Kinetic deoxyribose degradation assay and its application in assessing the antioxidant activities of phenolic compounds in a Fenton-type reaction system

Pro-oxidant properties of phenolic antioxidants, which are derived from their iron recycling reactivity, render the traditional deoxyribose degradation assay invalid to assess the hydroxyl radical-scavenging activity in Fenton-type reaction systems. In the present paper, we studied in detail the interactions between iron and phenolic compounds, and established a kinetic deoxyribose method by taking advantage of the distinct difference between the completion time of Fenton reaction and that of the iron-reducing process. With the newly established kinetic method, we investigated the effects of phenolics on hydroxyl radical formation in a Fenton-type system and determined successfully the second rate constants of hydroxyl radical-scavenging reactions. The site-specific and non-site-specific hydroxyl radical-scavenging ability suggested that both direct hydroxyl radical-scavenging potency and iron-chelating capacity accounted for their inhibitory effects on deoxyribose oxidation degradation. This method, more simple, time saving, and applicative than the traditional deoxyribose assay, produces as accurate results (RSD<0.05, with dynamic range from 7.5 to 575 μM) as typical methods, such as radiolysis technology, and may be of significance in evaluating and screen the hydroxyl radical-scavenging antioxidants.     

Synthesis of Hexadentate Hexahydro-1,3,5-triazine-Based Ligands and their Copper(I) Complexes

Summary.  Hexadentate ligands were formed by the reaction of primary dimethylaminoethyl- or methoxyethylamines with formaldehyde. The resulting N, N′, N″-functionalized hexahydro-1,3,5-triazines contain pending amino or ether functionalities which are able to coordinate to metals in addition to the ring nitrogen atoms. Both ligands were reacted with CuBr, and novel tricopper clusters were isolated and characterized by X-ray structure analysis. In these compounds a ring nitrogen atom, the pending amino or ether functionality, and two bridging bromine atoms coordinate each of the copper atoms. Received January 22, 2002; accepted (revised) March 22, 2002     

有机液体化学试剂馏程测定注意事项

对有机液体化学试剂馏程测定过程中应注意的一些问题如加热源选择、蒸馏速度控制、温度计选择、蒸馏收率以及同一样品不同特性测量结果的相关性分析等进行了分析，为正确测定馏程提供经验和依据。     

Determination of paraquat in human blood plasma using reversed-phase ion-pair high-performance liquid chromatography with direct sample injection

This report describes the determination of paraquat (PQ) in human blood plasma samples by a direct-injection reversed-phase ion-pair chromatographic method. Blood plasma filtrate was injected directly into the LiChrospher® RP-18 alkyl-diol silica (ADS) precolumn integrated in a column switching system using a mixture of 3% 2-propanol and 10 mM sodium octane sulfonate (SOS) in a 0.05 M phosphate buffer (pH 2.8). After washing with this phase, the ADS precolumn was back-flushed with the analytical mobile phase consisting of 40% of methanol and 10 mM SOS in a 0.05 M phosphate buffer (pH 2.8) at a flow rate of 1.0 ml min⁻¹, in order to carry the analyte to a conventional reversed-phase analytical column, where the separation of PQ was achieved and finally detected by UV at 258 nm. The recoveries of PQ from human blood plasma samples ranged between 95.0 and 99.5% at nine different concentrations (from 0.05 to 3.00 μg of PQ ml⁻¹) with coefficients of variation <2.5% (n=3). The precision expressed as relative standard deviation was below 3.5% for between-day and below 4.3% for within-day measurements (n=5). The detection limit (signal-to-noise ratio, S/N>3) was 0.005 μg ml⁻¹ with an injection volume of 200 μl. The proposed method is promising for the identification and quantification of PQ at low concentration levels and is suitable for its analysis in human blood plasma samples from intentional or accidental poisonings cases with a sample throughput of 5 samples per hour.     

高镍钢中镍的测定

以王水溶解试样，用氨水作沉淀剂，并加入适量三乙醇胺及柠檬酸进行掩蔽，以消除铁及铬等元素的干扰，在pH=3-6的酸性介质中，加入过量的EDTA标准溶液，使镍与EDA形成稳定的络合物，以PAN为指示剂，用硫酸铜标准溶液滴定过量的EDTA标准溶液，从而求得镍的含量。     

Kinetic resolution of vic-amino alcohols catalyzed by a chiral Cu(II) complex

Kinetic resolution of N-benzoylated vic-amino alcohols was achieved by benzoylation in the presence of copper triflate and (R,R)-Ph-BOX as catalysts. The observed enantioselectivity was moderate to high. The method was applied to a kinetic resolution of racemic prolinol and piperidinemethanol derivatives as well as an asymmetric desymmetrization of 2-amino-1,3-diol derivatives.     

Spectrophotometric determination of lead in vegetables with dibromo-p-methyl-carboxysulfonazo

A new highly sensitive and selective chromogenic reagent dibromo-p-methyl-carboxysulfonazo (DBMCSA) was synthesized and studied for the spectrophotometric determination of lead in detail. In 0.25 M phosphoric acid medium, which greatly increases the selectivity, lead reacts with DBMCSA to form a 1:2 blue complex, having a sensitive absorption peak at 648 nm. Under the optimal conditions, Beer's law is obeyed over the range from 0 to 0.8 μg ml⁻¹ Pb(II) and the apparent molar absorptivity is 1.04×10⁵ l mol⁻¹ cm⁻¹. The detection limit and the variation coefficient were found to be 2.14 ng ml⁻¹ and 1.0%, respectively. It is found that, except for Ca(II) and Ba(II), all foreign ions studied do not interfere with determination. The interference caused by Ca(II) and Ba(II) can be easily eliminated by prior extraction with potassium iodide-methylisobutylketone. The method has been applied to the determination of lead in vegetables with satisfactory results.     

Cobalt(II) and nickel(II) complexes of a cyclam derivative as carriers in iodide-selective electrodes

The ligand 1,4,8-tri(n-octyl)-1,4,8,11-tetraazacyclotetradecane (L¹) containing pendant octyl groups has been synthesised. L¹ is a tetraazamacrocycle derived from the well-known cyclam unit, and the Ni²⁺ and Co²⁺ complexes, [Ni(L¹)]²⁺ and [Co(L¹)]²⁺, have been isolated and characterised. The ability of the nickel(II) and cobalt(II) complexes to act as anion receptors has been studied by using them as ionophores in membrane-based ion-selective electrodes (ISEs). The PVC membrane containing the complex [Ni(L¹)]²⁺ and 2-nitrophenyloctylether as plasticizer shows a Nernstian response against iodide in a concentration range from 1×10⁻¹ to 4×10⁻⁵ M I⁻ with a detection limit of 1.6×10⁻⁵ M I⁻ and a slope of 58.6 mV/pI⁻ at pH 7 (25 °C). In comparison, the electrode containing [Co(L¹)]²⁺ as ionophore gave a sub-Nernstian slope and a low lifetime. A comparison between the iodide-selective electrode containing [Ni(L¹)]²⁺ and other reported iodide-selective electrodes is also reported.     

混合食用色素的卡尔曼滤波光度分析

本文用联机卡尔曼滤波光度法成功地同时测定了混合合成食用色素样品中五个组分。它们分别是40号红、苋菜红、柠檬黄、日落黄和亮蓝。方法准确、快速,无需予分离。     

Determination of total fluoride in HF/HNO3/H2SiF6 etch solutions by new potentiometric titration methods

In the photovoltaic industry the etching of silicon in HF/HNO₃ solutions is a decisive process for cleaning wafer surfaces or to produce certain surface morphologies like polishing or texturization. With regard to cost efficiency, a maximal utilisation of etch baths in combination with highest quality and accuracy is strived. To provide an etch bath control realised by a replenishment with concentrated acids the main constituents of these HF/HNO₃ etch solutions including the reaction product H₂SiF₆ have to be analysed. Two new methods for the determination of the total fluoride content in an acidic etch solution based on the precipitation titration with La(NO₃)₃ are presented within this paper. The first method bases on the proper choice of the reaction conditions, since free fluoride ions have to be liberated from HF and H₂SiF₆ at the same time to be detected by a fluoride ion-selective electrode (F-ISE). Therefore, the sample is adjusted to a pH of 8 for total cleavage of the SiF₆²⁻ anion and titrated in absence of buffers. In a second method, the titration with La(NO₃)₃ is followed by a change of the pH-value using a HF resistant glass-electrode. Both methods provide consistent values, whereas the analysis is fast and accurate, and thus, applicable for industrial process control.