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： M9681322

~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 N2 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: N2 ,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

●Temperature

●Effect of sample to headspace volume ratio

●Addition of sodium

Extraction timeWB-HS-SPEMMA-HS-SPEM

30min40min

Better!!

TemperatureMA-HS-SPEM WB-HS-SPEM

2,6DNT

HCB

Effect of sample to headspace volume ratio

MA-HS-SPEM WB-HS-SPEM

20/20

Addition of NaCl MA-HS-SPEM WB-HS-SPEM

NB

2,4-DNT

2,6-DNT

2,6-DNT

NB

2,4-DNT

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

S-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

HCDB1,2,4-TBC

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 sa

mples. • 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