Identify a commonly used EPA SW-846 method for volatile organic compounds (VOCs) in soils/groundwater and briefly describe the method principle.

• A. SW-846 Method 8082 (HPLC) for VOCs.
• B. SW-846 Method 8260C (GC-MS); principle: extract VOCs via purge-and-trap or purge-and-trap GC-MS to quantify volatile organics.
• C. Method 5030: Atomic absorption for metals.
• D. Method 9060: Total organic carbon.

Answer: (B)

A key idea here is how VOCs are captured and measured at very low levels in soils and groundwater. A commonly used SW-846 method for this purpose is a GC–MS approach that employs purge-and-trap. The principle is to concentrate the volatile organics from the sample by purging the matrix with an inert gas. As the VOCs are released from the water or soil extract, they are carried onto a sorbent trap (purge-and-trap). The trap is then heated to thermally desorb the compounds, and they are introduced into a gas chromatograph where they are separated, and a mass spectrometer provides identification and quantification. This pre-concentration step enables very low detection limits and broad VOC coverage, making it a standard choice for analyzing VOCs in soils and groundwater. The other options refer to methods used for metals or total organic carbon, not VOCs.