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Volume XXIII - Nr.1 - November 2008


Powerful solubilizer for the cosmetic industry

Oil substances (such as perfumes, aromas, vitamins, drugs) usually are solubilized in clear water or water-alcohol or water-glycerol -based forms by thorough subdivision into micelles using high HLB surfactants (16-20).

This process is also called pseudosolution and is characterized by the fact that small percentages of the non solubilizing lipid body are presubdivided into micelles at ratios ranging between 1:15 and 1:2 (solubilizing oil) according to the kind of lipid or surfactant, and subsequent addition of a large amount of water; thus obtaining a clear solution (a typical example in cosmetics is the preparation of a tonic or hair lotion).

Surfactants used as solubilizers have characteristics such as to place them among primary surfactants as well as among emulsifiers. Foaming agents have a structure with a rather weak lipophilic fraction but with a rather strong hydrophilic fraction.

Conversely the structure of emulsifying agents have a better lipophilic/hydrophilic balance. Solubilizing agents may have intermediate characteristics: short fatty chain and medium strength hydrophile fraction or a longer fatty chain with double bonds and stronger hydrophile fraction.

Highly purified, odourless Poliglicoleum® (Vevy codex 02.1150) is a solubilizing agent belonging to this latter group, i.e. to the class of ethoxylated fatty alcohols.

It is a versatile, highly effective product perfectly tolerable even with respect to similar products, and it is characterized by a smaller foam volume compared to other components of the same category.

A systematic procedure was adopted to assess the properties of Poliglicoleum using:

  1. Perfumed compounds with different aromas (rose, lavender, mint, lemon, Cologne)
  2. Chemically defined odorous substances (linalool, menthol, isoeugenol, citral and linalyl acetate)

Each solubilization test was performed in:

  • Demineralized water
  • Hydroalcoholic solution (20% ethanol)
  • Hydroalcoholic solution (25% ethanol)
  • Hydroalcoholic solution (30% ethanol)

In many cases solubilization ratios were 1:1, 1:2, 1:3 (oil: solubilizing agent) until a clear solution was obtained even though, as we will see, higher ratios were needed in some cases.

Solubilizers and perfume/odorous substance are premixed together by stirring; then preheated water (40ºC) or the hydroalcoholic solution are added. The solution is stirred for 3 minutes and checked for its cloudy/opalescent/clear appearance.

Each clear or opalescent complex is kept at 15ºC for a week before re-examination. Opalescent/opaque solutions are then rejected and new tests are made with a higher solubilizer content.

However, if the solutions are perfectly clear, new tests are made with a lower Poliglicoleum content provided they can ensure an appropriate organoleptic appearance.

Results showed that the solubilization degree depends on perfume polarity. The “rose” perfume, in which strong polar substances are prevailing is easily solubilized in water whereas, less Poliglicoleum is needed when a strongly cosolvent such as ethanol is used. Lavender and mint based perfumes can well be solubilized in water and in this case too the Poliglicoleum content can be reduced when adding alcohol.

Quite different results are obtained with Cologne and lemon based perfumes, which are character­ized by non polar or weak polar substances requiring a greater solubilizer amount even in presence of a cosolvent.

Experiments with chemically defined substances confirm the data obtained from tests on perfumes. Linalool and menthol, which are present in rose and menthol compounds, can easily be solubilized.

On the other hand isoeugenol, linalyl acetate and citral, having a weak polarity, call for a higher Poliglicoleum content.

There can be no doubt that the results we obtained are confirming the importance of Poliglicoleum for the formulation of cosmetic products because of its excellent solubilization properties which allow for doses three times smaller than the normal dose and because of its above mentioned harmlessness.



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