Abstract
The release of soluble aluminum from chlorobutyl rubber closures into a parenteral solution has been investigated. Extraction rates of soluble aluminum varied with different lots of closures of supposedly the same rubber composition. Nitric acid digestion of closures from various lots indicated that the levels of soluble aluminum varied from less than 5000 ppm to greater than 25,000 ppm. A high correlation was found between the amount of soluble aluminum in the closure and the amount released into the parenteral solution. The source of the soluble aluminum was found to be the clay used as a reinforcing agent in the rubber formulation. The quantity of soluble aluminum in the different lots of clay was demonstrated to be inversely proportional to the calcining temperature used by the supplier of the clay. The effects of temperature, closure pretreatment, and storage position were studied with respect to their effect on the aluminum extraction. The release profiles indicate that the extraction process can be described by either a diffusion or desorption process.
- Received December 23, 1981.
- Accepted January 25, 1982.
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