All of the following are used as sclerosing agents for haemorrhoids, EXCEPT:

The injection of bleeding internal hemorrhoids with sclerosing agents is another effective office technique for treatment of first-, second-, and some third-degree hemorrhoids. One to 3 mL of a sclerosing solution (phenol in olive oil, sodium morrhuate, or quinine urea) is injected into the submucosa of each hemorrhoid. Few complications are associated with sclerotherapy, but infection and fibrosis have been repoed. Ref: Schwaz's principle of surgery 9th edition, chapter 39.