Cetyl ammonium bromid

The liver is homogenized in a solution which contains ATP (final concentration 0.01 M) and MgS04 7H20, (final concentration 0.01 Af) adjusted to pH 6.7 at 37°C with solid KHCO3. This homogenate is diluted 1 1 with cetyl ammonium bromide (CTAB) a final liver concentration of 1 in 10 is achieved, and the preparation is kept cold imtil used. 

The poly aniline nanospheres (PANI-NS) were synthesized by oxidative polymerization of aniline monomer at 0 °C in an ice bath using ammonium persulfate as the oxidant in the presence of surfactant. Aniline, ammonium persulfate, Polyvinylpyrrolidone, cetyl ammonium bromide, and camphorsulfonic acid are used as received from Sigma-Aldrich. Camphorsulfonic acid surfactant as the dopant and ammonium persulfate as the oxidant were used in the present synthesis of polyaniline nanospheres (see flow chart in Fig. 8.11). Calculated quantities of aniline monomer (0.005 mol) were mixed with 50 mL of distilled water and stirred using magnetic stirrer for 10 min. Meanwhile, calculated quantities of surfactant (0.75 mol) and oxidant (0.005 mol) were dissolved separately in distilled water and stirred for 10 min in an ice bath. The surfactant solution was first added to the aniline monomer aqueous solution, and then the previously cooled oxidant solution was added drop wise after which the mixture was allowed to react for 10 h in an ice bath. The precipitate was filtered and washed several times with distilled water and... 

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

Cetyl trimethyl ammonium bromide [CTAB]/w-alkanol [13-15]... 

Note PEO = polyethylene oxide PVA = polyvinyl alcohol SDS = sodium dodecyl sulfate CTAB = cetyl trimethyl ammonium bromide. 

Avigad and Milner224 used a turbidimetric method based on the measurement of residual turbidity caused by complexing the acid polysaccharide with such quaternary ammonium detergents as cetyl-pyridinium bromide. The activity unit was expressed as the amount of enzyme bringing about a decrease of absorbance at 400 nm of 0.01/min. 

MS—MS was applied to characterise alkyl quats. The blend of cetyl-dimethyl-ammonium bromide was examined by FIA—APCI—MS— MS(+). Besides the nitrogen-containing fragment at m/z 46, mainly alkyl chain fragments from the C46 chain could be observed at m/z 43, 57, 71, and 85. The APCI(-I-) product ion spectrum is presented in Fig. 2.12.12. The inset contains the pattern of the CID fragmentation behaviour observed on a triple quadrupole instrument [39]. 

CTAB, cetyl trimethyl ammonium bromide STAC, stearyl trimethyl ammonium chloride DSDMAC, distearyl dimethyl chloride. 

Surface-active agents used as adjuvants in pharmaceutical preparations to improve drug dissolution may affect the stability of /3-lactams. Thus, the presence of micelles of cetyl(trimethyl)ammonium bromide (CTAB) enhanced up to 50-fold the rate of alkaline hydrolysis of penicillins [140]. In the case of cephalosporins, micelle-promoted catalysis of the intramolecular degradation process (see Sect 5.2.2) was also observed [85][141], It has been proposed that the negatively charged penicillins and cephalosporins are attracted by the cationic micelles. This attraction increases substrate concentration in the micellar phase, in turn accelerating the rate of HO- ion attack. Ion exchange at the micellar surface and electrostatic stabilization of the transition state may also contribute to the increased rate [142][143],... 

Dialkyl tellurides (general procedure) A mixture of TUDO (0.2 g, 2 mmol), NaOH (0.112 g, 2.6 mmol), Te powder (0.128 g, 1 mmol) in H2O (0.75 mL) and THF (0.75 ml) is refluxed for 1 h. The alkyl halide (2 mmol) and (cetyl trimethyl ammonium bromide) CTBA (0.004 g, 1.1 X 10 mmol) in THF (0.5 mL) are added to the pale pink solution. After 1 h of additional reflux the mixture is worked up in the usual manner and the residue purified by column chromatography on Si02 (elution with petroleum ether 40-60°C). 

Surfactants such as cetyl trimethyl ammonium bromide (CTAB), Triton X-100 (TX-lOO) and sodium dodecyl sulphate (SDS) are the most commonly used. CTAB forms large micelles [24-26] with aggregation number 61, cmc 9.2 X 10 M, and a positive micellar Stem layer TX-lOO has aggregation number 139 with neutral OH groups on the Stern layer, and SDS forms negative micelles with cmc 8.3 x 10 M and aggregation number 131. The... 

SDS sodium dodecyl sulphate CTAB cetyl trimethyl ammonium bromide TX-lOO Triton X-100 Mb myoglobin... 

Cetyltrimethyl ammonium bromide (CTAB) dodecyltrimethyl ammonium bromide (DTAB) tetradecyltrimethyl ammonium bromide (TTAB) trioctyl-methyl ammonium chloride (TOMAC) N-benzyl-N-dodecyl-hf-bis(2-hy-droxy ethyl) ammonium chloride (BDBAC) cetyl pyridinimn chloride (CPC) quaternary ammonium salt with carbon atoms of R ranging from 8-10 (CHj Rj N+ CL) (Aliquat 336)... 

Triazine containing polysulfides having high molecular weights have been readily synthesized by the phase-transfer catalyzed polycondensation of 6-diethylamino or dibutylamino-l,3,5-triazine-2,4-dithiols with 1,10-dibromodecane in the presence of cetyl trimethyl ammonium bromide in a nitrobenzene-aqueous alkaline solution system <99MI294>. 

Schultz and Matijevic (16) prepared nanoparticles of palladium sulfide (PdS) by the continuous double-jet mixing of PdCl2 or Na2(PdCl4) and Na2S. They found that the particle size was 20-30 nm in mean diameter obtained in acidic media (pH = 2-3), but 2-5 nm in alkaline media, probably due to the high equilibrium concentration of sulfide ions S2- by dissociation of H2S and HS in the alkaline media (pH = 10-12). A cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), was found to be useful for stabilizing the small particles prepared in alkaline media. 

Duynstee and Grunwald present some experimental data for Reaction (F) in the presence of hexadecyl trimethyl ammonium bromide (CTABr, C = cetyl) and sodium dodecyl sulfate (NaLS, L = lauryl). Sodium hydroxide was the source of OH" in all cases. A pseudo-first-order rate constant of 2.40 x 10-2 s-1 is observed for A CTABr. Use the following absorbance data to evaluate NaLS for this reaction ... 

CTAB surface area m2/g ASTM D 3765 ISO 6810 adsorption of CTAB (cetyl trimethyl ammonium bromide) from aqueous solution as a measure of the specific outer surface area... 

The effect of various surfactants, the cationics-eetyl trimethyl ammonium bromide (CTAB), and cetyl pyridinium chloride (CPC), the anionic-sodium lauryl sulfate (SLS), and the nonionic-polysorbate 80 (Tween 80), on the solubility and ionization constants of some sparingly soluble weak acids of pharmaceutical interest was studied (Gerakis et al., 1993). Benzoic acid (and its 3-methyl-, 3-nitro-, and 4-tert-butyl-derivatives), acetylsalicylic acid, naproxen, and iopanoic acid were chosen as model drugs. The cationics, CTAB and CPC, were found to considerably increase th< ionization constant of the weak acidS Ka ranged from-0.21 to-3.57), while the anionic, SLS, showed a negligible effect and the nonionic, Tween 80, generally decreased the ionization constants Solubility of the acids increased in aqueous micellar and in acidiLed micellar solutions. 

Figure 4.22 ir-A curves for cetyl trimethyl ammonium bromide at air-water and oil-water interfaces at 20°C... 

Baxendale, Evans and coworkers reported in 1946 that the polymerization of methyl methacrylate (MMA) in aqueous solution was characterized by homogeneous solution kinetics, i.e. where mutual termination of free radicals occurred, in spite of the fact that the polymer precipitated as a separate phase. Increases in the rates of polymerization upon the addition of the surfactant cetyl trimethyl ammonium bromide (CTAB) were attributed to the retardation of the rate of coagulation of particles, which was manifested in a reduction in the effective rate constant for mutual termination,... 

Two other shapes of micelles may be considered, namely, the rod-shaped micelle suggested by Debye and Anacker and the lamellar micelle suggested by McBain. The rod-shaped micelle was suggested to account for the light-scattering results of cetyl trimethyl ammonium bromide in KBr solutions, whereas the lamellar micelle was considered to account for the X-ray results in soap solutions. A schematic picture of the three type of micelles is shown in Fig. 2. 

CTAB/DTAB = Cetyl/Dodecyl trimethyl ammonium bromide, DSB = Dodecyl sulfo betaine... 

Cetyl trimethyl ammonium bromide O +(CH2CHO)nH O rcn(ch2)2n(ch2)2ncr ch3oso- 1% ... 

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