although he probalby doesn't have to worry about trace elements from the AC
unless his compressor coils have a leak (which would be something to consider) I would be more concerned with other contaminants from corrosion and such as suggested from pm64971.
if you could somehow create a hermeticaly seperate chamber that would allow air to pass through and condensation form and flow to your tank I might consider it.. but I think you'd be hard pressed to find an efficient solution that won't affect the performance of your AC
I would suggest, IMO
, you find another means. surry