Gerry,
We have run thousands of GF/F filters for freshwater and marine 
phytoplankton without seeing these problems, but we reduced the 
temperature of the combustion column to 850 C to avoid melting of 
filters. Above 850 C melted filters were clogging the insert and 
combustion tube and caused problems with the base line. The other option 
is to scrape the material off the filters but that is time consuming and 
non-quantitative.
Bjoern

-- 
Björn Wissel, PhD
EQAL Manager, Faculty of Science
Adjunct Professor, Department of Biology
265.2 Laboratory Building
University of Regina
Regina, SK S4S 0A2 Canada
phone    306 585-4890
fax      306 337-2410
e-mail   [log in to unmask]
www.uregina.ca/biology/faculty/Wissel/Wissel.html