Detection of Cyanuric Acid and Melamine in Infant Formula Powders by Mid-FTIR Spectroscopy and Multivariate Analysis

Table 2

External validation data of the PLS1 chemometric models.

Validation set	Actual value; (µg/L)	Predicted value; (µg/L)	Mahalanobis distance	Residual error
Infant formula-melamine	3.0	3.02	0.22	1.22
	7.0	6.93	0.28	1.47
	7.5	7.42	0.08	1.35
	11.5	11.68	0.27	0.99
	16.0	16.05	0.23	1.08
Infant formula-cyanuric acid	2.0	2.00	0.25	1.10
	5.0	5.04	0.30	1.17
	10.0	10.02	0.03	1.07
	10.5	10.31	0.02	0.99
	14.5	14.46	0.08	1.39

distance should be as low as possible, not to exceed 1. error should be as low as possible, not to exceed 3.