A Novel Langmuir Trough for Equilibrium and Dynamic Measurements on Air−Water and Oil−Water Monolayers

A new “Langmuir” trough is described which allows accurate, symmetric compression and expansion of a spread or adsorbed film of molecules. Compression/expansion of films is equally easy at an air−water (A−W) interface or oil−water (O−W) interface. Several different modes of operation of the trough are described which allow measurement of surface/interfacial pressure (π)−area per molecule ( A ) isotherms and measurement of dilatational rheology of interfacial films. Equlibrium and dilatational measurements are consistent with those obtained via other techniques. The π− A isotherms of spread films of the proteins, β-lactoglobulin (β-L) and bovine serum albumin (BSA) are considerably more expanded at the O−W interface compared to the A−W interface.