应用一种微波消解液直接测定食品中7种元素

针对食品检测前处理时间和检测周期过长的难题,用硝酸及双氧水作为消解溶剂,在设定的微波消解条件下,可以将样品消解完全,消解液中加入硫脲和L盐酸,不需任何处理可直接进行砷等7种元素的测定。硫脲将高价砷和汞离子还原为三价砷和汞原子,而对其它元素无影响,从而实现氢化物发生原子荧光法同时测定食品中砷、汞的含量,原子吸收火焰法测定食品中铜、锌、铁、镁、锰的含量。通过测定标准物质和加标回收实验,对方法进行验证,结果表明,方法简便快速、准确度与精密度令人满意。

21世纪中国地理学发展的若干思考

20世纪我国现代地理学的发展取得了辉煌成就,同时也面临着许多挑战和机遇。基于地球系统科学的最新研究成果与发展态势,结合我国地理学发展的自身特点及国家需求,本文从理论研究、方法论、学科建设、能力建设等方面,对21世纪我国地理学发展的若干问题进行了思考和探索。

Lanthanum zirconate ceramic toughened by BaTiO3 secondary phase

La2Zr2O7 (LZ) is a promising thermal barrier coating material for the high-temperature applications, which could be significantly toughened by the BaTiO3 piezoelectric phase incorporated into the matrix. The composites of xBaTiO(3)/(l-x)LZ (x=5, 10, 15, 20 vol%, LZ-x-BaTiO3) were densified by means of high-pressure sintering (HPS) under a pressure of 4.5 GPa at 1450 degrees C for 10 min, by which a high relative density above 93% could be obtained.

Preparation, structure and dielectric properties of (Ba1-xSrx)(2)NaNb5O15 ceramics

In this study the tungsten-bronze type tetragonal (Ba1-xSrx)(2)NaNb5O15 system as a kind of lead-free ferroelectric ceramics has been synthesized by low-temperature combustion method. Microstructure and dielectric properties of (Ba1-xSrx)(2)NaNb5O15 system were also investigated. X-ray diffraction (XRD) study confirms the formation of single-phase tetragonal compounds in the crystal system at room temperature. The TEM photograph shows that the particles synthesized by low-temperature combustion method are uniform with an average particle size of 30nm in diameter.

An unusual organic-inorganic chain-like hybrid complex [(CuCl)(2)(o-phen)](infinity) (o-phen=o-phenanthroline)

A novel organic-inorganic hybrid complex [(CuCl)(2) (o-phen)](infinity) 1 (o-phen = o-phenanthroline) has been hydrothermally synthesized and structurally characterized by elemental analyses, XPS spectrum, TG analysis, and single-crystal X-ray diffraction. Compound I crystallizes in the monoclinic system, space group P2(1)/n, a = 3.7285(7) Angstrom, b = 19.603(4) Angstrom, c = 16.757(3) Angstrom, beta = 95.83(3)degrees, V = 1218.4(4) Angstrom(3), Z = 4, lambda(MoKalpha) = 0.71073 Angstrom (R(F) = 0.0643 for 2559 reflections). Data were collected on an R-axis RAPID diffractometer at 293 K in the range of 1.60 < θ < 27.48degrees. The title compound exhibits a one-dimensional chain-like scaffolding constructed by the unusual [Cu3Cl3] hexagon motifs by, sharing opposite edges. Only Cu(1) sites of the [Cu3Cl3] hexagon are coordinated with N donors of o-phen groups. Furthermore, the three-dimensional supermolecular architecture is formed by C-H...Cl hydrogen bonds between o-phen groups and CuCl chains.

人参四逆汤成分的研究

利用ESI/MS~n、LC/MS、MALDI-TOF/MS等技术,从人参四逆汤水煎液中分析和鉴定了10种二萜生物碱:苯甲酰中乌头碱benzoylmesaconitine、苯甲酰乌头碱henzoylaconitine、苯甲酰次乌头碱benzoylhypacoitine、尼奥灵neoline、附子灵fuziline、14-乙酰基塔拉地萨敏14-acetyl-talatisamine、苯甲酰次乌头碱亚油酸酯14-benzoylhypaconine-8-linoleate、苯甲酰去氧乌头碱亚油酸酯14-benzoydeoxyaconine-8-oleate、苯甲酰次乌头碱棕榈酸酯14-benzoylhypaconine-8-palmitate、塔拉地萨敏talatisamine和人参皂甙R_(a1)、R_(a2)、R_(b1)、R_(b2)、R_(b3)、R_c、R_d、R_e、R_(g1)、R_(g2)、R_(g3)、R_f等12种人参皂甙。脂肪酸酯型生物碱和苯甲酰类生物碱的提取组分有抗失血性休克作用和弱的正性肌力作用。人参皂甙的提取组分具有明显的负性肌力作用。

Degradation of polyimide induced by nitrogen laser irradiation

The degradation behavior of polyimide (PMDA-ODA) induced by nitrogen laser irradiation was studied. The changes in the surface morphology and the composition of the irradiated polyimide films were examined by scanning electron microscopy, X-ray photoelectron spectroscopy and FT-IR spectroscopy. The initial reaction was achieved by photochemical degradation of polyimide in the highly electronic excited state by the absorption of a second 337 nm photon. Atmospheric oxygen sequentially reacted with the produced radicals to form a highly oxidized layer. The formation of carbonyl group was enhanced by the heat remaining on the irradiated polyimide film surfaces. (C) 2000 Elsevier Science B.V. All rights reserved.

Isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone)

The isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone) are investigated by differential scanning calorimetry over two temperature regions. The Avrami equation describes the primary stage of isothermal crystallization kinetics with the exponent n approximate to 2 for both melt and cold crystallization. With the Hoffman-Weeks method, the equilibrium melting point is estimated to be 406 degrees C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter (K-g) of the isothermal melt and cold crystallization is estimated. In addition, the K-g value of the isothermal melt crystallization is compared to those of the other poly(aryl ether ketone)s. (C) 2000 John Wiley & Sons, Inc.

ABF_3:Eu,Gd(A:K,Li;B:Ba,Mg)中Gd~(3+)→Eu~(2+)的能量传递

通过高温固相反应法,在高纯N_2气氛中合成了BaLiF_3,KMgF_3中单掺和双掺Eu,Gd的ABF_3型复合氟化物。研究了各类掺杂体系的光谱特性,观察到了Gd~(3+)→Eu~(2+)的能量传递,分析了能量传递过程,探讨了能量传递机理,并讨论了Gd~(3+)和Eu~(2+)的取代格位。

Linear and nonlinear optical properties of KNbO3

Linear and nonlinear optical (NLO) properties of KNbO3 in various phases are calculated from their crystal structures. Nonlinear optical tensor coefficients are found to be very sensitive to the atomic geometry, changing as much as 85% between the ferroelectric tetragonal and rhombohedral phases. The predicted principal refractive indices are also found to be sensitive to their structural changes. In the tetragonal phase KNbO3 has the largest NLO responses, in the orthorhombic phase KNbO3 has the relative larger NLO coefficients, and in the rhombohedral structure KNbO3 has the large and homogeneous NLO properties. (C) 1998 Elsevier Science B.V. All rights reserved.

Thermal decomposition processes of polyaniline and poly-o-toluidine investigated by direct pyrolysis mass spectrometry

The thermal decomposition of polyaniline(PAn) and poly-o-toluidine(POT) was studied by means of direct pyrolysis mass spectrometry(DM) and MS/MS, The results showed that both benzene-diamine and quinone-diimine units were produced, and the intensities of fragments corresponding to quinone-diimine units increased as the oxidation degrees increased, The mechanism of thermal decomposition of PAn and POT was given for the first time.

{[Sm_2(Gly)_6(H_2O)_4](ClO_4)_6(H_2O)_5}_n的合成和晶体结构

本文合成了标题配合物,对其红外光谱进行了研究.测定了配合物的晶体结构,结果表明,晶体属三斜晶系,P1空间群,单胞参数:α=11.549(2)(?),b=14.122(3)(?),c=15.654(?),α=97.01(2)°,β=102.70(2)°,γ=105.43(2)°,V=2355.94(0.87)(?)~3,Z=2.晶体结构是采用Patterson法和差值Fourier合成解出.经全矩阵最小二乘法修正,最后偏差因子R=0.0337,R_w=0.0364.晶体中甘氨酸与Sm原子的结合方式有三种:第一种甘氨酸的羧基离子以螯合桥式与Sm原子配位;第二种甘氨酸以羧基桥式与同一单元的两个Sm原子配位;第三种甘氨酸以酸基桥式连结两个相邻单元中的相邻Sm原子而形成一维无限长链结构.此外,每个Sm原子还与两个水分子成键,其配位数为9.

超高灵敏显色反应及其应用的研究Ⅷ.铅-乙基罗丹明B-碘化物体系

本文研究了在聚乙稀醇-阿拉伯胶共存下,乙基罗丹明B和PbI_4~(2-)的超高灵敏显色反应并制定了新的光度法。缔合物最大吸收为605nm,ε值为1.0×10~6·L·mol~(-1)·cm~(-1)。经巯基棉分离、富集,本法成功地用于硫酸镁、硫酸锌和硫酸亚铁铵等试剂中痕量铅的测定。

SYNTHESES OF BIS(TERT-BUTYLCYCLOPENTADIENYL)LANTHANOID CHLORIDE COMPLEXES AND CRYSTAL-STRUCTURES OF BIS(TERT-BUTYLCYCLOPENTADIENYL)CHLORO(BISTETRAHYDROFURAN)-PRASEODYMIUM AND BIS(TERT-BUTYLCYCLOPENTADIENYL)-CHLOROTETRAHYDROFURANYTTERBIUM

Reaction of lanthanoid trichloride with two equivalents of sodium t-butylcyclopentadienide in tetrahydrofuran affords bis(t-butylcyclopentadienyl)lanthanoid chloride complexes (t-BuCp)2LnCl. nTHF (Ln = Pr, Nd, n = 2; Ln = Gd, Yb, n = 1). The compound (t-BuCp)2PrCl.2THF (1) crystallizes from THF in monoclinic space group P2(1)/c with unit cell dimensions a = 15.080(3), b = 8.855(2), c = 21.196(5) angstrom, beta = 110.34(2)degrees, V = 2653.9 angstrom-3 and D(calcd) = 1.41 g/cm3 for Z = 4. The central metal Pr is coordinated to two t-BuCp ring centroids, one chlorine atom and two THF forming a distorted trigonal bipyramid. The crystal of (t-BuCp)2YbCl.THF (2) belongs to the monoclinic crystal system, space group P2(1)/n with a = 7.726(1), b = 12.554(2), c = 23.200(6) angstrom, beta = 97.77(2)degrees, V = 2229.56 angstrom-3, D(calcd) = 1.50 g/cm3 and Z = 4. The t-BuCp ring centroids, the chlorine atom and the oxygen atom of the THF describe a distorted tetrahedron around the central ion of ytterbium.