Using GC-MS for the quick analysis of carbon dioxide for soil microbial biomass determination

Abstract

Microbial biomass carbon is a common soil parameter used to evaluate microbial abundance in soil environments, and microbial biomass can change in response to disturbances and/or changing environmental conditions. Microbial biomass carbon was determined on 192 soil samples using the chloroform fumigation-incubation method, and after 10 days, gas samples were collected. Gas samples were analyzed for carbon dioxide (CO₂) concentration. Determination of CO₂ concentration is usually conducted by infrared gas analysis or chemical analysis (an alkali trap and subsequent titration, or soda lime absorption), and these methods were either unavailable or too time consuming for the number of samples analyzed. As a result, we have developed an analytical method for the determination of CO₂ in gases using the gas chromatograph/mass spectrometer (GC-MS). This method requires a 5 μL injection, 5 minute analysis time, and the resulting figures of merit are comparable to most procedures present in the literature. Additionally, the microbial biomass carbon values obtained were consistent with previously published values in similar ecosystems.