Organic acids and sugars determined by HPLC

Organic acids (tartaric, malic, citric, lactic and acetic acids) and individual sugars (glucose and fructose) in pulp were determined using an Agilent 1260 Infinity LC HPLC system (Agilent Technologies, Santa Clara, CA, USA) coupled to a diode array detector (DAD, model G1315D) and refractive index detector (RID, model G1362A), according to the methodology described and validated by Coelho et al. [13]. Separation of the compounds was performed on a Hi-Plex H ion exchange column (300 × 7.7 mm, 8.0 μm internal particles) protected by a PL Hi-Plex H (5 × 3 mm) guard column (Agilent Technologies, Santa Clara, CA, USA). The phase was 0.004 mol L⁻¹ H₂SO₄ in ultrapure water.