CONTINUOUS AUTOMATIC MONITORING OF VOLATILE ORGANIC-COMPOUNDS IN AQUEOUS STREAMS BY A MODIFIED PURGE-AND-TRAP SYSTEM

A new inexpensive modification approach enabled continuous on-line automatic analysis of volatile organic compounds (VOCs) in small (0.1-70 ml/min) sample streams while maintaining all capabilities on a purge-and-trap system. Commerically available automated VOC analyzers require large (liters-per-hour) sample streams. VOCs in laboratory experiments and small sample streams are usually monitored by grab analysis. This paper evaluates the performance of continuously and automatically monitoring VOCs in small sample streams on a modified purge-and-trap system. A 1 ml/min stream with 30 ppb (10(9)) trichloroethane and 260 ppb tetrachloroethene aqueous standards was monitored unattended for 3 days with 2-3% relative standard deviations. The competitive breakthrough of VOCs through liquid chromatography carbon minicolumns was studied.