They have lipophilic cavities with inner diameters of 0.45 The partitioning behavior of pyrene and anthracene between nto 0.95 nm and are known to form host -guest inclusion decane and aqueous solutions containing a partially methylated complexes with many different types of molecules ( 1, 2 ) . g-cyclodextrin (M-g-CD) and sodium dodecyl sulfate (SDS) was Owing to its unique fluorescence properties pyrene was studied by extraction experiments. At concentrations below the frequently used as a fluorescent probe in complex binding aqueous solubility of pyrene and anthracene both were found to studies concerning cyclodextrins and a lot of data are form 1:1 complexes with M-g-CD. Formation constants were deavailable ( 3 -9 ) . Because of their low solubility in water termined as 1843 M 01 for pyrene and 624 M 01 for anthracene. In and their different complex binding constants with g-CD micellar solutions of SDS pyrene was found to be better solubilized pyrene and anthracene seemed to be a perfect pair for than anthracene. At constant concentrations of M-g-CD the demass transfer studies with cyclodextrins as carriers in o / pendence of the partition coefficients on increasing concentrations of SDS could be divided into three linear regions. At concentra-w / o-liquid membrane permeation ( LMP ) ( 10 -12 ) . In tions below a critical surfactant concentration (CSC SDS ) the partiaddition to the parameters of simple cyclodextrin-modition coefficients of both polyaromatic hydrocarbons as well as the fied solvent extraction ( 13 ) in LMP the influence of the fluorescence intensity of pyrene increased linearly with the addisurfactant, which is needed for emulsion stabilization, has tion of SDS. In the fluorescence spectra of anthracene the addition to be taken into account. Pyrene and anthracene are known of SDS led to a shift of the maxima to higher wavelengths. These to form 1:1 complexes with g-CD at concentrations below data suggest the formation of ternary complexes of M-g-CD with their aqueous solubility, whereas pyrene at higher conceneach of the polyaromatic hydrocarbons and SDS. The ternary trations is also reported to form 2:1, 1:2, and 2:2 comcomplex with anthracene was found to be more stable than that plexes ( see Table ) . The influence of surfactants on the of pyrene, which resulted in higher partition coefficients than seen complexing of cyclodextrins with pyrene was already rewith pyrene. Increasing the surfactant concentrations above the ported for b-CD , where ternary complexes CSC SDS the partition coefficients remained constant until micelles are formed. Similar interactions were recently reported were formed and another linear increase of the partition coefficients could be observed. CSC SDS and the critical micellization for g-cyclodextrin and pyrene with various alcohols ( 5, concentration (CMC) were found to increase linearly with cyclo-16, 17 ) . So far no such interactions were reported for dextrin concentration. For CSC SDS a molar ratio of 3/1 was found anthracene.
for M-g-CD/SDS. Mixed micelles between SDS and g-CD are As g-CD was precipitated from the aqueous phase by supposed to be formed above CSC SDS . ᭧ 1997 Academic Press equilibrating with the organic phase (n-decane), a more Key Words: g-Cyclodextrin; pyrene; anthracene; sodium dodesoluble, partially methylated g-cyclodextrin M-g-CD was cyl sulfate (SDS); ternary complexes; fluorescence measurements; used during all experiments. The methylated form has the complex binding constant.
advantage that no interactions between the hydroxyl groups of different cyclodextrin molecules are possible and no bigger aggregates, which tend to precipitate, can be formed.