The main portion of the test consisted of live cultures involving nine(9) commercial Colloidal Silver brands along with three(3) home-brewed product variants. All of which were subject to measurements of rate(time) and efficacy(count). Each iteration was was carried out using three(3) active samples along with three(3) control samples to reduce the risk of cross-contamination and other external factors. All tests were conducted under an SCC Accredited lab and work practices.
With that said, each of the products were measured for total ppm through spectrometry, whereas the soluble and insoluble(ionic:particulate) were differentiated through nano filtration and spectrometry.
In addition to this, the persistence tests were conducted at home using a similar method to your own(with salt) with the exception of using Hydrochloric acid(0.155 Molar) and temperature control to mimic gastric acids. After which, each sample was measured(time) for disassociation with a colorimeter. Of which, I'd add, the results were quite revealing to say the least, as many Colloidal Silver manufacturers rely heavily on the notion that Elemental(metallic) or Particulate Silver products offer superior persistence in low pH environments, of which testing provided no support for whatsoever.