Multiwalled Carbon Nanotubes as SPE Adsorbents for Simultaneous Determination of Seven Sulfonylurea Herbicides in Environmental Water by LC-MS-MS

An effective and rapid method was developed for simultaneous determination of seven sulfonylurea herbicides in environmental water using multiwalled carbon nanotubes as solid-phase extraction sorbent coupled with liquid chromatography-tandem mass spectrometry. Important parameters influencing the extraction efficiency such as pH of the sample solution, flow rate of sample loading, the eluent and its volume were optimized. Under optimum conditions, good linearity was obtained for all herbicides (r (2) > 0.99) over the range of 0.05-5,000 ng L-1, and precisions (RSD) for nine replicate measurements of a standard mixture of 200 ng L-1 were 1.9-7.4%. The limits of detection and quantification were 0.01-0.20 and 0.05-1.00 ng L-1, respectively. The proposed method was successfully applied to the analysis of tap water, spring water, ground water and well water, and mean recoveries for seven analytes at three spiked concentration levels were from 81.5 to 110.5% with RSDs between 0.3 and 7.0%. The results showed that the established method has wide application to analyze sulfonylurea herbicides at trace level in water.