A highly sensitive and selective mercuric oxide–based reduction gas detector was successfully used for parts-per-billion level gas chromatography (GC) determination of ethylene in various matrices such as in the monitoring of fruit ripening, ambient air, and industrial solvents. Separation of ethylene from the sample matrix was achieved by isothermal analysis using a silica-based packed column. Backflushing was incorporated to ensure overall system cleanliness and to improve sample throughput, keeping analysis time under 4 min.