Colin Buchanan arrived with his wife Catherine (nee Glassen) on the Andromache in February 1839. The Andromache departed Plymouth on 8th October 1838 with 231 emigrants and several cabin passengers including Mrs. Glassen and two daughters. James Douglass was employed as surgeon superintendent.
In 1844 he joined Captain King in the pursuit of armed convicts who had escaped from the Hospital at Newcastle. The pursuit party included two mounted police, and nine black trackers who followed the track for nearly twenty miles. The runaways were captured at their bivouac and lodged in the lock up at Stroud before being taken to Newcastle to answer charges of piracy. Read more about these bushrangers here
He resided for a time in the Clarence River district where he adopted a child. When Mrs. Eliza Dent died at Toowoomba in 1899 her obituary mentioned Dr. Buchanan.....Mrs. Dent was a native of the Clarence River, where she was born in 1835, her parents being among the pioneer residents of that locality. When a mere child she lost both parents, and was adopted by the late Dr. Buchanan, under whose care she grew up. She came to Drayton with Dr. Buchanan 49 years ago, the same year that the first land sale was held in Dratyon. In 1851 she married Mr. Josiah Dent. 
In 1850 - 51 Dr. Buchanan, wife and two children headed north to Drayton on the Darling Downs. There was no hospital at that time so he fitted up a small private one. He complained that men who came from the bush to take advantage of it passed it on their arrival, went to the public house, spent all their money and then came to him to be cured with their disease aggravated and their money gone. 
Colin Buchanan's wife Catherine died at 35 Gilmore road, Paddington, Sydney on 14 August 1887.
Colin Buchanan died at Paddington, Sydney on 20 July 1891