An Improved Capillary Gas Chromatography Method for Triethylamine. Application to Sarafloxacin Hydrochloride and GnRH Residual Solvents Testing

ABSTRACT

A capillary gas chromatography (GC) method for residual solvents in the veterinary antibacterial compound sarafloxacin hydrochloride included triethylamine (TEA). Despite the use of commercially available deactivated columns and inlet liners, the peak shape and reproducibility for the TEA peak were very poor. The use of glass inlet liners and glass wool which were treated with methanolic potassium hydroxide resulted in marked improvement for TEA. This method was also used to determine residual TEA in the polypeptide GnRH.     

Polar and Hydrogen-Bonding Effects of Alcohols on the Emission Spectrum of Styrene–Triethylamine System

The emission spectra of styrene (ST)–triethylamine (TEA) systems were measured under steady-state illumination conditions in some tetrahydrofuran (THF)–protic solvent mixtures. The fluorescence spectrum of the ST–TEA system in THF consists of two bands (band A at 304 nm (fluorescence of ST) and band B at 460 nm (emission from an exciplex)). The intensity of band A increased and that of band B decreased with increasing amounts of protic solvents in THF–protic solvent mixtures. The increase in the intensity of band A was explained by the decrease in the concentration of free amine owing to the hydrogen-bonding interaction (or protonation) between TEA and protic solvents. The decrease in the intensity of band B was considered to be caused by the decrease in the concentration of free amine upon the addition of protic solvents and the enhanced conversion of the exciplex to an ion pair with increasing solvent polarity. The polar effect was expressed as a function of the relative permittivity of the solution.     

油酸/三乙醇胺/液体石蜡水体系层状润滑性能

采用^2HNMRT和IR,表征了油酸／三乙醇胺／液体石蜡／水体系层状液晶的结构,并以该体系为润滑剂,测定了其在铝合金表面的磨痕宽度和摩擦系数,同时与液体石蜡和商用润滑剂12－羟基硬脂酸锂进行了比较。结果表明,OLA／TEA／LP／H2O体系丑状液晶具有较好的极压性能,对于铝合金材料是一种较好的润滑剂。     

Coupled transport of Ag(I) ions through triethanolamine–cyclohexanone-based supported liquid membranes

Facilitated transport of silver(I) ions in acidic medium, across a supported liquid membrane (SLM) by using triethanolamine (TEA) as carrier, dissolved in cyclohexanone, has been investigated. The parameters studied are HNO₃ concentration variation in the feed, pH of the feed solution, carrier concentration in the membrane phase, silver(I) ions concentration in the feed phase and KCN concentration in the stripping phase. Increase in H⁺ concentration by increasing HNO₃ concentration from 0.5 to 1 M results into an increase in silver ions flux but a decrease in flux has been found beyond 1 M HNO₃ concentration in the feed, providing a maximum flux of 3.21 × 10⁻⁷ mol/m² s at 1 M HNO₃. Increase in TEA concentration inside the membrane enhances flux with its maximum value at 2.25 M TEA. Further increase in the concentration of TEA leads to a decreased rate of transport due to the increase in viscosity of membrane liquid. The optimum conditions for Ag(I) ions transport are 1 M HNO₃ (feed), 2.25 M TEA (membrane) and 1.5 M KCN in the stripping phase. It has been observed that Ag(I) flux across the membrane tends to increase with increase in Ag(I) ions concentration in the feed phase. Applying the studied conditions to silver plating waste solutions, Ag ions have been removed up to 99% in a time interval of 5 h.     

含氧光敏引发体系的研究——Ⅳ.硫杂蒽酮/叔胺/氧体系的研究

本文研究了硫杂蒽酮(TX)/三乙胺(TEA)/氧体系引发甲基丙烯酸甲酯(MMA)光聚合的动力学及影响聚合速度的各种因素。结果表明,聚合速度和[TX]~0.1[TEA]~0.3及[MMA]成正此,同时,由于TX的nπ~*和ππ~*激发态能级接近,溶剂的性质对聚合速度有显著的影响。体系中的氧对聚合反应有明显的加速作用,特别在硬脂酸存在时,使量子收率增加2.3倍。     

A comparative evaluation on the anodic behavior of Cu and Ag electrodes in non-aqueous fluoride and fluoroborate media

The voltammetric responses of copper and silver had been extensively studied and compared in a variety of non-aqueous solvents such as acetonitrile (AN), propylene carbonate (PC) and sulfolane containing two different supporting electrolytes namely triethylaminetrishydrogen fluoride (TEA.3HF) and tetrabutylammonium tetrafluoroborate (TBABF₄). The dissolution rate and surface transformation on the electrode surfaces as a result of anodic polarization was investigated using atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM), respectively. In solvent-free TEA.3HF medium, the copper electrode shows high charge recovery ratio (Q _c/Q _a), and the difference between the initial anodic and cathodic potentials, obtained at a current density of 2 mA cm⁻², is around 0.11 V, suggesting that in this medium, Cu can certainly serve as reference electrode. On the other hand, on Ag electrode, substantial dissolution was observed leading to very high anodic (Q _a) and cathodic (Q _c) charges, and the surface morphology after the cyclic polarization results in roughened surface with large pores. The effects of incorporating AN and water as additives in TEA.3HF on the solubility and stability of these metal fluoride films are also reported. The dissolution pattern and film formation behavior of these two metals in the different solvents containing fluoride and fluoroborate ionic species have several qualitative similarities, as noted from cyclic voltammetry responses and SEM morphology. Anodic dissolution and precipitation process for both Cu and Ag depends significantly on the nature of supporting electrolytes as well as solvents. In AN containing 0.1 M TEA.3HF, the dissolution of Cu and Ag electrodes was very high. Fluoride salts of Cu show lesser solubility than Ag in those solvents, while fluoroborate salts exhibit the reverse trend. The AAS data suggest that for a particular salt, which may be either fluoride or fluoroborate of Cu and Ag, the relative solubility decreases in the order AN > PC > sulfolane.     

Mass transfer model of triethylamine across the n-decane/water interface derived from dynamic interfacial tension experiments

This publication presents a detailed experimental and theoretical study of mass transfer of triethylamine (TEA) across the n-decane/water interface. In preliminary investigations, the partition of TEA between n-decane and water is determined. Based on the experimental finding that the dissociation of TEA takes place in the aqueous and in the organic phase, we assume that the interfacial mass transfer is mainly affected by adsorption and desorption of ionized TEA molecules at the liquid/liquid interface. Due to the amphiphilic structure of the dissociated TEA molecules, a dynamic interfacial tension measurement technique can be used to experimentally determine the interfacial mass transport. A model-based approach, which accounts for diffusive mass transport in the finite liquid bulk phases and for adsorption and desorption of ionized TEA molecules at the interface, is employed to analyze the experimental data. In the equilibrium state, the interfacial tension of dissociated TEA at the n-decane/water interface can be adequately described by the Langmuir isotherm. The comparison between the theoretical and the experimental dynamic interfacial tension data reveals that an additional activation energy barrier for adsorption and desorption at the interface has to be regarded to accurately describe the mass transport of TEA from the n-decane phase into the aqueous phase. Corresponding adsorption rate constants can be obtained by fitting the theoretical predictions to the experimental data. Interfacial tension measurements of mass transfer from the aqueous into the organic phase are characterized by interfacial instabilities caused by Marangoni convection, which result in an enhancement of the transfer rate across the interface.     

廉价离子液体体系中玉米芯生成糠醛优化

采用廉价绿色离子液体[TEA][HSO4]作为溶剂,利用微波加热法辅助玉米芯水解并脱水制备糠醛.通过响应面法优化糠醛生成反应条件,有效转换玉米芯中的木糖,并得到82.2％糠醛收率.利用2-丁醇作为萃取剂对糠醛进行回收.重复4次萃取实验,从[TEA][HSO4]中回收99.7％糠醛.在2次[TEA][HSO4]的回收实验...     

TEA法测定NO2的反应机理研究

应用FABMS、NMR、IR、HPLC和紫外吸收光谱研究了室温下三乙醇胺与较高浓度NO₂(2.48%)的反应情况,证明反应产物为三乙醇胺硝酸盐和三乙醇胺亚硝酸盐,提出了可能的反应机理,为TEA法监测空气中NO₂的浓度提供了依据.     

On the Role of Hydrogen Bonds in Photoinduced Electron‐Transfer Dynamics between 9‐Fluorenone and Amine Solvents

Using ultrafast fluorescence upconversion and mid‐infrared spectroscopy, we explore the role of hydrogen bonds in the photoinduced electron transfer (ET) between 9‐fluorenone (FLU) and the solvents trimethylamine (TEA) and dimethylamine (DEA). FLU shows hydrogen‐bond dynamics in the methanol solvent upon photoexcitation, and similar effects may be anticipated when using DEA, whereas no hydrogen bonds can occur in TEA. Photoexcitation of the electron‐acceptor dye molecule FLU with a 400 nm pump pulse induces ultrafast ET from the amine solvents, which is followed by 100 fs IR probe pulses as well as fluorescence upconversion, monitoring the time evolution of marker bands of the FLU S₁ state and the FLU radical anion, and an overtone band of the amine solvent, marking the transient generation of the amine radical cation. A comparison of the experimentally determined forward charge‐separation and backward charge‐recombination rates for the FLU‐TEA and FLU‐DEA reaction systems with the driving‐force dependencies calculated for the forward and backward ET rates reveals that additional degrees of freedom determine the ET reaction dynamics for the FLU‐DEA system. We suggest that hydrogen bonding between the DEA molecules plays a key role in this behaviour.     

Triethylaluminum as a concentration-dependent coinitiator and chain-transfer agent of free-radical polymerization of methyl methacrylate in the presence of benzoquinone

Yields in methyl methacrylate (MMA) polymerization as a function of triethylaluminum (TEA) concentration have been determined at a constant benzoquinone (BQ) concentration. The polymerization is negligible at [TEA]/[BQ] concentration ratios smaller than 1, but reaches a maximum yield and then decreases for larger TEA concentrations. Molecular weight measurements show a similar trend, although the maximum is shifted with respect to that corresponding to polymer yield. The existence of two reaction mechanisms is shown by rate measurements at constant initial concentrations. One is a fast reaction, over in a few minutes, which accounts for most of the yield after 30 min reaction time. The other is a slower photoinitiated reaction of the products of the fast reaction. The mechanism proposed is based on a chain-transfer reaction between the inhibitor radical, formed by the addition of the polymer radical (M·) to BQ and TEA, giving a reactive ethyl radical: The competition between a pair of reactions of TEA and BQ, i.e., a free-radical reaction corresponding to the conjugate addition and a molecular reaction leading to the BQ reduction product, is held responsible for the observed yield maximum, since the molecular reaction prevails at larger TEA concentrations. The observed drop in the molecular weight is the result of a chain-transfer reaction on TEA, i.e., the substitution of an ethyl group by the growing polymer radical.     

Direct photoreduction and ketone-sensitized reduction of nitrospirobenzopyranindolines by aliphatic amines

The photoreduction of 6-nitrospiro[2H-1-benzopyran-2,2'-indoline] (N1) and two derivatives (N2 and N3) by diethylamine or triethylamine (TEA) in solution was studied by pulsed and steady-state photolysis. The quantum yield of coloration of the ring-closed Sp form, due to photoinduced ring opening, decreases in acetonitrile with increasing the TEA concentration. The main reason is reaction of TEA with the triplet-excited open merocyanine form. Quenching of this triplet state by amines is rather inefficient for N1-N3; the rate constant for triplet quenching by TEA is k(6) = (2-3) × 10(6) M(-1) s(-1). The secondary transient with an absorption maximum at 420 nm is ascribed to the radical anion. This and the corresponding α-aminoethyl radical subsequently undergo slow termination reactions, yielding a relatively stable product with a maximum at 420-450 nm, which is attributed to a ring-opened dihydromerocyanine (MH(-)). The mechanisms of the two subsequent reduction reactions are discussed. Using acetone as sensitizer the same dihydroproduct was obtained with the Sp form as acceptor, indicating a reaction sequence from photogenerated radicals via a ring-opened radical to MH(-)/MH(2). The effect of TEA concentration on the direct and ketone-sensitized reduction mechanisms was analyzed. Photoreduction by amines, due to competing triplet quenching, is strongly decreased on admission of oxygen.     

Determination of tetraethyl ammonium by ion-pair chromatography with indirect ultraviolet detection using 4-aminophenol hydrochloride as background ultraviolet absorbing reagent

A method was developed for the determination of tetraethyl ammonium (TEA) by reversed-phase ionpair chromatography with indirect ultraviolet detection. Chromatographic separation was achieved on a reversed-phase C18 column using background ultraviolet absorbing reagent - ion-pair reagent - organic solvent as mobile phase. The effects of the background ultraviolet absorbing reagents, detection wavelength, ion-pair reagents, organic solvents and column temperature on the determination method were investigated and the retention rules discussed. Results found that TEA could be successfully analyzed by using 0.7 μmol/L 4-aminophenol hydrochloride and 0.15 μmol/L 1-heptanesulfonic acid sodium mixed with 20% (v/v) methanol asmobile phase at a UV detection wavelength of 230 nm. Under these conditions, the retention time of tetraethyl ammonium was 2.85 min. The detection limit (S/N = 3) for TEA was 0.06 mg/L. The relative standard deviations (n = 5) for peak area and retention time were 0.35% and 0.02%, respectively. The method has been successfully applied to the determination of synthesized tetraethyl ammonium bromide. Recovery of tetraethyl ammonium after spiking was 99.1%.     

Analysis of commercial ceramides by non-aqueous reversed-phase liquid chromatography with evaporative light-scattering detection

Summary This paper describes the development of a chromatographic system for analysis of commercial ceramides structurally similar to those found in the stratum corneum. The ceramides used in this study contain different amine based (phytosphingosine, sphingosine and dihydrosphingosine) and fatty acids of different chain lengths and with different functional groups (hydroxylated and unsaturated). Non-aqueous reversed-phase (NARP) liquid chromatography with evaporative light-scattering detection (ELSD) were the techniques chosen in accordance with the nature of the ceramides. The eluent strength and the potential selectivity of different organic solvents were investigated. On a C₁₈-bonded silica, the most promising chromatographic conditions employed a gradient from ACN-THF, 95∶5, to ACN-THF-PrOH, 35∶5∶60, in 15 min with a constant concentration of TEA (10 mM) and a stoichiometric amount of formic acid.     

Kinetics of the Absorption of Pure CO2 by Mixtures of Diisopropanolamine and Triethanolamine in Aqueous Solution

This study analyzes the absorption of pure carbon dioxide in aqueous solutions of mixtures of di‐isopropanolamine (DIPA) and triethanolamine (TEA). A stirred tank batch reactor was used with a known flat interface area. The variables considered were temperature within the range 288–313 K and concentration in the interval 5–20% (in weight), being DIPA/TEA relations 75/25, 50/50, and 25/75. The temperature control for the DIPA/TEA 75/25, 50/50, 25/75 systems in the absorption experiments, at all the concentrations and temperatures assayed, showed no differences between that of the liquid phase with respect to the operation, implying that the processes occurred under isothermal conditions. The results show that for the DIPA/TEA 75/25 CO₂ was absorbed in a moderately fast reaction regime, following a second‐order reaction for the total alkanolamine and a first‐order reaction for the CO₂, whereas for the DIPA/TEA 50/50 and 25/75 systems the process followed first‐order kinetics with respect to CO₂ and the mixture of alkanolamines, in a moderately fast reaction regime.     

Rate‐Based Modeling of CO2 Absorption into Piperazine‐Activated Aqueous N‐Methyldiethanolamine Solution: Kinetic and Mass Transfer Analysis

A comprehensive two‐dimensional mathematical model based on surface renewal theory has been developed to analyze the CO₂ absorption into piperazine (PZ)‐activated aqueous N‐methyldiethanolamine (MDEA) solvent by taking into account the structured packed bed column hydraulics, mass transfer resistances, and chemical reactions. The modeling results have been validated with the experimental data reported in the literature, and they have been found to be in good agreement with the experimental results. The effects of amine concentration, liquid temperature, initial CO₂ partial pressure, liquid flow rate, and CO₂ loading on the mass transfer performance have been evaluated in terms of overall mass transfer coefficient (K _Ga_v). The overall mass transfer coefficient and absorption flux of CO₂ into aqueous MDEA+PZ blended solution have been calculated over the CO₂ partial pressure range of 4–16 kPa, temperature range of 298–333 K, and solvent concentration of 1–3 M. To evaluate the performance of different solvents on separation process, some common industrial chemical absorbents including monoethanolamine (MEA), diethanolamine (DEA), triethylamine (TEA), MDEA and PZ were compared with a MDEA+PZ blended solution. The results indicate that CO₂ absorption reaction with PZ is faster than that with MDEA, but also adding small amounts of PZ as a promoter to MDEA solvents improves significantly the absorption rate. The results show that CO₂ absorption reaction with the MDEA+PZ blended solution is faster than that with TEA and MDEA, also comparable with DEA, but slower than those with MEA and PZ. The modeling results illustrate that the K _Ga_v enhances with increasing the solvent concentration, liquid temperature, and liquid flow rate, but reduces with increasing the CO₂ loading and initial CO₂ partial pressure. In addition, the reaction kinetics in terms of enhancement factor was found to decrease as the CO₂ loading enhances and increase as the operating temperature rises.     

On the role of hydrogen bonds in photoinduced electron-transfer dynamics between 9-fluorenone and amine solvents

Using ultrafast fluorescence upconversion and mid-infrared spectroscopy, we explore the role of hydrogen bonds in the photoinduced electron transfer (ET) between 9-fluorenone (FLU) and the solvents trimethylamine (TEA) and dimethylamine (DEA). FLU shows hydrogen-bond dynamics in the methanol solvent upon photoexcitation, and similar effects may be anticipated when using DEA, whereas no hydrogen bonds can occur in TEA. Photoexcitation of the electron-acceptor dye molecule FLU with a 400?nm pump pulse induces ultrafast ET from the amine solvents, which is followed by 100?fs IR probe pulses as well as fluorescence upconversion, monitoring the time evolution of marker bands of the FLU S(1) state and the FLU radical anion, and an overtone band of the amine solvent, marking the transient generation of the amine radical cation. A comparison of the experimentally determined forward charge-separation and backward charge-recombination rates for the FLU-TEA and FLU-DEA reaction systems with the driving-force dependencies calculated for the forward and backward ET rates reveals that additional degrees of freedom determine the ET reaction dynamics for the FLU-DEA system. We suggest that hydrogen bonding between the DEA molecules plays a key role in this behaviour.     

Non-aqueous dispersion properties of pure barium titanate for tape casting

The dispersion properties of concentrated (25.0 and 50.0 vol.%) dispersions of high purity barium titanate powder dispersed in a methyl ethyl ketone (MEK) -ethanol solvent of moderate dielectric constant were studied in an effort to improve the uniformity of tape cast and sintered bodies. An amphoteric phosphate ester surfactant was found to be an effective dispersant. The dispersion properties of the phosphate ester were subsequently investigated by rheological, adsorption, conductivity, and electrophoretic mobility methods in order to evaluate a dispersion mechanism.Optimum dispersion occurred at an azeotrope solution of MEK and ethanol. The barium titanate particles dispersed in dry solvents exhibited a greater degree of dispersion than particles dispersed in hydrated solvents. The adsorption isotherm for the adsorption of the phosphate ester onto barium titanate particle surfaces using dry solvents exhibited a well-defined plateau corresponding to monolayer surface coverage. The plateau was less well defined for particles dispersed in hydrated solvents. Polymer coverage remained essentially constant with varying solvent composition. Optimum dispersion and maximum zeta potential occurred at a concentration of phosphate ester which corresponded to initial monolayer coverage. A maximum in the zeta potential also occurred at the azeotrope solution of MEK-ethanol and again coincided with optimum dispersion.Conductivity data indicate a dynamic adsorption-desorption dissociation mechanism for the ionic phosphate ester at the solid/liquid interface. The adsorption and conductivity data indicate the mechanism of dispersion stability is a combination of electrostatic and steric phenomena.     

Near- and supercritical fluid solvents for living anionic polymerizations

Near- and supercritical fluids are investigated as solvents for anionic polymerizations of 1,3-dienes. Solvent strength (solubility parameter) of mixtures of light hydrocarbons containing cyclohexane is shown to be adjustable using solvatochromic probe methods. The results indicate that these mixtures have solubility parameter values that are lower than conventional liquid solvents and represent a regime of solvent strength that has remained unexplored for ionic polymerizations. The anionic initiator 3-methyl-1,1-diphenyl-pentyllithium (MDPPL) was shown to be soluble in supercritical ethane and that its ultraviolet/visible absorption maximum was sensitive to systematic density changes of the supercritical fluid induced by pressure profiling. These results were extended to the anionic polymerization of isoprene in butane/cyclohexane mixtures.     

甲壳素类液晶高分子的研究--用CD谱研究N-邻苯二甲酰化壳聚糖溶致胆甾相的形成临界浓度

N邻苯二甲酰化壳聚糖在多种常见有机溶剂中能形成胆甾液晶相.用圆偏光二向色性谱(CD)研究了N邻苯二甲酰化壳聚糖的DMF、DMSO、DMAC和吡啶4种溶剂体系,在形成溶致胆甾液晶相前后的手性变化信息.CD谱图上观测到两类吸收,即在400nm附近较宽的吸收和330nm附近较尖锐的吸收.前者归属于胆甾相层片的超分子螺旋构象,而后者可以归属于分子链的螺旋构象.圆偏光二向色性可以作为测量胆甾液晶临界浓度的一种手段,它能捕捉到胆甾螺旋层片出现那一瞬间的浓度,以CD谱上在波长400nm左右刚出现肩峰的浓度为临界浓度,其值均比偏光显微镜法低1%,说明其灵敏度比偏光显微镜法高,且避免了偏光显微镜法的某种主观性.分别用两种方法旋转玻片进行CD测试,结果证明线性二向色性分量和双折射分量对胆甾层片螺旋的CD信号强度没有大的影响.