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A supercritical fluid extraction procedure and a chromatographic separation/detection method were developed for the detection of Earth-based microorganisms. After microbes in a sand or a soil sample were hydrolyzed in a diluted NH4OH/acetone solution, several redox compounds from bacteria could be effectively extracted with trimethylamine-modified supercritical CO2 at 35degreesC and 300 atm. These signature redox-active compounds were separated by a reversed-phase HPLC column in an ion-pair mode and then monitored with a diode array detector and an electrochemical detector. The analytical results demonstrated the feasibility of using the reported techniques to detect the chemical signature of life in barren desert sand Samples. (C) 2002 Elsevier Science (USA).