Determination of 21 phenolic compounds in soil by ultrasonic extraction- gas chromatography

An effective method was developed to determine phenolic compounds in soil by ultrasonic extraction-gas chromatography (GC). The soil sample was extracted with methylene dichloride-hexane (2: 1, v/v) for 3 min with the extraction temperature lower than 50 degrees C for 3 times. The extract was purified by alkaline aqueous solution (pH > 12), and the phenolic compounds were dissolved in aqueous solution. After the organic solution was discarded, the aqueous solution was adjusted to pH <3 and subsequently extracted with methylene dichloride-ethyl acetate (4: 1, v/v) twice. The analytes were determined by GC-FID and quantified by external standard method. The limits of quantification for all tested phenolic compounds were 0.01 - 0.06 mg/kg in about 10 g soil samples. The recoveries were between 62.9% and 111.4% with the relative standard deviations (RSDs) in the range of 4.3% -24.0% (n = 6). The results showed that this method is sensitive, accurate, and suitable for the determination of the 21 phenolic compounds in soil.