Optimization of headspace solid-phase microextraction technique for the determination of trace organochlorine pesticides in surface sediments

Abstract

     Headspace solid-phase microextraction (HS-SPME) with gas chromatography – electron capture detection
(GC-ECD) for the determination of trace organochlorine pesticides(OPCs) in sediment was developed. The optimum condition of GC-ECD was as follows. The injector and ECD temperatures were 270oC and 280oC, respectively. A 15-m DB-1 capillary column was held at 100 oC for 2 min, increased to 180 oC at a rate of 10 oC/ min, held for 4 min, and finally ramped to 280oC at a rate of 10 oC/ min, held for 6 min. The nitrogen gas was used as a carrier gas and making up gas at a flow rate of 1.5 mL/min and 28 mL/min, respectively. The
HS-SPME technique was used for extraction of the OCPs from sediments samples. The suspension of 0.5-g dried sediment in 1- mL of water was extracted using 100-μm PDMS fiber with extraction temperature of 70oC for 60 min with stirring. The addition of other hydrophilic solvents and salt had different effects on the extraction of OCPs . Higher responses of OCPs were obtained when water was added to the sediment. The linear regression was greater than 0.995 (0.004 - 0.4 ng/g, dry weight of sediment). The relative standard deviation was found to be lower than 10% (n=5). Limit of detection was lower than 0.01 ng/g, dry weight. The mean recoveries were between 80 and 99% (2 level of concentration; 0.01 ng/g and 0.1 ng/g). The optimized HS-SPME procedure has been shown to be reliable for fast, accurate and precise monitoring of OCPs in extracted sediment samples. This method has been expanded for application to a wide range of sediment and soil matrices.