Effects Of Tetraalkylammonium Salts Research Articles

Effects of tetraalkylammonium salts on the micellar electrokinetic chromatography of aniline and substituted anilines

Experiments investigating the effects of tetraalkylammonium (TAA) ions on the micellar electrokinetic chromatography (MEKC) of aniline and a series of 12 substituted anilines using sodium n-dodecyl sulfate (SDS) are reported. Increasing the concentration of tetramethylammonium (TMA) ions results in increases in the elution range ( t mc− t 0) and the migration times for the aniline solutes. In contrast the addition of small concentrations of tetrabutylammonium (TBA) ions leads to changes in the elution order and a considerable improvement in the separation of the anilines without a significant increase in the elution range. Further increases in the concentration of TBA ions to levels above 1/3 the concentration of SDS narrows the elution range and has a detrimental effect on the separation. The effects of the TBA ions are attributed to changes in the structure of the SDS micelles resulting in a more open and disordered SDS micelle which enhances the transfer of anilines with polar ring substituents into the micelle.

Determination of cinnamic acid in human urine by differential-pulse polarography

The differential-pulse polarographic behaviour of cinnamic acid was studied in acetate and phosphate buffer solutions (pH 3.5-7.5). The reduction mechanism is discussed. The drug can be determined at pH 5.0 over the concentration range 5 x 10(-5)-1 x 10(-3) mol l-1. The effect of tetraalkylammonium salts on the electroanalytical determination of cinnamic acid was investigated. The direct determination of the drug (0.7-5.5 micrograms ml-1) in urine samples diluted with acetate buffer (pH 5.0) can be effected in the presence of 1 x 10(-3) mol l-1 cetyldimethylethylammonium bromide solution. The detection limit was found to be 0.1 microgram ml-1. The relative standard deviation from six determinations at the 5.5 micrograms ml-1 level was 1%.

Effect of tetraalkylammonium salts on the tacticity of poly(methyl methacrylate), 1. Initiation by ethyl α‐lithioisobutyrate

AbstractThe anionic polymerization of methyl methacrylate (MMA) was carried out in the presence of ethyl α‐lithioisobutyrate (α‐LiEtIB)/quaternary ammonium salts (QAS) in toluene and tetrahydrofuran/toluene (vol. ratio 75/25) at −60°C. It was found that the tacticity of PMMA strongly depends on size and shape of QAS. A highly isotactic polymerization in toluene was observed, when using the system α‐LiEtIB/trimethylhexadecylammonium bromide. The initiator system α‐LiEtIB/tetrahexylammonium chloride produces polymers with a high (>50%) syndiotactic content and relatively low polydispersity. The influence of QAS on the mode of polymerization is due to specific salt effect resulting from the cation exchange reaction, from the participation of the bulky substituent in the primary solvation shell, and ionic aggregation between the growing anion, Q+ and LiX.

Interaction between Electrolyte and Charge-Transfer States: Evidence for Complex Formation

The effects of tetraalkylammonium salts on intramolecular charge-transfer absorption and emission spectra in solution are measured. Addition of tetrabutylammonium hexafluorophosphate (TBAPF 6 ) to methylene chloride solutions of the donor-spacer-acceptor compound 2 reduces the intensity of the charge-transfer emission band and red shifts the emission maximum. The band maximum (cm -1 ) and width of the lowest-energy, charge-transfer absorption transition in 1 increase upon addition of salts. The observed shift and broadening are strongly dependent on the structure of the salt cation, being larger for tributylmethylammonium (TBMPF 6 ) than for tetrabutylammonium (TBAPF 6 ) salts, but are independent of the salt anion

Determination of 3-methylflavone-8-carboxylic acid, the main metabolite of flavoxate, in human urine by capillary electrophoresis with direct injection

The effects of tetraalkylammonium salts and sodium dodecyl sulphate on the migration behaviour of human urinary components and other negatively charged or neutral solutes were investigated. The sulphate acted mainly on hydrophobic and positively charged substances, whereas the ammonium salts acted mainly on negatively charged solutes. By choosing the components of the eluent carefully, the free and conjugate forms of 3-methylflavone-8-carboxylic acid (MFA) in human urine, the major metabolites of flavoxate, could be simultaneously determined without pretreatment, using fenprofen as an internal standard. The calibration curve of MFA was linear in the range 1–50 μg/ml and the detection limit was 0.2 μg/ml, which covered the urine levels encountered in pharmacokinetic studies. The intra-day and inter-day precisions of the method, expressed as the relative standard deviation, were less than 2 and 3%, respectively. This method was successfully applied to an excretion study of MFA in eight healthy volunteers, and the results were in agreement with data in the literature obtained by gas chromatography.

Effects of tetraalkylammonium salts on the activity coefficient of N-acetyl ethyl esters of phenylalanine, norleucine, and norvaline

Effects of tetraalkylammonium salts on the activity coefficient of N-acetyl ethyl esters of phenylalanine, norleucine, and norvaline

The Effects of Tetraalkylammonium Salts on the Structure and the Temperature of the Maximum Density of Water

Abstract The effects of the tetraalkylammonium halides on the temperature of the maximum density of water were measured by means of dilatometry. Contrary to the expectation that the hydrophobic nature of the alkyl radicals would elevate the temperature of the maximum density of water, these salts lowered it, as other, more usual salts do, obeying the Despretz rule. Among the salts represented as R4NBr, where R is either H or an n-alkyl radical, the Despretz constant, kD, increases in the sequence: H<CH3<C2H5<n-C3H7<<n-C4H9, while the deviation of kD from k, which is a hypothetical constant of the ideal mixing where there is no interaction between the solute and the solvent, varies in the following sequence: H\simeqCH3\simeqC2H5\simeqn-C3H7 <<n-C4H9. The latter fact is attributable to the specific occurrence of a clathrate-like structure formed in the aqueous solution, only when R is n-C4H9. This is in accordance with another peculiarity of (n-C4H9)4NBr which shows a minimum in its partial molar volume at a certain concentration in water.