Brij® type surfactants

The most frequently used ionic SDAs are again CTAB/CTAC, OTAB/OTAC as well as hexadecylpyridinium bromide/chloride (CPB/CPC), whereby the syntheses are carried out under basic conditions, and most commonly surfactants of the Pluronic and Brij type 86 are used as nonionic SDAs under acidic conditions. In rare cases also Gemini surfactants or long alkyl chained ionic liquids were applied as SDAs, whereby an ethane-bridged PMO with a Fm-3m symmetry was successfully prepared for the first time.88... 

HLB values of the surfactants 6a-c, f, g and llg have also been evaluated experimentally by using the required HLB concept of the oil/water system [40]. The HLB system predicts the optimum emulsion stability when the HLB value of the surfactant systems matches the required HLB of the oil/water system. The required HLB is the value at which enhanced emulsion stability will be attained. Optimization of the performance can be achieved by only including surfactant systems with similar HLB values. Mixtures composed of a mannuronate-type surfactant and a commercial cosurfactant with a known HLB value (Span 85, Brij 72, Span 40, Span 20) were formulated with various surfactant/cosurfactant ratios (20, 40, 60, and 80 wt%) to create different HLB values of the system. Then, the performance was determined and plotted vs the HLB. A maximum appears in the plot and the... 

Anionic surfactants are the most commonly used type in the emulsion polymerization. These include sulfates (sodium lauryl sulfate), sulfonates (sodium dodecylbenzene sulfonate), fatty acid soaps (sodium or potassium stearate, laurate, palmitate), and the Aerosol series (sodium dialkyl sulphosuccinates) such as Aerosol OT (AOT, sodium bis(2-ethylhexyl) sulfosuccinate) and Aerosol MA (AMA, sodium dihexyl sulphosuccinates). The sulfates and sulfonates are useful for polymerization in acidic medium where fatty acid soaps are unstable or where the final product must be stable toward either acid or heavy-metal ions. The AOT is usually dissolved in organic solvents to form the thermodynamically stable reverse micelles. [22] Nonionic surfactants usually include the Brij type, Span-Tween 80 (a commercial mixture of sorbitol monooleate and polysorbate 80), TritonX-100[polyoxyethylene(9)4-(l,l,3,3-tetramethylbutyl)-phenyl... 

We have found that the use of 3% n-propanol in the micellar mobile phase and column temperatures of 40° C appear to offer a broadly applicable solution to the low efficiency previously reported for micellar mobile phases. These conditions have resulted in reduced plate heights of 3-4 for SDS, cetyltrimethylammonium bromide (CTAB), and Brij-35 (15). This efficiency optimization scheme then appears to be a broadly-based solution for micellar mobile phases of any surfactant. This means that the surfactant type can be varied to affect separational selectivity with no loss in column efficiency. 

Figure 8.5. Plot of the system constants (solvation parameter model) against composition for a mixed micelle electrolyte solution containing 50 mM sodium N-dodeconyl-N-methyltaurine and different amounts of the non-ionic surfactant Brij 35 (polyoxyethylene [23] dodecyl ether) (Left). Plot of the system constants for a mixed micelle buffer containing 50 mM sodium N-dodecanoyl-N-methyltaurine and 20 mM Brij 35 against the volume fraction of acetonitrile added to the electrolyte solution (Right). System constants m = difference in cavity formation and dispersion interactions r = difference in electron lone pair interactions s = difference in dipole-type interactions a = difference in hydrogen-bond basicity and b = difference in hydrogen-bond acidity. (From ref. [218] Royal Society of Chemistry).

Hinzu studied the adsorption of nonionic surfectants on a C18 bonded phase (Resolve C18, Table 4.1) [16]. H-type isotherms similar to the ones obtained with ionic surfactants (Figures 4.2 and 4.4) were establish for two polyoxyethylene dodecyl ether surfactants (Brij 22 and Brij 35). The surfactant adsorption increased beyond the surfactant cmc. The adsorbed Brij 22 amount increased from 1.4 pmol/m at 20 cmc (0.0002 M, cmc=10 M) to 2 pmol/m at 1700 cmc (0.16 M or 100 g/L), a 40% increase. The increase of the Brij 35 adsorbed amount was almost continuous. It was about 0.3 pmol/m at 2 cmc (0.0002 M, cmc=10 M) and 0.9 pmol/m at 850 cmc (0.08 M or 100 g/L), a 200% increase. The log Cg versus log C , Freundlich plot of the Brij 22 ackorption data showed a bilinear curve similar to the plots found in Figures 4.3 and 4.5. The log Cg versus log C Freundlich plot of the Brij 35 adsorption data was a straight line without a break at the cmc concentration. Brij 35 is a polar and highly water soluble surfactant, it may have a low affinity for the apolar bonded Resolve C18 stationary ph e [16]. 

The practical potential of nonionic MLC was demonstrated by the use of micellar solutions of Brij 35 in the analysis of tobacco [18], Samples of smoking tobacco were extracted with an ueous solution of 30% Brij 35, and an aliquot of the extract was chromatographically separated without further preparation, with a 6% Brij 35 mobile phase. Comparison with an aromatic aldehyde standard mixture enabled verification of vanillin and ethylvanillin as two of the extract components. Brij 35 was chosen for this study over other nonionic surfactants (such as Tritons , Spans , Igepals or Tweens ) on the basis of its commercial availability, high purity, low cost, low toxicity, high cloud temperature, and low background absorbance, compared to the other types of surfactants mentioned. Brij 35 does not possess a strong chromophore and its absorption is minimal. 

The feasibility of using MLC to separate organotin compounds with a C18 reversed-phase column was investigated [14]. Among the three types of surfactants (anionic SDS, cationic dodecyltrimethylammonium bromide, DTAB and nonionic Brij 35), only SDS was found to resolve these compounds. The use of positively charged or nonionic micelle mobile phase resulted in a lack of interaction with the organotin cations. Therefore, these mobile phases caused the compounds either to come off with the void volume or to become irreversibly adsorbed on the stationary phase. 

Several surfactants of different types (nonionic, anionic, cationic, and zwitterionic) have been assayed, but most reported procedures use the anionic surfactant sodium dodecyl sulfate (SDS, CMC = 8.2xl0 moll-i at 25°C), which is readily available. Other common surfactants are the cationic cetyltrimethylammonium bromide (CTAB, CMC = 9 X 10 moll ), and the nonionic Brij-35 (polyoxyethylene (23) dodecyl ether, CMC = 1 X 10 moll ). Common solvents in RPLC (methanol, ethanol, propanol, acetonitrile, and tetrahydrofuran) are suitable modifiers. Other less polar solvents, such as butanol and pentanol, can... 

Three types of multiple emulsions may be distinguished [16] (Figure 12.11). This classification is based on the predominance of the multiple emulsion droplet type. Using isopropyl myristate as the oil phase, 5% Span 80 to prepare the primary W/O emulsion, and various surfactants to prepare the secondary emulsion, three main types of multiple emulsions were observed [16] Type A droplets contained on a large internal droplet, similar to that observed by Matsumoto et al. [17]. This type was produced when polyoxyethylene oxide (4) lauryl ether (Brij 30) was used as secondary emulsifier at 2%. Type B droplets contained several small internal droplets. These were prepared using 2% polyoxyethylene (16.5) nonylphenyl ether (Triton X-165). Type C drops entrapped a large number of small internal droplets. These were prepared using a 3 1 Span 80-Tween 80 mixture. 

The behavior of liquid primary alcohols in various surfactant systems is of course not universally the same. It can depend on the type of surfactant and/or of the other components in the microemulsion system [7,8,18,19,106-132] the latter fact justifies and increases the importance of the previous sections, which reveal the properties of pure alcohols and alcohol/water systems. The effects of alcohols also strongly depend on their partition between the water phase, oil phase, and interface surfactant film. Alcohol partition behavior in ionic surfactant systems was thoroughly reviewed by Zana [7]. In the following we focus more on their different roles and the variety of effects on the structure and intermolecular interactions in microemulsion systems. These phenomena will be presented for the example of a ternary system composed of the nonionic surfactant Brij 35 at moderate concentrations, water and one of the simple alcohols from ethanol to 1-decanol, and will be supported with an additional literature review [7,109-119]. 

Based on the example of SAXS results for ternary systems composed of the nonionic surfactant Brij 35, water and various primary alcohols from ethanol to 1-decanol, we reviewed the various structural and interactional situations in such microemulsion systems. Three specific types of alcohol behavior depending exclusively on their individual chemical nature were revealed alcohols behaving as cosolvents inducing the so-called structure breaking effect, as cosurfactants enhancing the structure of the media by increasing the hydrophobicity of the... 

Florence and Whitehill [38] distinguished between three types of multiple emulsions (W/O/W) that were prepared using isopropyl myristate as the oil phase, 5 % Span 80 to prepare the primary W/0 emulsion and various surfactants to prepare the secondary emulsion (a) Brij 30 (polyoxyethylene 4 Lauryl ether) 2%. (b) Triton X-165 (polyoxyethylene 16.5 nonyl phenyl ether (2%). (c) 3 1 Span 80 Tween 80 mixtures. A schematic picture of the three structures is shown in Fig. 1.34. The most common structure is that represented by (b) whereby the large size multiple emulsion droplets (10-100 pm) contain water droplets 1 pm. A schematic representation of some breakdown pathways that may occur in W/O/W multiple emulsions is shown in Fig. 1.35. 

Results forthcoming from the literature do not always assist in building a picture of events. The observation [65] that 2- and 4-hydroxylation of biphenyl was competitively inhibited by polysorbate 80 in the hamster contrasts with the finding that in the rat, polysorbate 80 (2mM) had no effect on the linear microsomal demethylation of aminopyrine (also a Type V substrate) [66]. The question arises whether surfactants such as polysorbate 80 produce their effects by interaction as an alternative substrate or by perturbation of a membrane bound enzyme system. Commercial samples of polysorbate 80, Brij 35 and Triton X-100 all enhance the activity of a sarcosine dehydrogenase isolated from a strain of Pseudomonas, due to the presence of free oleic acid in these non-ionic surfactants. Deoxycholate and a sarcosine surfactant (N-dodecanoyl N-methyl glycine) inhibit activity [67]. Correlations between the CMC of the non-ionic surfactants and the concentrations required for enzyme activation are seen in Table 10.9. 

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