Development and Validation of a Method for the Analysis of Zinc Oxide in Cosmetic Matrices by Flame Atomic Absorption Spectroscopy

Table 4

Average found concentration, standard deviation, and total variation (%RSD) for the precision levels considered in this study.

		Raw material	Lipstick	Emulsion	Foundation
Repeatability (mean ± SD% w/w; %RSD)	Level 1		3.155 ± 0.053; 1.69	6.629 ± 0.130; 1.95	5.593 ± 0.120; 2.15
	Level 2	59.13 ± 0.69; 1.16^a	3.954 ± 0.066; 1.66	8.796 ± 0.113; 1.28	7.793 ± 0.091; 1.16
	Level 3		4.627 ± 0.076; 1.64	9.784 ± 0.133; 1.36	9.613 ± 0.136; 1.42
Global intermediate precision (mean ± SD% w/w; %RSD)	Day 1	56.16 ± 0.73; 1.30	3.628 ± 0.067; 1.85	8.310 ± 0.120; 1.45	8.469 ± 0.290; 3.43
	Day 2	58.09 ± 0.77; 1.32	3.810 ± 0.036; 0.95	8.443 ± 0.071; 0.84	8.577 ± 0.146; 1.70
	Global	57.13 ± 1.23; 2.16	3.719 ± 0.108; 2.91	8.377 ± 0.117; 1.40	8.523 ± 0.226; 2.65
Global reproducibility (mean ± SD% w/w; %RSD)	Laboratory 1	59.55 ± 0.33; 0.55	3.722 ± 0.055; 1.47	3.517 ± 0.022; 0.64	8.697 ± 0.051; 0.58
	Laboratory 2	56.80 ± 1.36; 2.39	4.025 ± 0.166; 4.12	3.673 ± 0.089; 2.42	8.983 ± 0.095; 1.05
	Global	58.17 ± 1.75; 3.01	3.873 ± 0.200; 5.15	3.595 ± 0.103; 2.88	8.840 ± 0.171; 1.93

^aRaw material was evaluated at its nominal concentration, as declared by the certificate of analysis.