Austrian Yvonne Meusburger beat Cornet 6-4, 6-1 in a match lasting just under two hours.
China's Zheng Jie recovered from a first set mauling to send Robson packing, 1-6, 7-6 (8/6), 6-2.
Zheng plays Vania King in the semi-finals after the US player won a topsy-turvy clash with Puerto Rican Monica Puig, the eighth seed, 1-6, 7-5, 7-6 (7/5).
All the seeds have now tumbled out of the Guangzhou tournament.
In the other last-four tie, Meusburger takes on Zhang Shuai after the Chinese enjoyed a comfortable 7-5, 6-3 victory over British qualifier Johanna Konta. (AFP)
