表面活性剂增敏动力学光度法测定痕量钴(Ⅱ)

研究了在十二烷基二甲基氧化胺(OB-2)活化下,Co(Ⅱ)催化过硫酸钠氧化甲基紫的褪色反应,并建立了甲基紫褪色催化动力学光度法测定痕量Co(Ⅱ)的新方法。该法测定波长为580nm,线性范围为0.05～3.00μg/25mL,相关系数r=0.9992。检出限为2.0×10-9g/mL,最大相对标准偏差为1.67%,回收率为98.1%～102.3%。     

N,N-二甲基乙醇胺三个季铵盐衍生物的合成与表征

以N，N－二甲基甲酰胺为溶剂，乙酸乙酯为催化剂，N，N－二甲基乙醇胺分别与苄基氯、十二烷基溴和十八烷基溴作用，得到了3个N，N－二甲基乙醇胺的季铵盐衍生物。标题化合物结构经IR，^1H NMR,^13C NMRt FAB-MS表征。     

十二烷基二甲基苄基溴化铵离子选择电极的制备与性能

以四苯硼钠作为电活性物质,用溶胶-凝胶方法制备的阳离子表面活性剂离子选择电极对十二烷基二甲基苄基溴化铵具有良好的能斯特响应特性,其线性响应范围为1.0×10-3~1.58×10-6mol·L-1,斜率为57.8mV/pc(pc=-logc),适宜的pH范围为4.0~10.0.同时该电极显示了较好的选择性,重现性和稳定性.用该电极对十二烷基二甲基苄基溴化铵进行了回收率试验,效果很好,对其溶液试样进行了分析,结果和标准方法一致.     

光散射法研究氧化胺胶束与聚苯乙烯磺酸钠的相互作用

采用光散射法研究了十二烷基二甲基氧化胺(DDAO)胶束与聚苯乙烯磺酸钠(NaPSS)的相互作用,浊度滴定和激光光散射结果表明,DDAO胶束与NaPSS的相互作用受介质离子强度影响,但与胶束浓度无关,浊度滴定曲线出现一个转折点(β_c),而平均流体力学半径R_h对胶束离解度β的关系曲线出现2个转折点,在第一个转折点(β₁)时,胶束与NaPSS开始缔合,在第二个转折点(β₂)时,胶束与NaPSS的缔合达到饱和,β₂相当于浊度滴定曲线的转折β_c,β₂,和β₁不随离子强度而变化,采用β₁和β_c分别计算胶束与NaPSS发生缔合时的临界表面电荷密度,两者差距约为15％,电泳光散射也证实了β₁的存在.     

曙红催化褪色光度法测定痕量锰

催化光度法测定锰，由于其灵敏度高、检出限低而倍受关注，但此类方法的选择性不够理想。本研究发现，锰（Ⅱ）能催化高碘酸钠氧化曙红使其褪色，邻菲哕啉对此体系有活化作用，两性表面活性剂十二烷基二甲基氧化胺（OB-2）有增稳效果，褪色反应速度可用1g（A0／A）=kCMn（Ⅱ）方程式表示，从而拟定了催化光度法测定痕量锰的方法。该法所用指示物质曙红显色灵敏，此类报道一般只加入活化剂（如邻菲罗啉或氨三乙酸），试验发现两性表面活性剂十二烷基二甲基氧化胺（OB-2）可增加体系的稳定性，降低检出限，选择性也有较大改善，将此法用于水样中锰的测定，获得了满意的结果。     

十二烷基二甲基苄基氯化铵从碱性氰化液中固相萃取金的研究

建立了一种用十二烷基二甲基苄基氯化铵(BDMDAC)从碱性氰化液中固相萃取金的新方法:在碱性介质中,十二烷基二甲基苄基氯化铵溶液(BDMDAC)与Au(CN)2-络阴离子生成离子缔合物,该离子缔合物可被反相键合硅胶固相萃取柱萃取、富集,用乙醇洗脱,反相键合硅胶固相萃取柱可重复使用。该方法用于从碱性氰化液中固相萃取痕量金,萃取回收率可超过98%。     

十二烷基二甲基苄基氯化铵从碱性氰化液中固相萃取金的研究

建立了一种用十二烷基二甲基苄基氯化铵(BDMDAC)从碱性氰化液中固相萃取金的新方法：在碱性介质中,十二烷基二甲基苄基氯化铵溶液(BDMDAC)与Au(CN)2-络阴离子生成离子缔合物,该离子缔合物可被反相键合硅胶固相萃取柱萃取、富集,用乙醇洗脱,反相键合硅胶固相萃取柱可重复使用。该方法用于从碱性氰化液中固相萃取痕量金,萃取回收率可超过98%。     

羧甲基淀粉与烷基二甲基苄基氯化铵的相互作用研究

通过电导法、荧光法、粒度法等方法研究了羧甲基淀粉与3种不同碳数烷基二甲基苄基氯化铵之间的相互作用。结果表明,羧甲基淀粉与长链烷基二甲基苄基氯化铵在小于单纯表面活性剂临界胶束浓度（cmc）1～2个数量级的浓度下发生复合,并产生沉淀。当表面活性剂烷基链增加且浓度增大时,表面活性剂长碳链间的疏水作用及与羧甲基淀粉间的疏水作用...     

甲基橙光谱法测定杀菌剂中DDBA的含量

十二烷基二甲基苄基铵(DDBA)是一种广泛使用的杀菌剂。基于甲基橙(MO)与DDBA在水中能够形成离子复合物使其吸收光谱显著改变的现象,建立了一种简单、快速测定DDBA的方法。该方法检测的线性范围是6~40μmol·L^-1,线性方程为y=-0.01556x+0.7784,其线性相关系数R2为0.9964,检出限为0.58μmol·L^-1。溶液中的常见阴离子、溶液pH值和温度对该检测方法都没有明显影响。用精确度、精密度和灵敏度等方法进一步验证了该方法的可靠性。该方法应用于商品新洁尔灭消毒液中的DDBA测定,结果满意。     

以N-十二烷基二甲基铵基乙酸为增敏剂催化光度法测定痕量锰

报道了以氨三乙酸为活化剂,以N-十二烷基二甲基铵基乙酸(DDMAA)为增敏剂,高碘酸钾氧化天青(Ⅱ)催化光度法测定痕量锰的新方法.本法在两性表面活性剂DDMAA存在下,灵敏度提高了3.3倍(锰量为 0.4～2.0 μg/L)和 5.6倍(锰量为2.0～6.0μg/L);相对标准偏差为1.3%(n=11),方法的检出限为5.2×10~(-11)g/mL.可用于茶叶中锰的测定.     

Micellar Interactions in Nonionic/Ionic Mixed Surfactant Systems

To study the influence of the chemical nature of headgroups and the type of counterion on the process of micellization in mixed surfactant systems, the cmc's of several binary mixtures of surfactants with the same length of hydrocarbon tail but with different headgroups have been determined as a function of the monomer composition using surface tension measurements. Based on these results, the interaction parameter between the surfactant species in mixed micelles has been determined using the pseudophase separation model. Experiments were carried out with (a) the nonionic/anionic C(12)E(6)/SDS ((hexa(ethyleneglycol) mono-n-dodecyl ether)/(sodium dodecyl sulfate)), (b) amphoteric/anionic DDAO/SDS ((dodecyldimethylamine oxide)/(sodium dodecyl sulfate)), and (c) amphoteric/nonionic C(12)E(6)/DDAO mixed surfactant systems. In the case of the mixed surfactant systems containing DDAO, experiments were carried out at pH 2 and pH 8 where the surfactant was in the cationic and nonionic form, respectively. It was shown that the mixtures of the nonionic surfactants with different kinds of headgroups exhibit almost ideal behavior, whereas for the nonionic/ionic surfactant mixtures, significant deviations from ideal behavior (attractive interactions) have been found, suggesting binding between the head groups. Molecular orbital calculations confirmed the existence of the strong specific interaction between (1) SDS and nonionic and cationic forms of DDAO and between (2) C(12)E(6) and the cationic form of DDAO. In the case for the C(12)E(6)/SDS system, an alternative mechanism for the stabilization of mixed micelles was suggested, which involved the lowering in the free energy of the hydration layer. Copyright 2000 Academic Press.     

Effects of protonation on the thermodynamic properties of alkyl dimethylamine oxides

The effects of protonation on alkyldimethyl amine oxide micelles are reviewed, mainly with regard to dodecyl and tetradecyl homologs. The topics discussed are hydrogen ion titration properties, critical micelle concentration (CMC), area per surfactant and micelle aggregation number. A hydrogen bond hypothesis is proposed to interpret the several characteristic results associated with protonation: between two cationic species as well as between the non-ionic-cationic pair. The dipole-dipole interaction of the non-ionic micelle is discussed in relation to both: (a) the unusually high CMC values of the non-ionic micelles compared with other non-ionic surfactants with the same hydrocarbon chain; and (b) the reversal of the stability of the non-ionic and the cationic micelles at high ionic strengths. Two different approaches of the salting out effect on the ionic micelles are compared, the Chan-Mukerjee approach and ours, in relation to the non-linear Corrin-Harkins relation. The obtained salting out constants of the surfactants carrying a dodecyl chain decreased as the head group becomes more polar. Infrared and 13C-NMR spectra data are examined from the point of the specific interaction claimed by the hydrogen bond model. Mixed surfactant systems including amine oxides and the solid state phase behavior of amine oxides are both briefly reviewed.     

Surface Tension,Activity of Counterion,and Conductivity of the Quaternary System Dodecyldimethylamine Oxide,TX‐100, HCl,and Water

We have investigated the mixing behavior of the mixtures of dodecyldimethylamine oxide (DDAO) and Triton X‐100 (TX‐100) at different ratios of the two surfactants and at different values of pH. From the equilibrium surface tension measurements, the critical micelle concentration (CMC) and surface tensions at CMC data were obtained as functions of the composition. For the binary mixtures of dodecyldimethylamine oxide and TX‐100 at different ratios in the natural values of pH, the behaviors of the mixtures deviate positively from ideal during micellization. The minimum of CMC of the mixtures of dodecyldimethylamine oxide and Triton X‐100 was observed in the range 4.0?) increased with the decrease of pH. At pH=4.99, the activities of the counterion decreased with the increase of the concentration of TX‐100 at a constant concentration of DDAO. At pH=1.96, the activities of the counterion increased with the increase of the concentration of TX‐100. However, the conductivities of the solution decreased with the increase of the concentration of TX‐100 at both pH=4.99 and pH=1.96. The experimental results show that the effect of TX‐100 on the activities of the counterion at pH=4.99 is different from that at pH=1.96.     

Influence of Surfactants Synergism on the Adsorption Behavior at Air/Water and Solid/Water Interfaces

The influence of synergistic interaction between sodium dodecylsulfate (SDS) and N,N-dimethyldodecan-1-amine oxide (DDAO) on their adsorption at air/water and solid/water interfaces at 20°C is investigated. The critical micelle concentration values obtained from surface tension measurements indicated strong synergism between SDS and DDAO, according to regular solution model. The excess surface concentration (Γ) and the minimum occupied area by single and mixed surfactant monomers (A_min) at liquid/air interface were also calculated. The adsorption onto the activated charcoal and silica was then measured to find out the correlation between surfactant synergism and their adsorption at solid/water interface. The amounts of surfactant adsorbed onto 1 wt% activated charcoal follow the trend: SDS/DDAO > DDAO > SDS. SDS molecules do not adsorb onto 5 wt% silica substrate, while SDS/DDAO mixed system was found to have the highest adsorption behavior. The obtained indicate that SDS can be removed from water by mixing it with amphoteric surfactant.     

Properties of Surface and Micelle in a pH‐Mediated Ternary Surfactant Mixture in Salt Solution

We have investigated the mixing behavoir of a pH‐mediated ternary surfactant mixture at constant ratio of dodecyldimethylamine oxide (DDAO) and Triton X‐100 (9:1). From the equilibrium surface tension measurements at different pHs, the critical micelle concentration (cmc) data were obtained as functions of the pH. Values of the cmc and composition of the micelles were predicted using the regular solution approximation. To some extent, the experimental cmc values agree with the predicted cmc. The average degree of ionization of dodecyldimethylamine oxide in the mixed surfactant systems was estimated using potentiometric titrations. The surface electric potential of the micelles (Ψ_o) was determined using two methods, one by hydrogen ion titration and the other by the dissociation constants of an acid‐base indicator. In a high degree of ionization of DDAO in the micelles phase (a_m), Ψ_o estimated from acid‐base indicator is much higher than that from hydrogen ion titration. In the protonated dodecyldimethylamine oxide/TX‐100 binary surfactant system, Ψ_o estimated from hydrogen ion titration was as high as 89 mV. The micellar aggregation numbers evaluated by the steady‐state fluorescence probe method increase with pH except at pH=5.03. At pH=5.03, the maximum micelle aggregation number was observed.     

Enhanced adsorption of alkyl glucosides on the silica/water interface by addition of amine oxides

The effect of adding a small amount of dodecyl dimethylamine oxide (DDAO) on adsorption on silica from an aqueous solution of dodecyl maltoside (C12G2) has been investigated. The C12G2 itself does not adsorb significantly on silica at any concentration. DDAO on the other hand readily adsorbs in a bilayer-like structure at concentrations approaching the critical micelle concentration (cmc), but the adsorbed amount at the concentrations it has been applied in these mixtures is small. In contrast, by combination of the two surfactants, significant adsorption is observed at concentrations where the adsorption of the pure DDAO, as well as pure C12G2, is very low. We thus see a strong enhancement of the adsorption from the mixed system. The adsorption is suggested to be a two-step process, where individual DDAO molecules first adsorb to the silica surface through electrostatic interactions, and then C12G2 adsorbs at the hydrophobic sites the DDAO tails constitute through hydrophobic bonding. A minimum concentration of DDAO is required to induce adsorption from a solution with constant C12G2 concentration. This concentration is lower for C12G2 solutions below and equal to cmcC12G2 than above cmcC12G2. In addition, the total adsorbed amount shows a maximum around cmcC12G2 of the mixture for a solution with low DDAO contents. Both these effects are explained by incorporation of DDAO in the mixed micelles above cmc(mix), which leads to a desorption of DDAO from the surface.     

DNA condensation induced by cationic surfactant: a viscosimetry and dynamic light scattering study

The compaction of DNA induced by two simple amphiphiles, cetyltrimethylammonium bromide [CTAB] and dodecyldimethylamine oxide [DDAO], has been investigated by means of combined viscosity and dynamic light scattering measurements, to demonstrate the formation of soluble DNA/surfactant complexes, undergoing a coil-globule transition, upon the increase of the amphiphile concentration. In both of the two systems investigated, the complexation process reaches a maximum for a value of the surfactant to DNA phosphate groups molar ratio of about X = 1. Below this critical concentration, the coil and the globule state coexist in the solution, as clearly shown by the bimodal size distribution obtained from the light scattering intensity correlation functions. Some suggestions are given to support a molecular mechanism responsible for the complex formation, both in the case of a cationic surfactant (CTAB) and of a pH-dependent neutral or cationic amphiphile (DDAO), where the hydrophobic interactions play an important role.     

Effect of the protonation equilibrium on the interaction of mixed micelles with their counterions

Ionic/nonionic mixed micelle formation of dodecyldimethylamine oxide (DDAO) was studied by measuring the activities of DDAO⁺ ions and Cl⁻ ions using surfactant-selective electrodes and Ag/AgCl electrodes at three pH values in the absence of added salt. DDAO monomer exists as either a nonionic or a cationic species depending on the pH of the aqueous solution and hence the two species are not independent of each other. A new relation between the activity of the surfactant ions and that of the counterions is presented which differs from the corresponding relation valid for ionic/nonionic mixed micelles consisting of independent components. Received: 15 May 1998 Accepted in revised form: 30 September 1998     

Thermodynamic study of the protonation of dimethyldodecylamine N-oxide micelles in aqueous solution at 298 K. Establishment of a theoretical relationship linking critical micelle concentrations and pH

Dodecyldimethylamine N-oxide (DDAO) is a zwitterionic surfactant with acid-base properties. The proton dissociation constant of this surfactant was determined by a novel potentiometric method at "controlled chemical potential" of the proton using a classical pH-glass electrode. When the DDAO was in its monomeric form, the pKa was about 5, consistent with the value commonly reported in the literature. However, a unique proton dissociation constant specific to the micellar form of this surfactant could not be obtained. We found that the acid-base behavior of the DDAO micelles depended on their environment. Indeed, we were able to establish thermodynamic relations linking the critical micellar concentration to the degree of protonation of the micelles. The experimental values were in good accordance with this model.