Non-Destructive In-Situ Study of White and Black Coating on Painted Pottery Sherds From Bancun Site (Henan,China) by Raman Microscopy

Abstract

Pottery sherds from the archaeological site of Bancun (Henan, China) were analyzed by Raman microscopy and the pigments used in the coating of this ancient (c. 4000–5000 BC) pottery were determined. It was found that bauxite was used to make the white pigment. The black coating was identified as a magnetite and its particle size was in the nanometer range. This work also showed that the size of pigment had influence on the color of the coating. In principle, Raman spectra could be used not only to identify the mineral source of the pigment but also to estimate the particle size of the pigments.     

UV/Vis光谱法研究红子色素的稳定性

本文报导了从红子提取，分离天然色素及酸碱和温度等对该色素稳定性的影响。     

奥美拉唑在碳糊电极上的吸附伏安测定法研究

研究了奥美拉唑在碳糊电极上的电化学行为及检测方法 ;在1.2mol·L -1H2SO4 底液中 ,通过富集用碳糊电极吸附伏安法测定奥美拉唑 ;阴极峰电位为0.403V(vsSCE) ,峰电流与奥美拉唑的浓度在7.8×10-8～3.7×10-5 mol·L-1 范围内呈良好的线性关系 ;该法的检出限为1.43×10-8 mol·L-1;用标准加入法测得回收率范围为94 %～102 % ;对奥美拉唑胶囊用该法进行了测定 ,获得了满意的结果 ;该法的优点是成本低 ,操作方便 ,重复性好及检出限较低 ;对电极响应机理进行了探讨 ,奥美拉唑的电极过程是一个两电子两质子的准可逆过程     

Voltammetric Determination of Leucoindigo Adsorbed on Pretreated Carbon Paste Electrodes: Its Application in a Flow System

The determination of leucoindigo adsorbed on the surface of pretreated carbon paste electrodes has been performed by cyclic (CV) and alternating current voltammetry (ACV). The water‐soluble compound called leucoindigo is obtained through the reduction of water insoluble indigo in an alkaline media and in presence of a dithionite salt (Na₂S₂O₄) as a reducing agent. Cyclic voltammograms of leucoindigo show two reversible electrodic processes, in the aqueous 0.1 M Tris‐HCl pH 7.2, at the formal potential of ?0.4 V and +0.3 V (vs. Ag/AgCl/sat. KCl). In a batch protocol, leucoindigo was quantified by CV with a change of medium between accumulation and detection steps. Reversible voltammetric processes of leucoindigo were greatly enhanced by other voltammetric technique like alternating current voltammetry. Limit of detection in the nanomolar range was achieved for a 2 min accumulation time by ACV in a batch procedure. A flow system was also employed, with adsorptive voltammetric detection of leucoindigo, since this automates the methodology and decreases analysis time. Parameters related to the electrochemical technique are optimized and calibration plots obtained are reported. These data provide useful information about the suitability of using leucoindigo in the detection system of alkaline phosphatase (AP) and horseradish peroxidase (HRP) based affinity devices, in which indigo is generated by the enzymatic hydrolysis of the 3‐indoxyl phosphate substrate.     

聚吡咯碳糊电极的研制及应用

研制了聚吡咯电极，探讨了该电极的性能和实用性，实验结果表明，该电极可用于伏安法快速测定Ｌ－抗坏血酸，在０．１ｍｏｌ／ＬＫＮＯ３底液中，线性范围为１．０×１０＾－１１～９．０×１０＾－９ｍｏｌ／Ｌ检测限为５．０×１０＾－１２ｍｏｌ／Ｌ，电极具有具有良好的重现性和高选择性，响应迅速，使用寿命３个月以上。     

Calorimetric determination of enthalpies of lysozyme folding at a liquid-solid interface

Summary Two hydrated and aged cement pastes from India (NCB), w/c=0.4, of a similar chemical composition but of a different specific surface and different strength (OPC, C-33 and C-43), hydrated at w/c=0.4 for 1 month, were studied by XRD after 1 year and 5-6 year ageing on contact with air. They were tested by static heating (SH) in fresh state, and by DTA/DTG/TG, IR and mass spectrometry (MS), after ageing, presented elsewhere. The main XRD peaks of (i) portlandite were decreasing with T and disappearing about 450°C, (ii) calcite peak at room T was small and broad, it increased gradually, especially after portlandite disappearance; above 600°C it was lowered and it was lost above 700°C. Important variation in the d(001) of portlandite with ageing was observed, exceeding the standard value of d(001)=4.895 Å (72-0156). It was higher in the paste C-33 (4.925-4.936 Å), containing more carbonates, than in the paste C-43 (4.916-4.927 Å). Small variations only were found in the value of d(101), i.e. 2.627-2.635 Å (nominally 2.622 Å), whereas the d(104) of calcite could be used as internal standard and other calcium carbonates (vaterite and aragonite) showed a small variation only. The increase ind(hkl) with temperature was straight linear (in portlandite d(001)=0.095 Å, at 30-400°C) and the thermal expansion coefficient estimated thereform was high (4.75-4.95·10^-5 K^-1). Close to the T of decomposition the d/T became steeper. The thermal variation of d(104)=3.035 Å of calcite (d=0.015 Å at 30-400°C) was smaller than that ofd(101) of portlandite (d=0.025 Å at 30-400°C) and was similar in C-33 and C-43. The thermal expansion coefficient was 1.54 10^-5 K^-1, thus higher than the reported _a=0.65·10^-5 K^-1.     

Surface energy and mechanical behaviour of hardened cement paste

The Bangham equation indicates a direct proportionality between the length change of a porous body and a change of surface energy. In our experiments surface energy of hardened cement paste has been modified by desorbing or adsorbing water molecules. The internal pressure created by surface energy could be directly determined with the help of Mössbauer experiments. Based on these results it is possible to determine to what extent shrinkage or swelling is caused by a change of surface energy. Using Griffith's criterion our findings can explain quantitatively the decrease of stength as a function of increasing water content. Results are in good agreement with other methods of studying surface energy such as experiments to determine van der Waals forces.     

Crystal Growth and Structure Determination of Pigment Orange 82

The crystal structure of the important industrial orange pigment PO82, major part of the BASF Colors & Effects^® product Sicopal^® Orange K/L 2430, was solved from combined X‐ray single crystal, X‐ray and neutron powder diffraction, ¹¹⁹Sn Mössbauer spectroscopy, transmission electron microscopy, electron diffraction, and chemical analyses. The structure contains Keggin type clusters composed of four [M₃O₁₃] trimers consisting each of three MO₆ octahedra that share edges and one common oxygen atom connecting the trimers to the central ZnO₄ tetrahedron. The octahedrally coordinated metal atom position is mixed occupied by Ti⁴⁺, Sn⁴⁺, and Zn²⁺. Adjacent Keggin clusters share vertices and are further interconnected to four ZnO₄ tetrahedra. This framework of interconnected MO₆ octahedra and ZnO₄ tetrahedra contains channels along [110], in which the Sn²⁺ cations are located.     

Methylthiouracil‐modified Carbon Paste Electrode as a New Voltammetric Sensor Based on a 1,4‐Michael Addition Reaction for Detection of Dopamine

A sensitive dopamine sensor was constructed based on the modified carbon paste electrode with methylthiouracil as a nucleophile in the 1,4‐Michael addition reaction. An ECE mechanism was suggested for dopamine oxidation at the modified electrode. Design of experiments was used in the optimization of variables. Under the optimum conditions, calibration graph was linear in the range of 0.20–15.0 µM with a detection limit of 73 nM. The relative standard deviations (n=5) for 0.50 µM of dopamine was 3.83 %. The selectivity of the sensor was also studied. The developed sensor was applied for analysis of pharmaceutical and biological samples.