FORMALDEHYDE IN SHAMPOOS 165 The amount of free formaldehyde released changes when protein is incorporated into the shampoo. The amount of free formaldehyde found at 23øC (Figure 3) is now depressed for all four preservatives as compared to the non-protein shampoo. The order of free formaldehyde measured is the same for all preservatives in the presence of protein as in the absence of protein. The relationships were the same at 60øC as at 23øC in 8OO 60O 4OO 2OO . '"" I I I I 0.2 0.4 06 0.8 PRESERVATIVE, % Figure 3. Free formaldehyde in protein shampoos at 23øC as a function of preservative type and concen- tration. O, DMDM Hydantoin g], Imidazolidinyl Urea A, Imidazolidinyl Urea II q-, Quaternium 15.

166 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS this protein-containing shampoo. It is obvious from this portion of the work that the free formaldehyde, which was present in the non-protein systems, has been complexed by the protein introduced. The percentage of free formaldehyde released in the non-protein shampoo increases as the concentration of the preservative decreases. This is shown in Figure 4 for the non- _3 w w o• h 100 75 50 25 I I I I O. 2 0.4 0.6 O. 8 PRESERVATIVE, ø/o Figure 4. Percentage of free formaldehyde in non-protein shampoos at 23øC as a function of preservative type and concentration. O, DMDM Hydantoin [•, Imidazolidinyl Urea /•, Imidazolidinyl Urea II +, Quaternium 15.

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