Analytical method for dioxin and organo-chlorinated compounds: (II) comparison of extraction methods of dioxins from XAD-2 adsorbent

Supercritical fluid extraction (SFE), ultrasonic extraction (USE), and acce lerated solvent extraction (ASE) were compared with the well known Soxhlet extraction for the extraction of polychlorinated biphenyls (PCBs) and polyc hlorinated dibenzo-p-dioxins (PCDDs) from the XAD-2 resin which was used to adsorb PCDDs in the atmosphere. XAD-2 resin spiked with five PCDDs was cho sen as a sample. The optimum conditions for the extraction of PCDDs by SFE were turned out to be the use of CO2 modified with 10% toluene at 100 degre es C and 350 arm, with 5 min static extraction followed by 20 min dynamic e xtraction. SFE gave a good extraction rate with good reproducibility for PC DDs ranging from 68 to 98%. The ultrasonic extraction of PCDDs from XAD-2 w as investigated and compared with other extractions. A probe type method wa s compared with a bath type. Two extraction solvents, toluene and acetone w ere compared with their mixture. The use of their mixture in probe type, wi th 9 minutes of extraction time, was found to be the optimum condition. The average recovery of the five PCDDs for USE was 82-93%. Accelerated solvent extraction (ASE) with a liquid solvent, a new technique for sample prepara tion, was performed under elevated temperatures and pressures. The effect o f temperature on the efficiency of ASE was investigated. The extraction tim e for a 10 g sample was less than 15 min, when the organic solvent was n-he xaneacetone mixture (1 : 1, v/v). Using ASE, the average recoveries of five PCDDs ranged from 90 to 103%. SFE, USE, and ASE were faster and less labor ious than Soxhlet extraction. The former three methods required less solven t than Soxhlet extraction. SFE required no concentration of the solvent ext racts. SFE and ASE failed to perform simultaneous parallel extractions beca use of instrumental limitations.