McMaster, 20, was one of the favourites for the event in the London Stadium, but reacted too quickly out of the blocks in the second heat and was disqualified for a false start.
European champion Yasmani Copello showed why he is the Diamond League leader by setting the fastest time.
Turkey's Copello, who won bronze at the Rio Olympics last year, won the third heat in a time of 49.13, the fastest in the competition so far to qualify automatically for Monday’s semi-final.
American Kerron Clement, the Olympic champion and two-time world champion, won his heat in a time of 49.46.
The winners of the other heats included Clement’s compatriot TJ Holmes, Juander Santos of the Dominican Republic and Mamadou Kasse Hann of France.
(Reporting by Christian Radnedge; Editing by Toby Davis)
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