Detection of Organophosphorous Pesticides in Soil Samples with Multiwalled Carbon Nanotubes Coating SPME Fiber

A headspace solid phase microextraction (HS-SPME) technique using stainless steel fiber coated with 20 μm multi-walled carbon nanotubes (MWCNTs) and gas chromatography with thermionic specific detector (GC-TSD) was developed to determine organophosphorous pesticides (OPPs) in soil. Parameters affecting the extraction efficiency such as extraction time and temperature, ionic strength, the volume of water added to the soil, sample solution volume to headspace volume ratio, desorption time, and desorption temperature were investigated and optimized. Compared to commercial polydimethylsiloxane (PDMS, 7 μm) fiber, the PDMS fiber was better to be corrected as phorate, whereas the MWCNTs fiber gave slightly better results for methyl parathion, chlorpyrifos and parathion. The optimized SPME method was applied to analyze OPPs in spiked soil samples. The limits of detection (LODs, S/N = 3) for the four pesticides were <0.216 ng g −1 , and their calibration curves were all linear ( r 2 ≥ 0.9908) in the range from 1 to 200 ng g −1 . The precision (RSD, n = 6) for peak areas was 6.5 %–8.8 %. The recovery of the OPPs spiked real soil samples at 50 and 150 ng g −1 ranged from 89.7 % to 102.9 % and 94.3 % to 118.1 %, respectively.