SinS - Abstract

Abstract Information :

New methods have been developed and optimised using Ultra-High-Performance Supercritical Fluid Chromatography (UHPSFC-MS) for the analysis of pesticides. The regulatory control of pesticides has been tightening in recent years, and extensive data is required to demonstrate control and safety of low-level impurities. Often methodology for analysis and isolation of these impurities is environmentally costly, particularly at preparative scale where litres of toxic organic solvents are consumed followed by an energy intensive solvent evaporation process. The drive to move towards more sustainable chromatographic techniques has pushed UHPSFC into the spotlight, with its reduced solvent consumption and a more efficient evaporation process at preparative scale. However, it is imperative to understand the scope of the technique and optimise it to maximise its capabilities. A library of pesticide active ingredients has been analysed by UHPSFC-MS using various method conditions to understand the impact on the separation. Each compound within the library was selected to reflect the range of physicochemical properties of pesticide active ingredients. A Waters Acquity UPC2 TQD with positive and negative ion ESI was used and the performance of ten achiral columns was assessed. A primary mobile phase of supercritical CO2 was employed with various organic polar co-solvents, and gradient conditions were modified to afford separation between compounds. Several injection solvents were investigated across a range of polarities. The impact of column temperature and column back-pressure on the chromatography was also assessed. Advantages of UHPSFC-MS over techniques such as reversed-phase liquid chromatography (RP-LC) and normal-phase liquid chromatography (NP-LC) have been highlighted in terms of its sustainability and chromatographic performance for the analysis of pesticides. Stationary phases, mobile phases and sample diluents were assessed based on retention times, resolution, and peak symmetry. The most suitable conditions have been found for the full library and individual classes of compounds within the set such as basic or acidic pesticides. Sample diluent was shown to be critical to achieve good peak shape for a group of molecules within the library. Column temperature and pressure had a significant impact on both retention and selectivity of the separation. A library of pesticide active ingredients has been separated using UHPSFC-MS and key method parameters identified that significantly impact retention and resolution. This data can be used to streamline the method development process and drive the replacement of less sustainable techniques such as NP-LC with UHPSFC.