Extraction by a fixed volume of gas continuously recycled through the sample and a sorbent trap by a pump in a closed-circuit arrangement.
Note: Closed-loop extraction was developed for trace analysis of volatile compounds (at mass concentrations of \(\pu{ng L-1}\)) in drinking water.

Typical apparatus for closed-loop stripping analysis.
Source:
PAC, 2016, 88, 517. 'Glossary of terms used in extraction (IUPAC Recommendations 2016)' on page 527 (https://doi.org/10.1515/pac-2015-0903)