1 µg/mL, adjusted on basic pH with 1 N NaOH

Column conditioning: 5 mL methanol, then 5 mL water (Do not let run the column dry!)

Sample aspiration: The prepared sample is passed through the column by vacuum.

Washing: With the following washing mixtures impurities are removed: a) 2.5 mL water b) 2.5 mL 0.1 N NaOH c) 5.0 mL methanol

Drying: With nitrogen or air

Elution: Analytes are eluted with 5 mL methanol / 5 % formic acid

Evaporation: to dryness and reconstitution with 1 mL of mobile phase from subsequent HPLC