微波萃取-衍生化-气相色谱质谱联用法测定土壤中酚类化合物

土壤样品基质复杂且酚类化合物含量很低,未经衍生的酚在气相色谱中峰型和稳定性较差,灵敏度较低,应用衍生化的方法时流程复杂,耗时长。用二氯甲烷和正己烷混合溶剂(2∶1,V/V)作为溶剂,75 ℃微波20 min提取土壤中的酚类化合物,在提取液中加入pH>12的强碱性水,使得酚类化合物生成对应的盐溶于水,弃去有机相后,将得到的水相调节至pH<12,用二氯甲烷和乙酸乙酯混合溶剂(4∶1,V/V)萃取酚类化合物。提取液经五氟苄基溴衍生后采用气相色谱质谱联用法检测,内标法定量,建立了微波萃取-衍生化-气相色谱质谱联用法测定土壤中14种酚类化合物的方法。在最佳的衍生条件下,以10 g土壤样品计,方法中酚类化合物的检出限为0.002~0.006 mg/kg。按照实验方法测定土壤样品,加标回收率为73.2%～119%,结果的相对标准偏差(RSD,n=6)为3.0%～9.5%。方法简化了衍生化步骤,有效改善了各酚类化合物峰形,增强了检测的灵敏度和稳定性,可用于土壤中酚类化合物的测定。

Determination of phenolic compounds in soil by gas chromatography- mass spectrometry after microwave extraction and derivatization

The soil sample had complex matrix, and the content of phenol compounds was very low. If phenols were not derivatized, their peak shape and stability in gas chromatography were poor with low sensitivity. However, the derivatization methods were usually complex and time-consuming. The mixture of dichloromethane and n-hexane (2∶1, V/V) was used as solvent to extract phenol compounds in soil by microwave at 75 ℃ for 20 min. The strongly alkaline water (pH>12) was added into the extracting solution to convert phenol compounds into their corresponding salts, which were water soluble. After removing the organic phase, the aqueous solution was adjusted to pH<12. The phenol compounds were extracted with the mixture of dichloromethane and ethyl acetate (4∶1,V/V).Then the extracting solution was derived with pentafluorobenzyl bromide, and determined by gas chromatography-mass spectrometry with internal standard method. Thus, a method for determination of 14 types of phenolic compounds in soil was established by microwave extraction-derivatization-gas chromatography-mass spectrometry. Under the optimal derivatization conditions, the limits of detection for phenol compounds were 0.002-0.006 mg/kg in about 10 g of soil samples. The soil sample were determined according to the experimental method. The recoveries were between 73.2% and 119%. The relative standard deviations (RSD,n=6) of determination results were between 3.0% and 9.5%. The proposed method simplified the derivatization operation and effectively improved the peak shapes of phenol compounds. Moreover, the detection sensitivity and stability were enhanced. The proposed method could be applied for determination of phenol compounds in soil.