取干燥的土壤样品5.00 g，用含有1%（体积分数）氨水和50 mg·L^-1硫代硫酸钠（防止联苯胺的氧化）的甲醇溶液（作为提取剂）10 mL超声提取30 min，加冰保持温度低于10℃，静置10 min。取上清液2.0 mL，经0.22 μm聚四氟乙烯针式过滤器过滤后，以ZORBAX C₁₈反相色谱柱为固定相，体积比25：75的乙腈-0.01 mol·L^-1乙酸铵溶液的混合液为流动相，直接采用附荧光检测器的高效液相色谱法测定其中联苯胺的含量。结果表明，联苯胺的质量浓度在0.50~50.0 μg·L^-1内与对应的峰面积呈线性关系，检出限为0.20 μg·kg^-1。按标准加入法对空白土壤样品进行回收试验，回收率为75.9%~99.1%，测定值的相对标准偏差（n=6）均小于4.0%。

5.00 g of dry soil sample was taken and extracted ultrasonically for 30 min in 10 mL of methanol solution (as extractant) containing 1% (volume fraction) ammonia and 50 mg·L^-1 sodium thiosulfate (to prevent the oxidation of benzidine). Ice was added to keep the temperature below 10℃, and the mixture was settled for 10 min. 2.0 mL of the supernatant was taken and passed through 0.22 μm polytetrafluoroethylene needle filter. Benzidine in the filtrate was directly determined by high performance liquid chromatography with fluorescence detector, with ZORBAX C₁₈ reversed-phase chromatographic column as the stationary phase and a mixture of acetonitrile and 0.01 mol·L^-1 ammonium acetate solution at a volume ratio of 25:75 as the mobile phase. As shown by the results, linear relationship between values of peak area and mass concentration of benzidine was found in the range of 0.50-50.0 μg·L^-1, with detection limit of 0.20 μg·kg^-1. Test for recovery was made on blank soil sample by standard addition method, giving results in the range of 75.9%-99.1%, with RSDs (n=6) of the determined values less than 4.0%.