Rat tissue and blood partition coefficients for n-alkanes (C8 to C12)

Rat tissue:air and blood:air partition coefficients (PCs) for octane, nonane, decane, undecane, and dodecane (n-C-8 to n-C-12 n-alkanes) were determined by vial equilibration. The blood:air PC values for n-C-8 to n-C-12 were 3.1, 5.8, 8.1, 20.4, and 24.6, respectively. The lipid solubility of n-alkanes increases with carbon length, suggesting that lipid solubility is an important determinant in describing n-alkane blood:air PC values. The muscle:blood, liver: blood, brain:blood, and fat:blood PC values were octane (1.0, 1.9, 1.4, and 247), nonane (0.8, 1.9, 3.8, and 274), decane (0.9, 2.0, 4.8, and 328), undecane (0.7, 1.59 1.7, and 529), and dodecane (1.2, 1.9, 19.8, and 671), respectively. The tissue:blood PC values were greatest in fat and the least in muscle. The brain:air PC value for undecane was inconsistent with other n-alkane values. Using the measured partition coefficient values of these n-alkanes, linear regression was used to predict tissue (except brain) and blood:air partition coefficient values for larger n-alkanes, tridecane, tetradecane, pentadecane, hexadecane, and heptadecane (n-C-13 to n-C-17). Good agreement between measured and predicted tissue:air and blood:air partition coefficient values for n-C-8 to n-C-12 offer confidence in the partition coefficient predictions for longer chain n-alkanes.