Rapid Determination of Volatile Phenol in Soil by Automatic Flow Injection-Spectrophotometry

The fresh soil sample （10.0 g） was taken and placed in a 500 mL-polyethylene bottle, and 10 mL of 5 g·L⁻¹ copper sulfate solution and 190 mL of 10 g·L⁻¹ sodium hydroxide solution were added. The mixture was shaken horizontally for 10 min and settled for 5 min. The supernatant was taken and passed through 0.45 μm filter membrane. Online distillation was performed using a flow injection analyzer at （165±2） ℃. The distilled volatile phenol was reacted with 0.65 g·L⁻¹ 4-aminoantipyrine solution in a potassium ferricyanide buffer solution （pH 10.3）, to form an orange-red indophenol antipyrine dye. Colorimetric determination was performed at 510 nm. As shown by the results, linear relationship between the corresponding peak area and mass concentration of volatile phenol was kept within 2.0 mg·L⁻¹, with detection limit of 0.07 mg·kg⁻¹. Parallel analysis of soil volatile phenol certified reference materials was conducted 6 times, and the determined values were basically consistent with the certified values, with the relative error of the determined values in the range of −3.9%−2.7%, and RSDs in the range of 1.4%−3.2%. This method was applied to analysis of 6 actual soil samples, and the determination results were basically consistent with those by the standard method HJ 998—2018.