Sensitive determination of amide herbicides in environmental water samples by a combination of solid-phase extraction and dispersive liquid-liquid microextraction prior to GC-MS

In this paper, solid-phase extraction (SPE) in combination with dispersive liquid liquid microextraction (DLLME) has been developed as a sample pretreatment method with high enrichment factors for the sensitive determination of amide herbicides in water samples. In SPE-DLLME, amide herbicides were adsorbed quantitatively from a large volume of aqueous samples (100 mL) onto a multiwalled carbon nanotube adsorbent (100 mg). After elution of the target compounds from the adsorbent with acetone, the DLLME technique was performed on the resulting solution. Finally, the analytes in the extraction solvent were determined by gas chromatography-mass spectrometry. Some important extraction parameters, such as flow rate of sample, breakthrough volume, sample pH, type and volume of the elution solvent, as well as salt addition, were studied and optimized in detail. Under optimum conditions, high enrichment factors ranging from 6593 to 7873 were achieved in less than 10 min. There was linearity over the range of 0.01-10 mu g/L with relative standard deviations of 2.6-8.7%. The limits of detection ranged from 0.002 to 0.006 mu g/L. The proposed method was used for the analysis of water samples, and satisfactory results were achieved.