动力学光度法测定食品中的碘

催化动力学光度法测定痕量碘 ,大多使用Ｃｅ(ＩＶ) -Ａｓ(ＩＩＩ)体系[1 3] 。我们的实验发现在硫酸介质中 ,Ｉ- 能强烈催化高碘酸钾氧化苋菜红的褪色反应 ,在波长 5 2 5ｎｍ处 ,其反应速度与碘离子的浓度之间符合动力学一级反应关系式 ,并且此法灵敏度、选择性均较高。1　实验部分取两支 2 5ｍｌ比色管 ,各加入 2 0ｍｌ浓度为8 0× 1 0 - 3ｍｏｌ/Ｌ苋菜红溶液 ,3 5ｍｌ( 1 0ｍｏｌ/Ｌ)Ｈ2 ＳＯ4,2 0ｍｌＫＩＯ4( 0 2 0ｍｏｌ/Ｌ)溶液。向其中一支加入适量碘标准溶液 ( 1 μｇ/ｍｌ) (吸光度为Ａ) ,另一支不加碘 (吸光度为Ａ0 ) ,用水…     

催化示波极谱法测定电解铅中痕量硒碲

本文用催化示波极谱法 ,在亚硫酸钠 氯化铵 酒石酸钠 ＥＤＴＡ 氨水的混合底液中 ,以高碘酸钾与硝酸催化硒波 ,以高碘酸钾催化碲波 ,可以得到硒与碲的两个良好的催化波 ,波峰电位硒约 - 0 .92Ｖ ;碲约 - 1.0 5Ｖ ,互不干扰 ,可在一份溶液中同时测定0 0 0 0 0 5 %左右的硒碲 ,浓度在 0～ 1.0 μｇ/ 10ｍｌ之间保持线性关系。1　试验部分1.1　试剂与仪器亚硫酸钠溶液 :2 0 0ｇ·Ｌ- 1混合底液 :称取氯化铵 10ｇ ,酒石酸钠 8ｇ ,ＥＤＴＡ二钠 0 .4ｇ ,加水 70ｍｌ,氨水 30ｍｌ,移入 10 0ｍｌ容量瓶中 ,混匀 (冬天应先微热溶解 )。高碘酸钾…     

铜-铬天青S-十二烷基苯磺酸钠褪色光度法测定痕量钡

1　引　　言测定痕量钡有Ｂａ 偶氮氯膦 Ｃｕ 邻菲咯啉 (ｐｈｅｎ) (ε≈ 1.0× 10 5Ｌ·ｍｏｌ- 1 ·ｃｍ- 1 )、Ｂａ 偶氮氯膦 Ｚｎ Ｐｈｅｎ(1.8×10 5Ｌ·ｍｏｌ- 1 ·ｃｍ- 1 和Ｂａ 联吡啶 间溴偶氮酸 (1.5× 10 5Ｌ·ｍｏｌ- 1 ·ｃｍ- 1 )等多元离子缔合光度法 ,邻氨基苯磺酸Ｓ、偶氮胂ＩＩＩ、金属钛和二苯卡巴腙 (检出限 :均约为 10 - 6ｇ ｍＬ)等光度分析法 ,以及催化褪色光度法 (4 .0× 10 - 1 1 ｇ ｍＬ)等。实验观察到 ,在ｐＨ =5 .40弱酸性介质中和加热条件下 ,钡能使 [Ｃｕ(Ｒ) 4]2 +·[(ＤＢＳ) 2 ]2 - (Ｒ为铬天…     

催化分光光度法测定食品中痕量锰

文献报道了锰的催化动力学分析法^[1-5],但使用高碘酸钾-二甲苯兰FF体系,尚未见报道,本文的研究表明:高碘酸钾氧化二甲苯兰FF(Xylene Cyanole FF,简称XCIFF)使之褪色,有较佳的催化效应,溶液颜色由亮兰变为棕黄,同时使用邻菲罗啉作活化剂,反应灵敏度能进一步提高,方法的线性范围为1.85～11ngMn·mL^-1,利用此方法测定了某些食品中的痕量锰。     

催化十二烷基苯磺酸钠-溴化钾-亚甲基蓝褪色光度法测定痕量锌

1　引　　言实验表明 ,在ｐＨ =5 .95弱酸性和 1 0 0± 2℃加热 3 0ｍｉｎ的条件下 ,Ｚｎ2 + 能催化十二烷基苯磺酸钠 (ＤＢＳ) 亚甲基蓝(ＭＢ) 溴化钾褪色反应 ,据此建立了催化十二烷基苯磺酸钠 溴化钾 亚甲基蓝褪色光度法测定痕量锌的新方法。探讨了催化反应的动力学参数。本方法的灵敏度高 (检出限 4 .0ｎｇ Ｌ) ,精密度好 ,选择性与重现性均佳 ,操作简便 ,已用于奶粉和人发中痕量锌的测定。2　实验部分2 .1　主要试剂与仪器　Ｚｎ2 + 工作液 :取 1 .0 0ｇ ＬＺｎ2 + 基准试剂 ,用水逐级稀释成 1 0 .0 μｇ Ｌ ;1 .0× 1 0 - 3ｍｏｌ …     

铱(Ⅳ)-甲基橙-高碘酸钾体系催化动力学光度法测定痕量铱（Ⅳ）

1 引言 动力学光度法测定铱(Ⅳ)的试剂有罗丹明B、DBS-偶氮氯膦、耐尔蓝、丁基罗丹明B、乙基罗丹明B等,诸方法稳定性欠佳,操作繁琐.实验观察到在硫酸介质中,铱(Ⅳ)能催化高碘酸钾氧化甲基橙褪色,由此建立了测定痕量铱(Ⅳ)的新方法.该方法操作简便、体系稳定,重现性好.     

催化动力学光度法测定痕量铁

铁广泛存在于自然界中 ,与人类生命活动密切相关 ,检测样品中铁含量是十分重要的。动力学光度法由于灵敏度高、检出限低而受到重视。用于测定铁的研究[1 ,2 ] 近年逐步增多 ,但未见有 Fe( ) -甲基橙 -过氧化氢体系催化光度研究报道 [3]。本文发现 ,在硫酸介质中 ,Fe( )对过氧化氢氧化甲基橙褪色反应具有强烈的催化作用 ,采用固定时间法 ,催化反应与非催化反应的吸光度差值与 Fe( )的浓度在 0～4 0 ng/2 5ml范围内呈线性关系 ,由此 ,建立了一个催化动力学光度法测定痕量铁的新方法。其检出限为8.0× 1 0 - 1 2 g· ml- 1 ,Fe( )浓度在 …     

二溴对甲基偶氮羧催化动力学光度法测定岩石及粮食中铁

研究了痕量铁对高碘酸钾氧化二溴对甲基偶氮羧的催化作用 ,发现其在H2 SO4 介质中具有高灵敏的反应 ,检出限为 8.2 2× 1 0 -11g/m L,线性范围为 Fe( ) 0～ 0 .1 8μg/2 5m L。可用于测定岩石及粮食中的铁     

硅钼蓝光度法测定五氧化二钒中微量硅

采用氢氧化钠对试样进行前处理 ,在硝酸 0 .0 8～ 0 .4 0ｍｏｌ·Ｌ- 1酸度下 ,硅与钼酸铵形成硅钼酸络离子 ,在硫酸 0 .8～ 1.6ｍｏｌ·Ｌ- 1酸度下 ,被还原生成硅钼蓝 ,借此进行光度测定[1] ,硅量在 10～ 10 0 μｇ/5 0ｍｌ范围内遵守比耳定律。1　试验部分1.1　仪器与试剂72 2光栅分光光度计硅标准溶液 :10 μｇ·ｍｌ- 1五氧化二钒标准溶液 :2 .5ｍｇ·ｍｌ- 1,称取五氧化二钒 (99.99%) 0 .2 5 0 0 ｇ置于 30 0ｍｌ聚四氟乙烯烧杯中 ,加入 10 0ｇ·Ｌ- 1ＮａＯＨ溶液 10ｍｌ,低温加热溶解 ,取下 ,加入数滴酚酞 ,用ＨＮＯ3 (1+ 1)调至无…     

高碘酸钾氧化偶氮胭脂红B动力学光度法测定微量钌

在 Ru( )催化高碘酸钾氧化偶氮胭脂红 B的褪色反应基础上 ,提出了测定钌的新催化光度法。钌质量浓度在 0～ 2 .8μg/ 2 5 m L范围内符合比尔定律 ,检出限为 3.83× 1 0 -4 μg/ m L。对 1 .0 μg/ 2 5 m L Ru( )测定的相对标准偏差为 3.8% ( n=1 1 )。催化反应的表观活化能为 5 1 .9k J/ mol,为假一级反应     

Regioselectivity of olefin oxidation by iodosobenzene catalyzed by metalloporphyrins : control by the catalyst

The regioselectivity of the oxidation of three monosubstituted olefins, 6-phenoxyhex-1-ene, hex-1-ene and styrene, by iodosobenzene in the presence of various Fe-, Mn- or Cr-tetraaryl-porphyrins, was studied. It was found that, besides epoxides, known products from such systems, allylic alcohols and aldehydes were formed, the latter not being derived from the corresponding epoxides. The relative importance of these reactions greatly depends upon both the metal and porphyrin constituents of the catalyst. More particularly, the competition between epoxidation and allylic hydroxylation can be efficiently controlled by non-bonded interactions between the olefin and porphyrin substituents. No hydroxylation of the aromatic rings and no oxidative dealkylation of the ether function was detected.     

Substitution of 2-phosphaindolizines by bromine and by chlorophosphines

Bromine does not add to phosphorus in a 2-phosphaindolizine 1 but substitutes its 1-position. The 1-bromo derivatives 2 are best prepared with Br₂/NEt₃ or N-bromosuccinimide. Their hydrolysis is remarkable; it involves a debromination of C-1, an oxidation of P and a selective opening of the P/C-3 bond. PCl₃ also causes a substitution of the 1-position. The resulting 1-dichlorophosphino derivatives 5 easily undergo a substituent exchange at the exocyclic phosphorus. More 1-phosphino derivatives are formed in the reaction of 1 with phenyl and diazaphospholyl dichlorophosphine.     

Desymmetrization of Dicationic Diboranes by Isomerization Catalyzed by a Nucleophile

Cationic monoboranes exhibit a rich chemistry. By constrast, only a few cationic diboranes are known, that all are symmetrically substituted. In this work, the first unsymmetrically substituted dicationic diboranes, featuring sp²–sp²‐hybridized boron atoms, are reported. The compounds are formed by intramolecular rearrangement from preceding isomeric symmetrically substituted dicationic diboranes, a process that is catalyzed by nucleophiles. From the temperature‐dependence of the isomerization rate, activation parameters for this unprecedented rearrangement are derived. The difference in fluoride ion affinity between the two boron atoms and the bonding situation in these unique unsymmetrical dicationic diboranes are evaluated.     

Oxidation of 1,4-dimethylcyclohexane by perchloric acid catalyzed by polyphenylferrosiloxane

The reaction of oxidation of 1,4-dimethylcyclohexane (DMCH) by perchloric acid at ～20 °C catalyzed by polyphenylferrosiloxane has been found. The chromatographic analysis has revealed the formation of several products, including the tertiary alcohol with 100% retention of the configuration of the initial configuration. The specific feature of the process is the following: along with the high stereospecific formation of the tertiary alcohol,cis-trans isomerization in the starting 1,4-DMCH is observed. The data obtained are discussed on the basis of the mechanism, including the formation of a ferryl intermediate with the subsequent transfer of the oxygen atom to the tertiary C?H bond of 1,4-DMCH through the intermediate complex with the five-coordinated carbon.     

Production of Enzymes by Plant Cells Immobilized by Sol-Gel Silica

Ajuga reptans cells are cultivated and used for production of invertase. These plant cells are immobilized by a sol-gel SiO₂ membrane, which is built up directly on the cell surface by exposure to a gaseous flow of silicon alcoxide precursors. The immobilization modifies the metabolic activity of cells, resulting in a 40-fold increase in invertase production with respect of free cells. Results concerning total release of proteins, cell growth and produced invertase activity are discussed, considering the absence of breeding, induced by SiO₂ immobilization, the prominent factor promoting the observed exceptional increase in invertase productivity.     

Optimal acidity of complexes by solution of polynomials and by iteration

The methods for optimal acidity of complexes M(x)L(y)(OH)(m)H(n) based on direct iteration or solution of polynomials are described and discussed. Then, by a direct straightforward method of computation (that does not require any iteration) the complexes M(x)L(OH)(m)H(n) and ML(y)(OH)(m)H(n) are treated (where 1 x 3 and 1 y 3). Finally, the conditions leading to formation of polynuclear complexes are shown and discussed. The importance of study of polynuclear complexes for solving of biochemical problems is pointed out. Practical examples are given for each method.