超声波萃取—气相色谱-质谱法测定土壤中7种酚类化合物

酚类化合物在土壤中含量低,且性质活泼,提取与分析比较困难。利用二氯甲烷-正己烷混合溶剂(V/V=2)作为溶剂,超声20 min提取了土壤中的有机成分。再利用酚类化合物中酚羟基的弱酸性,在提取液中加入pH>12的强碱性水溶液,使得酚类化合物与强碱反应生成对应的盐而溶于水,从而与有机相分离。在分离后的水相中加入二氯甲烷-正己烷混合溶剂(V/V=2)进行净化,进一步将碱性水溶液中的有机干扰组分除去。然后将溶液调至酸性(pH<3),用二氯甲烷/乙酸乙酯混合溶剂(V/V=4)萃取酚类化合物。最终,采用气相色谱-质谱法(GC-MS)对样品中的苯酚、2-氯酚、2-硝基酚、2,4-二甲基酚、2,4-二氯酚、4-氯-3-甲基酚、2,4,6-三氯酚共7种酚类化合物进行了测定。方法检出限为0.03～0.48 mg/kg。将方法应用于实际样品中7种酚类化合物的检测,结果的相对标准偏差(RSD,n=7)为1.6%～7.9%,加标回收率为82%～111%。

Determination of seven phenols in soil by gas chromatography-mass spectrometry after ultrasonic extraction

The content of phenols in soil was low. Moreover, their chemical properties were active. As a result, the extraction and analysis of phenols in soil were relatively difficult. The organic components in soil were extracted by ultrasonic for 20 min using dichloromethane and n-hexane (V/V=2) as mixed solvent. The strongly alkaline aqueous solution (pH>12) was added into extracting solution. The phenols could react with alkali to form corresponding water-soluble slats due to the weak acidity of phenolic hydroxyl groups. Therefore, the phenols could be separated from the organic phase. The dichloromethane and n-hexane (V/V=2) mixed solvent was added into water phase after separation for purification. The interference organic components in alkaline aqueous solution were further removed. Then, the solution was adjusted to acid (pH<3). The phenolic compounds were extracted with dichloromethane/n-hexane (V/V=4) mixed solvent. Finally, seven types of phenols (including phenol, 2-chlorophenol, 2-nitrophenol, 2,4-dimethylolphenol, 2,4-dichlorophen, 4-chlor-3-methylolphenol and 2,4,6-trichlorophenol) in sample were determined by gas chromatography-mass spectrometry (GC-MS). The detection limit of method was 0.03-0.48 mg/kg. The proposed method was applied to the detection of seven phenols in actual samples. The relative standard deviations (RSD,n=7) were between 1.6% and 7.9%, and the recoveries were between 82% and 111%.