Surface tension and cloud point changes of polyoxyethylenic non-ionic surfactants during autoxidation

Abstract

Changes in the surface tension-concentration curves of the non-ionic surfactant cetomacrogol, a polyoxyethylenic (POE) hexadecyl ether containing about 24 ethylene oxide (EO) groups, have been examined during autoxidation of aqueous solutions. The curves exhibit decreases in cmc values and changes in the slopes below and above the cmc which lead to the loss of the sharp break characteristic of micelle-formation. There is also a progressive decrease in the cloud point during autoxidation. Surface tensions and cloud points of a series of known POE hexadecyl ethers containing from 10 to 60 EO units have been measured and related to the number of EO units present. From these data, it is apparent that autoxidation of cetomacrogol is accompanied by degradation of POE chain rather than the hydrocarbon chain, the number of EO units lost up to the time at which the solution becomes turbid being about 14. The significance of such measurements is discussed in relation to the detection of decomposition and pending rapid decomposition in synthesized and commercial surfactants.

Polysorbates 20 and 80 Used in the Formulation of Protein Biotherapeutics: Structure and Degradation Pathways

“…CMC values can be determined by a number of techniques including surface tension,43, 51, 52 osmotic pressure,53 fluorescence,54–59 micellar electrokinetic chromatography,60 calorimetry,61–63 light scattering,64–66 electron paramagnetic resonance,67 and analytical ultracentrifugation 68. For illustrative purposes surface tension measurements and dye partitioning will be discussed here.…”

“…Low concentrations of formaldehyde have also been identified as contaminants in polysorbate solutions86, 87 consistent with formaldehyde identified by Donbrow et al73 resulting from the CC fission of the hydroperoxides or free radicals. The chain shortening will change the hydrophilic to lipophilic ratio of the surfactants resulting in modification of their physical characteristics such as CMC value and cloud point formation 34, 51. Jaeger et al75 used catalase to demonstrate that 75% of the peroxide formed in polysorbate 80 is in the form of hydrogen peroxide with the remainder being other types of peroxides.…”

The Degradation of Polysorbates 20 and 80 and its Potential Impact on the Stability of Biotherapeutics

“…Polysorbates are known to be degraded by autooxidation and hydrolysis (16,(18)(19)(20)(21). This could lead to a decrease in the apparent concentration of polysorbate in the protein formulation over long shelf life, the rate of decrease being proportional to increasing temperature.…”

Pharmaceutical Sciences—1975: Literature Review of Pharmaceutics II∆∆Editor’s note: Part I of this article appeared in the July 1976 issue of the Journal of Pharmaceutical Sciences

“…Changes in the surface tension-concentration curves of cetomacrogol during autoxidation were observed (1109). Decreases in CMC values and cloud points were found.…”