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991.
为增强有机锗化合物的生物活性,合成了一系列有机锗氨基酸酯类倍半氧化物,并重点研究了它们的快原子轰击质谱(FABMS)。研究结果表明:该系列化合物的各碎片离子峰与其组成及结构均有很好的对应关系及很强的规律性 相似文献
992.
993.
Ziegler-Natta催化剂催化乙烯气相聚合 总被引:1,自引:0,他引:1
本文综述了乙烯气相聚合催化剂研究状况,列举了一些制备气相聚合催化剂有代表性的方法。同时对预聚合的作用及气相聚合与淤浆聚合表观动力学行为的不同性也作了简要介绍。 相似文献
994.
A method based on in-tube solid-phase microextraction and capillary zone electrophoresis (CZE) was proposed for simultaneously determining four amphetamines (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine) in urine. A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column, which can provide sufficient extraction efficiency, was introduced for the extraction of amphetamines from urine samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the samples were analyzed by CZE. The best separation was achieved using a buffer composed of 0.1 M disodium hydrogen phosphate (adjusted to pH 4.5 with 1 M hydrochloric acid) and 20% methanol v/v, with a temperature and voltage of 25 degrees C and 20 kV, respectively. By applying electrokinetic injection with field-amplified sample stacking, detection limits of 25-34 microg/L were achieved. Excellent method of reproducibility was found over a linear range of 0.1-5 mg/L. Determination of these analytes from abusers' urine sample was also demonstrated. 相似文献
995.
A SPME-HPLC-post-column fluorescent derivatization method for the direct determination of saxitoxin (STX), the most potent paralytic shellfish poisoning (PSP) toxin, in water has been developed. Commercially available SPME devices with 50 microm Carbowax templated resin (CW/TPR) coating was found to be able to pre-concentrate STX from aqueous media. A special pre-conditioning treatment of soaking the SPME coating in 0.1 M NaOH solution significantly improved the extraction efficiency. The optimal pH for the SPME process is 8.1 and the equilibration time is 40 min. The partition coefficient, K, of the distribution of STX between the SPME coating and the aqueous media was measured to be 2.99 +/- 0.04 x 10(3). Extracted toxin on the SPME stationary phase was difficult to be desorbed by the HPLC mobile phase under dynamic desorption mode. A static ion-pairing desorption technique using a desorption solvent mixture of 20 mM sodium 1-heptanesulfonate in 30% aqueous acetonitrile acidified with 50 mM sulfuric acid was developed to overcome this problem. The method detection limit and repeatability achieved by this SPME-HPLC method were 0.11 ng ml(-1) and 3.7%, respectively, with a sample volume of just 5 ml of water. This analytical method is adequate for the monitoring of the PSP toxin in fresh/drinking waters. However, serious interference was observed when this technique was applied to saline water samples. This is probably due to competition of sodium ions with the cationic STX for absorption into the SPME stationary phase. 相似文献
996.
Resonance interaction in the deformation (1400 to 1500 cm?1) region of the Raman spectrum of n-C23 H48 and n-C44H90 at high pressures are reported. Implications of these results concerning the interpretation of the corresponding bands of the Raman spectrum of crystalline polyethylene are discussed. 相似文献
997.
998.
Redox reactions of Co(edta)? with Ru(NH3)5L2+ (L = 3- and 4-aminopyridine (AmPy)) were found to follow an outer-sphere electron transfer mechanism. The specific rate constants are (3.26 ± 0.03) × 102 and (3.07 ± 0.04) × 103 M?1S?1, for L = 3- and 4-AmPy, respectively, at μ, = 0.10 M LiClO4, pH = 8.0 (tris) and T = 25 °C. The rate constants of oxidations for a series of Ru(NH3)5L2+ complexes are higher than those of the corresponding Fe(CN)5L3- complexes by factors of 4 to 15 even after corrections for differences in reduction potentials and in charges of the complexes. Nonadiabaticity in the reactions of Fe(CN)5L3 complexes may account for the difference in the relative reactivities. 相似文献
999.
藉高锰酸钾氧化双乙酰的化学发光反应测定微量锰 总被引:10,自引:0,他引:10
研究了高锰酸钾氧化双乙酰的化学发光反应。根据微量Mn62+对上述体系化学发光山峰时间的影响,建立了测定Mn62+的分析方法。该法线性范围为1.0×10^-4-8.0×10^-67mol/L,相对标准偏差为3.5%,检出限为6.0×10^-8mol/L。应用于合金中锰的测定,结果良好。 相似文献
1000.
Jo‐Nan Chen Fang‐Ming Hsu Hui‐Chun Wang Chung‐Wen Wu Pao‐Swu Cheng Wen‐Liang Tsai 《中国化学会会志》2006,53(4):931-938
Four series of compounds 11?50 containing terminal alicyclic rings such as cyclohexylmethyl, cyclopentylmethyl, cyclobutylmethyl, and cyclopropylmethyl rings were synthesized and their liquid crystal behavior studied. The ring size and the length of flexible alkoxy chain influence the phase formation in different ways. While the smaller ring and the shorter alkoxy chain tend to favor the formation of the N phase, the larger ring and the longer alkoxy chain tend to favor the formation of the SmC phase. All the compounds except 11 and 21 exhibit SmA phases. The widest temperature range of the N, SmA, and SmC phases are found in the compounds 41 , 46 , and 20 , respectively, which are 75 °C for 41 , 115 °C for 46 , and 100 °C for 20 . 相似文献