Interaction of Hexachlorophene with Human Epidermis II: Comparison of Kinetic and Equilibrium In Vivo Results Obtained by Direct and Bioelectrometric Methods

The equilibrium uptake and release as well as the kinetics of hexachlorophene sorption and desorption on human epidermis were studied in vivo, utilizing a bioelectrometric technique and, more directly, a spectrophotometric assay for hexachlorophene cleared from and elutriated into aqueous solution. Kinetic and equilibrium results were obtained with 10 initial concentrations ranging from 0.116 to 1.26 mmoles/1. in a buffered medium at pH 10. Direct determinations of the uptake and subsequent studies of the release kinetics of hexachlorophene from the skin revealed that an average 41.6% of the hexachlorophene is recoverable by elutriation from the contents of three apparent kinetic compartments. Least-squares values of the half-lives of 1.42, 12.1, and 30.9min. were found to correspond to each compartment. Wash-off experiments conducted for up to 400min. revealed the operation of a fourth compartment with a half-life of approximately 274min. Comparable kinetic and equilibrium results obtained electrometrically, in the form of the time course and equilibrium variation of the net fixed-charge density on the epidermal colloids, correlated with those obtained by direct assay for the slower compartments. The slower compartments were attributed to tissue-interacted hexachlorophene and the fastest compartment to its distribution into tissue-free space.