Developing a novel Solid-Phase Extraction (SPE) method to determine biostimulants from complex matrices and saline conditions accurately

Fish wastes contain the essential mineral nutrients (nitrogen and phosphorus) and biostimulants (BS) that are required for plant growth. However, its value as organic fertilizers and sources of plant nutrients have not been adequately recognized nor characterised. The integration of fish wastes from aquaculture into the regular fertilising regimes in conventional farming represents an effective method of reducing reliance on chemical fertilisers, with the added benefit of providing an organic waste management solution contributing to a circular economy.

BSs are emerging as the unseen connections between food production, wastes and the natural cycles of life. However, due to the diversity of organic materials, complex chemistry and trace levels, BSs are poorly characterized to date and often treated as "Blackboxes". This is the major bottleneck restricting the wider re-use of aquaculture wastes for growing plants within Sweden and globally. Accurate and reliable analytical methods are needed for trace analyses of BSs from aquacultural and non-aquacultural animal wastes (involving composts, soils and non-fish animal wastes). Earlier proven methods developed are well suited for a low salt environment but have not been extensively tested under high salt (greater than 25 ppt) or any other complex matrix conditions that these aquaculture and non-aquaculture-derived samples are likely to pose.

The aim is to develop a novel Solid-Phase Extraction (SPE, using C18 cartridges)-based pre-concentrating strategy capable of 'trapping' or pre-concentrating the trace natural BSs present in waters (freshwater, brackish, and marine) or wastes. After the critical SPE steps, high-precision MS analytical approach will be used for the selected wastes (e.g. UPLC-MS/MS for the trace phytohormone measurement at the nanogram levels). Once the SPE protocol has been evaluated and confirmed for a certain type of matrix, the appropriate sample collection automation step will be developed and customised.

Both the Swedish Metabolomics Centre and Czech Republic-based colleagues will be engaged to support the initial MS analytical needs. For the long term, the plan is to customise the MS facilities at SLU Ultuna and SLU Alnarp to handle the trace phytohormone measurement at the nanogram levels.