Supercritical fluid chromatography-mass spectrometry for the analysis of agrochemicals and formulated products

Abstract

New methods have been developed using supercritical fluid chromatography-mass spectrometry (SFC-MS) for the analysis of agrochemical materials. Tightening regulatory control of crop protection products has increased the cost of developing a new product, and so reducing waste during the development process is critical to ensure new products reach the market. A library of AIs was compiled and analysed using various SFC and MS conditions, building understanding to suggest SFC method conditions based on modelled analyte chemical properties. By understanding the types of agrochemical materials that are amenable to SFC-MS separation and the best set of method conditions for different classes of compounds, the development of SFC-MS methods can be accelerated. Experimental conditions that are unlikely to result in suitable chromatography can be removed from screening experiments, reducing time, solvent and energy waste during the development process.

A Derringer desirability approach was used to assess the performance of 10 achiral columns and 10 co-solvents for the separation of the AI library, evaluating factors such as elution, retention and peak shape. Other parameters such as detection method, diluent, column temperature and backpressure were also investigated. The results were used to develop a workflow for SFC method development, suggesting columns based on modelled chemical properties. SFC methods for several examples were developed using the knowledge gained from the Derringer desirability study. Methods were developed for the analysis of agrochemical materials in complex formulation matrices, including a method for quantitation of three AIs and an impurity, and a method for low-level detection of 4 biocide co-formulants. SFC was also explored as a more sustainable technology for the preparative isolation of emamectin benzoate by-products.

The versatility of reversed-phase high-performance liquid chromatography (RP-HPLC) and gas chromatography (GC) cover most of the chemical space of agrochemical AIs, and often analysts default to these techniques even when another approach could outperform them. This research highlighted where SFC-UV-MS can provide fast methods for separation of agrochemical materials. The orthogonal selectivity of SFC compared to RP-HPLC can also allow resolution of analytes that co-elute using RP-HPLC. It is also becoming increasingly important where both techniques can provide suitable separation to move towards SFC for its sustainability. This is particularly important at preparative scale where SFC has lower solvent consumption and less energy intensive solvent evaporation post-separation.

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Identifiers

ORCID for John Langley: orcid.org/0000-0002-8323-7235

ORCID for Julie Herniman: orcid.org/0000-0003-4834-1093

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