Solid phase extraction of organochlorine pesticides with modified poly (styrene-divinylbenzene) microbeads using home-made solid phase extraction syringes

Poly (styrene-divinylbenzene) (PS-DVB) microbeads, having 8 μm diameters were modified with -NH2, -CN and -COOH functional groups. These modified microbeads were used in home-made solid phase extraction cartridge for the recovery and the pre-concentration of chlorinated pesticides from aqueous media. Characterization of pristine and -NH2, -CN and -COOH functional groups modified microbeads were examined by Fourier transform-infrared spectrometer (FT-IR), porosimeter, scanning electron microscope (SEM) and thermogravimetric analyzer (TGA). It was found from gravimetric analyses that high amount of functional groups were modified onto the polymeric microbeads. For the recovery and pre-concentration of chlorinated pesticides, a standard mixture containing 17 different chlorinated pesticides in acetone were used and diluted in water to prepare dilute working solution of the pesticides. Flow rate of 0.3 mL/min was found to be optimum flow rate for the high recovery and high pre-concentration factor for the studied pesticides. The highest recovery value of all studied pesticides were obtained when -CN modified microbeads were used. Recovery and the pre-concentration factors for the other microbeads modified with -NH2 and -COOH was found to be lower than -CN modified microbeads. However, these two different type microbeads could also be used for the recovery and pre-concentration of chlorinated pesticides. For the desorption of the chlorinated pesticides from the modified microbeads, ethyl acetate was found to be the best desorbing agent instead of hexane, dichloromethane and the other desorbing agents. Recovery of the chlorinated pesticides was higher than 85% and pre-concentration factor was found to be at least 200-fold.