玄参、生地黄、紫草等六种中药中微量元素含量的测定

为了解中药中微量元素的含量与其药物的作用机制关系,用原子吸收分光光度计测定了玄参、生地黄、紫草、水牛角、牡丹皮、赤芍中铁(Fe)、镁(Mg)、铜(Cu)、钙(Ca)、锌(Zn)、铬(Cr)、钼(Mo)等7种微量元素的含量.结果表明,Ca的含量最高,Cu的含量几乎最低.这6种中草药含有多种对人体有益的微量元素,与它们的药...     

恒电流电解-BCO分光光度法测定纯铜中铜含量不确定度的评定

对采用恒电流电解-BC0分光光度法测定纯铜中铜含量的不确定度进行了评定.对测量重复性、电解重量法、光度法等影响测量结果的不确定度分量进行了分析和量化.当纯铜中铜的质量分数为99.93%时,扩展不确定度为0.01%,k=2.     

顺序注射催化光度分析法测定环境水样中痕量钼

基于钼（VI）对碘化钾/过氧化氢反应体系催化作用的反应产物在350 nm处的吸光度与钼在一定浓度范围内呈线性关系的原理,建立了灵敏的顺序注射催化动力学光度分析新方法。方法的线性范围是2~300 μg/L,方法的检出限（3s）为1.1μg/L,相对标准偏差（RSD）为 0.6%（n=11）。 每次测定仅消耗100μL试样,75μL KI和125μL H2O2 , 对4个不同水样的钼测定回收率在95.2%~105.2%之间。顺序注射催化动力学光度分析测定环境水样中痕量钼的方法是一种快速、准确的新方法。     

催化动力学光度法测定青霉素G及其机理研究

研究了在青霉素G存在下双氧水氧化苋菜红的褪色反应,建立了催化动力学光度法测定微量青霉素G的方法.方法线性范围为0.20～4.00μg/mL,回归方程y=-0.015p(μg/mL)+0.311,r=0.9998;方法线性范围为4.00～50.0μg/mL,回归方程y=0.001p(μg/mL)+0.280,r=0.99...     

阻抑高碘酸钾氧化甲基紫褪色光度法测定苯酚

基于HAc-NaAc缓冲体系中,反应温度为25℃时,苯酚阻抑高碘酸钾氧化甲基紫的褪色反应,建立了测定苯酚的阻抑褪色光度新方法.该方法最大吸收波长为580 nm,线性范围为0.02μg/mL～2·2μg/mL,检出限为3.8×10<'-3>μg/mL,方法用于环境水中苯酚的测定,相对标准偏差为1.97%～2.25%,回收...     

气体扩散耦合顺序注射光度分析法测定葡萄酒中的二氧化硫*

依据在微碱性条件下,亚硫酸根离子可与孔雀绿溶液发生加成反应并使其褪色的原理,建立了气体扩散耦合顺序注射分光光度法测定葡萄酒中二氧化硫的新方法。当接收液流速为1.2mL/min和4.2mL/min时,方法的线性响应范围分别为1.0-5.0μg/mL和5.0-50.0μg/mL,方法的检出限为0.33μg/mL,相对标准偏差（RSD）≤0.43%,对葡萄酒样中二氧化硫测定的加标回收率为98.7%-104.7%。     

2‐Ethylsulfanyl‐7‐(furan‐2‐yl)‐4‐(thiophen‐2‐yl)pyrazolo[1,5‐a][1,3,5]triazine: π‐stacked chains of hydrogen‐bonded R22(10) dimers

In the title compound, C₁₅H₁₂N₄OS₂, the bond distances in the fused heterocyclic system show evidence for aromatic‐type delocalization in the pyrazole ring with some bond fixation in the triazine ring. The thiophenyl substituent is slightly disordered over two sets of atomic sites having occupancies of 0.934 (4) and 0.066 (4). The non‐H atoms in the entire molecule are nearly coplanar, with the planes of the furanyl substituent and the major orientation of the thiophenyl substituent making dihedral angles of 5.72 (17) and 1.8 (3)°, respectively, with that of the fused ring system. Molecules are linked into centrosymmetric R₂²(10) dimers by C—H...O hydrogen bonds and these dimers are further linked into chains by a single π–π stacking interaction. Comparisons are made with some related 4,7‐diaryl‐2‐(ethylsulfanyl)pyrazolo[1,5‐a][1,3,5]triazines which contain variously substituted aryl groups in place of the furanyl and thiophenyl substituents in the title compound.     

差示法测量Cu30W70钨铜合金中钨的含量

研究了广泛用于军工、高压开关、电火花电极、电子封装的新型材料钨铜合金[1]中钨含量的定量分析,采用传统的湿化学差示分析方法。由于该材料的耐腐蚀性,试样溶解是关键,通过实验决定采用9 1盐硝酸和1 3硫磷酸混合酸低温加热溶解。加入草酸胺掩蔽铜的干扰。用硫氰酸胺显色。以Cu30W70为例用40%的钨为参比,配制一系列标准制作工作曲线。钨含量在5～10μg/ml内服从比耳定律。方法的精密度RSD=1.6%,回收率为97.2%～101.4%。适用范围为含钨45%以上的钨铜合金。     

Catalytic and kinetic spectrophotometric method for determination of vanadium(V) by 2,3,4-trihydroxyacetophenonephenylhydrazone

A new catalytic and kinetic spectrophotometric method for the determination of vanadium(V) was studied using 2,3,4-trihydroxyacetophenonephenylhydrazone (THAPPH) as an analytical reagent. The present method was developed on the catalytic effect of vanadium on oxidation of THAPPH by hydrogen peroxide in hydrochloric acid–potassium chloride buffer (pH = 2.8) at the 20th minute. The metal ion has formed 1:2 (M:L) complex with THAPPH. Beer’s law was obeyed in the range 20–120 ng/mL of V(V) at λ_max 390 nm. The sensitivity of the method was calculated in terms of molar absorptivity (1.999 × 10⁵ L mol⁻¹cm⁻¹) and Sandell’s sensitivity (0.000254 μg cm⁻²), shows that this method is more sensitive. The standard deviation (0.0022), relative standard deviation (0.56%), confidence limit (±0.0015) and standard error (0.0007) revealed that the developed method has more precision and accuracy. The stability constant was calculated with the help of Asmu’s (9.411 × 10⁻¹¹) and Edmond’s & Birnbaum’s (9.504 × 10⁻¹¹) methods at room temperature. The interfering effect of various cations and anions was also studied. The present method was successfully applied for the determination of vanadium(V) in environmental and alloy samples. The method’s validity was checked by comparing the results obtained with atomic-absorption spectrophotometry and also by evaluation of results using F-test.     

Stereocontrolled Synthesis of 1,5‐Stereogenic Centers through Three‐Carbon Homologation of Boronic Esters

Allylic pinacol boronic esters are stable toward 1,3‐borotropic rearrangement. We developed a Pd^II‐mediated isomerization process that gives di‐ or trisubstituted allylic boronic esters with high E selectivity. The combination of this method with lithiation–borylation enables the synthesis of carbon chains that bear 1,5‐stereogenic centers. The utility of this method has been demonstrated in a formal synthesis of (+)‐jasplakinolide.