The H-ESI-II interface worked with a capillary temperature of 275 °C
and the source heater temperature was 50 °C. The sheath gas flow (N2)
was set at 40 (arbitrary units) and the auxiliary gas flow (N2) at 5. The
H-ESI-II interface worked in negative (for phenolics), or in positive
ionization mode (for caffeine). During polyphenol analysis, the source
voltage was 4 kV, and the capillary voltage and tube lens were −26
and −77.71 V, respectively. During caffeine analysis, the source voltage
was 4 kV, the capillary voltage was set at 40 V and tube lens at 120 V.