Solubilization and applications of single-walled carbon nanotubes into aqueous and organic media by the use of nanometer size-controlled fluoroalkyl end-capped oligomeric aggregates

We have studied on the solubilization of single-walled carbon nanotubes (SW-CNTs) into aqueous and organic media by the use of a variety of nanometer size-controlled fluorinated self-assemblies, which were formed by the aggregations of end-capped fluoroalkyl segments in fluoroalkyl end-capped acrylic acid oligomers [R_F-(ACA)_n-R_F], N,N-dimethylacrylamide oligomers [R_F-(DMAA)_n-R_F], acryloylmorpholine oligomers [R_F-(ACMO)_n-R_F], and N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers [R_F-(DOBAA)_n-R_F]. Fluorinated self assemblies formed in organic media (colorless solutions) could solubilize SW-CNTs into organic media to afford the transparent pale yellow solutions. The dynamic light scattering measurements showed that the size of fluorinated self-assemblies increased after the solubilization of SW-CNTs into organic media. It was suggested that the solubilization of SW-CNTs into organic media is due to the encapsulation of SW-CNTs into fluorinated assemblies. Fluorinated assemblies were also able to solubilize SW-CNTs into water to give the transparent gray solutions. Among a variety of fluorinated assemblies, fluorinated assemblies formed by R_F-(ACMO)_n-R_F [R_F = CF(CF₃)OC₆F₁₃] oligomer was more effective for the solubilization of SW-CNTs into both aqueous and organic media. Contact angle measurements of dodecane and the fluorescence spectra for poly(methyl methacrylate) cast film modified by fluorinated self-assemblies—SW-CNTs complexes showed that SW-CNTs are dispersed above the PMMA surface.     

Osmotic Coefficients of Aqueous Solutions of Some Poly(oxyethylene) Glycols at the Freezing Point of Solution

Summary. The freezing temperatures of dilute aqueous solutions of some poly(oxyethylene) glycols (PEG, HO–(CH₂CH₂O) _n –H, n varying from 4 to 117) were measured over a solute to solvent mass ratio from 0.0100 to 0.3900. The second and third osmotic virial coefficient (A ₂₂ and A ₂₂₂) of poly(oxyethylene) glycols in aqueous solution were determined. The molecular weight dependence of the second virial coefficient can be described by a simple relation A ₂₂=2×10^–5 M _n ^1.86, and the third virial coefficient is A ₂₂₂=0.038A ₂₂ ². The activity coefficients of the solute were calculated using the Gibbs-Duhem equation as applied by Bjerrum. From the osmotic and activity coefficients the excess Gibbs energies of solution, as well as the respective partial molar functions of solute and solvent and the virial pair interaction coefficients for the excess Gibbs energies were estimated. The second and the third osmotic virial coefficients are correlated with the Mc-Millan-Mayer virial coefficients.     

Semi-micro solvent extraction as a rapid and efficient preconcentration technique for the determination of n-alkanes in oil-contaiminated water and soil samples by capillary gas chromatography

Summary In this study, a rapid and efficient semi-micro extraction procedure is presented for the extraction of some higher n-alkanes from water and soil samples. In the case of water samples n-hexane was used as the organic phase in a phase volume ratio (volume of aqueous phase/volume of organic phase) higher than 285, while in the case of soil samples, extraction with n-hexane was carried out in the presence of an excess of 2 M NaCl solution. The extraction rate from soil samples is very high and is better than Soxhlet extraction, comparable with supercritical fluid extraction. High preconcentration factor in water samples allows the limits of detection to be in the ng.mL⁻¹ level with the use of gas chromatographic analysis. Flame ionization detector was used for monitoring the analytes. The obtained recoveries of all studied compounds from both water and soil samples are higher than 90%. This method was successfully used to determine some n-alkanes in municipal wastewater and contaminated soil.     

Immunoaffinity-based extraction of phenylurea herbicides using mixed antibodies against isoproturon and chlortoluron

Summary The analysis of several phenylurea herbicides in different waters is described using an immunoaffinity column clean-up and determination by high performance liquid chromatography. The pesticides were selectively retained on a solid phase extraction column containing antibodies to chlortoluron and to isoproturon immobilised onto silica. Selected phenylureas were eluted using a simple phosphate buffered saline/ethanol mixture at low pH. The immunoaffinity approach gave extracts free of interfering substances and allowed detection limits comparable to those required for pesticides in water in the European Community. The proposed method was successfully applied to the determination of chlortoluron, isoproturon, linuron and chlorbromuron in tap and river water. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Simultaneous determination of alkylphenol ethoxylates and their biotransformation products by liquid chromatography/electrospray ionisation tandem mass spectrometry

Reversed-phase LC-MS/MS is used to determine major estrogenic alkylphenol ethoxylates (APEOs) and their biotransformation products. It allows the simultaneous analysis of eight APEOs, alkylphenoxy carboxylates (APECs) and alkylphenols (APs) in sewage treatment plant (STP) effluents in the same extract after solid-phase enrichment on polymeric Oasis HLB. As precursor ions, [APEO + NH4]+, [APEC - H]- and [AP - H]- were monitored. Instrumental limits of detection (LOD) were 2-600 pg, corresponding to sample concentrations of 0.04-12 ng l(-1), without correction for overall method recoveries. Matrix-induced signal suppression during electrospray ionisation (ESI) and extraction as well as overall method recoveries were assessed and the suitability of deuterated surrogates as internal standards was evaluated.     

Voltammetric Behavior of Arsenic(III) in the Presence of Sodium Diethyl Dithiocarbamate and Its Determination in Water and Highly Saline Samples by Adsorptive Stripping Voltammetry

This paper describes the voltammetric behavior of As(III) at the hanging mercury drop electrode (HMDE) in the presence of sodium diethyl dithiocarbamate (SDDC) and a new voltammetric method for the determination of As(III) at trace levels. The method is based on the adsorptive deposition of a As(III) complex with SDDC at ?0.45 V (vs. Ag/AgCl) on the HMDE in acidic medium of 0.01 mol L^?1 HCl (pH 2.0) and its cathodic stripping during the potential scan (100 mV s^?1). The linear range for the determination of As(III) in the presence of SDDC (4 μmol L^?1) in water samples was between 1 and 10 μg L^?1 for a deposition time of 300 s (r=0.994) and between 10 and 100 μg L^?1 for a deposition time of 60 s (r=0.999). For the determination of As(III) in dialysis concentrate samples, the linear range was between 5 and 25 μg L^?1 for a deposition time of 180 s (r=0.992) and between 10 and 100 μg L^?1 for a deposition time of 60 s (r=0.996). Detection limits of 0.3 and 2.2 μg L^?1 in water and dialysis concentrate samples were calculated for the method using a deposition time of 300 and 180 s, respectively. Recovery values between 93.0 and 110.0% for As(III) added to deionized, mineral, seawater (synthetic and real) and dialysis concentrate samples prove the satisfactory accuracy and applicability of the procedure.     

硝基苯在离子液体BMimBF4-H2O中的电还原

采用循环伏安法和恒电位电解法研究了离子液体BMimBF4-H2O 中硝基苯在微铂电极上的电还原特性. 实验表明, 在BMimBF4中, 随着硝基苯和水的浓度变化, 循环伏安曲线的峰电位和峰电流呈现复杂的变化规律; 硝基苯在铂电极上的电还原反应为双分子8 电子3 步骤电化学过程, 第一步反应为准可逆单分子单电子转移步骤, 产生阴离子自由基, 第二步为2 电子转移步骤, 并伴有随后的双分子不可逆自由基偶合化学反应, 主要产物为氧化偶氮苯, 第三步是2 电子转移产生偶氮苯的过程.     

水中痕量钼(Ⅵ)的4-(2-吡啶偶氮)-间苯二酚螯合活性炭吸附富集分光光度法测定

提出了一种简单快速预富集水中痕量钼（Ⅵ）的新方法，方法的机理在于4－（2－吡啶偶氮）－间苯二酚（PAR）与钼（Ⅵ）螯合后被活性炭中附，然后用NaOH解吸下来，再用水杨基荧光酮与钼（Ⅵ）显色，分光光度法测定钼（Ⅵ）的含量；详细研究了影响Mo-PAR螯合物定量吸附于活性炭上的各种参数，找出了最佳吸附－解吸条件，包括吸附酸度、PAR用量、吸附时间、解吸酸度等；该法的主要优点是操作简单、快速，干扰小，避免了常规方法中用浓硝酸消化活性炭费时和污染大的解吸方法，该法已用于测定水中痕量钼（Ⅵ），加标回收率达到94％－97％。     

Application of capillary electrophoresis with different sample stacking strategies for the determination of a group of nonsteroidal anti-inflammatory drugs in the low microg x L(-1) concentration range

Several on-column sample preconcentration modes--large-volume sample stacking using the EOF pump (LVSEP), LVSEP with anion-selective exhaustive injection (LVSEP-ASEI) and field-amplified sample injection with sample matrix removal using the electroosmotic flow (EOF) pump (FAEP)--were used to analyze some nonsteroidal anti-inflammatory drugs (NSAIDs) by capillary electrophoresis, and then compared. Methanol was the background electrolyte solvent to suppress the EOF. The effect of the type and length of the solvent plug, and the sample injection time were investigated in FAEP to determine the conditions that provided the best response. LVSEP, LVSEP-ASEI, and FAEP improved the sensitivity of the peak area by 100-, 1200-, and 1800-fold, respectively. The methodology developed, in combination with solid-phase extraction (SPE), was applied to the analysis of water samples.