Analysis of Diquat and Paraquat by Solid Phase Extraction Directly Coupled with Matrix Assisted Laser Desorption/Ionization Mass Spectrometry

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Abstract
The herbicides diquat and paraquat have been successfully analyzed through a process which combines solid phase extraction (SPE) with Matrix Assisted Laser Desorption/Ionization (MALDI) mass spectrometry. Ion pair interactions are utilized to selectively load the herbicides onto a solid phase extraction disc. A MALDI matrix is then applied and analysis takes place directly from the disc, eliminating the need to elute the sample. This SPE-MALDI combination produced detection limits comparable to those obtained from conventional analysis with U.S. EPA Method 549.1. The SPE-MALDI method was tested on a variety of water samples and found to be suitable for “real world” analysis.