A set of 30 phosphate fertilizers and 2 certified reference materials
(NIST SRM 695-Trace Elements in Multi-Nutrient Fertilizer, and BCR
032-NaturalMoroccan Phosphate Rock)were used formethod develop-
ment and validation. The laboratory samples ofmonoammoniumphos-
phate (MAP), single superphosphate (SSP), triple superphosphate
(TSP), and NPK mixtures, were provided by the National Laboratory
of Agriculture (LANAGRO, Brazil). The laboratory samples (ca. 100 g,
1 mm particle size) were dried in an oven at 65 °C for 10 h up to con-
stant weight, and stored in desiccators prior to analysis. After defining
the LIBSmethod, an exploratory study using principal component anal-
ysis (PCA)was also performed to verify the possible presence of outliers
by selecting the information from the whole spectrum (200–780 nm).
Matlab® 7.0 software was employed for obtaining PCA classifications.