1. Use a 50mL dispenser to add 50mL of 0.5M K2SO4 to each NF flask. Cover flasks with parafilm and place them in a rotary shaker for 30 minutes (at about 200 rotations per minute [rpm]).
2. While samples are shaking, prepare your funnel and filter paper setup. Wearing powder-free gloves, fold Whatman 42 filter paper, (15-cm diameter), so that it forms a cone, and place it into a plastic funnel. Fill each funnel with deionized water to rinse out any traces of soluable carbon in the paper.
3. After 30 minutes, take flasks out of the shaker. For each flask: transfer white tape label to a 60-mL plastic bottle; place vial under funnel; gently shake extract to suspend the soil and pour it immediately onto filter paper. Do not try to get all the soil onto the filter. Store the extracts in a freezer until analysis on the TOC analyzer.
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