2.4.1. Solid-phase extraction
2.4.1.1. Organic acids. Brewed coffee samples were diluted (1:2) in 50mM potassium phosphate buffer, pH 7.0. Anion exchange cartridges were conditioned with 3.0mL of methanol and 3.0mL of Milli-Q water. 3.0mL of diluted sample was passed through the cartridge that was then washed with 2.0mL of Milli-Q water (pH 7.0).