You could try running lots of water through the media and test after several water changes.
1) Rinse many times in lots of water changes. Never mind the chlorine.
2) Refill the container you are using with fresh water and the media and test the water for GH, KH, pH and TDS. Salt, if you have a test. If you can keep the water moving this is best. Small pump would be fine, or a bubbler.
3) Test again after 24 hours, and 48 hours.
If there is no change in the tests, then assume that any minerals that might be added to the tank water are in such small amounts it is not a problem.
Actually, I never bother testing. The few times I have used things from a salt water set up I just rinse and use.
a) Fish diseases and parasites won't survive the transition from salt water set up to fresh.
b) Salt is so water soluble that it cleans up with just a few rinses.
c) The remaining minerals (after rinsing) are not very water soluble, so will only add trace amounts of minerals to the water over time.