Octadecyl ammonium ion

Polypropylene (PP)-clay hybrids cannot be easily synthesized because PP is hydrophobic and has poor miscibility with clay silicates. Octadecyl ammonium ions were used as modifiers for the clay, and a polyolefin oligomer was used so that the clay became more compatible. Organophilic clay, a polyolefin oligomer and PP were blended using an extruder at 200 °C. It was confirmed by transmission electron microscopy (TEM) that the clay was dispersed in a monolayer state in the PP matrix. Thus, PP was directly intercalated into the clay gallery [15]. 

The organomontmorillonite was washed repeatedly with hot aqueous ethanol solution which will extract additional octadecyl ammonium ion from the montmorillonite. The WAXS and TEM pictures clearly indicate... 

Epoxies have been toughened with elastomer-dispersed phases with a decrease in modulus. Work by Balakrishnan et al. [35] utilized organo-montmorillonite as a dispersed phase in elastomer-toughened epoxies to recover this lost modulus. The montmorillonite was modified with octadecyl ammonium ion. The elastomer-dispersed phase in the epoxy was prepared by free radical polymerization of acrylic monomer within the epoxy. The acrylic elastomer-dispersed phase had epoxy functionality provided through the utilization of glycidyl methacrylate as a comonomer. 

WAXS and TEM indicated that the best dispersions were prepared with the trimethyl octadecyl quaternary ammonium and dimethyl octadecyl ammonium ion exchanged montmorillonite. The number-average particle length varied from 172 to 240 nm the number-average particle thickness varied from 4.19 to 4.5 nm. The Young s modulus increased from approximately 3.5 GPa for the pure polymer to approximately 5.5 GPa for an approximate 5.5% loading of the ammonium ion-exchanged montmorillonite in the SAN. 

Cationic They dissociate in water to yield positively charged ions e.g., octadecyl ammonium chloride (C,gH37N+H3 CL),... 

Thomson reported the reversed-phase ion-pair separation of psilocybin and psilocin. Because both alkaloids exist as zwitter-ions, cationic and anionic pairing ions can be used. Alkyl sulfonates (Cg-Cg) and tetraalkyl ammonium (C3-Cg) ions were found unsatisfactory for psilocybin. Good results were obtained with a long chain quaternary ammonium ion, cetrimonium. Optimal conditions for quantitative analysis on an octadecyl stationary phase were 0.15% pairing ion in methanol - 0.4% aqueous phosphate buffer (pH 7.Z). Some other quaternary indole alkaloids have also been separated by means of ion-pair HPLC. Parkin6 analyzed the bisquater-nary alkaloid alcuronium in biological fluids. After an ion-pair extraction, the alkaloid was analyzed on an octadecyl column with the mobile phase methanol - water (4 1) containing O.Z5% acetic acid and 0.005 M dodecylsulfate. 

Van der Maeden et al.6 determined tubocurarine in curare samples. The influence of cations and pH on the separation of the alkaloids on an octadecyl column were studied. Optimum pH was found to be 4. Better peak performance and increased resolution was obtained by using tetra-methylammonium as cation in the mobile phase, as compared with mobile phases containing potassium or ammonium ions. Optimum separation was obtained with gradient elution (see Chapter 6, Fig.6.3). 

Catalyst I, containing the small tetrapropyl ammonium ion, was insoluble in the reaction medium during the epoxidation, so both the conversion and selectivity were low, only 60.6% and 60.2%, respectively. Catalyst A is a reaction-controlled phase-transfer catalyst with high catalytic activity and selectivity. Although catalyst 11 also has good catalytic performance, it was totally soluble in the reaction system during and after the epoxidation, because it contains a big octadecyl benzyl methyl ammonium ion. This makes catalyst recovery difficult. 

Fig. 10 In-situ small angle scattering showing disappearance of initial d-spacing, and appearance of new exfoliated material at small angle (large d-spacing for 3% clay) for an organo-ion exchanged montmorillonite (surface treatment is octadecyl ammonium), with a bisphenol F epoxy [47]...

The work by Liu et al. exchanged the montmorillonite with dioctadecyl dimethyl quaternary ammonium ions the work by Ming et al. utilized octadecyl trimethyl quaternary ammonium ions to exchange on the montmorillonite. Both organomontmorillonites seem to exfoliate well in the molten e-caprolactam to produce exfoliated polymer nanocomposites. 

The organomontmorillonite was prepared by dispersing Kunipia F (produced by Kunimine Ind. Co., Japan) in distilled water at 80 °C. An aqueous solution of HCl neutralized octadecyl amine and different concentrations of stearic acid were added to the heated montmorillonite aqueous dispersion. The amount of ammonium ion utilized to exchange onto the montmorillonite (CEC = 115 meq/lOOg of montmorillonite) was close to the exchange capacity (120 meq). The amount of carboxylic acid that was added was 20, 50, and 100 meq. Low shear mixing... 

The third article in this series [33] evaluated the exfoliation efficiency of one organomontmorillonite (montmorillonite exchanged at 95 MER with trimethyl octadecyl quaternary ammonium ion) as a function of acrylonitrile content of SAN. Polystyrene was the control (Styron 685 D produced by Dow Chemical with a weight-average molecular weight of 300000 g/mol). The concentrations of acrylonitrile in the polystyrenes were ... 

By immobilizing Mn(III)-tetrakis(4-sulfonatophenyl)-porphyrin on dioctadecyl-dimethyl ammonium chloride bilayer membranes incorporated into a PVC film, Kuniyoshi et al. [65] developed an epinephrine CL sensor, which allowed determination of epinephrine down to 3 pM with an RSD of 1.0% for 50 pM of this biological compound. Compared with the previously reported epinephrine CL sensor [66], the present authors noted that the alkaline carrier solution, at high concentration levels, caused gradual deterioration of the immobilized catalyst, and this problem could be solved by the use of immobilization techniques other than ion exchange, e.g., solubilization of the catalyst that has octadecyl groups in the bilayer molecules. 

Figure 4.18 Analysis of anions in water using ion-pair liquid chromatography. Column, octadecyl-bonded silica gel, 15 cm x 4.6 mm i.d. eluent, 2 mM tetrabutyl-ammonium hydroxide (pH 5.3) in 3% acetonitrile-water flow rate, 1 ml min- detection, UV200 nm. Peaks 1, Br 2, N03 and3,1. ...

As earlier reported for electrochemical sensing, often the active chromo-phore will be dispersed in a polymeric matrix. For example, Mohr and Wolfbeis reported a nitrate sensor [121] where the active chromophore is a rhodamine B dye which had been modified with an octadecyl side chain to render it hydrophobic and prevent leaching. The dye was dispersed in a plasticised PVC membrane containing a hydrophobic anion carrier (tridodecylmethylammo-nium chloride). On exposure to nitrate, the fluorescence of the dye increased. This membrane, however, only displayed Hofmeister-type selectivity and was also affected by pH. Replacing the quaternary ammonium anion carrier with a palladium phospine chloride carrier led to selectivity for nitrite [ 122], probably due to a preferential interaction between Pd and nitrite ion. 

Hung, C.T. and Taylor, R.B. Mechanism of retention of acidic solutes by octadecyl silica using quaternary ammonium pairing ions as ion exchangers. J. Chmmatogr. 1980, 202,... 

Octadecyl (octyl) bonded phase with low percentage of free silanol groups ION-SUPPRESSION MODE methanol (acetonitrile) -water containing ca. 0.01 - 0.1 M phosphate buffer, ammonium carbonate or sodium acetate (pH 4-7). 

Imoto et al. by high performance liquid chromatography combined with atmospheric pressure ionisation mass spectrometry (API-MS). The crude saponin isolated from the leaves was chromatographed on octadecyl silica column and eluted with an aqueous methanol solution containing ammonium acetate. The fractions thus separated were directly introduced into an atmospheric pressure ionisation mass spectrometer connected with the liquid chromatograph by an interface consisting of a nebulizer and a vaporizer through a PTFE tube (Hitachi, Japan). The vaporized sample and solvent molecules at 300°C were introduced into the ion source of the atmospheric pressure ionisation system. 

Reversed-phase (RP) chromatography with an octadecyl-silyl column is usually employed for the separation of steroids from biological components. A conventional column (inside diameter, 4.0-4.6 mm) is used for LC-APCI-MS, whereas, because a low flow rate (0.05-0.2 ml/min) is required for ESI-MS detection, a semi-micro column (inside diameter, 1.0-2.1 mm) is usually employed in this mode. Methanol and acetonitrile are the most generally used organic modifiers for the mobile phase. In ESI-MS, acids (positive-ion mode) such as formic acid and acetic acid, bases (negative-ion mode) such as triethylamine or volatile salts (positive- and negative-ion modes) such as ammonium formate and ammonium acetate, are used as the mobile-phase additives to promote protonation or deprotonation of the analyte. 

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