Stephen wrote: > > Frank, > As I have told you.... > I wasn't really unhappy with the results before; they were obviously just > what I characterized them as.... "poppycock". I was more disturbed by your > lack of clarity and objectivity -- implicit in your arguments and explicit > in your "pursuit". > > I am still concerned inasmuch as the instrument you use is not meant to deal > with nanometer-sized particles, and your lop-sided denigration of the use of > TEM is a flat out contradiction to the scientist at Malvern I spoke with, > and would be to any educated member of the scientific community. You still > do not have adequate equipment to characterize such particles with that > machine of yours. The primary use of it, as far as I can see, is to > determine distribution of particles but then ONLY when there are no > nanometer sizes in the distribution and when it does not have to distinguish > the make-up of those particles .... as it cannot do the job of an electron > microscope. > > In any event, the analyses you purport are still incomplete and inadequate. > They do not do justice to the effort. You don't even address fundamental > issues like the quality of the water [or the solutions that carry the > silver], or other possibility of other contaminants? I would think that > these are primary considerations in any attempt at an authoritative > evaluation of commercial cs products. > > We do only random testing of the finished product for endotoxins [or > residual pyrogens]; I say random because each test costs some $85 and the > system filters we use are quality controlled. That is another important > qualification to quality that ought to be taken into account. > > And -- I don't enjoy repeating myself -- the efficacy of products can be > quantified, at least by relative analysis if not by absolute measurement. > Such independent analysis would be of great value to the community of > interest enjoyed here. > > Stephen
The Zetasizer is perfectly suited to measuring nanometer sized particles. That is exactly what it was designed for. If you looked at the specifications on their web site you find that to be the case. Before selecting the Zetasizer for purchase, we examined the other major manufacturers products for suitability for measuring nanometer particles. In total, we spent at least 1000 hours evaluating scientific instruments for particle size measurement. For the price of this instrument, I could have purchased any number of TEM instruments if I thought it was the right tool for the job. Universities and pharmaceutical companies alike have selected the PCS as the instrument of choice for doing particle size distribution measurements of nanometer particles. The Malvern instrument is by far the leader in its class (and the most expensive!). If you think there is an instrument better suited to such measurement, I challenge you to present reports generated from such an instrument. I do not mean a report an operator writes up, I mean a fully automated system that does the measurements, does the statistical analysis and prints out a report the way the Zetasizer does. I am aware of the instruments that do such a function and have evaluated most of them in my lab for a period of several months each. We are making every attempt to be completely objective and are using the best scientific instruments and practices possible. You stated we are not objective, which means we must be subjective. Please tell me exactly what you believe is subjective. Our instruments make the measurements, there is no subjectivity involved. The instruments chosen for the measurements are considered among the best for their intended purpose. We have specified the physical properties and explained in detail why they are considered important and exactly how each measurement is performed. This material has been reviewed and accepted by the scientific and academic community. We are only measuring physical properties and make no claims regarding efficacy. Furthermore, we are making no value judgements or adding commentary to the reports, we are simply reporting the values as measured. If you think we lack clarity and objectivity, please tell me specifically in what regard you make such a statement. Please advise me on exactly what you believe is "incomplete and inadequate" about our measurements. Regarding the TEM... My comments regarding the TEM are focused on the problem associated with high ionic solutions and what happens during sample preparation. If you are really interested in examining the particles in highly ionic solutions, why not first remove the ions? If the ions were removed, then you would see the particles. Alternatively, remove the particles and examine them separately away from the ionic solution. Either technique would solve the problem. Why do you insist on using a method that are not considered scientifically valid? I dare say, you would find it difficult to find anyone in the scientific or academic community who would review your practices and condone them (examination of highly ionic solutions with a TEM). frank key -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
