This research analyzed Tobramycin and Gentamycin elution characteristics for two antibiotic-impregnated bone composites: PMMA-based Simplex P and the novel, hybrid, bioactive, CORTOSS. Experimental results were correlated with composite hydrophilicity and antibiotic phase partitioning behaviors. The phase partitioning experiment was conducted to understand antibiotic solubility in aqueous environments. By comparing experimental results with calculated data, antibiotic release behavior was predicted. Total Tobramycin elution percentages from CORTOSS and Simplex P were 12.5 and 6.4%, respectively. Total Gentamycin elution percentages from CORTOSS and Simplex P were 6.95 and 10.17%, respectively. Phase partitioning data indicate 100% of Tobramycin remains in aqueous phases, being extremely hydrophilic. This is supported by its calculated theoretical value (log P = - 7.32). Results suggest that Tobramycin elution can be attributed to composite hydrophilicity as well as its high degree of hydrophilicity. Fifteen percent of Gentamycin distributes in hydrophobic phases (log P = - 4.22). Despite a lower Gentamycin hydrophilicity, its release was affected by its complexation with polar salts in the leaching buffer, thereby increasing its elution potential, making it appreciably water soluble. CORTOSS is more hydrophilic; therefore the migration of aqueous liquids into the polymer network of CORTOSS facilitates greater antibiotic elution compared with hydrophobic Simplex P.

1817interactions to w ' -4 5 ' when w is in the range 40-120' and then it rotates back to w' -180' in the range w = 140-340'.The carboxylate also rotates along the Cl-C2 axis, and the ammonium slides from one face of the planar carboxylate to the other face. The motion of the isobutyl group in 9 is even more complex.The third and final point is that the calculations employed an effective dielectric constant oft = 1.50. This is reasonable for ionic CSP's in hydrocarbon solvent, but the results become less tenable for more polar solvents. Additionally, even though solvent molecules were not included in these calculations, explicitly including nonpolar organic solvents would not change the qualitative trends presented above.Our results are consistent with chemical intuition and highlight the fact that these ionic CSP's are even more conformationally flexible that one would a priori predict. Both syn and anti conformations exist, and the barrier to interconversion is small. Furthermore the pendant ammonium group plays a key role by coordinating with both the carboxylate and with the amide C=O. The conformational flexibility of the phenyl group in the phenylglycine CSP and the isobutyl group in the lycine CSP is great enough to allow for a wide range of orientations for templating purposes;perhaps it is this inherent flexibility that serves to make these CSP's so effective. We are currently investigating the conformational and dynamic behavior of the covalently bonded analogues and will report this at a later date.Registry No.The adaptation of llquid chromatographk c o h n s as chemkal reactors for r e a c t h klnetk studies Is examlned. The overall rate constants, k -, for pyrldlne and 4-plcollne catalyzed esteriflcatlon reactlons of tetrachloroterephthaloyl chlorlde were determined for a llquld chromatographk reactor (LCR). I t Is shown that wHh a rate constant for reactbn In the moMle phase, a valid rate constant for thls system can be obtalned for reactbn In the statlonary phase. Thus conversbns In each

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