Coconut Shell Activated Carbon as Solid-Phase Extraction Adsorbent for Preconcentration of Selected Pesticides from Water Samples

Solid-phase extraction (SPE) on activated carbon derived from coconut shell (CSAC) for the preconcentration of four varying polarity pesticides (imidacloprid, acetamiprid, simazine, and linuron) prior to their determination using high performance liquid chromatography with diode array detector (HPLC-DAD) was investigated. The characteristics of the CSAC were analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) method. The effects of the solution pH, eluent type, eluent volume, and flow rate were investigated for optimization of the presented procedure. The adsorption was achieved quantitatively on the CSAC column in the pH range of 2.0-7.0, and then the retained pesticides were eluted with dichloromethane. The detection limit was found to be 0.025-0.039 mu g L-1, depending on the pesticide. The proposed SPE-CSAC method was used to determine selected pesticides in tap water samples. The recoveries ranged from 58.2 to 105.3%, with low relative standard deviations. The obtained results indicated that the CSAC could be efficiently used as a low cost alternative to commercially available SPE adsorbents for the determination of the varying polarity pesticides in environmental water samples at trace levels.