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

Table 5

Recovery rates for all the cosmetic matrices studied in this work.

	Raw material^c	Lipstick			Emulsion			Foundation
Added concentration (% w/w)	60.4	3.170	3.960	4.750	6.560	8.520	9.600	5.670	7.980	9.670
Average found concentration^a (% w/w, %RSD)	59.554, 0.51	3.186, 1.69	3.989, 0.49	4.639, 1.44	6.543, 1.19	8.728, 1.08	9.702, 1.01	5.663, 1.43	7.860, 0.95	9.640, 1.90
Recovery rate (mean ± SD)	98.66 ± 0.54	100.60 ± 1.89	100.86 ± 0.31	97.71 ± 1.51	99.70 ± 1.22	102.38 ± 1.08	101.10 ± 1.08	99.85 ± 1.54	98.45 ± 1.01	99.72 ± 2.05
Global recovery rate^b (mean ± SD)	98.66 ± 0.54	99.72 ± 1.94			101.06 ± 1.50			99.34 ± 1.54

^aSample size n = 6. ^bt values: 4.216 (raw material), 0.426 (lipstick), 2.119 (emulsion), and 1.283 (foundation). t critical value (0.05 significance level): 4.303 (raw material), and 2.306 (lipstick, emulsion, and foundation). ^cNo Zn was added to the raw material because its nominal concentration was assumed from the purity as declared in the certificate of analysis issued by the supplier.