GC-FID analysis was carried out using a Varian 3700 gas Chromatograph coupled to a Shimadsu C-R3A integrator. Separation was achieved using H2 as carrier gas (ca.1mL/min) with a fused silica capillary column (25 QC/BP5) obtained from SGE, Austalia (25 m×0.25 mm i.d., 0.25 m film thickness). The capillary column was connected to a Zguard column (3 ml of deactivated fused silica supplied by Phenomonex. Injector and detector temperatures were 260c and 280c, respectively ; oven temperature programme, 2 min isothermal at 40c, then at 4c/min to 280c (10 min isothermal)