The 23-year-old runner from Kerala, finished third in the Heat 2 at the Olympic Stadium to progress to tomorrow's semi-finals. There were seven runners in Heat 2.
Luka clocked 2:01.75 in the heats. She will have to better this time to make the final cut. The final is scheduled for Saturday. The Heat 2 was won by Russia's Mariya Savinova (2:01.56) while second was Alice Schmidt of USA (2:01.65).
There are six Heats and the final list of semi-finalists will be decided after the completion of all heats. The first three in each Heat qualify automatically while the fastest losers across all Heats will also be included. There are 24 runners for semi-finals.
Luka, who is part of PT Usha's Usha School of Athletics, holds the national record in 800m. She had won bronze at the 2010 Guangzhou Asian Games.
In 2010's Continental Cup in Croatia, Tintu broke a 15-year-old national record held by Shiny Wilson. She timed 1:59.17 to eclipse Shiny's mark of 1:59.85. However, the same year, she could not repeat that performance and disappointed at the Delhi Commonwealth Games. She finished sixth in Delhi with a time of 2:01.25.
She has cleared one step in her debut Olympics and will be hoping to go further on Thursday.
Earlier, in track and field events at this Olympics, India had two athletes in the finals. Vikas Gowda finished eighth in men's discus throw while Krishna Poonia was seventh in women's discus throw.