Hplc grade methanol meoh

The HPLC-grade acetonitrile (ACN) and HPLC-grade methanol (MeOH) were acquired from Carl-Roth (Carlsruhe, Germany), while the 2-propanol (IPA) and heptane were purchased from Panreac-AppliChem (Darmstadt, Germany). The ultrapure water was provided by a Milli-Q water purification system (Millipore, Bedford, MA, USA). The standard compounds that were utilized were all purchased by Sigma-Aldrich (Steinheim, Germany), namely α-tocopherol (96%), β-tocopherol (96%), γ-tocopherol (96%), and δ-tocopherol (96%). For each one of the standard compounds, stock solutions at a concentration of 1000 μg/mL were prepared in MeOH and they were then stored in dark brown bottles at −20 °C.

HPLC-grade Methanol (MeOH) and HPLC-grade acetonitrile (ACN) were purchased from Carl Roth (Carlsruhe, Germany). Isopropanol (IPA) was purchased from Panreac-AppliChem (Darmstadt, Germany). Acetic acid (99%) was purchased from Sigma-Aldrich (Steinheim, Germany). To obtain ultrapure water, a Milli-Q purification system (Millipore, Bedford, MA, USA) was utilized. Analytical standards of catechin (98%), diosmin (97%), epicatechin (97%), epigallocatechin (98%), gallic acid (98%), trans-cinnamic acid (97%), syringaldehyde (98%), rosmarinic acid (98%), sinapic acid (95%), syringic acid (95%), vanillic acid (97%), luteolin (98%), vanillin (98%), α-tocopherol (96%), β-tocopherol (96%), γ-tocopherol (96%), and δ-tocopherol (96%) were acquired from Sigma-Aldrich (Steinheim, Germany). Stock standard solutions at 1000 μg/g were prepared for each analyte in methanol and stored at –20 °C.