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The New Zealand-born winger was sent over on the blind side by Stuart Hogg after a smart piece of thinking that caught out the South American visitors and brought to life a dour tussle.
Greg Laidlaw kicked three penalties for Scotland but Nicolas Sanchez missed four out of seven kicks for the Pumas.
Scotland were 6-3 ahead at halftime as Argentina suffered a fifth successive test defeat which has included losses in Ireland and France during their November tour programme.
For Scotland it was a second victory in four internationals this month, having beaten Fiji but losing away to Wales and at home last weekend to South Africa.
Argentina looked more adventurous in the first half but were met by a sturdy Scots defence as both sides failed to generate any real excitement.
Laidlaw, the man of the match, was accurate with his two first-half efforts but Sanchez got over only one in three attempts.
But straight after the break he brought parity with a successful effort only to miss another kickable opportunity soon after. Laidlaw made it three from three in the 56th minute, restoring the Scotland lead 10 minutes before Maitland's try injected some life into a subdued sellout crowd.
Argentina won a penalty in front of the posts with some six minutes to go but surprisingly opted to kick to reduce the deficit when a scrum or lineout might have offered to opportunity for a much-needed try.
Sanchez reduced the score to 14-9 but time quickly caught up with the Argentines as they sought to advance forward again for a last-gasp score and Scotland were able to see them off.