There is considerable discussion and controversy regarding whether ionic silver or particulate (colloidal) silver is more efficacious. This has been discussed on the silver-list by many of the members; some of them having chemistry and/or medical backgrounds. It is claimed by MesoSilver that colloids are more effective at killing pathogens. Their product is about 90% colloidal while most ionic/ Colloidal Silver is typically 75-95% ionic. They claim that ionic silver is converted to silver chloride in the stomach by coming in contact with hydrochloric acid, thereby becoming ineffective.
The company Natural Immunogenics, manufacturer of Argentyn 23 claims the ionic portion is more effective at killing pathogens. Their product is about 95% ionic. In order to resolve the dispute Natural Immunogenics performed kill studies using a controlled comparison that diluted both MesoSilver and Argentyn 23 with hydrochloric acid to neutralize the ions in MesoSilver. Then the two were diluted to 20 PPM each so the comparison would have validity. They then combined the remaining fractions of Mesosilver and Argentyn with two strains of Staphylococcus Aureus. The dilutions were placed on petri plates and graded as to their effectiveness in killing the pathogens.
Please see the test results here. Look near the bottom right side of the report for the in vitro kill rates. This should resolve the issue. It seems clear the ionic portion is more effective at killing pathogens.