Exhaustive soxhlet extraction for the complete removal of residual compounds to provide a nonleaching silicone...

All commercially available silicone devices contain freely diffusible silicone oils, uncured oligomers, and other impurities (such as catalysts). These residuals have been found in quantities as high as 20% by weight in commercially available silicone medical devices. The fate and effects of these residuals have been the topic of much debate recently. In this study, a method for complete removal of these residual compounds was investigated. The total amount of extractable residuals was determined through exhaustive Soxhlet extraction of 5 silicone elastomers. LIM 6030 had 6.29%, LIM 6070 had 5.74%, Q7-4750 had 3.02%, Q7-4780 had 3.22%, and SE1935 had 0.13% extractables by weight. The amount of silicon containing residuals leaching from both the extracted and nonextracted samples was also evaluated for 3 and 18 days by inductively coiled plasma (ICP) analysis. A significant amount of leachable compounds, reported as microg Si/mg solid sample, was found in all nonextracted elastomers with the exception of SE1935 compared to blanks. The amount of leachable compounds found in the extracted elastomers was not found to be significantly higher than the amount found in the blanks. The residual compounds in silicone elastomers may be completely removed by exhaustive Soxhlet extraction and the resulting polymer does not leach silicon-containing compounds in vitro.