Anhydrous silver dihydrogen citrate compositions
Anhydrous silver dihydrogen citrate compositions comprise silver dihydrogen citrate and citric acid. The anhydrous compositions can be prepared by freeze-drying. The anhydrous compositions can be reconstituted with a suitable diluent to form silver dihydrogen citrate compositions. The anhydrous compositions can be reconstituted and applied to a variety of substrates to impart an antimicrobial effect on the substrates.
1. An anhydrous composition comprising silver dihydrogen citrate and citric acid prepared by removing water from an aqueous stock solution comprising an antimicrobial amount of silver dihydrogen citrate and citric acid,
wherein, when said composition is reconstituted by diluting in water, a stable aqueous solution containing an antimicrobial amount of silver dihydrogen citrate substantially equivalent to that present in said stock solution is obtained.
2. The composition of claim 1 , which contains less than about 0.5% water.
3. The composition of claim 1 , which is crystalline.
4. The composition of claim 1 , wherein the composition comprises a molar excess of citric acid over silver dihydrogen citrate.
5. The composition of claim 4 , wherein the composition comprises at least a 5 fold molar excess of citric acid over silver dihydrogen citrate.
6. A process to make the anhydrous composition of claim 1 comprising silver dihydrogen citrate and citric acid, comprising the steps of:
(a) providing a stock solution comprising silver dihydrogen citrate, citric acid and water;
(b) freezing the stock solution to form a frozen solution; and
(c) freeze-drying the frozen solution to form the anhydrous composition.
7. The process of claim 6 , wherein the citric acid is a molar excess of citric acid over silver dihydrogen citrate.
8. The process of claim 6 , wherein step (c) further comprises heating the frozen solutions.
9. A method to prepare a stable aqueous solution containing an antimicrobial amount of silver dihydrogen citrate which method comprises diluting the composition of claim 1 with an aqueous diluent.
10. The method of claim 9 , wherein the aqueous diluent is substantially pure water.
11. The method of claim 9 , wherein the aqueous diluent comprises water and one or more alcohols, one or more detergents, or both.
12. A method to disinfect a substrate which method comprises applying the antimicrobial aqueous solution prepared by the method of claim 9 to a substrate, whereby an antimicrobial effect is achieved.
13. The method of claim 12 , wherein the substrate is a solid surface, a food article or a non-food article.
14. The method of claim 13 , wherein the solid surface is the interior of a pipe, a holding tank, a swimming pool, a spa, a cooling system or a cooling tower.
15. The method of claim 12 wherein the antimicrobial effect is biocidal or biofilm control.
16. The method of claim 12 , wherein the antimicrobial effect is food preservation.
17. The composition of claim 5 , wherein the composition comprises at least a 15 fold molar excess of citric acid over silver dihydrogen citrate.
18. The composition of claim 1 , wherein the aqueous stock solution consists essentially of 20% wt/vol of citric acid and 2,400 ppm silver ion.