Uv 2070 plus

The quantification of organic acids was performed using a HPLC instrument (PU-2089 Intelligent HPLC quaternary pump, UV-VIS multiwavelength detector UV 2070 Plus; Jasco Corp., Tokyo, Japan) equipped with a manual Rheodyne injector with a 20 μL loop (Rheodyne, Rohnert Park, CA, USA) and a Bio-Rad Aminex HPX-87H column with a size of 300 × 7.8 mm (Bio-Rad Laboratories, Hertfordshire, UK).
The analysis was performed in isocratic conditions at 65 °C with a rate flow of 0.6 mL/min of mobile phase H₂SO₄ 0.005 M. The UV detector was set at 210 nm. Chromatographic peaks were identified by comparing retention times with those of standards (Sigma-Aldrich, St. Louis, MO, USA) and quantification was carried out by using the external standard method.

The chromatographic analyses of all prepared solutions and extracts were performed using an HPLC from Jasco that consisted of a quaternary piston pump (PU-2089 Plus), an autosampler (AS-2055 Plus), and an UV/Vis detector (UV-2070 Plus). The data treatment was performed using Chrompass software (Jasco, Tokyo, Japan, v.1.8.6.1). The elution conditions, being based on previous work, were as follows [21 (link)]: the stationary phase was a column Gemini C₁₈ from Phenomenex (150 mm × 4.6 mm, 3 μm), and the elution was performed in gradient mode using water and acetonitrile (0 min: 50% acetonitrile, 50% water; 20 min: 65% of acetonitrile, 35% water; 45 min: 100% of acetonitrile; 50 min: 50% of acetonitrile, 50% water; and 55 min: 50% of acetonitrile, 50% water); the mobile phase flow rate was 0.45 mL min⁻¹. The volume of the injected sample was 25 µL, and the wavelength of detection was set at 360 nm.
For the identification of carbonyl compounds, the extracts obtained using the fan assisted extraction procedure were analyzed using an HPLC-DAD-MS/MS system, model LTQ XL, from Thermo Scientific (Waltham, MA, USA). The same elution conditions as above-mentioned were used. The settings of the mass spectrum detector (see Supplementary Data S1) were adjusted via proper tuning with the hydrazones of the carbonyl compounds studied.

The concentration of organic acids in the samples was determined by an HPLC (PU-2089 Intelligent HPLC quaternary pump, UV-VIS multiwavelength detector UV 2070 Plus; Jasco Corp., Tokyo, Japan) and a manual Rheodyne injector with a 20 μL loop (Rheodyne, Rohnert Park, CA, United States), equipped with a Bio-Rad Aminex (Bio-Rad Laboratories, Hertfordshire, United Kingdom) HPX-87H column (300 mm × 7.8 mm). The analysis was performed in isocratic conditions, using mobile phase H₂SO₄ 0.005 M, with rate flow of 0.6 ml/min and temperature of 65°C. The UV detector was set at 210 nm. Chromatographic peaks were identified by comparing retention times with those of standards (Sigma-Aldrich, St. Louis, MO, United States) and quantification was carried out by using the external standard method.
Biogenic amines were detected and quantified according to the HPLC method reported by Bargossi et al. (2015) (link). Under these analytical conditions, the biogenic amines detected were 2-phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermine, and spermidine.