Used as a reference standard in environmental testing laboratories to calibrate analytical instruments such as gas chromatographs (GC) and mass spectrometers (MS). It ensures accurate detection and quantification of heptachlor epoxide residues in soil, water, and food samples. Commonly applied in monitoring pesticide contamination and assessing compliance with regulatory limits. Also used in research studies focused on persistent organic pollutants (POPs) due to its stability and environmental persistence.