On-line coupling of subcritical water extraction with high-performance liquid chromatography via solid-phase trapping

Although ambient water is very polar and cannot dissolve many organic speci es, water at elevated temperatures behaves like a polar organic solvent. Th us, subcritical water has been proven to be an effective extraction fluid f or several classes of organic compounds. While solvent trapping was used to collect the extracted analytes in most of previous subcritical water extra ctions, sorbent trapping has also been developed for subcritical water extr action. In this study, an on-line system for subcritical water extraction a nd high-performance liquid chromatography (HPLC) was built and tested. A so rbent trap was used as the interface between subcritical water extraction a nd HPLC. Several shut-off valves have been utilized to switch the system fr om one mode to another (e.g., from the extraction mode to HPLC mode). The c oupling technique of subcritical water extraction and HPLC eliminates the l iquid-liquid extraction used in solvent trapping subcritical water extracti on and provides higher sensitivity. Compared to the off-line system reporte d in an earlier work, the operation of this on-line system is even easier. Some peak broadening occurred after the coupling the water extraction with HPLC for the analytes studied. The performance of this on-line system was e valuated by the extraction and determination of caffeine, nitrotoluenes, po lychlorinated biphenyls, chlorophenols and anilines. (C) 2000 Elsevier Scie nce B.V. All rights reserved.