Determination of Phenols in Groundwater by Solid-Phase Membrane Extraction Combined with Ultrasonic Derivatization-negative Chemical Ionization Mass Spectrometry
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摘要: 酚类化合物由于极性较大，无法直接用气相色谱-质谱法测定，需要通过衍生来降低其极性，提高检测灵敏度；但是传统的衍生步骤繁琐，干扰因素多，操作难度大。本文对传统的前处理方法进行改进，建立了固相膜萃取、超声衍生负化学源质谱测定地下水中酚类化合物的方法。水样萃取后将萃取膜直接放入衍生瓶中，利用超声波的作用力将洗脱和衍生合二为一，超声完成后将溶液直接上机进行测定。测定低、中、高三个浓度水平的加标样品，各目标物的回收率均能达到70%~90%，检出限在0.25~0.35 μg/L之间，相对标准偏差小于10%，能够满足地下水中酚类物质的检测要求。本方法将洗脱和衍生集于一体，使用2 mL丙酮进行洗脱和衍生就可将全部目标物回收，简化了操作步骤，减少了有机溶剂的使用量；同时由于洗脱和衍生是在密闭的环境中进行，外界因素引入的干扰少，克服了二次污染的问题，测定数据更加可靠。Abstract: Due to their strong polarity, phenolic compounds cannot be directly determined by Gas Chromatography-Mass Spectrometry. Derivatization can reduce the strength of the polarity of phenols, and improve the detection sensitivity. However, the traditional derivative steps are tedious, with many interference factors and complex operations. By applying improvements to the traditional pretreatment method, phenols in groundwater were measured through solid-phase membrane extraction combined with Ultrasonic Derivatization-Negative Chemical Ionization Mass Spectrometry. The membrane was transferred into a derivative bottle after extraction, and then the elution and derivatization were processed simultaneously using ultrasound. The solution was determined by Gas Chromatography-Negative Chemical Ionization Mass Spectrometry directly. By determining the spiked samples at different concentration levels, the recoveries of the method for target components are in the range of 70%-90%, the detection limits are 0.25-0.35 μg/L and relative standard deviations (RSD) are less than 10%. The proposed method simplifies the traditional tedious steps by using 2 mL acetone for elution and derivation. All target objectives have good recoveries. Due to conducting the elution and derivation processes in an airtight environment, less interference factors were introduced without the problem of secondary pollution, and consequently the data were more reliable.
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表 1 定性定量主要参数
Table 1. The main qualitative and quantitative parameters
化合物 保留时间
(min)定量离子
(m/z)参考离子
(m/z)2-甲基苯酚 4.83 107 108 4-甲基苯酚 4.99 107 108 2-氯苯酚 5.35 127 128 4-氯-3-甲基苯酚 6.08 141 142 2,4-二氯苯酚 6.34 161 163 2,3,4,6-四氯苯酚 8.23 231 229,233 
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表 2 酚类化合物在不同萃取膜上的回收率
Table 2. Recoveries of phenols with different membranes
化合物 回收率(%) C18 C8 SDB-XC 2-甲基苯酚 7.7 9.9 78.9 4-甲基苯酚 14.6 10.5 82.5 2-氯苯酚 7.8 9.1 83.7 4-氯-3-甲基苯酚 15.7 63.4 89.1 2,4-二氯苯酚 9.7 64.9 91.2 2,3,4,6-四氯苯酚 25.6 72.3 83.4
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表 3 超声时间、超声功率和衍生温度对回收率的影响
Table 3. Effect of ultrasonic time, power and derivization temperature on recovery
化合物 不同衍生时间下的回收率(%) 不同功率下的回收率(%) 不同温度下的回收率(%) 10 min 30 min 40 min 50 min 280 W 420 W 490 W 560 W 30℃ 40℃ 50℃ 60℃ 2-甲基苯酚 32.3 57.6 81.3 79.9 46.2 53.3 65.4 78.9 65.2 71.2 78.2 79.5 4-甲基苯酚 25.7 48.1 79.4 81.3 46.9 56.6 72.3 82.5 61.3 69.5 79.9 80.1 2-氯苯酚 39.2 52.7 78.9 82.6 47.3 61.9 78.1 83.7 67.4 70.9 82.7 81.9 4-氯-3-甲基苯酚 20.9 47.4 89.7 88.2 35.6 53.2 79.4 89.1 52.8 55.4 88.5 87.3 2,4-二氯苯酚 34.8 57.9 90.8 89.7 42.8 69.1 78.2 91.2 59.9 62.9 89.7 90.2 2,3,4,6-四氯苯酚 32.5 47.3 85.9 81.7 45.6 59.7 72.1 83.7 62.7 73.1 83.1 85.3
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表 4 碳酸钾的加入量对回收率的影响
Table 4. Effect of K2CO3 dosage on recovery
化合物 300 g/L碳酸钾不同
加入量的回收率(%)100 g/L碳酸钾
加入量为200 μL
的回收率(%)10 μL 20 μL 30 μL 50 μL 2-甲基苯酚 10.2 47.8 78.9 80.1 65.1 4-甲基苯酚 13.1 50.2 82.5 81.3 72.3 2-氯苯酚 11.3 49.1 83.7 82.7 55.9 4-氯-3-甲基苯酚 12.9 63.1 89.1 90.2 61.2 2,4-二氯苯酚 10.8 55.3 91.2 92.1 60.7 2,3,4,6-四氯苯酚 15.9 63.1 83.4 81.8 71.3
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表 5 方法线性范围、相关系数、方法检出限
Table 5. The linearity range, correlation coefficient and LOD
化合物 线性范围
(μg/L)相关系数 检出限
(μg/L)2-甲基酚 10.0~500.0 0.995 0.25 4-甲基酚 10.0~500.0 0.995 0.31 2-氯苯酚 10.0~500.0 0.997 0.28 4-氯-3-甲基苯酚 10.0~500.0 0.996 0.35 2,4-二氯苯酚 10.0~500.0 0.998 0.27 2,3,4,6-四氯苯酚 10.0~500.0 0.995 0.30
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表 6 方法回收率及精密度
Table 6. Recovery and precision tests of the method
化合物 低浓度0.1 μg/L 中浓度0.5 μg/L 高浓度2.0 μg/L 回收率
(%)RSD
(%)回收率
(%)RSD
(%)回收率
(%)RSD
(%)2-甲基酚 71.2 6.9 81.6 5.7 82.2 5.0 4-甲基酚 72.3 7.1 77.7 6.2 83.9 5.3 2-氯苯酚 72.5 6.7 81.2 5.3 84.5 4.6 4-氯-3-甲基苯酚 75.2 7.3 81.6 6.3 87.1 5.7 2,4-二氯苯酚 78.1 8.3 85.1 8.7 87.8 7.3 2,3,4,6-四氯苯酚 74.9 9.6 76.5 8.8 83.1 7.2
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