Hello all, I recently had to filter water samples through glass fiber filters (I used Whatman brand, GF/C filters). I combusted the filters at 500 C for an hour, let them cool down, ran the water samples through them with a vacuum pump at 15 psi, dried them at 60 C for 24 hours, and then combusted them at 500 C for 3 hr once more in order to obtain ash free dry mass. To my dismay, the filters with the ash weighed less than the original weight of the filter after the initial combustion. Either my scale has done something funny or the filters have lost mass during the course of this process. I tried running some blank filters (doing everything the same way, except using pure water), and the filters did not lose any mass. Room temperature has stayed roughly the same during the course of this process.
Has anyone had any experience with this that might be able to explain to me what just happened? Thank you, Aaron Stoler -- University of Pittsburgh Department of Biology 101 Clapp Hall Pittsburgh PA 15260 410.365.7700 (cell) 412.624.4458 (office) [email protected] www.pitt.edu/~abs45/index.html
