溶出伏安法测定乌药中的铜铅镉

在KNO3底液下,用线性扫描阳极溶出伏安法同时测定了乌药样品中铜、铅、镉3种金属的含量.结果表明,在最佳实验条件下,铜、铅、镉的峰电位分别为0.067、-0.45和-0.64V(vs ScE);铜、铅、镉金属离子的质量浓度在0-0.8 mg·L-1范围内,呈现良好的线性关系,相关系数分别为0.991 3、0.990 5...     

示波极谱法同时测定尿中铅和镉

研究示波极谱法同时测定尿中铅和镉的方法.运用正交试验选择底液的组成为碘化钾-抗坏血酸-浓盐酸-磷酸.用硝酸、高氯酸、盐酸混合酸消化尿样,消化液在酸性介质中,置极谱仪的三电极系统,样品溶液在滴汞电极上产生还原电流,分别于-480 mV和-620 mV处测量铅和镉的峰电流,对尿样中铅和镉进行测定,铅、镉的质量浓度在100 μg·L-1以内与峰电流呈线性关系.铅、镉的相对标准偏差分别为6.91%,6.45%,检出限(3S/N)分别为2.0,1.0 μg·L-1,回收率分别为88.4%～101.4%,83.1%～103.5%.     

石墨炉原子吸收法测定食品添加剂甲壳素中的镉和铅

采用程序控制温度,一次完成甲壳素样品的炭化和灰化,通过氢氟酸-硝酸消除灰分中硅的干扰,用石墨炉原子吸收法直接测定其中的镉和铅.镉的浓度在0～50 ng/mL范围内与吸光度呈良好的线性关系,相关系数r= 0.9990;铅的浓度在0～300 ng/mL范围内与吸光度呈良好的线性关系,相关系数r=0.9990 .镉的回收率为90.6%～102.0%,测定结果的相对标准偏差为4.37%(n=8);铅的回收率为91.3%～102.1%,测定结果的相对标准偏差为8.67%(n=8).     

电感耦合等离子体原子发射光谱法测定易切钢中铅含量

采用电感耦合等离子体原子发射光谱法对易切钢中铅的含量进行测定,样品经硝酸-盐酸(1+1)混合酸溶解,选择220.353 nm波长为测定铅的分析线,铅的质量浓度在2.00～20.00 mg·L-1范围内与其谱线强度呈线性关系,测定下限(10S/N)为0.03 mg·L-1.该方法用于两个标准样品(GSBH 40064-93和GSBH 40061-93)中铅含量的测定,加标回收率在97.1%～99.1%之间,相对标准偏差(n=11)小于0.8%.     

电感耦合等离子体原子发射光谱法测定金属饰品中铅、镉、铬、汞、锑、砷、硒、钡、镍溶出量

金属饰品样品用硝酸(20+80)溶液浸泡过夜,采用电感耦合等离子体原子发射光谱法测定金属饰品中铅、镉、铬、汞、锑、砷、硒、钡和镍的溶出量。选择波长为216.9,228.8,267.7,194.2,206.8,189.0,196.0,455.4,216.6nm的9条谱线依次作为测定铅、镉、铬、汞、锑、砷、硒、钡和镍的分析线。铅、镉、铬、锑、砷、硒、钡和镍的质量浓度与其发射强度在10.0mg·L-1以内、汞在2.0mg·L-1以内呈线性关系,检出限(3s)在0.002～0.05mg·L-1之间。方法用于金属饰品的分析,回收率在95.4%～103.0%之间,测定值的相对标准偏差(n=11)在0.68%～2.0%之间。     

石墨炉原子吸收光谱法测定生活日用品中铅、镉、钴

日用品样品置于微波消解罐中,用硝酸及过氧化氢在WP 200 LG微波炉中消解.在所得样品溶液中加入钼酸铵、磷酸氢二铵作基体改进剂后直接进样进行石墨炉原予吸收光谱法测定.在优化的试验条件下,测得铅、镉、钴溶液的吸光度与质量浓度分别在100,50及20μg·L-1以内呈线性关系,方法的检出限(3S/N)分别为6.25,0.50,0.65μg·L-1.对5种样品分别加入铅、镉、钴的标准溶液进行回收试验,结果分别为80%～130%,80%～110%,92%～112%.     

通过与香草醛的显色反应检测冰片成分

冰片样品及纯冰片标准样用无水乙醇为溶剂,利用香草醛在浓硫酸中与龙脑及异龙脑的显色反应,用分光光度法测定冰片含量,测定波长为470 nm.在优化条件下,吸光度与龙脑浓度之间在0.06～0.30 g·L-1范围内呈线性关系,对应于线性回归方程A=2.850 1 C 0.015 6,相关系数为0.999 3;测得三批冰片样品中龙脑质量浓度分别为0.093,0.097,0.096 g·L-1.在同一试样中加入3种不同浓度的龙脑标准溶液按试验方法进行回收试验,测得回收率在93.3%～98.5%之间.     

悬浮液进样-石墨炉原子吸收光谱法测定巴戟天中痕量铅和镉

取经烘干粉碎并通过0.074mm网筛的巴戟天样品0.050 0g,加入琼脂溶液10.0mL(其中含磷酸二氢铵0.1g,作为基体改进剂),超声振荡5min,制成样品的悬浮液,直接进样,采用石墨炉原子吸收光谱法测定其中铅和镉的含量。设置铅和镉的灰化温度分别为850℃和800℃。结果表明:铅和镉的质量浓度在一定范围内与其吸光度呈线性关系,铅和镉的检出限(3s×V/b)分别为2.17×10-9 mg和3.4×10-10 mg。按照标准加入法进行加标回收试验,铅和镉的回收率分别在98.8%～103%和98.3%～104%之间。精密度试验表明铅和镉的测定值的相对标准偏差(n=7)分别为2.7%和1.2%。     

同时多组分分析动力学比均定中变换计算法的原理及其应用于光度法测定面包和水样中碘酸根和溴酸根

应用动力学方法,在不经分离的条件下,采用比均定中变换,同时测定面包与水样中溴酸根与碘酸根的含量.溴酸根、碘酸根的质量浓度在0.1～3.5 mg·L-1范围呈线性,比均定中值MC(D)与浓度C的线性回归方程的相关系数均在0.990 0以上,检出限分别为0.01 mg·L-1与0.02 mg·L-1,相对标准偏差分别为2.84%与1.96%,其回收率在82.2%～100.2%之间.     

铋膜电极溶出伏安法测定食品中痕量重金属

以铋膜电极为工作电极,采用微分脉冲阳极溶出伏安法直接测定食品样品中痕量铅、镉和锌。在富集电位-1.4V,富集时间180s,铋膜质量浓度150μg·L-1的条件下,铋膜电极对铅、镉和锌的氧化溶出具有良好的电化学响应。铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)的质量浓度在5.0~40μg·L-1的范围内与其阳极溶出峰电流呈线性关系,铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)的检出限(3S/N)分别为0.80,0.65,0.58μg·L-1。对25μg·L-1铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)溶液用铋膜电极连续测定15次,相对标准偏差分别为6.2%,5.1%,7.1%。方法应用于食品中痕量重金属的测定,测定结果与石墨炉原子吸收光谱法的测定值相符。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.