MacLean clocked 8:24.91 seconds, eclipsing the previous mark of 8:27.59 set by Brittany Reimer of Victoria at the 2005 FINA World Championships in Montreal.
MacLean and Tabitha Baumann of Ottawa — second in 8:32.37 — both went under the qualifying standard to be nominated to the Commonwealth Games and Pan Pacific teams.
"I've done a lot of racing this year and I wasn't sure how much my body would hold up," said MacLean, 20, a triple champion this week. "I'm glad it did. To get the record is a huge accomplishment."
Two-time Olympic medallist Ryan Cochrane of Victoria collected a third gold as well, winning the men's 1,500 freestyle — his main event — in 15:01.72, well under the qualifying standard.
"I wanted to come here and put up a fast time," said Cochrane. "It's not where I want to be yet."
Cochrane, who is one of 36 who will represent Canada at the Pan Pacifics in Australia in August, and one of 30 nominated to swim for Canada at Commonwealth Games in Scotland in July, says he won't settle for less than gold this summer.
"I'm looking forward to the Commonwealth Games because it was a dream of mine to compete at those Games since I was five," he said. "The Pan Pacs is a big event for the swimmers and the competition will be tough."
In addition to 19 swimmers with national team experience, 18 newcomers will be representing Canada at the senior level for the first time this summer.
The Pan Pacs team features 21 female swimmers and 15 males, while 20 females and 10 males are nominated to the Commonwealth Games.
Three Canadian women went under the qualifying standard in the 200 individual medley. Erika Seltenreich-Hodgson of Ottawa completed a golden individual medley sweep clocking a personal best 2:12.26, Marni Oldershaw of Oakville, Ont., followed in 2:13.72 and Sydney Pickrem of Halifax was third in 2:13.78.
"I'm pretty pumped," said 18-year-old Seltenreich-Hodgson. "To get two titles this week is really exciting. To have three girls go under the standard is something. We are an IM country."
Evan White of Oakville just missed notching a Canadian record in the men's 200 IM but still went under the qualifying standard with a personal best 1:59.84. The 18-year-old was 0.3 seconds under the Canadian record before heading into the final freestyle length.
"I was trying to break the record and I could hear the crowd," White said. "It was a good swim."
Katerine Savard won the women's 200 fly in 2:07.61, while Audrey Lacroix followed in 2:08.84. Both Pont-Rouge, Que., racers went under the qualifying standard as they did in the 100 butterfly on Friday, which featured a national record for Savard.
"I don't really believe I did that time," said the 20-year-old Savard. "It's really good for me."
Victoria Poon of Montreal was first in the 50 freestyle for her second win of the competition. Yuri Kisil took the men's 50 freestyle in a personal best 22.53 for his second title this week, and Zack Chetrat of Oakville, won the men's 200 butterfly.