Determination of Very Low Level of Free Formaldehyde in Liquid Detergents and Cosmetic Products Using Photoluminescence Method

Table 1

Levels of independent variables established based on five-factor three-level design.

Variable	−1	0	+1
() reaction time	5 min.	10 min.	15 min.
() ethanol (% v/v)	10	20	30
() ammonium acetate (M)	0.5	1.5	2.5
() 2-methyl acetoacetanilid (M)	0.025	0.050	0.075
() temperature	20	30	40