The leaching from soft lining materials into an aqueous buffer with the same esterase activity as that of saliva was compared to leaching into buffer without esterase activity. The buffer contained 0.1% non-ionic detergent, giving the medium a capacity to dissolve phthalates to the same degree as saliva. The hypothesis that esterase in the immersion medium will increase the rate of diffusion of plasticizers from denture soft-lining material was confirmed by the results. The average leaching of phthalates from 5.5 g of one of the materials was 4.5 mg kg(-1) d(-1) within the first 2 d and 1.1 mg kg(-1) d(-1) within the first 28 d. These levels may be compared to a LOAEL (lowest observed adverse effect level) of 52 mg kg(-1). It is concluded that an esterase activity, equivalent to that in saliva, in the immersion medium for soft lining materials increased the rate of diffusion of plasticizer from the materials. The measured levels of phthalates leaching from these materials might in vivo only be slightly less than 1/10 of the LOAEL given above. 相似文献
The loss of the plasticizers dibutylphthalate, butylphthalylbutyl glycolate, benzylbenzoate, methylsalicylate, and benzylsalicylate from four soft lining materials was measured. A 0.1% aqueous solution of triton X-100, reduced was used as immersion medium, since the solubility of plasticizer in this medium was close to that of saliva. The loss of plasticizer was monitored up to 30 d after mixing. For two of the materials, the average amount of leached dibutylphthalate within the first day exceeded the proposed tolerable daily intake (TDI) by about 11 and 32 times, respectively, for an average adult person. Similarly, for these two materials, the average daily amount within the first 30 d of leached dibutylphthalate was 2.2 and 6.6 times larger, respectively, than the TDI limit. The cumulative amount leached over 30 d for each of the four materials was 128-253 mg plasticizer g(-1). The results indicate the need for further biological evaluations of these products. 相似文献
Purpose. To use an inverse gas chromatographic (IGC) method to determine the glass transition temperature (Tg) of some amorphous pharmaceuticals and to extend this technique for the in situ study of the plasticizing effect of water on these materials.
Methods. Amorphous sucrose and colyophilized sucrose-PVP mixtures were the model compounds. Both IGC and differential scanning calorimetry (DSC) were used to determine their Tg. By controlling the water vapor pressure in the IGC sample column, it was possible to determine the Tg of plasticized amorphous phases. Under identical temperatures and vapor pressures, the water uptake was independently quantified in an automated water sorption apparatus.
Results. The Tg of the dry phases, determined by IGC and by DSC, were in very good agreement. With an increase in the environmental relative humidity (RH), there was a progressive decrease in Tg as a result of the plasticizing effect of water. Because the water uptake was independently quantified, it was possible to use the Gordon-Taylor equation to predict the Tg values of the plasticized materials. The predicted values were in very good agreement with those determined experimentally using IGC. A unique advantage of this technique is that it provides complete control over the sample environment and is thus ideally suited for the characterization of highly reactive amorphous phases.
Conclusions. An IGC method was used (a) to determine the glass transition temperature of amorphous pharmaceuticals and (b) to quantify the plasticizing effect of water on multicomponent systems. 相似文献
Bisphenol‐A polycarbonate (BAPC) crystal with unusual morphology is obtained in the solution‐cast films of BAPC/plasticizer blends. It seems like Siamese twin spherulites, and owns a peanut‐like morphology with more than one nucleating sites. Furthermore, concentric black dotted rings, which should be the aggregation regions of plasticizers, are also observed within the peanut‐like crystals. The peanut‐like morphology has no selectivity to the kinds of plasticizer and the casting temperature. The development of these peanut‐like crystals is mainly ascribed to the local orientations of BAPC chains, which are induced by the concentration fluctuation during solvent evaporation and further fixed by the quick drying process. The concentric black dotted rings within the peanut‐like crystals shall be attributed to the driving effect of BAPC crystalline lamellae and phase separation between plasticizers and BAPC. This work opens a new window for the regular arrangement of small molecules.
