Working solutions were prepared daily by
appropriate dilution. All solutions were prepared using double distilled
water. Clove essential oils and pharmaceutical products were
purchased fromMerck. Phosphate buffer (0.1mol L−1)was prepared
by dissolving appropriate amount of phosphoric acid in water and
pH = 8 was adjusted by adding 1.0 mol L−1 NaOH to this solution.
Highly pure graphite powder, sulfuric acid, acetic acid and boric
acid were purchased from Merck.