How to get out of a one-on-one conversation:

OPTION 1

You: "So who are you hoping to meet tonight?"

Them: "I'm hoping to meet with someone that does $x."

You: "Oh I just met Bob, who's into $x. He's over there, do you want to meet him?"

Them: "Sure!"

You go and introduce them, then after a minute excuse yourself. They'll hardly notice.

OPTION 2

You: "So who are you hoping to meet tonight?"

Them: "I'm hoping to meet with someone that does $x."

You: "Great! I'm looking to meet someone that does $y. Have you met anyone here that's into that?"

Them: "Oh yeah, Steve over there works in $y!"

You: "Oh interesting. Would you introduce us?"

They go introduce you to Steve and will likely (hopefully) excuse themselves shortly thereafter.

OPTION 3

And finally, if neither of you can make an introduction (eg, if you both just arrived):

You: "So who are you hoping to meet tonight?"

Them: "I'm hoping to meet with someone that does $x."

You: "Great! I'm looking to meet someone that does $y. Have you met anyone here that's into that?"

Them: "Not yet, I just got here."

You: "Me too. Let's go meet some people together. That looks like a good group over there." (Point to group of 3+ people)

Them: "Sure!"

You walk up to the group together and make introductions. The group will naturally split up within a few minutes and you'll be left speaking with new people.