The 32-year-old started his second game for the Gunners but was the culprit when he pulled Salah's shirt for the spot-kick which led to the second of Liverpool's three goals.
Salah struck a brace after Joel Matip had given the home side the lead before half-time - Lucas Torreira did net a late consolation but the damage had already been done.
Luiz said, "You cannot take it out from the players, it is just a reflex. When I turned I see that I was touching and so I took off [my hand from Salah's shirt]. I spoke with Mo and he said 'I didn't feel you touch me, that's why I didn't go down to the floor' but now with the VAR, you cannot see the power so it is difficult for the referees. He saw the shirt like that, but I don't know.
"It's difficult for them so I cannot complain with their efforts because it is difficult for them too. If you play with an extra-large shirt now, there could be a penalty every time. It's interpretation, so I think if you pull someone with power and you change his strength to go to the ball, it's different. It was just a reflex but that's it, it made the penalty and after that he gave me the yellow.
"So on the third goal I could not make the foul and put my team in trouble with 10 men. So I think it conditioned my game a bit after that and it was more difficult. But like I said, the team fought until the end and the team created a lot of chances to score here today. It could be a different game but now we are still with the six points, in three games, we're going to play a tough game against Tottenham. I think you have to look forward and try to win."