Determination of Lead, Cadmium, and Mercury by On-Line Enrichment Followed by RP-HPLC

A new method for the simultaneous determination of lead, cadmium, and mercury ions as metal tetra-(4-chlorophenyl)-porphyrin (T₄CPP) chelates was developed using reversed-phase-high performance liquid chromatography (RP-HPLC) and combined with on-line enrichment technique. When the Hg-T₄CPP, Pb-T₄CPP, and Cd-T₄CPP chelates were injected into the injector and sent to the enrichment column with 0.05 mol/L of pH = 10 pyrrolidine-acetic acid buffer solutions (containing 10% of THF) as mobile phase, they were absorbed onto the tip of the enrichment column. By switching the six ports switching valve, the retained chelates can be back-flushed by mobile phase and travel towards the analytical column. With 0.05 mol/L of pH = 10 pyrrolidine-acetic acid buffer solution (containing 10% of THF) and tetrahydrofuran (THF) (containing 0.05 mol/L pH = 10.0 pyrrolidine-acetic acid buffer salt) gradient elution as mobile phase, the separation of chelates on the analytical column was satisfactory. The linearity ranges are 0.01 ± 120 g/L for each metal chelate. The detection limits (S/N = 3) of lead, cadmium, and mercury are 2.0, 1.5, and 2.0 ng/L, respectively. This method was applied to the determination of the g/L level of lead, cadmium, and mercury ions in a water sample with good results.     

Determination of sulphide, polysulphide, thiocarbonates and sulphur by extraction with tributyltin hydroxide, and of thiosulphate by hydrogenation

The methods presented involve the separation of sulphur compounds by means of a hexane solution of tributyltin hydroxide (TBT), followed by titration with o-hydroxymercuribenzoic acid in the presence of dithizone as indicator. Free sulphide is selectively extracted from strongly alkaline solution, whereas the polysulphides and thiocarbonates are extracted at pH 9-10. The polysulphide and thiocarbonate extracts decompose to form TBT-sulphide, sulphur and carbon disulphide. Treatment with sulphite, stannate(II), copper, vinyl cyanide and ethylenediamine, and hydrogenation with zinc and hydrobromic acid have been applied in the course of the analysis. The sulphur is determined by its attack on copper to form copper(I) sulphide which is subsequently dissolved in aqueous potassium cyanide solution and the sulphide separated by extraction.     

Bacteria and the Biodegradation of Chemicals Achieved Naturally,by Combination,or by Construction

The natural potential of bacteria for the biological degradation of synthetic compounds is greater than is commonly supposed and extends to many heteroarenes and even some chloroarenes. An increase in the number of substituents on the aromatic ring or a certain substitution pattern is what confers xenobiotic character to a compound. In addition, when enzymes with low substrate specificity encounter foreign compounds with random variations, products with very strong xenobiotic character often result. In this case, changing the conditions or introducing a cooperation between several different types of bacteria can be used to degrade these compounds. Finally, mineralization, the complete breakdown of organic substances into carbon dioxide and inorganic salts, of xenobiotics previously regarded as persistent can be achieved by taking advantage of natural or induced gene transfer to construct hybrid degradative pathways. After an introduction to the world of bacteria and their place in Nature, we will describe their natural potential for biodegradation with reference to aliphatic and aromatic hydrocarbons. The discussion will then turn to the types of the substituents that confer xenobiotic properties to compounds and how these compounds are degraded despite their xenobiotic character.     

Atom-Efficient,Solvent-Free,Green Synthesis of Chalcones by Grinding

An improved Claisen–Schmidt condensation reaction of methyl ketones and aromatic aldehydes can be achieved by grinding at room temperature in the absence of solvents. This process is simple, efficient, economical, and environmentally benign compared to classical reactions.     

Assay of d-cycloserine by chloramine-B,bromamine-T,and bromamine-B

The reaction between d-cycloserine (DCS) and aromatic N-haloamines proceeds quantitatively over a wide range of experimental conditions. Simple titrimetric procedures for the assay of DCS are described. Oxidation of DCS involves an eight-electron change and the oxidation products are identified. The methods can be used for the assay of the antibiotic in medicinal preparations as well as for calculating the number of ligand molecules present in metal complexes of DCS.     

X射线荧光光谱法快速测定FeSiB非晶薄带中Si,B,Fe的含量合金薄带中硅硼铁

提出了以自制的标准样品,采用单点法绘制校准曲线,利用X射线荧光光谱仪测定FeSiB非晶薄带样品中硅、硼和铁的含量。对于4个FeSiB非晶合金薄带样品中硅、硼和铁进行了10次测定,其分析结果的相对标准偏差分别为0.4~0.5%,1.3~4.2%和0.2~0.4%。本方法的分析结果与火花源原子发射光谱法、化学重量法和ICP-AES的测定值吻合较好。本方法快速、简便,薄带样品无需制样,适用于FeSiB非晶合金薄带的快速成分分析。     

Organic quantitative ultramicroanalysis by pyrolysis,and diffusion of hydrogen through quartz,and by carbonization

Summary Quantitative ultramicro determination of hydrogen, based on the diffusion of hydrogen set free by complete thermal destruction of an organic compound through the wall of a silica glass flask, in which the sample is sealed, has been achieved. Both the percentage of hydrogen and of the molecule residue can be determined. By crushing the flask and weighing, after complete diffusion of hydrogen, the determination of carbon and oxygen ought to be possible.

---

Zusammenfassung Auf der Grundlage der Pyrolyse einer organischen Substanz und der Diffusion des dabei freigesetzten Wasserstoffs wurde eine Ultramikromethode zur Bestimmung dieses Elementes ausgearbeitet. Die Probe wird in ein Quarzkölbchen eingeschmolzen, durch dessen Wandung der Wasserstoff diffundiert. Sowohl die Bestimmung des Wasserstoffgehaltes wie des Molekülrestes ist möglich. Nach vollständiger Diffusion des Wasserstoffes und Öffnen des Kölbchens sollten sich Kohlenstoff- und Sauerstoffgehalt durch Wägung bestimmen lassen.

---

Résumé On a réalisé la détermination quantitative de l'hydrogène à l'échelle ultramicro, en se fondant sur la diffusion de l'hydrogène mis en liberté par destruction thermique complète d'un composé organique à travers la paroi d'un récipient en silice contenant l'échantillon scellé. On peut doser à la fois les pourcentages de l'hydrogène et du résidu moléculaire. On a pu doser le carbone et l'oxygène en cassant le récipient et en le pesant, après la diffusion complète de l'hydrogène.

     

A novel,solventless reductive coupling of carbonyl compounds by alkali metals,catalysed by bromobenzene

Catalysed by bromobenzene, alkali metals including Li, Na, and K can mediate the reductive coupling of carbonyl compounds under mild, solventless conditions to furnish the corresponding pinacol products.     

人血清中镁钙铁铜锌的ICP-AES法同时测定

使用ICP－AES法同时测定了血清样品中的镁、钙、铁、铜、锌，加标回收率为95%-101%，11次测定的RSD（n=11）小于2.7%；方法操作方便，分析速度快，结果准确。     

电感耦合等离子发射光谱法测定镍铁中Si,Mn,P,Ni

建立ICP–AES法测定新型材料镍铁中的Si,Mn,P,Ni元素的方法。考察了镍铁基体和共存元素对测定结果的影响。通过基体匹配消除基体干扰,确定各待测元素谱线为Mn 293.930 nm,P 178.280 nm,Ni 231.604 nm,Si251.611 nm。Si,Mn,P,Ni的检出限分别为0.06,0.04,0.08,0.04 mg/L,测定结果的相对标准偏差均小于5%(n=11),加标回收率在95%~105%之间。该方法操作简便、测定结果准确可靠,可用于镍铁中Si,Mn,P,Ni的含量测定。     

火焰原子吸收光谱法连续测定香蕉中的铜铁锌锰

研究了香蕉中的金属元素的含量和火焰原子吸收光谱法在同一体系中测定香蕉中微量元素铜、铁、锌、锰的方法，考察了硝酸、过氧化氢的不同用量以及消化时间长短的影响和在同一体系中铜、铁、锌、锰的相互干扰情况。在选定条件下铜检测限为0．064μg／mL，铁为0．275μg／mL，锌为0．157μg／mL，锰为0．187μg／mL，相对标准偏差为1．9％-4．7％，回收率为92．3％-105．0％。     

高效液相色谱分离催化伏安检测微量稀土元素——钆、铽、镝、钬、铒

本文提出用Ag(Hg)-Pt-Ag三电极流动微电解池检测高效液相色谱柱流出液中痕量稀土的浓度。用Apple-Ⅱ微电脑采集伏安信号,再转换成色谱流出曲线。稀土元素的检测限可达0.5μg。     

Metal coordination by sterically hindered heterocyclic ligands, including 2-vinylpyridine, assessed by investigation of cobaloximes

Structural and 1H NMR data have been obtained for cobaloximes with the bulkiest substituted pyridines reported so far. We have isolated in noncoordinating solvents the complexes CH3Co(DH)2L (methylcobaloxime, where DH = the monoanion of dimethylglyoxime) with L = sterically hindered N-donor ligands: quinoline, 4-CH3quinoline, 2,4-(CH3)2pyridine, and 2-R-pyridine (R = CH3, OCH3, CH2CH3, CH=CH2). We have found that the Co-N(ax) bond is very long in the structurally characterized complexes. In particular, CH3Co(DH)2(4-CH3quinoline) has a longer Co-N(ax) bond (2.193(3) A) than any reported for methylcobaloximes. The main cause of the long bonds is unambiguously identified as the steric bulk of L by the fairly linear relationship found for Co-N(ax) distance vs CCA (calculated cone angle, CCA, a computed measure of bulk) over an extensive series of methylcobaloximes. The linear relationship improves if L basicity (quantified by pKa) is taken into account. In anhydrous CDCl3 at 25 degrees C, all complexes except the 2-aminopyridine adduct exhibit 1H NMR spectra consistent with partial dissociation of L to form the methylcobaloxime dimer. 1H NMR experiments at -20 degrees C allowed us to assess qualitatively the relative binding ability of L as follows: 2,4-(CH3)2pyridine > 4-CH3quinoline approximately = quinoline approximately = 2-CH3pyridine > 2-CH3Opyridine > 2-CH3CH2pyridine > 2-CH2=CHpyridine. The broadness of the 1H NMR signals at 25 degrees C suggests a similar order for the ligand exchange rate. The lack of dissociation by 2-aminopyridine is attributed to an intramolecular hydrogen bond between the NH2 group and an oxime O atom. The weaker than expected binding of 2-vinylpyridine relative to the Co-N(ax) bond length is attributed to rotation of the 2-vinyl group required for this bulky ligand to bind to the metal center, a conclusion supported by pronounced changes in 2-vinylpyridine signals upon coordination.     

Determination of Benzylpenicillin,Ampicillin, and Carbenicillin by Paper Chromatography

A mobile phase was developed for selective determination of benzylpenicillin, carbenicillin, and ampicillin in drugs by paper chromatography.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 613–615.Original Russian Text Copyright © 2005 by Alekseev, Nersesova, Khalyapina.     

Oxidation of unsaturated tertiary amines,amides, and imides by molecular oxygen catalyzed by palladium complexes

Conclusions Oxidation of higher unsaturated tertiary amines, amides, and imides has been carried out using PdCl₂-CuCl-CF₃COOH catalyst system and molecular oxygen, the products being the corresponding amino-, amido-, and imidoketones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimieheskaya, No. 9, pp. 2148–2151, September, 1988.