Alkana ranked 21st in the first round with a time of 13.64s, as Omar McLeod of Jamaica led the way with a time of 13.27s, followed by Ronnie Ash of the United States and Dimitri Bascou of France with a shared time of 13.31s.
The heats saw four unfortunate athletes disqualified for false starts, while Joao Vitor de Oliveira of host nation Brazil crossed the finish line sliding on his stomach to rank 18th.
"I always do that, it's no accident," he said. "I broke my ribs doing it in China. People tell me not to do it, but it comes from the heart. I put myself first."
The semi-finals are set to take place on Tuesday evening in Rio, or early Wednesday morning South African time.
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