A simple method for estimating surfactant impurities in solvents and subphases used for monolayer studies

✍ Scribed by J.M. Smaby; H.L. Brockman

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 257 KB
• Volume: 58
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(91)90099-w

✦ Synopsis

It is important to assess levels of surface active impurities in solutions used for characterization of monomolecular films and for deposition of Langmuir-Blodgett multilayers. Traditional surface pressure-area measurements lack sufficient sensitivity because of the extremely low surface pressures surfactants exhibit below the formation of a coherent film. In contrast, surface potential measurements at the gas-liquid interface increase in a surfactant-dependent manner in the gaseous-liquid expanded transition region. Using this property of such films together with area reduction, levels of impurities representing less than or equal to 0.1% of a typical coherent monolayer can be quantitated. The measurement does not require ultrapure reference materials and can be performed on a solution immediately before spreading and compression of an experimental monolayer film.