不同消解方法对火焰原子吸收光谱法测定乳制品中无机元素含量的影响

取鲜奶及酸奶样品分别用3种不同的消解方法(即常规湿法酸消解法、微波加热酸消解法和干法消解法)做预处理。在所得最终的试样溶液中分别用火焰原子吸收光谱法测定其中6种无机元素(即钙、镁、铜、锌、铁及锰)。试验结果表明:采用微波加热酸消解法处理的样品,6种元素的回收率可达94.5%～100.0%高于其他两种方法的回收率最高值,相关测定值的相标准偏差(n=6)在1.9%～4.2%之间。因此,用火焰原子吸收光谱法测定乳制品中无机元素含量时,用微波加热酸消解法处理样品的效果较好。     

微波消解样品-火焰原子吸收光谱法测定人发中10种微量元素

0.200 0g人发试样经5.0mL硝酸和1.0mL过氧化氢消解,用火焰原子吸收光谱法测定其中钙、铁、锌、锰、铜、铅、镉、钴和镍的含量,用氢化物发生-火焰原子吸收光谱法测定硒的含量。测定钙时,加入镧溶液,以消除共存物的干扰。用10种元素的标准溶液制作了各自的标准曲线,所得线性回归方程的相关系数在0.998 5～0.999 9之间,检出限(3σ)为0.002～0.009mg.L-1之间。以人发样品为基底,加入一定量10种元素的标准溶液做回收试验,得到回收率在95.6%～103.5%之间。     

原子吸收光谱法测定丹参及其近缘种中痕量元素

丹参及其近缘种样品用硝酸-高氯酸混合酸(体积比4比1)浸泡过夜,加热消解.在优化的仪器工作条件下,用火焰原子吸收光谱法测定所制得样品溶液中钙、镁、铁、锰、铜和锌的含量,并用石墨炉原子吸收光谱法(GFAAS)测定其中的钼、铅、铬及镉的含量.测定铅及镉时,用磷酸二氢铵作基体改进剂,而测定铬时,用抗坏血酸作基体改进剂.10种元素的检出限(3S/N)均小于0.26μg·g-1,测定钙、镁、铁、锰、铜和锌时,测得其回收率在99.0%～103.6%之间,其相对标准偏差(n=5)在0.54%～1.77%之间;测定钼、铅、铬和镉时,其回收率在100.O%～108.0%之间,相对标准偏差(n=5)在0.02%～1.9%之间.     

电感耦合等离子体原子发射光谱法测定铜电积液中锑、铋、钴、镍和砷的含量

样品(2.00mL)用盐酸10mL、硝酸3mL溶解后,蒸馏至2~3mL,加入100g·L-1酒石酸溶液2mL,用盐酸(5+95)溶液稀释定容至100mL。采用电感耦合等离子体原子发射光谱法测定样品溶液中锑、铋、钴、镍和砷的含量。选择锑、铋、钴、镍、砷元素的分析谱线分别为206.836,223.061,228.615,231.604,193.696nm。5种元素在一定的质量浓度范围内与其发射强度呈线性关系,方法的检出限(3s)在0.005~0.130mg·L-1之间。方法用于铜电积液分析,所得测定值与火焰原子吸收光谱法测定结果相符。加标回收率在95.8%~108%之间,测定值的相对标准偏差(n=11)在0.70%~6.4%之间。     

火焰原子吸收光谱法测定温里类中草药中痕量元素

应用火焰原子吸收光谱法测定了6种温里类中草药(即香附子、干姜、肉桂、细辛、高良姜及小茴香)中4种痕量元素铜、铁、锌及锰的含量。样品用硝酸-高氯酸(4+1)混合酸消解后加入过氧化氢,并蒸发至近干,残渣溶于硝酸(1+99)溶液中后用于火焰原子吸收光谱法分析,标准曲线分别用上述4种元素的标准溶液制作。按此方法分析了上述6种中草药中铜、铁、锌及锰4种痕量元素,并在此基础上用标准加入法作了回收试验,测得4种痕量元素的回收率在93.5%~109.0%之间。     

火焰原子吸收光谱法测定中江丹参植株不同部位12种微量元素含量

用火焰原子吸收光谱法测定了丹参根、茎、叶中微量元素钙、镁、钾、铜、锌、锰、铬、钴、镍、铁、鉛和镉的含量。经粉碎并通过孔径为0.30 mm样筛的样品,用硝酸-过氧化氢混合溶液消解处理后,经高氯酸冒烟。溶液中加入浓硝酸,并稀释至100 mL(于容量瓶中)后,供火焰原子吸收光谱法测定。对方法的回收率及精密度作了试验,回收率为95.2%～105.3%,相对标准偏差(n=9)均小于3.0%。丹参植株中12种微量元素的总含量(μg.g-1)由高到低顺序为:叶茎根。其中人体必需的微量元素锌、铁、锰、铜及有害元素铅和镉也均有显著的存在量。     

微波消解样品-火焰原子吸收光谱法测定淡竹叶中痕量元素

产自3个不同地区的淡竹叶样品用硝酸经微波辅助消解,采用火焰原子吸收光谱法测定所得样品溶液中锌、铁、铜、锰、钾、钙、钠、镁、镍、铅、铬、钴、铝和硒等14种痕量元素的含量。14种元素的质量浓度在一定的范围内均与其吸光度呈线性关系。以1#样品为基体,加入适量9种痕量元素的标准溶液做方法的回收试验,测得回收率在98.1%～108.0%之间,测定值的相对标准偏差(n=5)均小于8%。     

悬浮液进样-火焰原子吸收光谱法测定花粉中微量元素

提出了不使用稳定剂,直接用蒸馏水制成花粉样品的悬浮液进样,火焰原子吸收光谱法测定花粉中微量元素的方法.用三氯化镧和氯化铯消除干扰,在磁力搅拌下进样,应用标准加入法在同一溶液中用火焰原子吸收光谱法测定铜、铁、锰、锌、铅、镉、钙、镁、钾、钠等10种元素含量.方法的回收率在92.5%～112.5%之间,相对标准偏差(n=6)在0.24%～1.50%之间,并以高温灰化法的测定值为参考对测定结果进行F检验和t检验,发现两者无显著性差异,说明悬浮液进样法的测定结果准确可靠.     

微波消解和直接溶解进样法测定板蓝根颗粒剂中六种金属元素的比较研究

目的使用微波消解和热酸溶液直接溶解板蓝根颗粒,运用火焰原子吸收光谱法测定这两种溶液中Fe、Zn、Cu、Mg、Ca和Mn 6种金属元素的含量。方法分别采用浓HNO3湿法微波消解和直接溶解板蓝根颗粒样品,用原子吸收分光光度计测定上述样品中6种金属元素含量。结果所测定的板蓝根颗粒中含有丰富的金属元素,两种前处理方法测定的结果相差很小。采用此法回收率在92.0%~110.0%之间,样品相对偏差小于3%。结论板蓝根颗粒中金属元素可作为人体元素的重要补充。     

原子吸收光谱法测定过氧化氢-柠檬酸溶液中铁铬镍钴

研究了原子吸收光谱法测定压水堆主回路去污液过氧化氢-柠檬酸溶液中铁、铬、镍、钴的影响因素,选择了合适的测量条件,用合成样品进行了试验.结果表明.铁、钴、镍、铬含量在0.5～5mg·L~(-1)范围的回收率为100%±10%,相对标准偏差为6.0%～10%.     

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

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.