He first made state selection for New South Wales in the 2009 youth eight contesting the Noel Wilkinson Trophy at the Interstate Regatta within the Australian Rowing Championships.

[11] The following year Purnell again won a bronze medal, this time in the Australian men's coxless four at the 2011 World Rowing Championships in Bled, Slovenia.

[12] At the London Olympic Games, Purnell was in the stroke seat of the Australian men's eight which placed sixth in a thrilling final where all boats were overlapping at the finish line.

[14] In 2014 Purnell had a second international season in the single scull, improving on the previous year and placing 13th at the 2014 World Rowing Championships in Amsterdam, The Netherlands.

[16] In 2016 Purnell was in the Australian men's eight who were unsuccessful in attempting to qualify for the 2016 Rio Olympics at the final FISA qualification regatta.

[17] Purnell, Hargreaves, Hill, and O'Brien were selected to race Australia's coxless four at the 2019 World Rowing Championships in Linz, Austria.

[17] By the time of national team selections in 2021 for the delayed Tokyo Olympics, Purnell re-gained his seat in the Australian men's heavyweight eight.