Uhplc grade acetonitrile

To determine the Total Polyphenol Index (TPI), Folin–Ciocalteu reagent, anhydrous sodium carbonate and gallic acid were purchased from Merck (Darmstadt, Germany).
UHPLC grade acetonitrile from Panreac (Barcelona, Spain), acetic acid from Merck (Darmstadt Germany) were used to prepare the UHPLC phases. The standards for calibration were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Ultrapure water from EMD Millipore (Bedford, MA, USA) was used to prepare the chromatography phases, the reagents and the calibration standards.

For total polyphenol index (TPI) determination, Folin–Ciocalteu reagent was purchased from Merck (Darmstadt, Germany) and anhydrous sodium carbonate was supplied by Panreac (Barcelona, Spain).
Folin–Ciocalteu reagent, anhydrous sodium carbonate, and gallic acid, for total polyphenol index (TPI) determination, were purchased from Merck (Darmstadt, Germany), Panreac (Barcelona, Spain) and Sigma-Aldrich (Saint Louis, MO, USA), respectively.
For organic acid analyses, ethylenediaminetetraacetic acid (EDTA), 2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol (Bis-Tris), and trifluoroacetic acid (TFA) were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Standards for calibration were supplied by Panreac (Barcelona, Spain), Sigma-Aldrich (Saint Louis, MO, USA) and Scharlab (Barcelona, Spain).
UHPLC grade acetonitrile from Panreac (Barcelona, Spain), acetic acid from Merck (Darmstadt Germany) were used to prepare the UHPLC phases. Standards for calibration were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Deionized water from EMD Millipore (Bedford, MA, USA) was used to prepare the chromatography phases, reagents and standards for calibration.

For the preparation of the eluent for the determination of citric, tartaric, malic, succinic and lactic acids, ultrapure deionized water (EMD Millipore, Bedford, MA, USA); 0.2N concentrated sulphuric acid (Sigma-Aldrich, Saint Louis, MO, USA) and UHPLC grade acetone (VWR International, Radnor, PA, USA) were used.
For the determination of the Folin-Ciocalteau Index, ultrapure deionized water (EMD Millipore, Bedford, MA, USA), Folin-Ciocalteau reagent (Merck, Darmstadt, Germany) and anhydrous sodium carbonate (Merck, Darmstadt, Germany) were used. Gallic acid (Merck, Darmstadt, Germany) was used as a calibration standard.
UHPLC-grade acetonitrile (Panreac, Barcelona, Spain), acetic acid (Merck, Darmstadt, Germany) and ultrapure deionized water (EMD Millipore, Bedford, MA, USA) were used in the preparation of the UHPLC phases for the determination of phenolic and furfural compounds.
Standards for calibrations and reagents for routine oenological parameter analyses were supplied by Sigma-Aldrich (Saint Louis, MO, USA).