2.2.1. Analytical and chromatographic conditionsChromatographic separation was achieved on a reversed phaseACE®5 C18 column (250 mm × 4.6 mm, 5 m; Advances Chro-matography Technologies, Aberdeen, Scotland) protected by aAgilent Pursuit 5 C18 Meta Guard®column (10 mm × 4.6 mm,5 m; Agilent Technologies, Amstelveen, Netherlands). Columnand injection temperatures were both maintained at 25◦C. The sys-tem was operated isocratically at a flow rate of 1.5 ml/min. Thesample was injected through a fixed sample loop having a volumeof 50 l. The UV detector was set at 277 nm.