Try the search terms "contamination analysis" - this should take you to some consultants or laboratory services who might help with particle analyses .

The search terms "Particle Counting" or "particle counters" will take you to equipment manufacturers and services for determining the sizes of your particles.

You might also explore the websites and publications of the American Filtration and Separations Society ( http://www.afssociety.org/ ) and Filtration News ( http://www.filtnews.com/index.asp )

If you have a contamination or separations problem, many filter companies can help you analyze your particles. I work for a filter company - our website is porvairfiltration.com .

If you explain your challenge in more detail, perhaps forum participants can help a bit more. Regards, Joseph ■

Sorry for my late answer. In our case we wanted to detect the crystal growth. The idea was / is to store a suspension over an longer periode of time in a closed vial. In regular intervals the particle size should be determined. The aim is to monitor the beginning of crystal growth (nucleation step). So we need a lower detection limit smaller than 100nm.

In first experiment we have used "Dynamic Light Scattering" by comparing the correlation curves recorded over a certain period of time. But the results were inconclusive.

Is there anyone who has experience with such experiments or any suggestions.

Best regards ■