1076
Langmuir 1991, 7, 1076-1081
Interaction of p-Nitrophenol with Lipids at Hydrophobic Interfaces Z. Kozarac,* B. cosovi6, and B. Gaiparovi6 "Rudjer BoBkoviC" Institute, Center for Marine Research, 41001 Zagreb, P.O.Box 1016, Croatia, Yugoslavia
A. Dhathathreyan and D. Mobius Max Planck Institut fur Biophysikalische Chemie, Postfach 2841, 0-3400 Glittingen, West Germany Received June 21,1990. I n Final Form: November 26, 1990
d
Adsorption of p-nitrophenol (PNP) at two model hydrophobic interfaces, namely at the air solution interface and mercury electrode/solution interface, as well as its interaction with neutral an charged lipids has been studied in monolayers by light reflection spectroscopy and electrochemical methods. Investigations have been performed at pH = 10 and 11 where the dissociated form of PNP carrying a negative charge is predominant. In this pH region no accumulation of PNP from bulk solution to the free air/solution interface and slight adsorption at mercury surfacewas observed. PNP also does not accumulate in neutral phospholipid monolayers spread at the air/solution interface while phospholipid layers formed at mercury by adsorption from the bulk solution cause the inhibition of electrochemicalreduction of PNP. The attachment of PNP to the neutral phospholipid layers is enhanced and accelerated at both interfaces by the presence of quarternary ammonium salts in the solution.
Introduction Nitrophenols are frequently used as pesticides, explosives, and dyes and in chemical industry as solvents and precursors. They appear in wastewaters, as well as in all natural aquatic systems.' They are known to act as uncoupling agents in oxidative phosphorylation and to affect cell metabolism a t very low concentrations (
