Headspace concentration
1, 2-Dichlorobenzene was used as an internal standard (IS) for
GC analysis, as this compound is not found in the pennywort juice.
The sample (20 mL) containing 10 μL of added 1,
2-dichlorobenzene (100 μg/L water) was transferred to a 40-mL
amber vial which was capped with a PTFE septum. The vial was
incubated for 5 min at 35 ◦C, then a 75-μm Supelco (Bellefonte,
Pa., U.S.A.) SPME fiber carboxen/polydimethylsiloxane (PDMS)