FORMALDEHYDE IN SHAMPOOS 167 protein shampoo at 23øC. Again the relationship is the same at 60øC (Table IV). At 0.1%, a 60-69% release of formaldehyde was observed for all preservatives. All plots demonstrated sharply increasing slopes at 0.1%, which implies that the release of formaldehyde would approach 100% at infinite dilution. The percentage of free for- maldehyde measured was affected by the presence of protein. As shown in Figure 5, 100 75 50 25 I I I 0.2 0.4 0.6 PRESERVATIVE, ø/o Figure 5. Percentage of free formaldehyde in protein shampoos at 23øC as a function of preservative type and concentration. ¸, DMDM Hydantoin [•, Imidazolidinyl Urea A, Imidazolidinyl Urea II +, Quaternium 15.

168 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS there was essentially no change in the percentage of free formaldehyde found over the concentration range of 0.1-0.8% at 23øC. These relationships can also be examined on a molecular basis. Figure 6 depicts the Lfl 4.0 3.0 2.0 1.O I I I I 0.2 0.4 0.6 0.8 PRE S ERVAT IVE , ø/o Figure 6. Moles of free formaldehyde per mole of preservative released at 23øC as a function of preservative type and concentration. O, DMDM Hydantoin [•, Imidazolidinyl Urea •, Imidazolidinyl Urea II +, Quaternium 15.

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