The 23-year-old from Kerala made a brave attempt to qualify for the finals from heat 2 but the hot pace set by the other leading runners pulled her to her best show of the season without gaining her a berth in the finals on Aug 11.
Luka timed 1 minute, 59.69 seconds, 0.52 seconds off her personal best and a vast improvement on her show in the first round heats, as she ended up sixth in the heat and got eliminated.
Luka qualified for the women's semis yesterday after finishing third in heat two, clocking 2:01.75. Earlier, high jumper Sahana Kumari and wrestler Geeta Phogat also made their departure from the Games without making any serious attempt to climb the medal podium as India drew a blank on Day 13 of the Games.
The country's male boxers also ended their medalless campaign after the last man in the fray, Devendro Singh (49kg), lost 18-23 in the quarterfinals despite putting up a gallant fight last night against Ireland's Paddy Barnes in a contest marred by debatable refereeing to further dent the dwindling medal hopes.
Sahana performed well below her personal best and was knocked out of the women's high jump after clearing 1.80m and finishing at joint 15th in the Group B of the qualifying competition at the Olympic Stadium.
The 30-year-old athlete sailed over the bar at the first attempt with a 1.80m leap but failed in her endeavour to clear the 1.85m mark in all her three attempts and got eliminated.
Grappler Geeta, gold medal winner in the 2010 Delhi Commonwealth Games, was up against a formidable rival -- 2004 Athens silver medallist and 2008 bronze winner Tonya Lynn Verbeek of Canada -- and fought bravely before losing the 55kg bout in the last minute.
She got another chance to at least gain the bronze when Verbeek stormed into the finals, but was overwhelmed 3-0 by Ukraine's Turkmenistan-born rival Tetyana Lazareva in repechage round two and made her exit from the Games.