Study of Purified Multi-walled Carbon Nanotubes as a Sorbent of Solid Phase Extraction for Preconcentration of Organophosphorous Pesticides from Water Samples

Off-line solid phase extraction (SPE) coupled with GC-PFPD was applied in this study. 50mg purified multi-walled carbon nanotubes (PMWCNTs) were packed in a SPE cartridge for the extraction of 8 organophosphorous pesticides (OPPs) in water samples. Breakthrough volumes (BTVs) and recoveries of 8 OPPs on PMWCNTs cartridge were investigated and compared with those on laboratory-packed Carbopack B cartridge (50 mg) and on Oasis HLB cartridge (1 mL), respectively. The results showed that the BTVs of 20 μg/L methamidophos on three SPE cartridges were less than 10mL due to its high water solubility; the BTVs of dichorvos, diazion, parathion-methyl, chlorpyrifos and parathion on three SPE cartridges were more than 200 mL (1 μg/L for each analytes). For trichlorfon and dimethoate, PMWCNTs cartridge showed stronger retention ability than Carbopack B cartridge, and weaker than Oasis HLB cartridge. Except trichlorfon and dimethoate, the recoveries of 6 OPPs were more than 70% when 100 mL water sample spiked with 2 μg/L for each analyte was extracted with PMWCNTs cartridge. Some surface water samples were extracted with both PMWCNTs cartridge and traditional CHCl_3 liquid-liquid extraction method, and the results were comparable. It has been proven that PMWCNTs can be an excellent SPE sorbent.