Determination of N-acyl homoserine lactones in soil using accelerated solvent extraction combined with solid-phase extraction and gas chromatography-mass spectrometry

Understanding of quorum sensing based on N-acyl homoserine lactones (AHLs) and microbial communication in soil – possessing a high cell density and number of different species habitat – is limited due to the lack of an easy and sensitive identification and quantification method of signal molecules in soil. In this study, the extraction and purification method of AHLs in soil was investigated with seven commonly existing AHLs and formerly established GC/MS. Ethyl acetate was selected as the eluent for silica gel compacted solid phase extraction cleanup based on the recovery data and purification efficiency. Compared to ultrasonic extraction and shaking extraction, accelerated solvent extraction (ASE) showed better extraction recoveries of AHLs from soil. The extraction solution was further optimized using ethyl acetate/acetone (4/1, v/v). Using the optimized method, the recoveries of all AHLs ranged from 86.96–105.00% and 84.86–110.89% in latosolic red soil and yellow brown soil, respectively. The detection limits and quantification limits of AHLs were 0.75–1.25 μg kg−1 and 2.50–4.17 μg kg−1 based on a 2 g soil sample. Higher sensitivity will be obtained when a higher weight of the soil sample was analyzed. The method was successfully applied to quantify AHLs in four different soils. The results showed that the developed method is suitable for the identification and quantification of trace AHLs in environmental soil samples.