Hjelmer's final time, 52.39, was just below the qualifying time and is not even in her personal top 10.
"I am disappointed and angry with myself. I made a fool of myself when I was third in the finish run and didn't push hard enough. Two fast runners came from behind and overtook me," Hjelmer told Swedish Radio Sports.
In the 300-metre hurdle, Sweden's Charlotta Fougberg ended second last in her trial heat, with an end time of 9.59,17. Her personal best from earlier this summer is 9.45,12.
"When I saw the clock I only thought that I must at least finish at under 10 minutes. Of course I am disappointed," said the 28-year-old Fougberg who made her World Championship debut in Moscow.