Determination of organic acids
Organic acids were determined by ionic chromatography with photodiode
array detection (Waters 2998, Waters Corporation, Italy). Separation was
achieved on a cation exchange column (Aminex 87-H column, 300 × 7.8 mm,
9 μm, Bio-Rad) using an isocratic elution with 10 mM
H2SO4 as carrier, at a flow rate of 0.6
mL min-1. Detection was carried out at 210 nm.
Standard carboxylates were prepared as individual stock solutions using
Sigma (Italy) reagent grade compounds, and then combined to give diluted
working standards to be used for retention time comparison and for
quantification.