Synergism conditions required

When there exists a possibility of the participation of different types of equilibria, it is essential to consider all of them and no species should be excluded unless there is a strong evidence to do so. Thus it becomes a formidable task to find the type of species extracted in these systems. For these systems it may be of more practical utility to report the synergic coefficient values, under different experimental conditions, so that they may be useful in choosing the required extraction conditions. 

Based on these considerations, the following 2 minimal quality criteria for low-dose mixture experiments suggest themselves for assessments of studies published in the literature 1) The effects of individual mixture components should have been determined under conditions similar to those of the mixture. 2) NOAELs (or NOELs and NOECs when a neutral effect concept is adopted) should have been estimated for each mixture component, and the absence of observable effects demonstrated directly. In addition to these 2 minimal requirements, it would be desirable to calculate quantitative additivity expectations. This would allow evaluations of combination effects in terms of synergism, antagonism, or additivity. 

The basic information which the sanitary engineer requires is a quantitative evaluation of toxicity under any set of environmental conditions. As discussed below, it is difficult to arrive at such an evaluation. The magnitude of the toxicity observed or reported is a function of several factors including concentration, antagonism, synergism, complex formation, and acclimation. Each of these is discussed in turn. 

The synergisms of mixtures of anionic-cationic surfactant systems can be used to form middle-phase micro emulsions without adding short-chain alcohols [109, 110]. The surfactants studied were sodium dihexyl sulphosuccinate and benzethonium chloride. The amount of sodium chloride required for the middle-phase microemulsion decreased dramatically as an equimolar anionic-cationic surfactant mixture was approached. Under optimum middle-phase microemulsion conditions, mixed anionic-cationic surfactant systems solubilised more oil than the anionic surfactant alone. Upadhyaya et al. [109] proposed a model for the interaction of branched-tail surfactants (Fig. 8.16). According to this model the anionic-cationic pair allows oil to penetrate between surfactant tails and increases the oil solubilisation capacity of the surfactant aggregate. Detergency studies were conducted to test the capacity of these mixed surfactant systems to remove oil from... 

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