Frank wrote: > > 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.
Again, we're going to beat a dead horse! The Malvern scientist admitted that the machine cannot get to one nanometer or less, and that range [visible by TEM] is missing from your measurements. > 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. Again, poppycock! > 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. > There are later models of the TEM that do digital analysis of images and print out a distribution curve according to size. We have had such work done by one such university lab in the not too distant past. So, it is clear.... you either do not know what others in particle characterization or material sciences know.... or just are not open to science that does not suit you. And, yes, it could be rationally debated just how much error such narrowly-focused imaging will introduce.... but, I can tell you here and now, that I have no such interest in debating it with you. > 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. Your choice of analysis is subjective, and your beating of dead horses makes discourse impossible. Have I not said that water quality is a threshold issue in CS evaluation? but you just ignore that posit. And every other posit that you don't agree with... > > 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. See? No, you are not measuring physical properties. Where are the measurements of contaminants? And organics? And rnase and dna? > > 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. See all my above comments. > > 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. I would probably enjoy as well as learn from discussing such issues with someone who is oopen and interested in the opinions of others. Unfortunately, that is not the case here. > > 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 > We were not comparing [my] practices; this commentary-in-reply is and was directed to your attempt to set yourself up as THE authoritative source for CS quality.... Stephen > > > -- > 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: > silver-list-requ...@eskimo.com -or- silver-digest-requ...@eskimo.com > with the word subscribe or unsubscribe in the SUBJECT line. > > To post, address your message to: silver-list@eskimo.com > Silver-list archive: http://escribe.com/health/thesilverlist/index.html > List maintainer: Mike Devour <mdev...@eskimo.com> > >
