Separations were performed on a DB-5 (5%-phenyl–95%-dimethylpolysiloxane) megabore column (30m × 0.53 mm i.d.;1.0 ?m thickness; Agilent Technologies, Mississauga, ON, Canada)with high purity helium (Praxair) as the carrier gas at a flow rate of 11 mL/min.