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131.
Bord N Crétier G Rocca JL Bailly C Souchez JP 《Analytical and bioanalytical chemistry》2004,380(2):325-332
Alkanolamines such as diethanolamine (DEA) and N-methyldiethanolamine (MDEA) are used in desulfurization processes in crude oil refineries. These compounds may be found in process waters following an accidental contamination. The analysis of alkanolamines in refinery process waters is very difficult due to the high ammonium concentration of the samples. This paper describes a method for the determination of DEA in high ammonium concentration refinery process waters by using capillary electrophoresis (CE) with indirect UV detection. The same method can be used for the determination of MDEA. Best results were achieved with a background electrolyte (BGE) comprising 10 mM histidine adjusted to pH 5.0 with acetic acid. The development of this electrolyte and the analytical performances are discussed. The quantification was performed by using internal standardization, by which triethanolamine (TEA) was used as internal standard. A matrix effect due to the high ammonium content has been highlighted and standard addition was therefore used. The developed method was characterized in terms of repeatability of migration times and corrected peak areas, linearity, and accuracy. Limits of detection (LODs) and quantification (LOQs) obtained were 0.2 and 0.7 ppm, respectively. The CE method was applied to the determination of DEA or MDEA in refinery process waters spiked with known amounts of analytes and it gave excellent results, since uncertainties obtained were 8 and 5%, respectively. 相似文献
132.
133.
紫外分光光度法测定中草药中铁的含量 总被引:3,自引:0,他引:3
对白芍、党参、白术、茵陈、天冬、枸杞子、当归、菟丝子、金银花、桔梗中微量元素铁的含量进行了测定,为进一步研究其药理作用提供基础。中草药消化后配制成溶液,用邻二氮菲作显色剂,使用UV-1200型紫外分光光度计在510 nm处测定各样品的吸光度(A),求出样品中微量元素铁的含量。结果显示,当归和金银花中铁的含量较丰富,分别为(135.367 8±0.111 1)μg/g和(125.936 4±0.159 9)μg/g;桔梗含铁量最少,为(3.510 9±0.159 9)μg/g,10种中草药中铁含量有显著性差异(P<0.05)。结果为使用中草药治疗系统疾病提供了可靠数据,10种中草药在用量范围内Fe含量适合人体每天正常摄入量。 相似文献
134.
铝酸钠溶液的紫外吸收峰 总被引:4,自引:0,他引:4
分别用量子化学MNDO和DV-X_α方法计算了二聚铝酸离子[Al_2O(OH)_6]~(2-)和Al(OH)_4~-。结果表明前者旋转势垒很低, 只有10.08 kJ·mol~(-1), 最稳定平衡构型为C_s。用X_α过渡态理论计算获得这两个离子紫外吸收峰的理论值分别为266.6 nm和234.4 nm, 与实验值270.0 nm和230.0 nm相当接近。因此可以认为, 紫外吸收峰270.0 nm和230.0 nm分别为[Al_2O(OH)_6]~(2-)和Al(OH)_4~-离子的最高占有轨道电子向最低空轨道跃迁时产生的吸收峰。计算结果支持铝酸钠溶液中存在二聚铝酸离子的观点。 相似文献
135.
This Letter describes the amination of 3-bromoisoxazoles by a nucleophilic aromatic substitution reaction. We have found 3-bromoisoxazoles to be inert to substitution under thermal conditions, however, the employment of phosphazene bases under microwave irradiation facilitates the amination process and allows the corresponding 3-aminoisoxazoles to be isolated in moderate yield. 相似文献
136.
137.
Norimah Yusof Asnah Hassan M.N. Firdaus Abd Rahman Suzina A. Hamid 《Radiation Physics and Chemistry》2007,76(11-12):1756-1759
Most of the tissue banks in the Asia Pacific region have been using ionising radiation at 25 kGy to sterilise human tissues for save clinical usage. Under tissue banking quality system, any dose employed for sterilisation has to be validated and the validation exercise has to be a part of quality document. Tissue grafts, unlike medical items, are not produced in large number per each processing batch and tissues relatively have a different microbial population. A Code of Practice established by the International Atomic Energy Agency (IAEA) in 2004 offers several validation methods using smaller number of samples compared to ISO 11137 (1995), which is meant for medical products. The methods emphasise on bioburden determination, followed by sterility test on samples after they were exposed to verification dose for attaining of sterility assurance level (SAL) of 10−1. This paper describes our experience in using the IAEA Code of Practice in conducting the validation exercise for substantiating 25 kGy as sterilisation dose for both air-dried amnion and those preserved in 99% glycerol. 相似文献
138.
桥联双(甲巯咪唑)化合物的合成和配位性能 总被引:3,自引:0,他引:3
研究了桥联双(甲巯咪唑)化合物(Ⅰ_a—Ⅳ_a、Ⅰ_b)的合成和配位性能。UV谱显示Ⅰ_a—Ⅳ_a与UO_2~(2+)离子(硬酸)配位,溶液中形成3:1的配合物。Ⅰ_b与Hg~(2+)、Au~(3+)离子(软酸)配位形成2:1的配合物,用CNDO/2方法计算了各配体分子中原子净电荷密度和HOMO、LUMO能量。 相似文献
139.
Emulsion polymerization of methyl methacrylate (MMA) under pulsed microwave irradiation (PMI) with higher peak pulse power was studied. The effects of various parameters of PMI on the polymerization were analyzed and compared with that under conventional heating (CH) process. The results were summarized, as compared with that under CH, as follows. The amount of initiator used to reach constant conversion reduced by 50% at the same polymerization time; at the same initiator concentration 0.15 and 0.2 wt.%, the polymerization rate increased by 131% and 163%, respectively. The molecular weight of polymer obtained was 1.1-2.0 times larger than that under CH; at the same irradiation energy, the conversion achieved using a lower pulse power was greater than that using a higher pulse power. There seemed to be a factor of the irradiation energy efficiency; in other words, for the monomer conversion, the irradiation energy of low pulse power had a higher efficiency. The conversion achieved using a 3.5 μs pulse width was almost the same as that using a 1.5 μs pulse width. The results indicated that PMI had a significant non-thermal effect on the emulsion polymerization of MMA so as to effectively enhance the polymerization rate. The glass transition temperature (Tg), the polydispersity index (PDI) and the regularity of the polymer obtained using two processes were similar, indicating that the physical properties and microstructure of the polymer were not modified by the use of microwaves. 相似文献
140.
Feth MP Bolm C Hildebrand JP Köhler M Beckmann O Bauer M Ramamonjisoa R Bertagnolli H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(6):1348-1359
XANES and EXAFS spectroscopic studies at the Mn-K- and Br-K-edge of reaction products of (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) chloride ([(salen)Mn(III)Cl], 1) and (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) bromide ([(salen)Mn(III)Br], 2) with 4-phenylpyridine N-oxide (4-PPNO) and 3-chloroperoxybenzoic acid (MCPBA) are reported. The reaction of the Mn(III) complexes with two equivalents of 4-PPNO leads to a hexacoordinated compound, in which the manganese atom is octahedrally coordinated by four oxygen/nitrogen atoms of the salen ligand at an average distance of approximately 1.90 A and two additional, axially bonded oxygen atoms of the 4-PPNO at 2.25 A. The oxidation state of this complex was determined as approximately +IV by a comparative study of Mn(III) and Mn(V) reference compounds. The green intermediate obtained in reactions of MCPBA and solutions of 1 or 2 in acetonitrile was investigated with XANES, EXAFS, UV/Vis, and Raman spectroscopy, and an increase of the coordination number of the manganese atoms from 4 to 5 and the complete abstraction of the halide was observed. A formal oxidation state of IV was deduced from the relative position of the pre-edge 1s-->3d feature of the X-ray absorption spectrum of the complex. The broad UV/Vis band of this complex in acetonitrile with lambda(max)=648 nm was consistent with a radical cation structure, in which a MCPBA molecule was bound to the Mn(IV) central atom. An oxomanganese(V) or a dimeric manganese(IV) species was not detected. 相似文献