Carbon nanotubes as solid-phase extraction sorbents for the extraction of carbamate insecticides from environmental waters

Multiwalled carbon nanotubes have been used for the first time as solid-phase extraction sorbents for the extraction of five N-methylcarbamate insecticides (i.e., carbaryl, carbofuran, aminocarb, methiocarb, and zectran) from different surface water samples. An effective and sensitive method was developed by combining solid-phase extraction and liquid chromatography-electrospray ionization- mass spectrometry detection. Important parameters influencing the extraction efficiency such as kind and volume of elute, volume of water samples, and adsorbent mass were optimized. Under the optimized extraction conditions, good linearity was obtained for all carbamates (r2 > 0.995) over the range of 0.005-1 mg L-1. The limits of detection and quantification were 0.01-0.05 and 0.08-0.2 µg L-1, respectively. The optimized solid-phase extraction procedure was compared in terms of adsorption capacity to C18 silica and activated carbon. The adsorption capacity of multiwalled carbon nanotubes was larger than activated carbon. The proposed method was successfully applied to the analysis of tap and surface waters, and mean recoveries for five carbamates were from 92.2 to 103.9 % with relative standard deviation between 0.4 and 7.0 %.