A positive, aggressive game from the Catalans saw them pick up their 100th win in the El Clásico and move 12 points ahead
Barcelona missed out on signing LA Galaxy defender Julian Araujo on transfer deadline day as they were 18 seconds late in registering the paperwork, director of football Mateu Alemany said.
Barca had been trying to sign the 21-year-old right back for $6.5 million in a deal until 2026, Spanish newspaper Diario AS reported.
"We couldn't register due to a system error, it was just 18 seconds, we'll see what FIFA say," Barca's Alemany told Movistar on Wednesday, a day after the window closed.
Barcelona did not make any major signings in January, while Hector Bellerin left for Sporting Lisbon and Memphis Depay joined Atletico Madrid.
Barcelona lead LaLiga on 50 points, eight ahead of Real Madrid, who have played a game less.