|Messi lifts his third over Almunia's head [AFP]
Lionel Messi scored an exquisite hat-trick in 21 first-half minutes to kill off Arsenal's European Champions League challenge – before adding a fourth in the final minutes.
The London side had gone 1-0 up in the second leg of the quarter-final at the Nou Camp, to put the score at 3-2 and kindle hopes of an upset.
But Messi blasted a first, chipped a second and then beguilingly lifted a third beyond helpless Arsenal keeper Manuel Almunia, smashing a late fourth, to record a 6-3 aggregate score and set up a semi-final meeting with Jose Mourinho's Inter Milan on April 20.
Having weathered an early Barcelona storm in the 2-2 first leg draw in London, it was Arsenal who made an impact at the Nou Camp on Tuesday as Nicklas Bendtner put them 1-0 ahead.
Theo Walcott broke free on the right and squared for the Dane, who appeared to have lost out to a Dani Alves tackle but got up to stab a rebound off keeper Victor Valdes and put the Gunners 3-2 up on aggregate.
Valdes' emotional reaction raised the prospect of the European Champions going out to the English side but Messi intervened less than three minutes later to spark a goal spree from the Argentine.
Messi was attempting to force his way through three Arsenal defenders when a miscontrol bounced back to him off Mikael Silvestre and he hammered the ball past Almunia from the edge of the area.
The playmaker appeared to be getting too much protection from referee Wolfgang Stark when Denilson was booked for a challenge in which he cleanly got the ball.
But Abou Diaby, who had won the ball for Arsenal's goal, failed to track Messi on 37 minutes and an Eric Abidal cross found its way to him for a simple finish over Almunia.
With three minutes left of the half, Messi completed his fourth hat-trick of 2010 when he ran onto an Abidal header and outrageously lifted the ball over Arsenal's Spanish keeper.
It was his 38th of a remarkable season, and left Arsenal needing two goals to go through – without conceding any more.
But they couldn't reprise their two-goal comeback of a week ago as Bendtner and Tomas Rosicky squandered chances in the second half.
Coup de grace
Arsenal succumbed to Messi's 39th of the season when he took on the defence single-handed and, after Almunia had parried one shot, drove the coup de grace through the hapless keeper's legs to make it 4-1 with two minutes to go.
"If you're going to lose the game you want to lose by the other team playing you off the pitch," Bendtner told Sky Sports TV.
"The (first) goal they got was a bit funny because we gave (Messi) the ball after he lost it.
"He's a phenomenal player and he showed that again tonight."
Arsene Wenger's side must now win the English Premier League to prevent a fifth trophyless season – while Barca prepare for a title showdown with Real Madrid on Saturday.