To determine a hydrophobicity value for each of the compounds
the HPLC capacity factor (k0) was calculated. The capacity factor (k0)
refers to the relative retention time of a molecule within the C18
column, the greater the hydrophobic interaction between molecule
and stationary phase the greater the retention time. The capacity
factor (k0) of each compound was determined by injecting 10 ll
of each of the compounds on the Agilent Eclipse XDB-C18 column
with a phosphate buffer/methanol (50:50 v/v) mobile phase.
Detection wavelengths were as described in Section 2.8. The capacity
factor was calculated using Eq. (4) (Serban & Victor, 2013).