Do Polysaccharides Such as Dextran and Their Monomers Really Increase the Surface Tension of Water?

Abstract

It has been reported in the literature that sugars such as dextrose and sucrose increase the surface tension of water. The effect was interpreted as a depletion of the solute molecules from the water-air interface. This paper presents accurate measurements of the surface tension of different concentrations of dextrose solution as well as its polymer (i.e., dextran). An automated drop shape technique called axisymmetric drop shape analysis (ADSA) was used for the surface tension determination. The surface tension measurement is presented as a function of a shape parameter, P(s), which has been used to quantify the range of the applicability of ADSA. The results of the above study show that dextrose solutions decrease the surface tension of water in contradiction to the results obtained from the weight drop method in the literature. The surface tension decreases continuously with increasing concentration. A similar effect was observed for the dextran solutions. To verify that the setup and the methodology are capable of accurately measuring increases in surface tension, a similar experiment was conducted with a sodium chloride solution with a concentration of 1 M. It is well-known that electrolyte solutions, e.g., sodium chloride, increase the surface tension of water. The results obtained from ADSA verify that the sodium chloride increases the surface tension of water by 1.6 mJ/m(2). It is concluded that dextrose and dextran decrease the surface tension of water. Thus, there is no evidence of depletion. To identify the sources of discrepancy between the results of ADSA and those reported in the literature, the experiments were repeated for different concentrations and the rate of drop formation using the drop weight method. It was found that the rate of drop formation is most likely the source of error in the results reported in the literature.

Lepidopteran defence droplets - a composite physical and chemical weapon against potential predators

“…Given that free glucose constitutes almost 94% of all small metabolites detected in the defence droplets ( Table S1 ), glucose may also contribute to the viscosity/stickiness of defence droplets in addition to the proteinaceous content. The polysaccharide dextran and its monomer glucose are known to decrease the surface tension of solutions 36 , which may explain why Z. filipendulae larvae are able to wet and subsequently glue together the hydrophobic structures of predatory arthropods ( Fig. 2 ).…”

A small molecular size system giving unexpected surface effects: α-Cyclodextrin + sodium dodecyl sulfate in water

“…For non-aqueous systems, maxima in σ (coined as aneotropes [1,2] by analogy to the azeotropes observed in temperature-concentration or pressureconcentration liquid/vapour equilibrium curves) have been found in the past. In aqueous systems, there is an open discussion concerning the possible surface tension increments caused by polysaccharides [3], and it has been known for almost a century that salts can produce σ values above that of pure water [4,5]. However, the maximum increments observed are only of ∼2 mN m −1 .…”

Unveiling the mechanism of antisolvent vapour precipitation in producing ultrafine spherical particles

“…Typically, the formation of such 'self-emulsification' phenomenon is observed for water and oil components in incompatible aqueous solutions [22] or in the presence of surfactant [23]. The presence of maltodextrin, which was reported to decrease the surface tension of water [24], seemed to have induced a phase separation between water and ethanol into possibly a water-ethanol phase and predominantly water, water-maltodextrin phase. Interestingly, the formation of an emulsion (phase separation) from the fully miscible alcohol and water through the addition of lactose sugar has also been reported in brief without detailed investigation by Herrington [25].…”