Soil VOCs reside in vapours, dissolved in liquid and sorbed phases of the edaphic environment. VOCs in vapour and liquid phases are readily lost during sampling, whereas they are extracted with difficulty from the sorbed phase. Total soil VOCs are often extracted with methanol at room temperature, heat water-miscible solvents and soxhlet technique. Methanol extraction is an inexpensive method widely used and is described in the following experiment.
Experiment 6: Methanol Extraction
Soil samples collected for VOCs analysis must be handled minimizing losses due to volatilization and biodegradation. Field extraction/preservation of soil samples with methanol overcome these problems. The ratio of methanol to soil is 2.5:1 (v/w). A portion of methanol extract is combined with double distilled water and analyzed by a purge and trap GC or GC-MS system (Ramstad and Nestrick, 1981).
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