Analysis of semi-volatile organic compounds in aqueous samples by microwave-assisted headspace solid-phase microextraction coupled with gas chromatography-electron capture detection 指導教授：徐永源博士 報告者：曾培芬 學號： M ~Journal of Chromatography A,1140(2007)35-43 Yaping Huang, Yu-Chuan Yang, Youn Yuen Shu*

Introduction ◆ Sample pretreatment technology ◆ Liquid-liquid extraction (LLE) ● Drawback large amount of organic solvent time consuming labor intensive ◆ Solid-phase extraction (SPE) ● Advantage small amount of solvent relatively ● Drawback plugging channeling large sample size used

Introduction ◆ Solid-phase microextraction (SPME) ● first developed by Pawliszyn ● solvent free ● performed in two ways: - Direct immersion (DI-SPME) - Headspace (HS-SPME) ● Compare DI-SPME : influenced by sample matrix HS-SPME : reduce matrix interference for volatile compounds long sampling time relatively

Introduction ◆ Sample matrix heating before HS-SPEM ● water bath (WB) - slow and inefficient ● microwave-assisted (MA) - instantaneous localized superheating

Introduction ◆ MA-HS-SPME ● Advantage - quick - solvent-less - temperature monitoring (equipped with infrared sensor) - very good linearity and sensitivity

Introduction ◆ MA-HS-SPEM coupled with GC-ECD - Analysis of semi-volatile organic compounds ◆ Experimental purpose - Comparison WB-HS-SPME and MA-HS-SPEM - The optimum conditions for obtaining extraction efficiency - Application to the real sample

Experimental ◆ Reagents and materials ● 1,2-Dichlorobenzene （ 1,2DCB ） ● 1,3-Dichlorobenzene （ 1,3DCB ） ● 1,4-Dichlorobenzene （ 1,4DCB ） ● 2,4-Dinitrotoluene （ 2,4DNT ） ● 2,6-Dinitrotoluene （ 2,6DNT ） ● 1,2,4-Trichlorobenzene （ 1,2,4TCB ） ● Nitrobenzene （ NB ） ● Hexachlorobenzene （ HCB ） ● Hexachloro-1,3-butadiene （ HCBD ） ◆ Internal standards: ． 1,3,5-TCB ． 1,2,3,4-TeCB

Experimental SPME fiber:65μm PDMS-DVB （ conditioned by GC injector under N 2 stream for 1 hr at 250 ℃）

Experimental GC-ECD -Capillary column ： HP-5, 30m×0.25mm I.D×0.5μm -The column was programmed as : 65 ℃ (4min) → 5 ℃ /min to 80 ℃ (2min) → 10 ℃ /min to 120 ℃ (2min) → 10 ℃ /min to 270 ℃ (5min) -Injector port : splitless -ECD:300 ℃ -Carrier gas: N 2,flow-rate:0.7ml/min

Results and discussion Optimization of PDMS-DVB fiber desorption conditions in GC injection port -3min desorption time -at 250 ℃ -the fiber depth of 4.0cm -another 5 min desorption time

Results and discussion ◆ Optimization of MA-HS-SPEM and WB- HS-SPEM procedure ● Extraction time Extraction time ● Temperature Temperature ● Effect of sample to headspace volume ratio Effect of sample to headspace volume ratio ● Addition of sodium Addition of sodium

Extraction time WB-HS-SPEMMA-HS-SPEM 30min 40min Better!!

Temperature MA-HS-SPEMWB-HS-SPEM 2,6DNT HCB

Effect of sample to headspace volume ratio MA-HS-SPEMWB-HS-SPEM 20/20

Addition of NaCl MA-HS-SPEMWB-HS-SPEM NB 2,4-DNT 2,6-DNT NB 2,4-DNT

Results and discussion ◆ Comparison of MA-HS-SPME and WB-HS- SPME

Results and discussion ◆ Validation of the MA-HS SPEM method --Correlation coefficient greater than 0.997

Results and discussion ◆ Application to the real sample - sample collected from university campus and Jen-Ai river

Results and discussion Standard solution Artificial solution

Results and discussion River sample Campus sample HCDB 2,6-DNT HCB 2,4-DNT HCB 2,6-DNT HCDB 1,2,4-TBC

Conclusion The optimum conditions: -30W microwave power for 30min at 70 ℃ -20ml aqueous sample in 40ml headspace -no addition of sodium MA-HS-SPEM coupled with GC-EDC technique -acceptable accuracy -precision -wide-rang linearity -high sensitivity with detection limits at ng/L level in the analysis of water samples. The microwave-assisted technique -viable -better extraction efficiency than conventional heating. This method -fast, simple, low-cost, hazardous organic solvent free

Thanks for your listening