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全氟/多氟化合物(PFASs)是一类人工合成的有机化合物,高键能的碳氟键和多样的极性基团赋予了该类化合物极强的物理和化学稳定性、疏水疏油性和低浓度时就能表现出的极佳表面活性[1-3]。在过去70年里,该类物质被广泛应用于各类产品中,并随着产品的生产、使用和处置过程进入到环境中[4-5]。多项研究表明PFASs在人体和其他生物体内具有极强的蓄积能力[6],并可能造成如生殖毒性[7]、神经毒性[8]、甲状腺激素干扰[9]等多种不良健康效应, 其带来的生态环境问题和人体健康风险引起了广泛的社会关注。目前,PFASs相关研究成为了世界环境科学研究的热点。
近年来,国内外已有大量研究报道了PFASs在水体[10-11]、大气[12]、灰尘[13]、土壤[14]、沉积物[15-16]等环境介质以及生物体内[17-18]的广泛存在。特别是PFASs极性和水溶性较高,易通过水环境进行扩散和传播。因此,现有研究多集中于不同类型水体中PFASs的检测、赋存和行为。然而,一些离子型PFASs也存在以细小的大气颗粒物为载体的长距离迁移现象,已有研究在干湿沉降样品中检出了PFASs的存在[19],表明大气环境也是PFASs传输和转化的重要介质,尤其与人类接触密切的低层大气更是发生PFASs生物暴露的主要场所[20]。目前,大气细颗粒物(PM2.5)作为最受关注的一类大气污染物,具有成分复杂、高比表面积、高环境活性以及长距离传输性,并且其往往成为众多污染物的高浓度载体[21-22],PFASs也不例外。因此,开展大气环境PM2.5中PFASs赋存水平及其相关环境问题研究,尤其是对二者的复合污染引起的人类健康风险具有重要的现实意义。高效的分析方法是开展PM2.5中PFASs环境科学研究的前提,尽管目前在大量使用的以水环境为主的PFASs的固相萃取(SPE)-高效液相色谱(HPLC)-串联质谱(MS/MS)分析方法也在PM2.5中PFASs的分析检测中获得一定的应用,但仍然存在一些不尽如人意之处。
一方面,目前少量PM2.5中PFASs 污染赋存的研究仅涉及传统PFASs[23-24]。然而近年来随着部分传统PFASs被禁用或限用,巨大的市场需求促使大量新型PFASs被研发作为替代品使用,如氯代多氟醚磺酸(Cl-PFESAs)被作为PFOS的替代产品应用于电镀行业。研究表明Cl-PFESAs已在各种水环境介质中广泛存在,且具有比传统PFASs更高的生物毒性和更长的人体半衰期[25-26]。但目前已有的PFASs方法未对许多新型PFASs全面覆盖。另一方面,大气颗粒物存在复杂的样品基体,这些基体是否会对PFASs的分析产生影响仍然没有明确的研究,这样在一定程度上制约了大气颗粒物中PFASs的准确分析以及相关环境科学研究。因此,研究PM2.5中包括一些新型PFASs在内的PFASs的分析方法及其关键影响因素,对获得准确可靠结果,理解PFASs大气环境赋存、行为和远距离传输具有重要意义。
本研究关注包括Cl-PFESAs在内的16种PFASs,比较了不同采样膜对PM2.5及其中PFASs的富集效率,考察了对方法可能产生影响的基质效应,通过优化色谱-质谱参数,建立了基于弱阴离子交换(WAX)SPE-HPLC-MS/MS的分析方法,为后续大气环境中PFASs的污染研究提供有效的方法支撑。
固相萃取-高效液相色谱-串联质谱法测定大气细颗粒物中全氟/多氟化合物
Determination of per- and polyfluoroalkyl substances in PM2.5 by high performance liquid chromatography-tandem mass spectrometry combined with solid phase extraction
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摘要: 大气细颗粒物(PM2.5)中全氟/多氟化合物(PFASs)浓度的测定对于了解大气环境中PFASs的赋存水平和远距离传输具有重要意义。本研究通过比较采样膜对PM2.5以及PFASs的富集效率差异,选取了效果最佳的石英纤维滤膜(QFF)为采样膜。利用基质提取液添加法对基质效应进行评估,发现样品基质对短链PFASs存在一定的信号抑制,通过采用相对应的内标可消除部分影响。最终优化建立了固相萃取-高效液相色谱-串联质谱(SPE-HPLC-MS/MS)同时测定PM2.5中包括氯代多氟醚磺酸(Cl-PFESAs)在内的16种PFASs的方法。PM2.5样品经甲醇超声-振荡萃取后,选用弱阴离子交换(WAX)固相萃取柱富集净化,使用Acclaim 120 C18色谱柱,以甲醇和50 mmol·L−1乙酸铵水溶液为流动相对目标PFASs进行梯度洗脱和分离,经电喷雾离子源离子化后在负离子多重反应监测模式(MRM)下进行检测。在优化的分析条件下,16种PFASs的方法检出限(MDLs)为0.09—1.53 pg·m−3,加标回收率为76.6%—122.3%,相对标准偏差为0.5%—13.1%。该方法灵敏度好,准确度高,适用于实际环境PM2.5中PFASs的分析检测。对北京市采暖期前后PM2.5中PFASs进行测定,结果表明∑PFASs浓度在8.9—101.3 pg·m−3之间,以PFOA和PFBA为代表的全氟烷基羧酸(PFCAs)为主,冬季采暖期PM2.5中PFASs污染水平有一定升高,其原因有待进一步研究。
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关键词:
- 高效液相色谱-串联质谱 /
- PFASs /
- PM2.5 /
- 基质效应 /
- 富集效率
Abstract: Determination of per- and polyfluoroalkyl substances (PFASs) in PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 micrometres) is important for understanding their occurrence and long-range transportation in the atmospheric environment. In this study, quartz fiber filter (QFF) was selected as the appropriate filter based on comparable findings of enrichment efficiency of PM2.5 and PFASs. The matrix effects of PFASs in PM2.5 were evaluated by post-extraction spiking method. The results indicated that matrix suppression was found for the measurement of short-chain PFASs, but it could be eliminated by using their corresponding mass labeled standards. The method was developed successfully for simultaneous determination of 16 PFASs, including chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs), in PM2.5 by using solid phase extraction (SPE) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Target PFASs in PM2.5 samples were extracted with methanol using ultrasonic and shaking, and then purified using weak anion exchange (WAX) cartridges. An Acclaim 120 C18 column was applied to separate all compounds. The mobile phase was the mixture of methanol and 50 mmol·L−1 ammonium acetate, which were run in a gradient program. The PFASs were detected using electrospray ionization tandem mass spectrometry (ESI-MS/MS) operated in negative and multiple reactive monitoring (MRM) mode. Under the optimized analysis condition, the method detection limits (MDLs) for 16 PFASs ranged from 0.09 pg·m−3 to 1.53 pg·m−3. Average recoveries of 16 PFASs in PM2.5 ranged from 76.6% to 122.3%, with relative standard deviations (RSDs) of 0.5%—13.1%. Hence, this method is accurate, sensitive and suitable for analysis of PFASs in PM2.5 from real environment. Moreover, the method was used to determine PFASs in PM2.5 around heating period in Beijing. It was found that the concentrations of ∑PFASs in PM2.5 ranged from 8.9 pg·m−3 to 101.3 pg·m−3. Perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA) were the predominant compounds. The concentrations of PFASs in heating period were higher than that before the heating period, the reason of which needs to be further studied.-
Key words:
- HPLC-MS/MS /
- PFASs /
- PM2.5 /
- matrix effect /
- enrichment efficiency
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表 1 16种PFASs的英文名称、缩写、化学式和对应内标
Table 1. Full names, abbreviations, formulas and mass labeled standards of 16 PFASs
化合物名称
Full name缩写
Abbreviation化学式
Formula对应内标
Mass labeled standardPerfluorobutanoic acid PFBA C4F7O2H 13C4PFBA Perfluoropentanoic acid PFPeA C5F9O2H 13C4PFBA Perfluorohexanoic acid PFHxA C6F11O2H 13C4PFOA Perfluoroheptanoic acid PFHpA C7F13O2H 13C4PFOA Perfluorooctanoic acid PFOA C8F15O2H 13C4PFOA Perfluorononanoic acid PFNA C9F17O2H 13C4PFOA Perfluorodecanoic acid PFDA C10F19O2H 13C2PFDA Perfluoroundecanoic acid PFUnDA C11F21O2H 13C2PFDA Perfluorododecanoic acid PFDoDA C12F23O2H 13C2PFDoDA Perfluorotridecanoic acid PFTrDA C13F25O2H 13C2PFDoDA Perfluorotetradecanoic acid PFTeDA C14F27O2H 13C2PFDoDA Perfluorobutanesulfonic acid PFBS C4F9SO3H 18O2PFHxS Perfluorohexanesulfonic acid PFHxS C6F13SO3H 18O2PFHxS Perfluorooctanesulfonic acid PFOS C8F17SO3H 13C4PFOS 6:2 Chlorinated Polyfluoroalkyl ether sulfonic acid 6:2 Cl-PFESA C8ClF16SO4 13C4PFOS 8:2 Chlorinated Polyfluoroalkyl ether sulfonic acid 8:2 Cl-PFESA C10ClF20SO4 13C4PFOS 表 2 PFASs及其同位素内标的质谱参数
Table 2. MS parameters of the PFASs and mas labeled standards
化合物
Compound母离子
Precursor ion
(m/z)子离子
Product ion
(m/z)解簇电压/V
Declustering
potential入口电压/V
Entrance
potential碰撞能量/V
Collision
potential碰撞出口电压/V
Collision cell
exit potentialPFBA 212.8 168.8 −15.5 −10 −16.2 −4.7 PFPeA 262.8 218.9 −21.5 −10 −15.5 −5.8 PFHxA 312.8 269.0 −18.7 −10 −15.6 −7.8 PFHpA 362.8 319.0 −23 −10 −13 −9 PFOA 412.8 369.0* −16.5 −10 −15.2 −10.4 412.8 168.8 −20.6 −10 −24.5 −4.4 PFNA 462.8 419.1 −31.4 −10 −19.1 −12.1 PFDA 512.8 469.1 −24.4 −10 −24 −7.4 PFUnDA 562.8 519.1 −23.4 −10 −30 −8.5 PFDoDA 612.8 569.0 −24 −10 −25.6 −9.2 PFTrDA 662.8 619.0 −33.4 −10 −24 −10.3 PFTeDA 712.8 669.0 −52.9 −10 −21.1 −11.2 PFBS 298.8 79.9* −71.2 −10 −51.2 −3.5 298.8 99.0 −70.2 −10 −40 −5.1 PFHxS 398.8 79.9* −75.3 −10 −66 −3.1 398.8 99.0 −72.6 −10 −51.4 −2 PFOS 498.8 79.9* −89.1 −10 −86.1 −3.4 498.8 99.0 −82 −10 −62.7 −2 6: 2 Cl-PFESA 530.6 351.0* −66 −10 −41.6 −9.8 530.6 83.0 −56 −10 −50.6 −1.6 8: 2 Cl-PFESA 631.0 451.2* −31 −10 −35 −7 631.0 83.2 −75 −10 −53 −4.3 13C4PFBA 216.9 171.9 −24 −10 −13.5 −4.8 13C4PFOA 416.8 372.1 −25.4 −10 −13.5 −5.45 13C2PFDA 515.0 470.0 −22.3 −10 −18.2 −13.2 13C2PFDoDA 614.8 570.0 −25.6 −10 −22 −9.4 18O2PFHxS 403.0 102.9 −81.2 −10 −48 −2.5 13C4PFOS 502.8 79.9 −91.8 −10 −78.3 −3.6 * 定量离子 Quantitative ion. 表 3 PM2.5中16种PFASs的加标回收率、相对标准偏差、方法检出限和定量限
Table 3. Recoveries, RSDs, MDLs and MQLs of the 16 PFASs in PM2.5
PFAS 加标浓度水平Spiked concentration 方法检出限/(pg·m−3)
MDL方法定量限/(pg·m−3)
MQL1 ng·mL−1 2 ng·mL−1 10 ng·mL−1 回收率/% RSD/% 回收率/% RSD/% 回收率/% RSD/% PFBA 112.3 5.9 93.5 4.2 100.9 2.5 0.28 0.88 PFPeA 101.4 9.6 85.3 7.5 118.9 3.9 0.23 0.69 PFHxA 106.7 5.2 93.3 2.2 98.7 12.1 0.18 0.55 PFHpA 99.6 7.1 89 4.8 99.3 12.1 0.14 0.46 PFOA 110 5.1 94.7 8.5 104.1 12.7 0.18 0.60 PFNA 76.8 13.1 88.8 4.1 94.9 9.2 0.09 0.28 PFDA 105.7 7.4 79.2 12.4 97.5 12.6 0.18 0.60 PFUnDA 122.3 5.3 98.7 11.9 113.2 5.6 0.09 0.28 PFDoDA 115.3 4.4 96 4.3 110.5 5.0 0.18 0.69 PFTrDA 92.7 7.1 92.8 1.6 100.2 7.7 0.32 1.02 PFTeDA 87.8 8.2 91 3.8 93.7 7.3 1.53 5.13 PFBS 116.3 3.5 99.1 5.3 90.9 5.4 0.09 0.23 PFHxS 104.3 5.8 101.2 7.2 98.7 9.6 0.09 0.32 PFOS 104.7 8.7 95.1 8.7 99.2 4.9 0.09 0.28 C8 Cl-PFESA 104.6 8.2 120.3 3.5 119.2 1.5 0.09 0.32 C10 Cl-PFESA 76.6 11.2 96.3 4.5 80.8 0.5 0.28 0.88 -
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