原子吸收分光光度法测定红豆、绿豆和黄豆中微量元素

为探讨红豆、绿豆和黄豆中微量元素的含量,采用原子吸收分光光度计测定了红豆、绿豆和黄豆中的Cu、Zn。结果表明,红豆、绿豆和黄豆中均含有对人体健康有益的元素。该法简便、快速、准确、灵敏度高、再现性好。     

Protein Fractionation of Cowpea (Vigna unguiculata (L.) Walp) Leaf, Flower and Seed by Capillary Electrophoresis and Its Potential for Variety Identification

The proteins of different faction of cowpea [Vigna unguiculata (L.) Walp] were fractionated by capillary electrophoresis (CE). The extracting solvent system was one of the most critical factors in the optimization exercise. To improve reproducibility, seed samples needed to be defatted with chloroform/methanol (V:V=2:1) as preferred prior to protein extraction. Proteins were extracted from seeds, leaves and flowers with 50% aqueous 1‐propanol and separated on a 50 (m×20 cm fused silica capillary column using a UV detector at 200 nm. Separation was conducted at constant voltage (10 kV, 40°C), using iminodiacetic acid (pH 2.5) containing 0.05% hydroxypropylmethylcellulose (HPMC) and 20% acetonitile. The results showed that proteins extracted from all fraction of cowpea were successfully separated by CE in less than 20 min. Seed extracts provided the greatest number of eluted protein peaks, followed by flower and leaf, respectively. The seed‐protein extracts provided unique CE patterns for different varieties; hence the seed was the tissue chosen as being most suitable for variety identification. As a result, an optimized procedure was developed to provide rapid identification of cowpea varieties, based on capillary electrophoregram patterns.     

Studies of New 2,7-Carbazole (CB) Based Donor-Acceptor-Donor (D-A-D) Monomers as Possible Electron Donors in Polymer Solar Cells by DFT and TD-DFT Methods

The new donor-acceptor-donor (D-A-D) monomers have been studied using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to evaluate the optoelectronic and electronic properties for bulk heterojunction (BHJ) organic solar cells. The TD-DFT method is combined with a hybrid exchange-correlation functional using the B3LYP method in conjunction with a polarizable continuum model (PCM) and a 6–311G basis set to predict the excitation energies and absorption spectra of all monomers. The predicted bandgap (E_g) of the monomers decreasing in the following order D1<D2<D3<D4<D5<D6<D7<D9<D8. Furthermore, open-circuit voltage (V_OC) estimates for monomers with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) acceptor. The V_OC of the studied monomers ranges from 0.976 to 1.398 eV in the gas and from 1.109 to 1.470 eV in the solvent phase with PC71BM acceptor, which is sufficient for efficient electron injection into the acceptor‘s LUMO. The results show that theoretically, a maximum energy conversion efficiency of roughly 5 % for D8 and 5.8 5 % for D7.     

Determination of Cd(II), Cu(II) and Ni(II) in aqueous samples by ICP-OES after on-line preconcentration in column packed with silica modified with 2-aminothiazole

This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT) and the studies of adsorption and pre-concentration (in batch and using a flow-injection system coupled with optical emission spectrometer) of Cd(II), Cu(II) and Ni(II) in aqueous medium. The adsorption capacity for each metal ions in mmol g⁻¹ was: Cu(II) = 1.18, Ni(II) = 1.15 and Cd(II) = 1.10. The results obtained in the flow experiments showed about 100% of recovering of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 μL of 2.0 mol L⁻¹ HCl solution as eluent. The quantitative sorption–desorption of the metal ions made possible the application of a flow-injection system in the pre-concentration and quantification by ICP-OES of metal ions at trace level in natural water samples. Correspondence: Pedro M. Padilha, Departamento de Química e Bioquímica, I.B., UNESP, 18618-000 Botucatu, SP, Brazil