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烷基酚类化合物(alkylphenols, APs)是典型的内分泌干扰物,具有环境雌激素活性. 壬基酚、辛基酚等可通过食物链进入人体,具有致癌和破坏生殖系统等严重毒性,已被联合国环境规划署列入持久性有毒污染物清单[1]. 而作为环氧树脂等工业原料起始物的双酚A(BPA)也可与细胞内雌激素受体结合,干扰生物体内分泌系统,诱发动物性别紊乱或生殖系统障碍[2 − 3].
由于工业上的普遍应用,烷基酚和双酚A等已在环境中广泛分布,且不同环境介质中污染物含量存在较大差异,因此检测方法很难统一[4]. 目前常用的前处理方法包括加速溶剂萃取、QuEChERS、液液萃取等[5 − 7]. 常用的检测方法有液相色谱法[8 − 9]、液相色谱串联质谱法[10 − 11]、气相色谱质谱法[12 − 14]等. 但这些方法主要针对水质、饮料、鱼类、谷物、尿液等介质中APs、BPA的测定. 此外,D7065[15]、D7574[16] 、HJ1192-2021[17]等环境标准仅针对水样中壬基酚、双酚A、对叔辛基苯酚等目标物进行测定,研究对象相对单一.
环境中沉积物样品基质更复杂,内分泌干扰物含量更低,样品前处理和检测方法建立更为困难. 目前针对沉积物中同时测定APs和BPA的相关研究相对较少[18 − 20],标准检测方法仍未建立. 因此,有必要建立高效、快速、准确的测定方法,为沉积物中APs和BPA的赋存状况和潜在风险提供数据支撑. 本文以沉积物中APs和BPA为研究对象,通过优化目标物提取、净化等条件,建立了加速溶剂萃取-固相萃取净化结合气相色谱质谱法测定沉积物中APs和BPA的检测方法,进一步评估该方法的检出限、精密度和回收率等方法学参数,应用于天津某河流沉积物中APs和BPA的测定.
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气相色谱仪(GC 8890, Agilent公司);质谱仪(MS 5977B EI源, Agilent公司);色谱柱:HP-5MS UI(30 m×250 μm×0.25 μm, Agilent公司);加速溶剂萃取(E-916, BUCHI公司);旋转蒸发仪(Rotavapor R-300 EL, BUCHI公司);氮吹仪(EFAA-DC24-RT, ANPEL公司);冷冻干燥机(Alpha1-4 LDplus,CHRIST公司);电子天平(LS120Ascs, Precisa公司);硅胶柱(1 g, CNWBOND公司);HLB柱(500 mg,Waters公司);C18柱(500 mg, CNWBOND公司);弗罗里硅土柱(1 g, CNWBOND公司).
酚类标准贮备液(双酚A、4-叔丁基苯酚、4-丁基苯酚、4-戊基苯酚、4-己基苯酚、4-叔辛基苯酚、4-庚基苯酚、4-正辛基苯酚、4-壬基酚质量浓度均为1000 mg·L−1,安谱璀世公司);内标标准贮备液(2, 5-二溴甲苯、2, 2’, 5, 5’-四溴联苯质量浓度均为1000 mg·L−1,安谱璀世公司);石英砂(25-40目,国药集团);硅藻土(安谱璀世公司);丙酮、正己烷、二氯甲烷(均为色谱纯,Fisher公司).
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微量注射器准确吸取适量的酚类标准贮备液(或内标标准贮备液),用二氯甲烷稀释并定容,摇匀,制成10 mg·L−1的酚类标准中间液(或100 mg·L−1的内标标准中间液).
混合标准工作溶液系列:使用微量注射器准确吸取适量的酚类和内标标准中间液,用二氯甲烷稀释并定容1 mL,摇匀,制成10、50、100、200、500、1000、2000 μg·L−1的混合酚类标准系列溶液,内标质量浓度均为1000 μg·L−1.
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将沉积物样品进行冷冻干燥、研磨、过0.25 mm孔径的金属筛,均化处理成250 μm(60目)左右的颗粒. 称取10.00 g沉积物样品使用加速溶剂萃取进行前处理,使用丙酮-二氯甲烷(V/V = 1/2)进行目标物提取,设置萃取温度为100℃,萃取压力为1000 psi,提取次数为2次.
上述提取液浓缩至2 mL,转移至硅胶柱进行净化. 使用甲醇(5 mL)对硅胶柱进行活化;将浓缩后的提取液转移至硅胶柱后,依次使用丙酮(2 mL)和二氯甲烷(8 mL)对其进行洗脱;洗脱液浓缩至1 mL,加入与标准工作溶液相同浓度的内标,待测.
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色谱条件:进样口温度250℃;进样口方式不分流;流速1.0 mL·min−1;进样量1 μL;程序升温35℃,以40℃·min−1升至170℃(保持10 min),以10℃·min−1升至310℃. 分析条件见表1. 质谱条件:传输线温度270℃,离子源230℃,四极杆150℃.
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对比了索氏提取、超声振荡萃取及加速溶剂萃取对沉积物样品中APs和BPA的提取效率. 索氏提取的提取时间长,不适合批量样品提取;超声振荡萃取回收率相对较低;而加速溶剂萃取通过高温高压下将目标物溶解并迅速萃取,提取效率高、操作时间短,且有机溶剂用量少. 因此选用加速溶剂萃取进行样品提取.
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APs和BPA均含酚羟基,需要极性较强的溶剂进行提取. 以加标APs和BPA质量分数为100 μg·kg−1的石英砂为待测对象,萃取温度100℃条件下,按照1.2.2对样品进行提取. 分别考察丙酮-正己烷(V/V =1/1)、正己烷-二氯甲烷(V/V =1/1)、丙酮-二氯甲烷(V/V =1/1)、丙酮-二氯甲烷(V/V =1/2)条件下,不同提取溶剂对回收率的影响. 结果显示,APs在不同溶剂比例下均获得了良好回收率(82.7%—97.4%),且当溶剂中含有二氯甲烷时,BPA的提取效率明显提高,因此,本文选择丙酮-二氯甲烷(V/V =1/2)作为萃取溶剂进行后续测试.
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萃取温度直接影响提取效率. 采用丙酮-二氯甲烷(V/V =1/2)为萃取溶剂,选取60℃、80℃、100℃、120℃的温度梯度进行对比. 结果显示,双酚A的回收率在这4个温度梯度下没有显著变化,而烷基酚的回收率随温度升高而逐渐升高. 综合选择100℃作为萃取温度.
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对比了HLB柱、C18、氟罗里硅土净化柱、硅胶柱的净化效率. 配制加标APs和BPA质量分数为100 μg·kg−1的石英砂样品,按照1.2.2的前处理条件,分别选择HLB柱、C18、氟罗里硅土净化柱、硅胶柱进行净化. 结果表明,使用硅胶柱时目标物回收率介于89.8%—107%之间,回收率良好. 因此选择硅胶柱作为净化柱对目标物进行测定.
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对比了HP-5(30 m × 250 μm × 0.25 μm,Agilent公司)和HP-5MS UI(30 m × 250 μm × 0.25 μm,Agilent公司)两个色谱柱的分离效果. 结果显示二者均可达到基线分离,但使用HP-5色谱柱时目标物色谱峰存在明显拖尾,因此选择HP-5MS UI作为本方法的色谱柱(图1).
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按照1.2.3的仪器条件,对烷基酚和双酚A标准溶液系列进行测定. 以目标物浓度为横坐标,以目标物与内标物定量离子响应值的比值和内标化合物质量浓度的乘积为纵坐标,绘制标准曲线. 结果表明各目标物在质量浓度为10—2000 μg·L−1范围内,线性关系良好,相关系数均大于0.9994. 石英砂中加入20 μL质量浓度为10 mg·L−1的APs和BPA混合标准溶液,以3.143倍标准偏差(s)计算检出限(3.143s),试验平行重复分析7次,结果见表2.
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按照1.2.3的仪器工作条件,对200 μg·L−1,500 μg·L−1的烷基酚和双酚A混合标准溶液分别进行精密度试验,计算各目标物测定值的RSD,试验平行重复测定7次.
向石英砂中分别加入100 μL、200 μL质量浓度为10 mg·L−1的APs和BPA混标溶液,制备石英砂加标样品. 对石英砂加标样品(加标量为1.0 μg、2.0 μg的APs和BPA),按照1.2.2试验方法分别重复测定7次,计算回收率. 各目标物测定值的RSD为1.9%—5.4%,回收率为85.7%—99.5%,该方法的精密度和准确度较好.
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按照1.2的实验条件对天津某河流沉积物样品进行测定,并进行了加标回收试验,所有样品均平行测定3次,取平均值进行回收率分析. 样品中检出了4-丁基苯酚、4-叔辛基苯酚、4-壬基酚、双酚A,检出量分别为4.8、10.9、7.4、6.9 μg·kg−1. 目标物回收率在84.5%—97.4%之间,准确性好.
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本文建立了加速溶剂萃取-硅胶柱净化-GCMS测定沉积物中的烷基酚和双酚A的检测方法. 分别对提取溶剂、萃取温度、净化色谱柱、气相色谱质谱参数进行优化,结果显示该方法重现性好、准确度高. 采用该方法对天津某河流沉积物样品进行分析,检出了4-丁基苯酚、4-叔辛基苯酚、4-壬基酚和双酚A,实际样品中APs和BPA的加标回收率为84.5%—97.4%. 结果表明,使用该方法检测沉积物中的BPA和APs,操作简单,灵敏度高,准确性和重现性良好,可满足沉积物样品中痕量APs和BPA的检测需要.
气相色谱-质谱法测定沉积物中的烷基酚和双酚A
Determination of alkylphenols and bisphenol A in sediment by gas chromatography-mass spectrometry
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摘要: 本文以内分泌干扰物烷基酚和双酚A为研究对象,使用加速溶剂萃取-硅胶柱净化-气相色谱质谱联用仪,建立了同时测定沉积物中8种痕量APs和BPA的检测方法. 沉积物样品经冷冻干燥后,用丙酮-二氯甲烷(V/V=1/2)为萃取溶剂,在100℃下进行加速溶剂萃取. 萃取液浓缩后使用硅胶柱净化,经气相色谱分离、质谱检测,根据保留时间、质谱碎片及其丰度定性,内标法定量. 结果显示,待测物在10—2000 μg·L−1范围内线性关系良好,相关系数大于0. 9994,检出限在0. 6—1.9 μg·kg−1之间. 目标物在200、500 μg·L−1标准溶液中相对标准偏差(n=7)为1.9%—5.4%,加标样品回收率为85.7% — 99.5%. 用本方法检测天津某河流的沉积物样品,4-丁基苯酚、4-叔辛基苯酚、4-壬基酚、双酚A被检出,实际样品中APs和BPA的加标回收率为84.5%—97.4%. 实验表明,使用该方法检测沉积物中的APs和BPA,操作简便,灵敏度高,准确性和重现性良好,可满足沉积物中痕量APs和BPA的检测需要.Abstract: A method was developed for the simultaneous determination of 8 trace APs and BPA in sediments by accelerated solvent extraction, silica gel column purification and gas chromatography-mass spectrometry. After freeze-drying, the samples were extracted with acetone-dichloromethane (V/V=1/2) as the extraction solvent under 100℃. The extracts were purified by silica gel column, separated by gas chromatography and detected by mass spectrometry, qualitatively determined according to retention time, mass spectrum and abundance of fragments, and quantified by internal standard methods. The results showed that the target compounds showed a good linear relationship in the range of 10—2000 μg·L−1, and the correlation coefficients were greater than 0.9994, and the limits of detections (LODs) were between 0.6 and 1.9 μg·kg−1. The relative standard deviations (RSDs, n=7) of the compounds in 200 μg·L−1 and 500 μg·L−1 standard solutions were in the range of 1.9% —5.4%, and the spiked recoveries were in the range of 85.7%—99.5%. And the method was applied to the detection of sediment samples from a river in Tianjin. And 4-butylphenol, 4-tert-octylphenol, 4-nonylphenol and bisphenol A were detected. In addition, the spiked recoveries of APs and BPA in the actual samples were in the range of in the range of 84.5%—97.4%. The results show that this method was simple, high in sensitivity and recoveries, good in accuracy and reproducible, and could meet the requirements of trace APs and BPA detection in sediment samples.
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Key words:
- Gas chromatography-mass spectrometry /
- alkylphenols /
- bisphenol a /
- sediment.
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表 1 烷基酚和双酚A的色谱条件
Table 1. Gas chromatography conditions for alkylphenols and bisphenol A
序号 目标物
AnalyteCAS号
CAS Number保留时间/min
Retention time定量离子(m/z)
Quantitative ion定性离子(m/z)
Qualitative ion1 4-叔丁基苯酚 98-54-4 4.78 135 107, 150 2 2,5-二溴甲苯(内标) 615-59-8 4.98 250 169 3 4-丁基苯酚 1638-22-8 5.23 107 150, 77 4 4-戊基苯酚 14938-35-3 6.06 107 164, 77 5 4-己基苯酚 2446-69-7 7.06 107 178, 108 6 4-叔辛基苯酚 140-66-9 7.75 135 107, 136 7 4-庚基苯酚 1987-50-4 8.13 107 192, 108 8 4-正辛基苯酚 1806-26-4 9.26 107 206, 108 9 4-壬基酚 104-40-5 10.37 107 220, 108 10 双酚A 80-05-7 13.34 213 228, 214 11 2,2',5,5'-四溴甲苯(内标) 59080-37-4 14.42 150 470 表 2 APs和BPA的线性方程、相关系数和检出限
Table 2. Linear equations, correlation coefficients and LOD of APs and BPA
目标物
Analyte线性方程
Linear equations相关系数
Correlation coefficient检出限/(μg·kg−1)
LOD4-叔丁基苯酚 y = 2.367546 x+ 0.072127 0.9995 0.8 4-丁基苯酚 y = 3.369165 x+0.127832 0.9996 0.7 4-戊基苯酚 y = 3.098017 x+ 0.081144 0.9998 0.6 4-己基苯酚 y = 2.890772 x+0.114997 0.9997 0.8 4-叔辛基苯酚 y = 2.434008 x+0.035877 0.9998 1.0 4-庚基苯酚 y = 2.640321 x+ 0.116284 0.9997 0.7 4-正辛基苯酚 y = 2.471447 x+ 0.108059 0.9996 0.8 4-壬基酚 y = 1.656250 x+ 0.066811 0.9996 1.9 BPA y = 0.840793 x+ 0.078697 0.9994 1.4 -
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