A method for preparing a concentrated solution containing water, citrate ions and silver ions, including providing an amount of trisilver citrate, providing an amount of citric acid, wherein the amount of the citric acid is at least 19 times the amount of the trisilver citrate by weight, and mixing the trisilver citrate and the citric acid in an amount of water to produce the concentrated solution, wherein the amount of water is selected so that the concentrated solution has a citrate ion concentration which is at least 300 grams per liter. A concentrated solution containing water, citrate ions and silver ions, wherein the concentrated solution has a silver ion concentration which is at least 10 grams per liter. A diluted solution prepared by adding water to a concentrated solution containing water, citrate ions and silver ions.