2. Methods
2.1. Materials
2.1.1. Chemicals
Styrene (STY), divinylbenzene (DVB), and glutaraldehyde (GA)
(25% w/v) were obtained from Merck. Sorbitan monooleate (Span
80) and p-nitrophenyl palmitate (p-NPP) were from Fluka. Potassium persulphate was purchased from Riedel-de-Haen. Vegetable
oils (sunflower, soybean, and waste cooking oil) were obtained
locally. The composition of the oils with regard to fatty acid content was determined by gas chromatography (GC) in accordance
with The American Oil Chemical Society official methods (AOCS,
1998) and the results were presented in Table 1 .