?, Br^?, AcO^?, NO₂ ^?, SCN^?, ClO₄ ^?, HCO₃ ^?, NO₃ ^?, Cd²⁺, Ba²⁺, Zn²⁺, Mg²⁺, and glutamate do not interfere, but ascorbate and Fe³⁺ can quench Au-NCs fluorescence. The fluorescent nanocluster probe responds to phosphate in the range from 0.18 to 250 μM, and the detection limit is 180 nM. The probe also responds to pyrophosphate and ATP. Figure

Off/on fluorescence sensor for phosphate based on Eu³⁺-modulated Au NCs thanks to the competition of oxygen-donor atoms from phosphate with those from the carboxylate groups was developed     

Powdered activated carbons as effective phases for bar adsorptive micro-extraction (BAμE) to monitor levels of triazinic herbicides in environmental water matrices

Bar adsorptive micro-extraction using three powdered activated carbons (ACs) as adsorbent phases followed by liquid desorption and high performance liquid chromatography with diode array detection (BAμE(ACs)-LD/HPLC-DAD), was developed to monitor triazinic herbicides (atrazine, simazine and terbutylazine) in environmental water matrices. ACs used present apparent surface areas around 1000 m² g⁻¹ with an important mesoporous volume and distinct surface chemistry characteristics (pH_PZC ranging from 6.5 to 10.4). The textural and surface chemistry properties of the ACs adsorbent phases were correlated with the analytical data for a better understanding of the overall enrichment process. Assays performed on 10 mL water samples spiked at the 10.0 μg L⁻¹ levels under optimized experimental conditions yielded recoveries around 100% for the three herbicides under study. The analytical performance showed good precision (RSD < 15.0%), convenient detection limits (≈0.1 μg L⁻¹) and suitable linearity (1.0-12.0 μg L⁻¹) with good correlation coefficients (r² > 0.9914). By using the standard addition method, the application of the present method on real water matrices, such as surface water and wastewater, allowed very good performances at the trace level. The proposed methodology proved to be a suitable sorptive extraction alternative for the analysis of priority pollutants with polar characteristics, showing to be easy to implement, reliable, sensitive and requiring a low sample volume to monitor triazinic compounds in water matrices.     

Cork-based activated carbons as supported adsorbent materials for trace level analysis of ibuprofen and clofibric acid in environmental and biological matrices

In this contribution, powdered activated carbons (ACs) from cork waste were supported for bar adsorptive micro-extraction (BAμE), as novel adsorbent phases for the analysis of polar compounds. By combining this approach with liquid desorption followed by high performance liquid chromatography with diode array detection (BAμE(AC)-LD/HPLC-DAD), good analytical performance was achieved using clofibric acid (CLOF) and ibuprofen (IBU) model compounds in environmental and biological matrices. Assays performed on 30 mL water samples spiked at the 25.0 μg L(-1) level yielded recoveries around 80% for CLOF and 95% for IBU, under optimized experimental conditions. The ACs textural and surface chemistry properties were correlated with the results obtained. The analytical performance showed good precision (<15%), suitable detection limits (0.24 and 0.78 μg L(-1) for CLOF and IBU, respectively) and good linear dynamic ranges (r(2)>0.9922) from 1.0 to 600.0 μg L(-1). By using the standard addition methodology, the application of the present approach to environmental water and urine matrices allowed remarkable performance at the trace level. The proposed methodology proved to be a viable alternative for acidic pharmaceuticals analysis, showing to be easy to implement, reliable, sensitive and requiring low sample volume to monitor these priority compounds in environmental and biological matrices.     

Charge, orbital and spin ordering in multiferroic BiMn2O5: density functional theory calculations

Charge, orbital, and spin ordering of multiferroic BiMn(2)O(5) are investigated by the full-potential linearized augmented plane-wave (FPLAPW) method as implemented in the WIEN2K package. Both the generalized gradient approximation (GGA) as well as GGA plus the one-site Coulomb interaction (GGA+U) methods are considered for the exchange-correlation energy functional. The obtained results show that BiMn(2)O(5) is found stable in ferrimagnetic state with band gap about 1.23 eV. The results suggest that BiMn(2)O(5) contains two kinds of manganese: the ionicity of Mn1 (Mn(4+)) is +3.6 with magnetic moment of 2.40 μ(B) and the ionicity of Mn2 (Mn(3+)) is +3.4 with magnetic moment of 3.22 μ(B). While charge disproportion between Mn1 and Mn2 is small, the difference between e(g) minority occupancies of Mn(3+) and Mn(4+) cations is large. Both these two properties give direct evidence of charge ordering. The analysis of the Born effective charge reveals that the partial ferroelectric polarization (P(ele)) originates from the charge ordering, which is in agreement with a recent work by Brink and Khomskii [J. Phys.: Condens. Matter, 2008, 20, 434217].     

Experimental and numerical investigation of thermal chaotic mixing in a T-shaped microchannel

In this paper, thermal chaotic mixing characteristics of two miscible fluids in a T-shaped microchannel are investigated experimentally and numerically. In the experiments, fluorescent dye Acid Yellow and Rhodamine B was employed to show the mass mixing behavior and temperature field, respectively. Power input and flow rate were studied to investigate the thermal mixing characteristics in the microchannel. The mixing efficiency increases with increasing power input, while decreases with increasing flow rate. A numerical simulation of conjugate forced convection-conduction heat and mass transfer was employed to investigate the thermal chaotic mixing processes in the T-shaped microchannel. The measured mixing efficiency versus applied voltage and flow rate were compared with numerical simulation results, which showed reasonably agreement.     

含有解析函数与亚纯函数的一些不等式

指出文献 [2 ]和文献 [4]中的错误 ,并且得到含有单位圆盘内接解析函数与亚纯函数的几个不等式 .