The samples (5 g) were diluted with 4.5% metaphosphoric acid.
Identification and quantification were done by HPLC with a Kinetex
5 lm C18 column (250 mm 4.6 mm) at an oven temperature
of 25 C. The mobile phase was Milli-Q water (Merck
Millipore, Billerica, Massachusetts, USA) acidified with H2SO4 (pH