Most store bought Colloidal Silver is not at the dosages they claim and many have been found to be 3-18ppm although marked up at 500, 1000 etc. Most store bought Colloidal Silver is junk and you must also think how their display methods with overhanging lights on the shelves etc can affect the product amongst other things.

If you make your own you know exactly what your getting and how its been stored etc etc. The best generators are Silvergen and Silverpuppy but I advised also the SOTA ZBB5 for the simple fact its a Bob Beck Blood Electrification unit also. If you can afford a generator then buy one. If your good at electronics and can make a good constant current, monitoring machine then go that route. Most people just use the wrong powered batteries or pathetic constant voltage powersupplies which don't make the best silver.