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液相色谱-串联质谱法测定面粉及其制品中的联二脲 总被引:1,自引:0,他引:1
建立了面粉及其制品中联二脲的液相色谱-串联质谱(LC-MS/MS)测定及确证方法。采用纯水振荡提取样品中的联二脲,联二脲经高锰酸钾氧化后,转变为偶氮甲酰胺,再加入对甲苯亚磺酸钠使偶氮甲酰胺衍生为对甲苯磺酰氨基脲。以乙腈和2 mmol/L乙酸铵溶液(含0.2%(v/v)甲酸)为流动相进行梯度洗脱,经Shimpak XR-ODSⅡ色谱柱(150 mm×2.0 mm,2.2 μm)分离,电喷雾正离子模式电离(ESI+),多反应监测(MRM)模式检测,同位素内标法定量。方法的线性范围为1~20000 μg/kg,相关系数为0.9999,定量限为5 μg/kg;当添加水平为5.0、10.0与50.0 μg/kg时,联二脲的平均回收率为78.3%~108.0%,相对标准偏差(RSDs)不大于5.73%。本方法新颖、可靠、灵敏、线性范围广,而且实用性强,可用于面粉及其多种制品中联二脲的测定和确证。 相似文献
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为探讨钼多酸根阴离子在有机化学反应中的催化机理,用菲醌作底物合成了[(n-C_4H_9)_4N]_2[(OC_(14)H_8O)_2Mo_4O(10)(OCH_3)_2]配合物。X射线单晶结构分析表明,该晶体属单斜晶系,空间群P2_1/c,a=1.3149(5)nm,b=1.8666(8)nm,c=1.8903(3)nm,β=104.06(3)°,Z=2.收集到独立衍射点3505个,其中1382个为可观测点,最终一致性因子R=0.078.结构分析结果表明,菲醌与钼多酸根在不同的实验条件下,能形成配比、氧化态以及结构不同的配合物。 相似文献
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利用密度泛函理论(DFT)计算研究了镍催化的溴苯(R1)与对溴苯甲酸甲酯(R2)生成非对称联芳化合物的还原性交叉偶联反应的机理.结果表明,相对于一价镍的催化机理,零价镍作为活性催化剂更有利于反应的进行,零价镍催化剂首先与R1络合或者首先与R2络合的反应机理十分相似,其决速步在气相时的能垒分别是70.50或者49.66 kJ?mol-1.零价镍催化机理包括如下步骤:一次氧化加成;还原;二次氧化加成;还原消除以及催化剂再生.另外,计算结果还表明有机锌试剂在这个反应体系中很难生成. 相似文献
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甲烷氧化偶联CaF_2/Sm_2O_3催化剂的研究周水琴,龙瑞强,黄亚萍,万惠霖,蔡启瑞(厦门大学化学系,固体表面物理化学国家重点实验室,厦门,361005)关键词甲烷氧化偶联,氟化钙,三氧化二钐,离子交换,氧物种甲烷氧化偶联制乙烯是催化领域中最活跃的?.. 相似文献
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双核金属钌膦酸配合物(NH_4)_3[Ru_2(hedp)_2]·2H_2O(hedp=羟基亚乙基二膦酸)在常温水溶性体系中,无需相转移催化剂,可以高效催化t-Bu OOH氧化各种醇类,包括一级醇、二级醇和长链醇。催化机理研究表明,双核金属钌膦酸配合物的[Ru~Ⅲ-Ru~Ⅱ]~(3-)单元与t-Bu OOH作用,可以形成含过氧键的Ru~Ⅲ-Ru~Ⅲ-OO~tBu过渡态,然后再对底物醇进行氧化。该机理得到实验印证,如发现酸抑制而碱催进该反应,紫外可见光谱表明Ru~Ⅲ-Ru~Ⅲ-OO~tBu的形成。 相似文献
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键联聚乙二醇高分子担载锰(Ⅲ)卟啉的合成及催化烯烃环氧化反应性能研究 总被引:1,自引:0,他引:1
本文研究了键联聚乙二醇高分子担载锰(Ⅲ)卟啉的合成,以及在CH_2Cl_2/H_2O两相体系中催化苯乙烯环氧化反应的性能.探索了催化反应体系中溶液pH值、NaOCl浓度、轴向配体及相转移催化剂对催化反应的影响.结果说明键联聚乙二醇高分子担载锰(Ⅲ)卟啉是烯烃环氧化反应的一种有效催化剂,其中聚乙二醇链可以络合Na,使OCl富集于金属卟啉周围,起到较好的相转移催化作用.在催化反应的各影响因素中,水相pH值对反应的影响最大. 相似文献
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甘氨酸工业生产中,同步快速分析母液中甘氨酸(Gly)、α-羟基乙酸(GA)和亚氨基二乙酸(IDA)含量,对于生产控制和母液循环利用具有重要意义。本文采用Hypersil SAX强阴离子色谱柱,对来自某企业的甘氨酸母液中的三种羧酸进行了快速分析方法研究。结果表明,以pH值为2.30的含0.020 mol/L磷酸二氢钾缓冲液为流动相,得到Gly、GA、IDA三种羧酸的色谱峰分离度好,峰形对称;在浓度为0.1~1.8 g/L范围内,Gly、GA、IDA的色谱峰面积与其浓度呈良好线性关系,甘氨酸母液中三种羧酸的平均回收率分别在106.4%~108.3%、99.2%~102.3%和82.4%~86.4%之间,日内及日间相对标准偏差为0.7%~7.4%,从而建立了一种简便、准确的高效液相色谱法用于甘氨酸母液的同步快速分析。 相似文献
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A water-soluble and "self-assembled" polyoxometalate as a recyclable catalyst for oxidation of alcohols in water with hydrogen peroxide 总被引:1,自引:0,他引:1
Sloboda-Rozner D Alsters PL Neumann R 《Journal of the American Chemical Society》2003,125(18):5280-5281
We have demonstrated that a simply prepared water-soluble polyoxometalate, Na12[WZnZn2(H2O)2(ZnW9O34)2], synthesized from readily available zinc and tungsten salts in the presence of nitric acid, is an effective catalyst for selective alcohol oxidation with hydrogen peroxide in biphasic (water-alcohol) reaction media. Experiments have shown that the "self-assembled" catalyst in its mother liquor was as active as the isolated catalyst. The aqueous catalyst solution is easily separated from the water-insoluble products and can be recycled without loss in activity or selectivity. 相似文献
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Dr. Jiho Shin Nak Ho Ahn Prof. Miguel A. Camblor Prof. Sung June Cho Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2014,53(34):8949-8952
The transformation from a disordered into an ordered version of the zeolite natrolite occurs on prolonged heating of this material in the crystallizing medium, but not if the mother liquor is replaced by water or an alkaline solution. This process occurs for both aluminosilicate and gallosilicate analogues of natrolite. In cross experiments, the disordered Al‐containing (or Ga‐containing) analogue is heated while in contact with the mother liquor of the opposite analogue, that is, the Ga‐containing (or Al‐containing) liquor. Therefore, strong evidence for the mechanism of the ordering process was obtained, which was thus proposed to proceed by intraframework migration of tetrahedral atoms without diffusion along the pores. Migration is first triggered, then fuelled by surface rearrangement through reactions with the mother liquor, and stops when an almost fully ordered state is attained. Classical dissolution–recrystallization and Ostwald ripening processes do not appear to be relevant for this phase transformation. 相似文献
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Shu-Zhen Yang Zhi-Qiang Dong Cheng-Cheng Yin Hui-Juan Yue Wei-Wei Gao Feng-Ke Yang 《中国化学会会志》2020,67(9):1715-1720
In this paper, a green process for the synthesis and separation of caffeine was reported. Theophylline sodium is used as the raw material, diazabicyclo[5.4.0]undec-7-ene as the catalyst, and Turkey red oil as the solvent, particularly, dimethyl carbonate was adopted in place of high toxic dimethyl sulfate to form a mixture of caffeine and by-product sodium bicarbonate. After converting sodium bicarbonate to sodium carbonate, the solubility difference between caffeine and sodium carbonate at 40°C was for the first time utilized to achieve the purpose of separating caffeine with an excellent yield of 98.4% and a purity of greater than 99.0%. Furthermore, both the reaction mother liquor and separation mother liquor can be recycled and reused during the reaction and separation processes, respectively, with little caffeine loss. No industrial waste was discharged in the process of the improved synthesis and separation, which is therefore environmental friendly. 相似文献
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Ultrasound (US)-induced cavitation is an effective way in oxidizing organic contaminants in wastewater either as the independent operation unit or in combination with other oxidation methods. In this paper, black liquor and filtrate after acidifying and settling were sonicated The effect of working parameters on ultrasonic degradation of black liquor, such as different combinationmethods, frequency, power supply, initial concentration, pH, duration time, ionic strength and catalyst were studied The results were as follows: (1) At the conditions of 4OkHz, IOOW, 4h, pH at 6 and temperature 30±2℃,, utilizing US/US-H2O2/US-Fenton, weak-orange filtrate turned to colloid with the increase of time and little sediment produced after settling. Especially filtrate came to be milk white collides and upper water approached to nearly achromatic by US-Fenton. Compared with the US, US-H2O2/US-Fenton COD (Chemical oxidation demand) removal ratio can increase 15%,30% respectively. Because of more hydroxyl radicals produced in tire reaction process; (2) At the condition of lOOW and 4h, the degradation efficiency of black liquor was better at 40kHz over at 20kHz. Moreover black liquor can be biodegraded easily Those based on that the big molecule of contaminants in aqueous solution can be changed into the little molecule with ultrasound (3) At the condition of 40kl-l: and 4h, the COD removal ratio of black liquor was more higher at 60W than at 80W, while the removal ratio of COD at 60W was nearly close to the ratio at 100W,“ (4) The initial concentration of black liquor influenced the effect of sonochemical degradation; (5) The variation of pH had no effect on degradation; (6) The longer the duration time, tire greater the removal ratio of COD. But this ratio increased slowly after 4h; (7) Adding 0.2g/L NaCI to change the ionic strength of the black liquor, the COD removal ratio can increase 10%; (8) The degradation rates increased by the coexistent catalysts of TiO2, Co^+2 and Ag^+. 相似文献
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Anna Chrobok 《Tetrahedron》2010,66(16):2940-2943
A new and efficient method for the synthesis of lactones involving the application of an oxygen/benzaldehyde system as the oxidant and ionic liquids as solvents is reported. A significant rate enhancement was observed at 90 °C when the oxidation of ketones was carried out in the presence of a free radical initiator. The oxidation of model cyclic ketones, such as cyclopentanone, cyclohexanone, 2-methylcyclohexanone, 2-norbornone, 2-adamantanone and cycloheptanone gave lactones in high yields (84-90%) within relatively short periods of time, with the possibility of effective ionic liquids recycling. Additionally, discussion of the free radical mechanism of this reaction is proposed. 相似文献
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多相条件下亚硫酸镁非催化氧化反应动力学及机理 总被引:2,自引:0,他引:2
副产物的氧化回收利用是影响镁法脱硫工艺发展的关键.本文通过真空旋转蒸发的方式制备了高纯度的亚硫酸镁样品,并利用鼓泡式反应装置,研究了亚硫酸镁非催化氧化的反应动力学,考察了pH、氧分压、亚硫酸镁浓度、气体流量、温度等因素对亚硫酸镁氧化反应速率的影响,得到了各反应物的分级数及表观活化能.结合三相反应过程的数学模型推断出亚硫酸镁氧化的本征反应在慢反应区进行,且氧的传质扩散是总反应的速率控制步骤.研究结果为氧化回收镁法脱硫副产物提供了理论依据. 相似文献
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J. A. Poquis V. García-García J. Gonzlez-García V. Montiel A. Aldaz 《Journal of membrane science》2000,170(2)
In the industrial synthesis of
-α-p-hydroxyphenylglycine the separation of amino acid is carried out by precipitation. During this process, a mother liquor is produced with a high salt content (2 M phosphates and sulphates) and an amino acid concentration of 0.11–0.12 M. The disposal of this mother liquor causes an environmental problem and an economic loss. The salt content of this mother liquor can be reduced in 70% of the initial by means of an electrodialysis process previously carried out by us, with only an amino acid loss of 15% of the initial. To improve and simplify this process, an electro-electrodialysis process (a membrane electrolysis process; the electrode processes and the transport process across the membrane are used) has been developed in which as a first step, the electro-neutralisation of solutions containing sulphuric acid and
-α-p-hydroxyphenylglycine is studied. The sulphuric acid content is reduced to 87% of the initial, without detected loss of amino acid. The final solution is posteriorly neutralised by working up the pH of the solution for precipitating the amino acid, and a mother liquor with approximately 0.10 M
-α-p-hydroxyphenylglycine and a low salt content (0.08 M Na2SO4) is produced. This mother liquor with low salinity can be recirculated again to a new electro-electrodialysis process. 相似文献
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2,4-dinitrophenylosazones from coriose and D-glucose : Formation in mineral acid by different routes
1-Deoxycoriose 2,4-dinitrophenylosazone 2 was obtained in strong mineral acid as the only crystalline osazone of coriose 1. Experimental evidence was obtained for the mechanism of formation of 2via 1-deoxyosone 10. The structure of D-glucose 2,4-dinitrophenylosazone produced analogously was proved to be 6, and the isolation of 2,4-dinitroaniline from the mother liquor is in accord with the mechanism of normal phenylosazone formation. Excess reagent did not cause further reaction down the chain of the sugars, and the large downfield shift of an imino proton in each osazone, showing that a chelate ring is formed between two phenylhydrazine moieties in these osazones in spite of the strong chelation between α-imino and o-nitro group in 2,4-dinitrophenylhydrazine. 相似文献