ISSN:
1432-1017
Keywords:
Key words Surface viscosity
;
Surface tension
;
Surfactant lipid
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract The oscillating drop surfactometer (ODS) measures surface tension (γ) and energy dissipation (damping constant b) of surfactant on a 1 μl sample. γ is obtained from the period of oscillation and b from its free decay or from the phase shift slope in resonance. After calibration with substances with different γ, corrections were made for capillary fixation and loss of mass by evaporation. Surface active substances are delivered from liposomes in the interior (subphase) or injected from outside, with microdrops (180 pl each) of solution. As an application example, we have investigated surfactant extract and pure phospholipid. In minutes after formation of a drop containing a diluted Survanta suspension, γ decreases by 20 mN/m, while b increases three-fold. This effect, assigned to spontaneous adsorption from liposomes to the surface, is not seen with pure dipalmitoylphosphatidylcholine (DPPC) under our conditions. However, microdrop injection of DPPC triggers a rapid decrease of γ and a delayed strong increase in b. The effect is modulated by DPPC in the subphase and by cholesterol. Investigations with l-α-lysophosphatidylcholine show the high sensitivity of the ODS technique in the determination of the energy dissipation at air-liquid boundary surfaces. Although the ODS is limited to applications with γ 〉 15 mN m−1, it offers the advantage to give, with small samples and within seconds, a simultaneous readout of both surface tension γ and the parameter b, as a measure of surface viscosity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002490050256
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