Authentic standard compounds were purchased from Merck
KGaA (Darmstadt, Germany) and Sigma–Aldrich (Chimie S.a.r.l.,
Lyon, France). For ascorbic acid and organic acids quantification,
external standard calibration curves for the identified components.
Five injections were made for each calibration level. For the linear
regression of the curves of external calibration standards, r2 values
were between 0.995 and 0.999.