Themobile phase was composed of 0.4 mM heptaflurobutyric acidand adjusted to flow at a rate of 1 mL min−1. The anion self-regenerating suppressor was provided with 5.0 mN tetrabutylammonium hydroxide and 5.0 psi N2in recycle mode to reducethe eluent background conductivity. Oxalic, citric, and malic acidwere identified by comparing their spectra with those of standards.The total organic acid content was calculated by combining therespective amount of those three acids.