马一嘉,罗冰虹,谭凯馨

硫在作物生长过程中必不可少的营养元素之一,主要参与作物生理代谢及生长发育。因此,土壤中硫的含量一直是人们关注的热点,快速准确的检测方法也成为人们研究土壤中硫的关键。在高温燃烧碘量法测定土壤硫含量中,碘酸钾溶液滴定亚硫酸时,对于低含量样品,滴定终点的判断较为困难。通过大量的试验,采用硫代硫酸钠滴定吸收器中反应后剩余的碘酸钾溶液,滴定终点由蓝色消失为无色。终点便于肉眼的观察,提高了分析结果的准确性和再现性;采用EXCEL中的LINEST函数回归标准物质滴定校准工作曲线,方法简便快速。通过国家一级标准物质的分析验证,方法准确度高、精密度好,适用于大批量土壤样品中低含量硫的测定。     

王玉功,倪能 ,杨发旺

采用电感耦合等离子体发射光谱法(ICP-AES)测定地表水和地下水中的全S、P、B来近似代替水中的SO42-、PO43-、H3BO3。结果表明,ICP-AES可同时测定地表水和地下水的SO42-、PO43-、H3BO3,方法检出限分别为0.0265mg/L、0.0320mg/L、0.0192mg/L。方法的精密度(RSD,n=6)为0.53﹪～6.09﹪,加标回收率为91.9﹪～102.2﹪,经与单个项目分别测定的方法比对实验,测定值无明显系统偏差。方法快速、准确,经国家标准物质验证,结果与标准值相符。     

Theoretical Study on the Structure and Stability of Si5X （X = Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl） Clusters

1 INTRODUCTION In the later 60s of last century, silicon substituted for germanium to present as mainstream in semicon- ductor. The semi-conductive devices made by silicon have many advantages, for example, refractory pro- perty, high radioresistance, simple and stable process- ing technic, high machinability and low cost. So it was widely used to manufacture large power appara- tuses, for instance, digit and linear integrated circuit, large scale integrated circuit (LSI), etc. Thus, th…     

硫酸镍中Ca,Mg,Cu,Fe,Pb,Zn的光谱测定

用发射光谱法测定结晶硫酸镍中Ｃａ,Ｍｇ,Ｃｕ,Ｆｅ,Ｐｂ,Ｚｎ等杂质元素,加入ＮａＣｌ为缓冲剂改善杂质元素的激发行为,以提高分析的灵敏度。用交流电弧激发,以镍为内标,一次摄谱,可同时测定上述六种元素。此法快速、准确,满足实际需要。     

Sn(Ⅱ)-X和Sn(Ⅳ)-X (X=O,S,N,C,P,As,Se,Te,F,Cl,Br,I)键价参数

基于剑桥晶体数据库中同配配合物的Sn(Ⅱ)-X和Sn(Ⅳ)-X (X=O,S,N,C,P,As,Se,Te,F,Cl,Br,I)键长数据,采用键价参数B=0.037 nm拟合得到Sn(Ⅱ)-X和Sn(Ⅳ)-X的键价参数R0,这样拟合的经验参数R0中有一些是首次推出.本文所报道的Sn(Ⅱ)-O键基于B=0.037 nm的R0值(0.1956 nm)可适用于多数Sn(Ⅱ)呈各种配位数时的氧化态指定,而文献报道的B=0.055 nm和R0=0.1859 nm主要对于低配位的情况能取得Sn(Ⅱ)原子价态指定的较好结果.本研究证明,进一步研究键价参数对键价和(BVS)计算至关重要的那些可能的因素实乃当务之急.     

ZH3,ZH+4及ZH4X(Z=N,P,As,Sb,Bi,X=F,Cl,Br,I)的结构与电子性质质

采用MP2/def2-TZVP理论方法考察了ZH3,ZH+4及ZH4X(Z=N,P,As,Sb,Bi,X=F, Cl, Br, I)的结构与电子性质。结果表明,随着氮族元素原子序数的递增,其氢化物(ZH3)中心原子杂化轨道中s成分减小,p成分逐渐增大,杂化轨道偏离平面的程度依次增大,导致NH3空间构型的最为“平面”,而BiH3最为“锥形”。尽管阳离子ZH+4由ZH3中Z的一个不等性sp3杂化轨道提供孤对电子与H+形成,但ZH+4中4个Z-H键等价,Z总体呈现等性sp3杂化。ZH4X均为C3v对称的四面体结构,ZH3与HX之间的作用驱动力来源于离子型的氢键(H3Z…H*-X)而非ZH+4与X－阴阳离子对(ZH+4X－)间的静电作用,H3Z…H*-X内的电子转移主要发生在轨道LP1(Z)与σ*(H*-X)之间。     

X射线荧光光谱法测定锌铝镁合金中锌,铝,镁,硅,铁,钛,钙,锆和铈

通过确立仪器的测量条件并在X射线荧光仪上拟合出检测锌铝镁合金中各元素的工作曲线,建立了X射线光谱法测定锌铝镁合金中Zn,Al,Mg,Si,Fe,Ti,Zr,Ce的快速分析方法。对实际样品进行测试,相对标准偏差(RSD,n=11)在0.12%~4.8%之间。与化学分析方法比对,测试结果基本一致。方法已应用到日常锌铝镁合金样品的检测。     

Sn(II)―X和Sn(IV)―X (X=O,S, N,C, P,As, Se,Te, F,Cl, Br,I)键价参数

基于剑桥晶体数据库中同配配合物的Sn(Ⅱ)―X和Sn(Ⅳ)―X(X=O,S,N,C,P,As,Se,Te,F,Cl,Br,I)键长数据,采用键价参数B=0.037nm拟合得到Sn(Ⅱ)―X和Sn(Ⅳ)―X的键价参数R0,这样拟合的经验参数R0中有一些是首次推出.本文所报道的Sn(Ⅱ)―O键基于B=0.037nm的R0值(0.1956nm)可适用于多数Sn(Ⅱ)呈各种配位数时的氧化态指定,而文献报道的B=0.055nm和R0=0.1859nm主要对于低配位的情况能取得Sn(Ⅱ)原子价态指定的较好结果.本研究证明,进一步研究键价参数对键价和(BVS)计算至关重要的那些可能的因素实乃当务之急.     

ICP-AES法测定镍铜合金中的Fe,Mn,Cr,Nb

建立了ICP–AES法测定镍铜合金中Fe,Mn,Cr,Nb元素的分析方法。进行了基体元素Ni,Cu及共存元素对分析元素的光谱干扰研究,分别选择259.940,257.610,283.563,316.340 nm作为分析谱线,确定内标用量为2.00 mL。测定结果的相对标准偏差为0.48%～4.71%(n=8),加标回收率为95.0%～103.4%。该法满足分析要求。     

灵敏度,检出限,测定限

1灵敏度灵敏度(sensitivity)源于词sensitive(敏感)。一架能称出微量试样的重量或质量的天平,称“这架天平很灵敏”;一个能测定很微量的分析物的分析方法,则称“这个方法很灵敏”。这些都是口头上的定性表述。按照国际理论化学与应用化学联合会(I UPAC)1976年制定的文件[1],灵敏度定义为分析物浓度或量的微小变化所产生的分析信号的变化,即Δs/Δc比值,它实质是校准曲线(也称为工作曲线,标准曲线,分析曲线等)的斜率。在光度分析中,Sandell在1959年提出表征光度分析方法灵敏度的指数,被称为Sandell灵敏度,沿用至今。Sandell灵敏度是当采…     

Optimization of parameters for semiempirical methods. III Extension of PM3 to Be,Mg, Zn,Ga, Ge,As, Se,Cd, In,Sn, Sb,Te, Hg,Tl, Pb,and Bi

Using a recently developed procedure for optimizing parameters for semiempirical methods,¹ PM3 has been extended to a total of 28 elements. Average ΔH_f errors for the newly parameterized elements are Be: 8.6, Mg: 8.4, Zn: 5.8, Ga: 14.9, Ge: 11.4, As: 8.5, Se: 11.1, Cd: 2.6, In: 11.3, Sn: 9.0, Sb: 13.7, Te: 11.3, Hg: 6.8, Tl: 6.5, Pb: 7.4, and Bi: 10.9 kcal/mol. For some elements the paucity of data has resulted in a method, which, while highly accurate, is likely to be only poorly predictive.     

Dendrimers Functionalized with Palladium Complexes of N-, N,N-, and N,N,N-Ligands

Pyridine, pyridine imine, and bipyridine imine ligands functionalized by a phenol have been synthesized and characterized, in many cases by X-ray diffraction. Several of these N-, N,N-, and N,N,N,-ligands have been grafted onto the surface of phosphorhydrazone dendrimers, from generation 1 to generation 3. The complexation ability of these monomers and dendrimers towards palladium(II) has been assayed. The corresponding complexes have been either isolated or prepared in situ. In both cases, the monomeric and dendritic complexes have been tested as catalysts in Heck couplings and in Sonogashira couplings. In some cases, a positive dendritic effect has been observed, that is, an increase of the catalytic efficiency proportional to the dendrimer generation.     

Extraction-flame atomic absorption determination of microtraces of Ag, Bi, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn in ammonium sulphate

Summary A method was developed for the determination of 10 trace elements in ammonium sulphate, or sulphuric acid, respectively. The detection limits for the separate elements vary from 1×10^–5 to 5×10^–7%. The method includes a new approach for calibration in organic medium, consisting of conversion of the aqueous metal standards into chelate compounds in a homogeneous solution.A three-step optimization scheme for pulse aspiration of organic extracts is proposed which permits to obtain a highly reproducible and accurate signal. The solutions of the organic reagents used are subjected to a purification procedure, which lowers their impurity level for approx. one order of magnitude.

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Extraktions-flammenatomabsorptiometrische Bestimmung von Mikrospuren Ag, Bi, Cd, Co, Cu, Fe, Mn, Ni, Pb und Zn in Ammoniumsulfat

Zusammenfassung Ein Verfahren wurde entwickelt zur Bestimmung dieser 10 Elemente in Ammoniumsulfat bzw. Schwefelsäure. Die Nachweisgrenzen der Elemente liegen zwischen 1 · 10^–5 und 5 · 10^–7%. Das Verfahren beinhaltet auch eine neue Methode zur Eichung in organischem Medium, die auf Umwandlung der wässrigen Metallstandardlösungen in Chelatverbindungen in homogener Lösung beruht. Eine dreistufige Optimierung des pulsierenden Ansaugens der organischen Extrakte wird vorgeschlagen, wodurch genaue und reproduzierbare Signale erhalten werden. Die Lösungen der organischen Reagentien werden einem Reinigungsverfahren unterzogen, das die Konzentration an Verunreinigungen um etwa eine Größenordnung senkt.

     

The discovery, isolation, elucidation of structure, and synthesis of antamanide

Antamanide is the name we have given to a constituent of the fungus Amanita phalloides. This substance counteracts the lethal action of the Amanita toxins phalloidine and α-amanatine if administered to the white mouse before, or simultaneously with, the poisons. Its concentration in the fungus is, however, so low that the toxic action of the latter predominates. Antamanide is a cyclic decapeptide formed from the L -amino acids alanine, phenylalanine, proline, and valine in the molar ratio 1:4:4:1. The amino-acid sequence was determined by a combination of gas chromatography and mass spectrometry. The structural formula assigned was confirmed by synthesis according to a classic route of peptide chemistry.     

3,3,6,6-四甲基-4a-羟基-9-邻甲氧基苯基-1,8-二氧代-2,3,4,4a,5,6,7,8,9,9a-十氢化-1H-氧杂蒽的合成和晶体结构

标题化合物C24H30O5是由邻甲氧基苯甲醛与5，5-二甲基-1，3-环己二酮在N，N-二甲基甲酰胺中反应而得。结构通过单晶X-射线衍射法确定，其晶体属于单斜晶系，空间群C2／c，a=33．942（6），b=7273（1），c=22667（4）A，β=128．989（9）°，Mr=398．50，V=4349（1）A3，Dc=1．2179·cm-3，Z=8，μ（MoKa）=840mm－1，F（000）=1712。晶体结构用直接法解出，经用全矩阵最小二乘法对原子参数进行修正，最后的偏离因子为R=0.043，Rw=0．052。在晶体结构中，存在一个分子间氢键。     

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I

Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability--being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be improved if the full potential of new linear scaling techniques, such as MOZYME and LocalSCF, is to be realized. Accordingly, in this article we present RM1 (Recife Model 1): a reparameterization of AM1. As before, the properties used in the parameterization procedure were: heats of formation, dipole moments, ionization potentials and geometric variables (bond lengths and angles). Considering that the vast majority of molecules of importance to life can be assembled by using only six elements: C, H, N, O, P, and S, and that by adding the halogens we can now build most molecules of importance to pharmaceutical research, our training set consisted of 1736 molecules, representative of organic and biochemistry, containing C, H, N, O, P, S, F, Cl, Br, and I atoms. Unlike AM1, and similar to PM3, all RM1 parameters have been optimized. For enthalpies of formation, dipole moments, ionization potentials, and interatomic distances, the average errors in RM1, for the 1736 molecules, are less than those for AM1, PM3, and PM5. Indeed, the average errors in kcal x mol(-1) of the enthalpies of formation for AM1, PM3, and PM5 are 11.15, 7.98, and 6.03, whereas for RM1 this value is 5.77. The errors, in Debye, of the dipole moments for AM1, PM3, PM5, and RM1 are, respectively, 0.37, 0.38, 0.50, and 0.34. Likewise, the respective errors for the ionization potentials, in eV, are 0.60, 0.55, 0.48, and 0.45, and the respective errors, in angstroms, for the interatomic distances are 0.036, 0.029, 0.037, and 0.027. The RM1 average error in bond angles of 6.82 degrees is only slightly higher than the AM1 figure of 5.88 degrees, and both are much smaller than the PM3 and PM5 figures of 6.98 degrees and 9.83 degrees, respectively. Moreover, a known error in PM3 nitrogen charges is corrected in RM1. Therefore, RM1 represents an improvement over AM1 and its similar successor PM3, and is probably very competitive with PM5, which is a somewhat different model, and not fully disclosed. RM1 possesses the same analytical construct and the same number of parameters for each atom as AM1, and, therefore, can be easily implemented in any software that already has AM1, not requiring any change in any line of code, with the sole exception of the values of the parameters themselves.     

Syntheses, structures, and physical properties of LnAsTe (Ln = La, Pr, Sm, Gd, Dy, Er)

Six rare-earth arsenic tellurides have been synthesized by the reactions of the rare-earth elements (Ln) with As and Te at 1123 K. LaAsTe (a = 7.8354(11) A, b = 4.1721(6) A, c = 10.2985(14) A, T = 153 K), PrAsTe (a = 7.728(2) A, b = 4.1200(11) A, c = 10.137(3) A, T = 153 K), SmAsTe (a = 7.6180(16) A, b = 4.0821(9) A, c = 9.991(2) A, T = 153 K), GdAsTe (a = 7.5611(15) A, b = 4.0510(8) A, c = 9.920(2) A, T = 153 K), DyAsTe (a = 7.4951(13) A, b = 4.0246(7) A, c = 9.8288(17) A, T = 153 K), and ErAsTe (a = 7.4478(1) A, b = 4.0078(1) A, c = 9.7552(2) A, T = 153 K) crystallize with four formula units in the orthorhombic space group D2h16-Pnma. These compounds are isostructural and belong to the beta-ZrSb2 structure type. In each compound, the Ln atoms are coordinated by a tricapped trigonal prism of four As atoms and five Te atoms. The entire three-dimensional structure is built up by the motif of the LnAs4Te5 tricapped trigonal prisms. Infinite nonalternating zigzag As chains are found along the b axis, with As-As distances in these compounds ranging from 2.5915(5) to 2.6350(9) A. Conductivity measurements in the direction of these As chains indicate that PrAsTe is metallic whereas SmAsTe and DyAsTe are weakly metallic. Antiferromagnetic transitions occur in SmAsTe and DyAsTe at 3 and 9 K, respectively. DyAsTe above 9 K follows the Curie-Weiss law.     

Synthesis of xyloketal A, B, C, D, and G analogues

A series of demethyl analogues of the natural products xyloketal A, B, C, D, and G have been prepared in a notably direct manner from 3-hydroxymethyl-2-methyl-4,5-dihydrofuran and a series of corresponding phenols. These syntheses featured a boron trifluoride diethyl etherate-promoted electrophilic aromatic substitution reaction as a key step. In the case of the synthesis of analogues of xyloketal A, the process was found to be highly efficient (up to 93% yield). The optimized isolated yield of these reaction products is remarkable in view of the fact that this transformation involves, minimally, six individual reactions. Moreover, these synthetic studies provide significant insight into the possible biogenic origin of the xyloketal natural products.     

3,3,6,6-四甲基-9-邻氯苯基-1,8-二氧代-3,4,5,6,7,9-六氧化氧杂蒽的合成和晶体结构

标题化合物C23H25对O3Cl是由邻氯苯甲醛与5，5-二甲基1，3-环己二酮在N，N-二甲基甲酸腹中反应而得。结构通过单晶X-射线衍射法确定，其晶体属于单科晶系，空间群=1632。晶体结构用直接法解出，使用全矩阵最小二乘法对原子参数进行修正，最后的偏离因子为R=0．054，Rw一0．063。在晶体结构中，吡喃环与苯环之间的两面角为92．43°。     

Calorimetry of nanoparticles,surfaces, interfaces,thin films,and multilayers

Calorimetry gives insight into the stability of nanophase materials. Using TiO₂ as an example, the interplay of energetics of polymorphism, surface energy, and surface hydration is discussed. Oxide melt solution calorimetry, water adsorption calorimetry, and adiabatic heat capacity studies together show the following. The metastability of bulk polymorphs increases in the order rutile, brookite, anatase, while the surface energy increases in the opposite order. This leads to crossovers in phase stability at the nanoscale, which appears to be a general phenomenon. Hydration plays a major role in stabilizing nanoparticles and the first layers of water are tightly bound. There is little excess heat capacity and no significant excess vibrational entropy in nanophase rutile or anatase. Further applications of calorimetry to thin films, interfaces, multilayers, and sub-milligram samples are presented.