Ultrasensitive Voltammetric Detection of Trace Lead(II) and Cadmium(II) Using MWCNTs‐Nafion/Bismuth Composite Electrodes

Multiwall carbon nanotubes were dispersed in Nafion (MWCNTs‐NA) solution and used in combination with bismuth (MWCNTs‐NA/Bi) for fabricating composite sensors to determine trace Pb(II) and Cd(II) by differential pulse anodic stripping voltammetry (DPASV). The electrochemical properties of the MWCNTs‐NA/Bi composites film modified glassy carbon electrode (GCE) were evaluated. The synergistic effect of MWCNTs and bismuth composite film was obtained for Pb(II) and Cd(II) detection with improved sensitivity and reproducibility. Linear calibration curves ranged from 0.05 to 100 μg/L for Pb(II) and 0.08 to 100 μg/L for Cd(II). The determination limits (S/N=3) were 25 ng/L for Pb and 40 ng/L for Cd, which compared favorably with previously reported methods in the area of electrochemical Pb(II) and Cd(II) detection. The MWCNTs‐NA/Bi composite film electrodes were successfully applied to determine Pb(II) and Cd(II) in real sample, and the results of the present method agreed well with those of atomic absorption spectroscopy.     

Inhibiting CO formation by adjusting surface composition in PtAu alloys for methanol electrooxidation

CO poisoning during methanol electrooxidation was investigated on PtAu alloys with different surface compositions. Results show that the CO formation can be reduced gradually with increasing surface Au fractions in PtAu alloys and CO poisoning can be almost eliminated by adjusting to a proper surface Au fraction.     

Kinetic resolution of β-lactams via enantioselective N-acylation

Enantioselective N-acylation of 4-aryl-β-lactams in the presence of acyl transfer catalyst Cl-PIQ provides an effective method for their non-enzymatic kinetic resolution.     

A symmetry-adapted shell transformation of core-shell nanoparticles for binary nanoassembly

Binary nanoassembly was realized by mixing gold@polyaniline nanoparticles with diblock copolymers in the DMF/H(2)O system and the products present a controlled transformation from symmetrical shells into spatially distributed petal-like polymer shells on gold cores.     

Metabolite identification of artemether by data-dependent accurate mass spectrometric analysis using an LTQ-Orbitrap hybrid mass spectrometer in combination with the online hydrogen/deuterium exchange technique

Artemether (ARM), the O-methyl ether prodrug of dihydroartemisinin (DHA), is a first-line antimalarial drug used in areas of multi-drug resistance. Artemisinin drugs can be metabolized extensively in vivo and this seems related to their autoinduction pharmacokinetics. In the present study, the metabolite identification of ARM was performed by the generic data-dependent accurate mass spectrometric analysis, using high-resolution (HR) liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (MS/MS) LTQ-Orbitrap hybrid mass spectrometer in conjunction with online hydrogen (H)/deuterium (D) exchange for rapid structural characterization. The LC separation was improved allowing the separation of ARM parent drugs and their metabolites from their diastereomers. A total of 77 phase I metabolites of ARM were identified in rat liver microsomal incubates and rat urine, including dihydroartemisinin and artemisinin. In rat bile, 12 phase II metabolites were found. Accurate mass data were obtained in both full scan and HR-MS/MS mode to support assignments of metabolite structures. Online H/D exchange LC/HR-ESI-MS experiments provided additional evidence in differentiating dihydroxylated deoxy-ARM from mono-hydroxylated ARM. The results showed the main phase I metabolites of artemether are hydroxylated, dehydro, demethylated and deoxy products, and they will undergo subsequent phase II glucuronidation processes. Most metabolites were reported for the first time. This study also demonstrated the effectiveness of high-resolution mass spectrometry in combination with an online H/D exchange LC/HR-MS(n) technique in rapid identification of drug metabolites.     

Structural elucidation and regioselective functionalization of an unexplored carbide cluster metallofullerene Sc2C2@C(s)(6)-C82

A Sc(2)C(84) isomer, previously assumed to be Sc(2)@C(84), is unambiguously identified as a new carbide cluster metallofullerene Sc(2)C(2)@C(s)(6)-C(82) using both NMR spectroscopy and X-ray crystallography. The (13)C-nuclei signal of the internal C(2)-unit was observed at 244.4 ppm with a 15% (13)C-enriched sample. Temperature-dependent dynamic motion of the internal Sc(2)C(2) cluster is also revealed with NMR spectrometry. Moreover, the chemical property of Sc(2)C(2)@C(s)(6)-C(82) is investigated for the first time using 3-triphenylmethyl-5-oxazolidinone (1) which provides a 1,3-dipolar reagent under heating. Regarding the low cage symmetry of this endohedral which contains 44 types of nonequivalent cage carbons, it is surprising to find that only one monoadduct isomer is formed in the reaction. Single-crystal X-ray results of the isolated pyrrolidino derivative Sc(2)C(2)@C(s)(6)-C(82)N(CH(2))(2)Trt (2) reveal that the addition takes place at a [6,6]-bond junction, which is far from either of the two Sc atoms. Such a highly regioselective addition pattern can be reasonably interpreted by analyzing the frontier molecular orbitals of the endohedral. Electronic and electrochemical investigations reveal that adduct 2 has a larger highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap than pristine Sc(2)C(2)@C(s)(6)-C(82); accordingly, it is more stable.     

Direct quantification of mono- and di-D-α-tocopherol polyethylene glycol 1000 succinate by high performance liquid chromatography

A simple and direct reversed-phase high performance liquid chromatography (RP-HPLC) method with UV detection was developed and validated for the determination of mono- and di-D-α-tocopherol polyethylene glycol 1000 succinate (TPGS 1000) in TPGS mixture. Before the HPLC analysis, mono- and di-TPGS 1000 were separated by simulated moving bed (SMB) chromatography system and characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The mass spectrometric results confirmed that the molar mass distribution of TPGS prepared in our laboratory was very close to that of the product of Eastman Chemical Company with similar nˉ (average polymerization degree), M(n)ˉ (number-average molecular weight) and M(w)ˉ (weight-average molecular weight). The HPLC analysis was carried out on a C30 analytical column with mobile phases comprised of acetonitrile (A) and isopropanol (B) in gradient conditions. Validation of the analytical method was done on the following parameters: system suitability, linearity, limits of detection and quantification, accuracy and precision, method robustness and solution stability. The linearity of the calibration curves for mono- and di-TPGS 1000 from both sources was found to be good (r(2)>0.9996). The recovery values were from 94.6% to 103.3% for mono-TPGS, and 93.5% to 103.3% for di-TPGS. This method could be successfully used in the direct quantification of mono- and di-TPGS in TPGS 1000 mixture using TPGS standards with similar molecular mass distributions although derived from different sources.     

Chiral salen-metal derivatives of polyoxometalates with asymmetric catalytic and photocatalytic activities

Immobilization of the chiral salen-metal complex [Mn(III)(salen)(H(2)O)(2)ClO(4)] on the Keggin-type polyoxometalate (POM) skeletons leads to the isolation of POM derivatives functionalized with chiral salen-metal complexes, which represent the first examples of introducing chiral salen-metal complexes into the POM systems.     

光谱法研究盐酸麻黄碱及盐酸伪麻黄碱与人血清白蛋白的键合

在模拟人体生理条件下,采用紫外光谱法、荧光光谱法和同步荧光光谱法研究盐酸麻黄碱及盐酸伪麻黄碱与人血清白蛋白(HSA)的结合作用.实验表明:盐酸麻黄碱和盐酸伪麻黄碱对HSA的荧光猝灭机制均为静态猝灭,盐酸麻黄碱和盐酸伪麻黄碱与HSA均形成1∶1复合物,结合常数K分别为2.53×104 L·mol-1和2.02×104 L...     

ASE/GC-MS法同时测定海洋沉积物中65种多氯联苯、多环芳烃与有机氯农药

建立了加速溶剂萃取/气相色谱-质谱法(ASE/GC-MS)同时测定海洋沉积物中28种多氯联苯(PCBs)、16种多环芳烃(PAHs)和21种有机氯农药(OCPs)的分析方法.结果表明,ASE的最佳萃取温度为100 ℃,最佳静态时间为5 min.GC-MS同时分析65种化合物时,PAHs的线性范围为0.05 ～5.00 ...