Lynsey Sharp suffered World Championships disappointment after finishing last in her 800m semi-final in Beijing.
The Scot, who ran a season's best one minute 58:98 seconds in her heat, was well placed at the halfway stage but came home eighth in 1:59.33.
There was better news for Steph Twell, who qualified for the final of the 5,000m as a fastest loser.
Twell, 26, finished seventh in her heat in 15:34.72.
"I've been watching the track like a hawk: it's so hot out there, I can't tell you," she said.
"Your legs feel good but your throat is so dry. It's been different to the humidity I've been training in and you can see that people were dropping like flies.
"It was even tougher 10 minutes later [in the second heat]. I'm just so grateful I've worked hard to get here and now I can relax. I think I've needed to get a race out of my legs and just run."
Fellow Scot Chris O'Hare qualified for the men's 1500m semi-finals.
"Job done - by the skin of my teeth," said the 24-year-old.
"I was getting a bit worried when I got tripped up with 380m to go but I managed to compose myself quickly. Then I saw that I had Silas Kiplagat in front of me and I thought just trace him, he's not going to be sixth, so if I can just trace him on the inside, that was my plan and it worked out in the end."
Sharp, 25, who picked up silver medals at last year's Commonwealth Games and European Championships, was the 14th fastest over the two semi-finals in China, with Canada's Melissa Bishop posting the best time of 1:57.52.