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混合甾醇中β-谷甾醇和豆甾醇的红外光谱法分析测定 总被引:4,自引:0,他引:4
用傅里叶变换红外光谱法测定了混合甾醇中 β 谷甾醇和豆甾醇的含量 ,结果表明 β 谷甾醇和豆甾醇中的红外特征吸收峰面积比与 β 谷甾醇和豆甾醇的含量比成线性关系 ,红外光谱法测得混合物中各组成的含量与由气相色谱法得到的结果相近 ,表明用红外光谱法测定混合甾醇的含量是可行的。 相似文献
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混合甾醇中β-谷甾醇和豆甾醇的紫外光谱法分析测定 总被引:8,自引:1,他引:7
用紫外光谱法测定了β-谷甾醇和豆甾醇与Deniges磺基醋酸汞络合物的紫外光谱,探讨了显色反应时间、显色剂用量及浓硫酸与冰醋酸配比对紫外吸收光谱的影响。结果表明在一定浓度范围内,甾醇络合物的吸光度A与其浓度成线性关系。并利用紫外光谱法测定了混合甾醇中β-谷甾醇和豆甾醇的含量,此法所得结果与用气相色谱法测试的结果相近。 相似文献
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研究了十二烷基磺酸钠(SDS)和乳化剂OP组成的混合胶束对植物叶片中痕量铅测定的增敏作用,建立了植物叶片中痕量铅的火焰原子吸收光谱测定新方法,灵敏度比不加混合胶束提高了29%,该法快速,简便,廉价。结果表明:在0—5.0μg/mL范围内吸光度与Pb2+浓度呈良好的线性关系,线性回归方程为APb+SDS+OP=0.0391C(μg/mL)+0.0073,r=0.9974,检出限为0.006μg/mL。植物样品采取先灰化再对干灰进行快速消解的方法处理后,应用该方法对不同地区不同植物叶片中的铅进行测定,测定的相对标准偏差RSD为0.50%—3.90%,加标回收率为96.9%—103%,结果显示同一地区植物叶片中的铅含量与植物种类有关、不同地区同种植物叶片中的铅含量与交通密度有关。 相似文献
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微波消解植物灰分与环境土壤中微量元素的ICP-AES方法研究 总被引:2,自引:0,他引:2
应用MDS-2002A犁压力自控密闭微波消解样品制备系统,针对研究样品的特性和共性,进行植物灰分和土壤样品相同微波消解条件的研究实验,并采用电感耦合等离子体原子发射光谱法测定其元素的含量.讨论了混合酸体系、混酸配比、固液比和微波消解时间对于样品制备结果的影响.最终的优选方案为A281C2,即微波程序为工步2,混酸配比为6:2:1:1,混合酸体系为HNO3-HCl-HF-HClO4,最高功率消解时间为10 min的条件下,消解结果最佳.在微波消解最佳条件下,进行了方法准确度实验和测量结果重现性实验,该方法经土壤(GBW07401)和植物(GBW07603)国家标准物质验证,所得测试结果的相对误差均在0.00%~7.14%之间,相对标准偏差均在0.87%~5.25%之间.结果表明,微波消解法处理植物灰分和土壤样品,具有快速、简便、节省试剂、消解完全等特点,测定结果的准确度和精密度令人满意. 相似文献
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松香与甘油酯化稀土催化剂的研究 总被引:1,自引:0,他引:1
本文分别用三氧化二钇、三氧化二钕、混合稀土氧化物作为松香与甘油酯化时的催化剂,研究了稀土氧化物的用量对酯化反应的温度和产物色泽的影响。并用比色法测定了产物的色泽。 相似文献
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Zheng MM Wang L Huang FH Dong L Guo PM Deng QC Li WL Zheng C 《Ultrasonics sonochemistry》2012,19(5):1015-1020
This study is focused on the enzymatic esterification of phytosterols with different acyl donors to produce the corresponding phytosterol esters catalyzed by Canadia sp. 99-125 lipase under ultrasound irradiation. An ultrasonic frequency of 35 kHz, power of 200 W and time of 1h was determined to guarantee satisfactory degree of esterification and lipase activity. The influence of temperature, substrates concentration and molar ratio was investigated subsequently. The optimum production was achieved in isooctane system at 60°C with phytosterol concentration of 150 μmol/mL and phytosterol to fatty acid molar ratio of 1:1.5, resulting in a phytosterol esters conversion of above 85.7% in short reaction time (8h). Phytosterols esters could also be converted in high yields to the corresponding long-chain acyl esters via transesterification with triacylglycerols (above 90.3%) under ultrasound irradiation. In optimum conditions, the overall esterification reaction rate using the ultrasonic pretreatment process was above 2-fold than that of mechanical stirring process without damage the lipase activity. 相似文献
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核磁共振技术在SIPM开发生产中的应用 总被引:2,自引:1,他引:1
本文利用核磁共振氢谱技术,建立了生产间苯二甲酸二甲酯磺酸钠(SIPM)工序中磺化率、酯化率的快速测定方法,为工艺的进一步优化及常规的中控分析方法的建立提供了依据。并尝试利用核磁共振技术测定SIPM在水中及8%硫酸钠水溶液中不同温度下的溶解情况。对生产所用的原料、产品的纯度以及废水处理中的副产物进行了测定,结果令人满意。 相似文献
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Sonochemical preparation of high surface area MgAl2O4 spinel 总被引:1,自引:0,他引:1
High surface area MgAl(2)O(4) has been synthesised by a sonochemical method. Two kinds of precursors were used, alkoxides and nitrates/acetates and in both cases nanostructured MgAl(2)O(4) was obtained. The effect of the addition of a surfactant during the sonication, cetyl trimethyl ammonium bromide, was also investigated. In the case of alkoxides precursors the as-made product is a mixture of hydroxides of aluminium and magnesium, while with nitrates/acetates a gel is obtained after sonication, containing the metal hydroxides and ammonium nitrate. Heating at 500 degrees C transforms the as-made products into MgAl(2)O(4) spinel phase. The surface area is up to 267m(2)/g after treatment at 500 degrees C and 138m(2)/g at 800 degrees C. 相似文献
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Yu. A. Khamzin U. B. Imashev E. A. Udalova R. R. Shiriyazdanov E. K. Maksotov A. R. Davletshin M. U. Imasheva O. N. Makhmutova E. G. Telyashev 《Russian Journal of Physical Chemistry B, Focus on Physics》2017,11(7):1197-1201
A study of esterification process of dicarboxylic acids with 2-ethylhexanol under supercritical conditions is presented. It was shown that the esterification reaction can be carried out without a catalyst. The esters formed with greater rate and selectivity. 相似文献
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Jacques RA dos Santos Freitas L Pérez VF Dariva C de Oliveira AP de Oliveira JV Caramão EB 《Ultrasonics sonochemistry》2007,14(1):6-12
The objective of this work is to discuss the main parameters that influence the sonication extraction of Ilex paraguariensis leaves. For this purpose, the extraction time, solvent polarity, solvent volume, sample mass and particle size were evaluated. Results showed that the main variable affecting the extraction process was the solvent polarity. Though in a less extent, temperature and extraction time also demonstrated to be important parameters, while the other variables did not present a significant influence on the extraction yield. The extracts at the optimized condition were compared with those obtained by maceration, in terms of mass yield and chemical composition. The major compounds identified in the extracts were caffeine and palmitic acid. Some saturated hydrocarbons such as fatty acids, fatty acid methyl esters, phytosterols, and theobromine were also identified in the fractions. 相似文献
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关于超声波在乙酸乙酯和乙酸甲酯中的吸收问题曾引起了多次热烈的争论,为此,作者采用了行波中的光衍射法做了进一步的实验研究。在实验过程中,特别注意了仪器的精确度问题,并且对许多种吸收系数已知的标准液体进行了多次重复的测量,结果很好地符合于一般的公认值,且误差不超出5%。对于两种乙酸酯,测量的频率范围是3-30Mc,温度保持20℃。测量结果表明,在实验的误差范围内,吸收的实验值很好地落在唯象单弛豫理论所预期的曲线上,弛豫频率对乙酸乙酯约在12Mc附近,对乙酸甲酯约在7Mc附近。并且通过对不同纯度的乙酸乙酯进行重复的测量,表示杂质引起的附加吸收并不影响吸收曲线的特性。因此也就明某些作者测量得到两个弛豫频率的结果是不真实的。作者并认为Karpovich首先提出的旋转异构的理论是适合于解释这两种液体的驰豫吸收的机理的。 相似文献
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陈化温度和Fe/Zr配比对SO42-/Fe2O3-ZrO2固体超强酸结构与性能的影响 总被引:6,自引:0,他引:6
用低温陈化法制备了SO42 -/Fe2 O3 ZrO2 (简称SFZ)固体超强酸催化剂 ,用红外光谱 (IR)和X光衍射(XRD)对其结构进行了表征 ,并考察了它对合成癸二酸二正丁酯的催化性能 .IR谱显示 ,低温陈化的SFZ样品在10 70cm-1处吸收峰远强于常温陈化样品 .XRD分析则显示 ,在焙烧温度为 6 5 0℃、Fe/Zr为 2∶1时 ,低温陈化的样品出现了亚稳态的ZrO2 四方晶相 .该样品在催化酯化反应中使产率达 90 %以上 ,高于常温陈化样品的 30 % .研究结果表明 :在其他条件不变时 ,低温陈化所出现的亚稳态的ZrO2 四方晶相是表面酸性和催化活性增加的微观原因 相似文献
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In this work, esterification of oleic acid by various alcohols is achieved with high yields under ultrasonic irradiation. This reaction performed with a novel heterogeneous catalyst that fabricated by heteropoly acid and Fe(III)-based MOF, namely MIL-53 (Fe). Syntheses of MIL-53 and encapsulation process carry out by ultrasound irradiation at ambient temperature and atmospheric pressure. The prepared composite was characterized by various techniques such as XRD, FT-IR, SEM, BET and ICP that demonstrate excellent catalytic activities, while being highly convenient to synthesize. The obtained results revealed that ultrasound irradiation could be used for the appropriate and rapid biodiesel production. 相似文献