I made some colloidal copper with 9V battery. To make this water I had to add small amount of salt. However, the salt itself shows up in PPM count of my PPM reader. So how can I discount the salt PPM and come up with correct copper PPM in distilled water.
First method is to look for Faraday's law of electrolysis and put in the equation your data.
Second method is to add to TDS reading the initial reading of the salt solution before the electrolysis.