Comparison of C18 silica and multi-walled carbon nanotubes as the adsorbents for the solid-phase extraction of Chlorpyrifos and Phosalone in water samples using HPLC.

A comparison between C18 silica and multi-walled carbon nanotubes (MWCNTs) in the extraction of Chlorpyrifos and Phosalone in environmental water samples was carried out using HPLC. Parameters affecting the extraction were type and volume of elution solvent, pH and flow rate of sample through the adsorbent. The optimum conditions obtained by C18 cartridge for adsorption of these pesticides were 4 mL dichloromethane as elution solvent, sample pH of 5, flow rate of 1 mL/min, and those for MWCNT cartridge were 3 mL dichloromethane, pH of 5 and flow rate of 10 mL/min, respectively. Optimized mobile phase for separation and determination of these compounds by HPLC was methanol/water (80:20 v/v) with pH=5 (adjusted with phosphate buffer). Under optimal chromatographic and SPE conditions, LOD, linear range and precision (RSD n=8) were 3.03×10−3, 0.01–5.00 μg/mL and 2.7% for Chlorpyrifos and 4.03×10−4, 0.01–5.00 μg/mL and 2.3% for Phosalone, in C18 cartridge, respectively. These values for MWCNT were 4.02×10−6, 0.001–0.500 μg/mL and 1.8% for Chlorpyrifos and 1.02×10−6, 0.001–0.500 μg/mL and 1.5% for Phosalone, respectively.