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Yes, there is a manual for the BI90 system, and no, it does not require calibration. Lack of reproducibility in light scattering measurements, 9 times out of 10, are a consequence of either dust/impurities in the sample or particles and/or concentrations that are outside the working range of the instrument (which will cause number fluctuations). Your best bet is to contact Brookhaven at www.bic.com. Someone there will be able to assist you. ■

Dear Sir,

We are sorry to learn that you are experiencing difficulty with your 90Plus. Since we do not have your contact information, we ask that you please call or e-mail our offices in New York at:

(631)758-3200 or info@bic.com

Someone here will be more than happy to be of assistance. ■

Thank you for everyone. We did contact with Brookhaven. And we were told that the computer and software are needed to be upgraded. Also, for service and training, there will be a fee of $2500. As this is an old model (running under windows 3.1), we need to know the problem first. Is that possible that the PMT detector is bad as we have seen the numebr (the effective particle size) went up and down randomly? Is there any way to test the system? When we check the software, it seemed that very simple to use. We don't have manual, is there anything need to be done before analysis? Thank you.

Optimumlu ■

It would be best to contact Mr. David Halversen, who is Brookhaven's After-Sales Service Manager, at (631)758-3200, ext. 111. ■