Effect of pH on charcoal adsorption of lidocaine, methadone, pilocarpine, and procaine.

ABSTRACT

The charcoal adsorption from aqueous solution of four weak bases (lidocaine, methadone, pilocarpine, and procaine) was studied at a variety of pH values representing large differences in percent ionization. The measure of charcoal adsorption used was percent of the ligand adsorbed (constant starting ligand concentrations of 3 X 10(-4) M) by a variety of quantities of charcoal ranging from 3 to 30 mg per 10 mL of mixture. In addition, moles of ligand adsorbed/gram of charcoal values were calculated. The data indicated that for a given ligand, charcoal adsorption was statistically the same (p = 0.05) at all pH values. It is concluded that the generalization for weak bases that charcoal adsorption increases with increasing pH may not be universally valid.