Isomalathion is primarily used as an analytical reference standard in environmental and agricultural testing laboratories. It serves as a key impurity marker for quality control and degradation studies of malathion, a widely used organophosphate insecticide. Due to its structural similarity and formation during the breakdown or storage of malathion, isomalathion is monitored to assess pesticide stability, formulation purity, and potential toxicity in crops and environmental samples. It is also used in research to evaluate the metabolic pathways and toxicological profiles of organophosphate compounds, helping to understand the safety and environmental impact of pesticide use.