Surfactant mixtures, composition sample

Table IV. Monoalkyl/dialkyl cationic surfactant mixtures sample composition...

Our premonitory conclusions are that significant variations in micelle size which are important in counting weak 3 emitters may not have visible effects. Neither SCR or ESCR (examples are shown in Table I and Figure 2) may be reliable indicators of losses of efficiency. To predict counting efficiency with confidence, we must examine the effect of sample composition and volume on the behavior of specific toluene, scintillator-surfactant mixtures. While we hope that the samples of our investigations of the performance of various surfactants will be helpful to workers who want to count aqueous samples in surfactant-toluene mixtures, we cannot overemphasize the importance of investigating the behavior of such systems using aqueous samples as similar as possible in composition to the anticipated unknowns. 

A study of the phase behavior of water/oil/surfactant systems demonstrated that emulsification can be achieved by three different low energy emulsification methods (A and B as schematically shown in Fig. 2.8). Method A stepwise addition of oil to a water surfactant mixture. Method B stepwise addition of water to a solution of the surfactant in oil. Method C mixing all the components in the final composition, pre-equilibrating the samples prior to emulsification. In these studies, the system water/Brij 30 (polyoxyethlene lauryl ether with an average of 4 moles of ethylene oxide)/decane Wcis chosen as a model to obtain 0/W emulsions. The results showed that nanoemulsions with droplet sizes of the order of 50 nm were formed only when water was added to mixtures of surfactant and oil (method B) whereby inversion from W/0 emulsion to 0/W nanoemulsion occurred. 

The detection sensitivity in FAB-MS analysis is a function of the chemical composition of the sample-matrix mixture and of the presence of other unwanted impurities. The surfactancy of a solute and the matrix also influences the analyte signal. Because hydrophobic compounds tend to occupy the upper layer of the hydrophilic matrix, they are ionized preferentially relative to the hydrophilic compounds. In contrast, hydrophilic compounds exhibit poor response, because they remain buried within the lower layers of the matrix. Also, alkali salts are known to suppress ionization. Therefore, to obtain a sufficiently high ion current of the target compound, the matrix surface composition must be optimized by adjusting its pH or by the addition of surfactants. 

Copolymers can be mixed with other copolymers, homopolymers, or solvents. Broadly speaking, there are three general problems related to the phase behavior of these blends the microphase behavior, the interplay between microphase and macrophase separation, and micelle formation at low copolymer concentration. The mixtures sometimes form one phase, which can be either ordered or disordered, and sometimes they separate into two macrophases. In the latter case, each of the macrophases can be ordered or disordered. For example, there could be coexisting phases of spheres and cylinders. The phase behavior of a two component system can be summarized by a temperature-composition phase diagram [102,103], that of a three component system by a series of ternary phase diagrams, and so on. Space permits touching only briefly on a small sample of these possibilities in this chapter. Copolymers can also be used as surfactant in homopolymer-homopolymer blends, but that topic is beyond the scope of this chapter. 

Nonionic surfactants of the type of CjEj show a strongly temperature-dependent phase behavior. In the present chapter we restrict ourselves to mixtures of water, octane (Merck, Darmstadt, Germany), and C12E5 (Nikko Chemicals, Tokyo, Japan). These intensively smdied mixtures show extended droplet phases [10,11,31,54,58,60], Sample compositions are given by the volume fractions of water ( ) , octane ( )o, and surfactant ( )s. 

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