FLUOROMETRIC DETERMINATION OF PRESERVATIVES 663 80 I I , I I I I , Ill 0.2 0.3 0.4 115 0.6 Concentration of HCHO (pg/ml) Figure 3. Day-to-day variation of fluorescence intensity of DDI. as a function of formal- dehyde concentration A = day x ß = day !/

664 JOUlqNAL OF THE SOCIETY OF COSMETIC CHEMISTS ß o / ..,.,_ 70 :' 60 m 50 • 4(2 u 30 ,- 20 10 0 0.1 O.2 O.3 O.4 0.5 O.6 Concentration of HCHO (yg/ml) Figure 4. Fluorescence intensity of DDL derived from formaldehyde, using fresh reagent methylene groups of Germall vas oxidized to formaldehyde, the one methylol group of hydroxymethyldimethylhydantoin was converted to formaldehyde, and at 60øC, Bronopol yiclded slightly more than a quarter of a mole of its potential formaldehyde.

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