近红外分光光度法测定高氯酸羟胺中的水含量

建立近红外分光光度法测定高氯酸羟胺中的水含量.以四氢呋喃水溶液为标准溶液,以四氢呋喃为参比溶液,测定系列标准溶液于波长1920 nm处的校正吸光度,标准曲线线性方程为y=113.76x+0.0065,相关系数为0.9996.样品重复性测定相对标准偏差小于2％(n=5),样品加标回收率为98.06％～99.92％.该方法操作简便.     

分光光度法测定桂西大米中铁的含量

用分光光度法直接测定了大米中铁的含量，方法简便快速准确，对指导人们合理食用大米进行补铁及进一步开发大米产品提供了可靠的理论依据。     

分光光度法测定桂西茶叶中铁的含量

茶叶既是食品,又是一味传统医药用的中药,药食同源.用分光光度法直接测定了茶叶中铁的含量,方法简便、快速、准确,对指导人们合理饮用茶叶进行补铁及进一步开发茶叶提供了可靠的理论依据.     

紫外分光光度法测定中草药中铁的含量

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。     

分光光度法测定豆类中铁的含量(Ⅱ)

豆类无污染,无农药残毒,营养丰富,具有特殊风味,并且很多豆类还有医疗保健作用.用分光光度法直接测定了豆类中铁的含量,方法简便快速准确,对指导人们合理食用豆类补铁及进一步开发豆类提供了可靠的理论依据.     

分光光度法测定野菜中铁的含量(Ⅲ)

野菜无污染、无农药残毒,营养丰富,具有特殊风味,并且很多野菜还有医疗保健作用.用分光光度法直接测定了野菜中铁的含量,方法简便快速准确,对指导人们合理食用野菜进行补铁及进一步开发野菜提供了可靠的理论依据.     

渐进因子分析—分光光度法测定Fe^3＋—SCN^—络合物的稳定常数

本文利用渐进因子分析与化学平衡相结合的方法迭代求解逐级生成络合物的各级稳定常数，对Ｆｅ＾３＋－ＳＣＮ＾－体系在水溶液及５０％丙酮溶液中的配体浓度－波长的两维双线性吸光度数据矩阵进行处理，求得水溶液中该络合物第一、二级稳定常数为１ｇｋ１＝２．２６，１ｇｋ２＝１．３０。同时该法还可确定各种组分的存在区间及吸收光谱，本文还对丙酮的存在对Ｆｅ＾３＋－ＳＣＮ＾－络合物的影响作了研究，结果表明丙酮，对高配位络     

盐酸羟胺的间接分光光度法测定

拟定了在铁（Ⅲ）—２－［２－（６－甲基苯并噻唑）偶氮］－５－二乙氨基苯甲酸（６ＭｅＢＴＡＥＢ）络合物和十二烷基硫酸钠存在下盐酸羟胺的间接分光光度测定方法,回收试验表明该法准确可靠,方便快捷。同时测定了盐酸羟胺与Ｆｅ（Ⅲ）－６＿Ｍｅ＿ＢＴＡＥＢ络合物的反应比。     

分光光度法测定乙二醇中的钼含量

提出了一种用分光光度法测定乙二醇中痕量钼的新方法．该方法是基于在强酸性溶液中,钼与水杨基荧光酮(SAF)和阳离子表面活性剂溴化十六烷基三甲铵(CTMAB)发生高灵敏度的显色反应,生成稳定的配合物,其λmax为524nm,表观摩尔吸光系数ε524为1．03x10^5．比较详细地研究了各种实验条件的影响．钼在乙二醇溶液中的回收率为94％～98％,结果满意．     

分光光度法测定黔江肾豆中Fe含量

采用邻菲罗啉分光光度法测定肾豆中铁含量,方法简单、快捷、准确。样品经过湿法V（HCl04）＋V（HN03）=4＋1消解预处理,探讨了最佳波长、温度、酸度、显色剂用量以及显色时间等对测定结果的影响,在最佳实验条件下测定肾豆中铁元素含量,为肾豆进一步的研究和利用提供一定的参考数据。     

Spectrophotometric Determination of Carboxylic acids with 2-Mitrophenylhydrazine in Aqueous Solution

Abstract

Carboxylic acids were determined spectrophotometrically by converting them into 2-nitrophenylhydrazides. The coupling reaction of carboxylic acids with 2-nitrophenylhydrazine was effected by a water-soluble carbociimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and proceeded efficiently in aqueous solution buffered at pH 4.5 with pyridine and hydrochloric acid. The yields of hydrazides from acetic and benzoic acids were nearly quantitative. The reaction mixture was then made strongly alkaline, and after heating to reduce the blank absorbance, the absorbance of the hydrazide was measured at around 540 nm. Calibration curves of various carboxylic acids were linear between 0.02 and 0.5 μmol through the origin.     

Spectrophotometric Determination of Perfluoro Carboxylic Acids (Heptanoic to Decanoic) and Sodium Perfluorooctanoate and Decyl Sulfate In Mixtures By Dye-Extraction

Abstract

Perfluorinated carboxylic acids were extracted into chloroform as a 1:1 ion-pairs with methylene blue and determined spectrophotometrically. the method gave linear calibration plots in the 10-⁵ range. A method is outlined for the analysis of sodium perfluorooctanoate and sodium decylsulfate in their mixtures.     

Spectrophotometric Determination of Steroid Oximes

Abstract

A spectrophotometric procedure for the determination of steroid oximes is described utilizing 11β-hydroxy-iia-methyl-5β-pregnane -3, 20 -dione dioxime (I) and iia-hydroxy-progesterone dioxime (II) as models. The method is based on (a) acid hydrolysis to release hydroxylamine, (b) oxidation of hydroxylamine to nitrous acid with iodine, (c) diazotization of sulfanilic acid with the nitrous acid, (d) coupling of the diazonium compound with N-(i-naphthyl)-ethylenediamine dihydrochloride, and (e) measurement of the azo dye at 550 nm. A stoichiometric yield of hydroxylamine is obtained. Analyses of I and II have given typical recoveries (mean ± S. D.) of 99.5 ± 1.1% and 97.8 + 3.5%, respectively. The method is sensitive to ≥ 0.3 × 10^?5 M dioxime.     

Hydrogen Bonding of Carboxylic Acids in Aqueous Solutions—UV Spectroscopy, Viscosity, and Molecular Simulation of Acetic Acid

The UV spectra of aqueous acetic acid solutions up to 2M were investigated. At these wavelengths, the carboxylic acids exhibit an absorption peak, attributed to the C=O group, which shifts when hydrogen bonds are formed.. The measured spectra were best fitted to several bands, either of Gaussian or Lorentzian shape, which can be explained as several types of structural units formed by hydrogen bonds established between acetic acid and water molecules and between acetic acid molecules themselves. Molecular dynamics simulation of these mixtures was also performed, confirming the occurrence of several types of hydrogen bonds and showing the presence of dimers at higher concentrations. The viscosity and density of these solutions were also measured at different concentrations and temperatures. These results give a more complete picture of the hydrogen bond network of the system.     

Selective and Efficient Oxidation of Aldehydes to Their Corresponding Carboxylic Acids Using H2O2/HCl in the Presence of Hydroxylamine Hydrochloride

A wide variety of aldehydes were efficiently converted to their corresponding carboxylic acids in high yields using H₂O₂/HCl in the presence of hydroxylamine hydrochloride. In addition, selective oxidation of aldehydes in the presence of other functional groups such as hydroxyl group, carbon‐carbon double bond and other heteroatoms can be considered a noteworthy advantage of this method.     

离子排斥色谱法测定马齿苋中低分子羧酸

以２．０ｍｍｏｌ／Ｌ对甲苯磺酸为淋洗液,用非抑制型电导检测离子排斥色谱法测定了马齿苋叶及茎中的柠檬酸、丙二酸、苹果酸、抗坏血酸、琥珀酸、反丁烯二酸和乙酸。     

中氮茚类羧酸化合物的合成及抑菌活性

合成了8个中氮茚类羧酸化合物, 产物经红外、 核磁、 质谱及元素分析表征, 并研究了其抑菌性能. 结果表明, 化合物3a, 3c, 5a, 5c和5d对大肠杆菌有一定抑制作用, 化合物3a和3c对金黄色葡萄球菌有抑制作用. 其中化合物3c对所选2个菌种均表现出较好的抑菌性能.     

Spectrophotometric Determination of Proline in Aqueous Solutions

The spectrophotometric determination of proline in aqueous solutions was studied. It was shown that pH, concentration, and time of storing the solution affect its spectral properties.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 8, 2005, pp. 802–805.Original Russian Text Copyright © 2005 by Davydova, Kotova, Krysanova, Selemenev.     

Reactions of Titanocene Derivatives with Molecular Carboxylic Acids and Copolymers Bearing Carboxylic Acid Groups

Linear, soluble copolymers containing titanium are of interest for use in targets for inertial-confinement fusion (ICF) experiments because the titanium is a useful spectroscopic probe for studying the nuclear fusion process. We have studied the reactions of dichloro- titanocene and diphenyltitanocene with carboxylic acids to determine if these can be used to prepare such polymers. Model reactions of dichlorotitanocene with p -toluic acid show that both mono- and di-carboxylates are formed. We have prepared a soluble titanium-containing copolymer via the reaction of poly(styrene- co -methacrylic acid) with an excess of dichlorotitanocene but attempts to remove the excess molecular titanocene from the copolymer result in crosslinking of the copolymer. Model reactions of benzoic and pivalic acids with diphenyltitanocene demonstrate that monosubstituted carboxylato(phenyl)titanocenes are formed but that these products are stable only at low temperatures and decompose readily at ambient temperature. Proton NMR studies of the reaction of diphenyltitanocene and benzoic acid at −20 °C indicate that this reaction is second order, suggesting that the reaction does not proceed through a benzyne intermediate. © 1997 by John Wiley & Sons, Ltd.     

Flow-Through Bulk Optode for the Spectrophotometric Determination of Perchlorate

A flow-through spectrophotometric bulk optode for the flow-injection determination of perchlorate is described. As active constituents, the optode incorporates the lipophilic pH indicator 5-octadecanoyloxy-2-(4-nitrophenylazo) phenol and methyltridodecyl ammonium chloride, dissolved in a plasticized poly(vinyl chloride) membrane which is entrapped in a cellulose support. The optode is applied in conjunction with the flow injection technique at pH 8.2 (TRIS buffer). The sensor is readily regenerated with a 10^–2M NaOH carrier solution. The analytical characteristics of this optode with respect to response time, dynamic measurement range, reproducibility and selectivity are discussed. The proposed FI method is applied to the determination of perchlorate in waters from different sources.Received December 16, 2002; accepted May 16, 2003 Published online August 8, 2003