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Published on: September 9, 2022
Dynamic surface tension analysis of dodecyl sulfate association complexes
W W Quigley1, A Nabi, B J Prazen
1Department of Chemistry, Box 351700, Center for Process Analytical Chemistry, University of Washington, Seattle WA 98195-1700, USA.
Talanta
|October 31, 2008
Summary
A new calibration method for the dynamic surface tension detector (DSTD) accurately measures surface tension by accounting for drop shape. This method enables sensitive detection of molecules like sodium dodecyl sulfate and chromium (III) at low concentrations.
Area of Science:
- Physical Chemistry
- Surface Science
- Analytical Chemistry
Background:
- Accurate on-line measurement of dynamic surface tension is crucial for understanding interfacial phenomena.
- Existing methods using the dynamic surface tension detector (DSTD) have limitations in precise drop shape analysis.
- Adsorption kinetics of surface-active molecules and their complexes at air-liquid interfaces require detailed study.
Purpose of the Study:
- To develop and validate a novel calibration method for the DSTD to improve the accuracy of surface tension measurements.
- To investigate the adsorption kinetics of sodium dodecyl sulfate (SDS) in the presence of cations like tetra butyl ammonium (TBA) and chromium (III).
- To assess the potential of the DSTD for sensitive, indirect detection of metal ions at low concentrations.
Main Methods:
- A novel surface tension calibration method was developed, calculating drop radius from experimental pressure data and comparing it to theoretical values.
- Pneumatic drop detachment was employed at a precise drop volume (2 µL) for rapid dynamic surface tension measurements.
- Dynamic surface tension measurements were performed for SDS solutions with and without TBA or Cr(III) using the calibrated DSTD.
Main Results:
- The novel calibration method accurately determined drop volume at which spherical deviation occurs (approx. 4 µL) and significant deviation (approx. 6 µL).
- Pneumatic drop detachment at 2 µL drop volume enabled rapid dynamic surface tension measurements.
- TBA and Cr(III) significantly enhanced surface tension lowering by SDS, but this process exhibited considerable kinetic dependence, being slow within the 2-second measurement window.
- The limit of detection for SDS and Cr(III) was determined to be in the 300-400 ppb (by mass) range.
Conclusions:
- The novel on-line calibration methodology and pneumatic drop detachment significantly enhance the precision and speed of DSTD measurements.
- The DSTD effectively reveals the kinetic aspects of association complexes at the air-liquid interface, demonstrating slow adsorption kinetics for SDS:cation complexes.
- The DSTD shows promise for sensitive, indirect detection of multiply charged metal ions like chromium (III) at low concentrations.
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