FORMALDEHYDE IN SHAMPOOS 163 Table IV Formaldehyde Recoveries From Non-Protein Shampoos Containing Various Preservatives as Determined by the Microdiffusion Method Free Formaldehyde - 23øC Imidazolidinyl Imidazolidinyl DMDM Hydantoin Urea Urea II* Quaternium 15 Preservative Concentration, % mg/kg % mg/kg % mg/kg % mg/kg % 0.10 108 61 92 60 150 69 482 67 0.20 183 52 140 45 262 61 546 38 0.40 294 42 230 37 452 52 731 25 0.80 505 36 270 22 740 43 777 14 Free Formaldehyde - 60øC 0.10 104 59 94 61 153 71 431 60 0.20 186 53 138 45 264 61 526 37 0.40 306 44 213 35 448 52 596 21 0.80 471 34 285 23 738 43 855 15 * Based on a release of two moles of formaldehyde. Table V Formaldehyde Recoveries From Protein Shampoos Containing Various Preservatives as Determined by the Microdiffusion Method Free Formaldehyde - 23øC Imidazolidinyl Imidazolidinyl DMDM Hydantoin Urea Urea II* Quaternium 15 Preservative Concentration, % mg/kg % mg/kg % mg/kg % mg/kg % 0.10 36 21 17 11 58 27 122 17 0.20 84 24 36 12 125 29 187 13 0.40 160 23 74 12 235 27 237 8 0.80 292 21 117 9 384 22 278 5 Free Formaldehyde -60øC 0.10 28 16 19 12 33 15 142 20 0.20 53 15 36 12 57 13 192 13 0.40 150 21 78 13 183 21 218 8 0.80 269 19 120 10 355 20 278 5 * Based on a release of two moles of formaldehyde. of free formaldehyde generated by hydrolysis increases. The order of formaldehyde released is Imidazolidinyl Urea DMDM Hydantoin Imidazolidinyl Urea II Quaterniurn 15. At times, cosmetic products are prepared at elevated temperatures. Therefore, free formaldehyde measurements were made of shampoos heated at 60øC for four hours to determine the effect of temperature on the release of free formaldehyde from the parent preservative. The findings at 60øC were essentially identical to those at 23øC. Free

164 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS I I 8OO 6OO 400 2OO I I I I 0.2 0.4 0.6 0.8 PRESERVATIVE , ø/o Figure 2. Free formaldehyde in non-protein shampoos at 23øC as a function of preservative type and concentration. ¸, DMDM Hydantoin [•, Imidazolidinyl Urea /•, Imidazolidinyl Urea II +, Quater- nium 15. formaldehyde was also determined periodically during the 2-4 days required to reach equilibrium in the Conway dish both at 23øC and 60øC. There was no indication that formaldehyde was released faster at the elevated temperature.