Multi-walled carbon nanotubes-agarose gel micro-solid phase extraction for the determination of triazine herbicides in water samples

Abstract

In this work, a new extraction procedure termed multi-walled carbon nanotubes-agarose gel micro-solid phase extraction (MWCNTs-AG-μSPE) combined with gas chromatography-mass spectrometry (GC-MS) was developed and used for the determination of triazine herbicides in water samples. A high performance synthetic adsorbent, MWCNTs-AG, was prepared using a simple stirring method. Different stoichiometric ratios of MWCNTs and agarose were mixed in deionized water for at least 24 h at room temperature in order to obtain agarose solutions with homogeneously mixed MWCNTs. Two selected triazine herbicides, namely, atrazine (ATR) and secbumeton (SEC) were employed as model compounds. Several important parameters, such as the effects of concentration of MWCNTs, type of conditioning solvent, extraction time, type of desorption solvent and desorption time, were comprehensively optimized. Under the optimized conditions, the calibration results showed good linearity with the correlations of determination (r²) in the range of 0.9925–0.9981 for both analytes. Limits of detection (LODs) were found to be 0.319 μg L⁻¹ and 0.340 μg L⁻¹, while the LOQs were found to be 1.064 μg L⁻¹ and 1.136 μg L⁻¹ for ATR and SEC, respectively. High relative recoveries were obtained in the range of 84.9–108% for the analytes with a relative standard deviation of <15.2% (n = 3). The results showed that MWCNTs-AG-μSPE method is superior to AG-μSPE for both the analytes. This new method was successfully applied for the determination of triazine herbicides in selected water samples. Atrazine was found to be present in the lake water sample because it had a signal higher than the LODs and lower than LOQs. The proposed technique proved to be simple and requires relatively short extraction time and low amounts of organic solvents; thus, contributing towards green chemistry.