Rapid Screening Method for the Analysis of Paraquat and Diquat by LC/MSD Using Selective Ion Monitoring and Large Volume Injection Application

A rapid and sensitive method for the analysis of paraquat and diquat was developed using LC/MS, electrospray ionisation (ESI), positive ion mode, selective ion monitoring (SIM) large volume injections, and minimal sample preparation. No trace enrichment was required to obtain limits of detection (LOD) below 1 μg/L, which is well below the World Health Organisation (WHO) advisory value of 10 μg/L. Introduction Paraquat and diquat, bipyridilium salts, are used in agriculture as non-selective contact herbicides. They are also commonly used in commercial weed killer formulations for domestic weed control. Rapid Screening Method for the Analysis of Paraquat and Diquat by LC/MSD Using Selective Ion Monitoring and Large Volume Injection Application Standard analytical methods for these herbicides in water matrices involve solid phase extraction as the enrichment technique and analysis by liquid chromatography using diode array detection (DAD) [1]. The LOD for paraquat and diquat is reported to be less than 0.4 μg/L. This application note gives details for the screening of these herbicides using liquid chromatography/ mass spectrometry (LC/MS) and a direct aqueous injection of the sample, thereby eliminating the trace enrichment step. The WHO has set an advisory value of 10 μg/L for paraquat in drinking water. In this application, a LOD of well below 1 μg/L is achieved for paraquat and diquat, as well as for amitrole and chlormequat. The method presented uses an ion-pairing reagent to help separate the compounds and to prepare Environmental