Adsorption characteristics of volatile anesthetics on activated carbons and performance of carbon canisters

The adsorption characteristics, such as the adsorption capacity, the nature of the mass transfer zone, and heats of adsorption, are important for evaluating the performances of carbon canisters for removal of waste anesthetic vapors. The adsorption capacities and the natures of the mass transfer zones were measured for halothane, methoxyflurane, enflurane, isoflurane, and trichloroethylene on Witcarb 965 activated carbon. In addition, adsorption capacities and heats of adsorption for nitrous oxide, cyclopropane and oxygen were measured on the same carbon. The data indicate that high adsorption capacities of dilute anesthetic vapors on this activated carbon permit the use of carbon canisters for removal of these volatile anesthetics from mixtures with oxygen or nitrous oxide. In contrast, high concentrations of anesthetics such as nitrous oxide and cyclopropane cannot be removed economically by disposable canisters. A simplified procedure using the "characteristic curve" concept and "LUB/equilibrium section theory" for approximate prediction of the adsorption capacities and evaluation of the performance of a canister is outlined.