摘要
基于乙腈-冷冻诱导液液萃取技术提取、净化和富集样品,以甲醇-水作为流动相,梯度洗脱程序,HSS T3色谱柱(2.1 mm×100 mm,1.8 μm)分离,高分辨质谱靶向单一离子监测模式测定,内标法定量。
7种OPEs在0.2~20 μg/L范围内呈良好的线性关系(
阻燃剂是一种可以防止易燃聚合物燃烧的化学助剂。近年来,作为已禁用的溴化阻燃剂替代品,有机磷酸酯类(Organophosphate esters,OPEs)阻燃剂已被广泛应用在食品包装、纺织品、电子设备及家具
目前检测OPEs的常见方法有气相色谱
分析OPEs时常用的前处理方法有超声萃取
基于以上背景,本研究拟开发一种同时分析牛奶中7种OPEs的检测方法。采用CI-LLE技术对样品进行提取、净化和富集处理,同时结合超高效液相色谱-高分辨质谱(Ultra high performance liquid chromatography-high resolution mass spectrometry,UPLC-HRMS)建立牛奶中OPEs的定性、定量分析方法,以期为液态奶中OPEs的监测工作提供准确、便捷的方法。
Dionex U3000/Q Exactive UPLC-HRMS、超低温冰箱(美国Thermo公司),Vortex Genie 2涡旋混合器(美国Scientific Industries公司),3K15离心机(德国Sigma公司)。
7种有机磷酸酯混合标准品溶液(10 mg/L):磷酸三(2-氯乙基)酯(TCEP,CAS 115-96-8)、磷酸三(2-氯丙基)酯(TCPP,CAS 1367-84-5)、磷酸三(1,3-二氯-2-丙基)磷酸酯(TDCP,CAS 13674-87-5)、磷酸三乙酯(TEP,CAS 78-40-0)、磷酸三丙酯(TPrP,CAS 513-08-6)、磷酸三丁酯(TnBP,CAS 126-73-8)、磷酸三苯酯(TPhP,CAS 115-86-6),纯度均>98%,购自美国Cambridge Isotope Laboratories(CIL)公司;7种同位素内标混合液(10 mg/L):磷酸三(2-氯乙基)酯-D12(TCEP-D12,CAS 1276500-47-0)、磷酸三(2-氯丙基)酯-D18(TCPP-D18,CAS 1447569-78-9)、磷酸三(1,3-二氯-2-丙基)磷酸酯-D15(TDCP-D15,CAS 1447569-77-8)、磷酸三乙酯-D15(TEP-D15,CAS 135942-11-9)、磷酸三丙酯-D21(TPrP-D21,CAS 1219794-92-9)、磷酸三丁酯-D27(TnBP-D27,CAS 61196-26-7)、磷酸三苯酯-D15(TPhP-D15,CAS 1173020-30-8),纯度均>98%,购自美国Cambridge Isotope Laboratories(CIL)公司。甲醇、乙腈、甲酸均为色谱纯,购自美国Fisher Scientific公司。试验用水由美国Millipore纯水仪制备。牛奶样品采购于超市和农贸市场。
分别准确移取100 μL混合标准和混合内标至1 mL容量瓶中,用乙腈稀释至刻度定容,作为中间液,混合标准中间液和内标混合中间液浓度均为1 mg/L,于-4 ℃贮存。
7种OPEs标准工作曲线:准确吸取适量混合标准中间液和混合内标混合中间液,用乙腈溶液稀释成质量浓度分别为0.2、0.5、1、5、10、20 μg/L的系列标准工作曲线,每个标准质量浓度点均含有50 μL 100 μg/L的混合同位素内标。
准确称取牛奶样品7 mL于15 mL离心管中,加入50 μL 100 μg/L混合同位素内标,涡旋混合60 s,加入4.5 mL乙腈混匀,置于-30 ℃冰箱冷冻处理40 min,待乙腈-水相分离后,吸取上层乙腈相1 mL,经13 000 r/min高速离心5 min后,取上清液检测分析。
色谱条件:HSS T3色谱柱(2.1 mm × 100 mm,1.8 μm),柱温40 ℃,流动相A:甲醇,B:水,梯度洗脱,流速为0.3 mL/min。梯度洗脱程序:0~1 min,30% A;1~8 min,30%~85% A;8~9.5 min,85% A;9.5~12 min,85%~99% A;12~12.1 min,99%~30% A;12.1~15 min,30% A,进样体积为5 μL。
质谱条件:采用HESI离子化方式;喷雾电压为3.5 kV;毛细管温度为320 ˚C;加热温度为400 ˚C;鞘气为40 arb(4 × 1
根据之前的研究,OPEs常用的流动相体系有甲醇-水体系和乙腈-水体

图 1 7种OPEs(2 μg/L)在tSIM模式下的色谱图
Figure 1 Extracted ion chromatograms of tSIM of seven OPEs (2 μg/L)
本研究还比较了高分辨质谱技术中全扫描采集(Full scan,FS)和靶向单一离子监测采集(Target single ion monitoring,tSIM)的定量检测模式。FS和tSIM采集模式均是以分析物的精确母离子信息进行定量。已有研究表明,由于质量范围窄,在低浓度水平下tSIM模式的检测灵敏度要明显优于FS模
分析物 | 保留时间/min | 母离子/(m/z) | 定性离子/(m/z) |
---|---|---|---|
TCEP | 6.57 | 284.961 2 | 160.976 7, 222.909 0 |
TCPP | 9.68 | 327.008 1 | 116.995 2, 174.992 3 |
TDCP | 5.63 | 428.891 2 | 158.963 9, 198.861 9 |
TEP | 10.33 | 183.078 0 | 127.015 7, 155.046 8 |
TPrP | 8.67 | 225.125 0 | 141.031 3, 165.054 9 |
TnBP | 9.76 | 267.172 0 | 155.048 7, 211.133 8 |
TPhP | 8.63 | 327.078 1 | 215.025 7, 233.036 8 |
TCEP-D12 | 6.55 | 297.036 5 | 130.030 1, 167.013 7 |
TCPP-D18 | 9.66 | 345.121 1 | 183.041 8, 264.177 9 |
TDCP-D15 | 5.61 | 443.985 3 | 215.996 4, 385.177 9 |
TEP-D15 | 10.31 | 198.172 2 | 134.059 2, 166.115 4 |
TPrP -D21 | 8.65 | 246.256 8 | 150.087 2, 198.171 6 |
TnBP -D27 | 9.75 | 294.341 4 | 123.024 0, 183.173 9 |
TPhP-D15 | 8.63 | 342.172 2 | 183.173 9. 221.116 6 |
已有研究发现,低温可以诱导乙腈与水产生相分离,且温度越低,相分离完成稳态的时间越
本研究首先分析了含20 μg/L OPEs的60%乙腈-水混合物在-30 ℃冷冻诱导后OPEs在上下层的分布情况。如

图2 OPEs在60%乙腈-水混合物中上层和下层的绝对回收率
Figure 2 Absolute recoveries of OPEs in the upper and lower layers of 60% acetonitrile-water mixtures
比较37%、38%、39%、40%和50%乙腈-水混合物比例的富集倍数和绝对回收率,结果见

图 3 7种OPEs在不同比例乙腈-水混合物中的富集倍数和绝对回收率
Figure 3 Enrichment factor and absolute recovery of seven OPEs at different proportion of acetonitrile-water mixture
此外,本试验还对不同冷冻诱导时间(30、40、50、60 min)的富集倍数和绝对回收率进行了优化,结果表明,当冷冻时间大于40 min以上时,乙腈-水的分层体积没有变化,并且OPEs的富集倍数和绝对回收率也无显著变化。因此本研究的冷冻诱导时间确定为40 min。
基质效应是影响分析方法灵敏度、精密度和准确度的关键参
分析物 | 线性范围/(μg/L) | 检出限/(μg/L) | 定量限/(μg/L) | 加标回收率/% | RSD/% | 基质效应 | |
---|---|---|---|---|---|---|---|
TCEP | 0.2~20 | 0.995 6 | 0.150 | 0.61 | 101.0~113.0 | 2.75 | 1.13 |
TCPP | 0.2~20 | 0.994 3 | 0.210 | 0.84 | 90.3~104.0 | 4.32 | 0.92 |
TDCP | 0.2~20 | 0.995 9 | 0.030 | 0.12 | 88.4~107.0 | 6.88 | 1.17 |
TEP | 0.2~20 | 0.994 6 | 0.430 | 1.72 | 94.3~114.0 | 7.15 | 1.11 |
TPrP | 0.2~20 | 0.996 2 | 0.015 | 0.061 | 97.0~115.0 | 2.27 | 1.14 |
TnBP | 0.2~20 | 0.996 7 | 0.046 | 0.18 | 90.6~117.0 | 1.15 | 1.08 |
TPhP | 0.2~20 | 0.995 3 | 0.012 | 0.048 | 107.0~118.0 | 3.98 | 1.13 |
配制质量浓度为0.2~20 μg/L的系列标准混合溶液,分别加入50 μL同位素内标混合液(100 μg/L)进行测定。结果如
以空白牛奶样品作为空白加标基质,选定低、中、高三个加标水平(0.2、0.4、2 μg/L),按照1.2.2方法处理样品,每个加标水平重复6次,考察方法的加标回收率和相对标准偏差(Relative standard deviation,RSD)。如
本研究采用已建立的方法对12种市售牛奶的OPEs进行测定,结果发现,除一份样品中检出TEP浓度为0.23 μg/L外,12份牛奶样品中未检出其它OPEs。

图 4 牛奶样品检出的TEP色谱图
Figure 4 The Chromatogram of TEP detected from milk sample
本研究采用CI-LLE技术作为牛奶样品的前处理技术,建立了牛奶样品中7种OPEs的高分辨质谱检测方法。该方法操作简单,重现性好,能显著降低基质效应对OPEs检测的影响,具有较高的灵敏度、准确度和精密度,为牛奶样品中OPEs的日常监测及食品中OPEs的检测方法开发奠定技术基础。
参考文献
YE L, SU G. Elevated concentration and high Diversity of organophosphate esters (OPEs) were Discovered in Sediment from Industrial, and E-Waste Recycling Areas[J]. Water Research, 2022, 217: 118362. [百度学术]
Murugavel R, Choudhury A, Walawalkar M G, et al. Metal complexes of organophosphate esters and open-framework metal phosphates: Synthesis, structure, transformations, and applications[J]. Chemical Reviews, 2008, 108(9): 3549-3655. [百度学术]
SANCHEZ C, ERICSSON M, CARLSSON H, et al. Determination of organophosphate esters in air samples by dynamic sonication-assisted solvent extraction coupled on-line with large-volume injection gas chromatography utilizing a programmed-temperature vaporizer[J]. Journal of Chromatography A, 2003, 993(1-2): 103-110. [百度学术]
Hou M M, Shi Y L, Na G S, et al. Increased human exposure to organophosphate esters via ingestion of drinking water from water dispensers: Sources, influencing factors, and exposure assessment[J]. Environmental Science & Technology Letters, 2021, 8(10): 884-889. [百度学术]
Bester K. Comparison of TCPP concentrations in sludge and wastewater in a typical German sewage treatment plant-comparison of sewage sludge from 20 plants[J]. Journal of Environmental Monitoring: JEM, 2005, 7(5): 509-513. [百度学术]
CUI K, WEN J, FENG Z, et al . Occurrence and distribution of organophosphate esters in urban soils of the subtropical city, Guangzhou, China[J]. Chemosphere, 2017, 175: 514-520. [百度学术]
LI J, ZHAO L, LETCHER R J, et al . A review on organophosphate Ester (OPE) flame retardants and plasticizers in foodstuffs: Levels, distribution, human dietary exposure, and future directions[J]. Environment International, 2019, 127: 35-51. [百度学术]
XING LQ, TAO M, ZHANG Q, et al . Occurrence, spatial distribution and risk assessment of organophosphate esters in surface water from the Lower Yangtze River Basin[J]. Science of the Total Environment, 2020, 734: 139380. [百度学术]
GUO X D, MU T N, XIAN Y P, et al. Ultra-performance liquid chromatography tandem mass spectrometry for the rapid simultaneous analysis of nine organophosphate esters in milk powder[J]. Food Chemistry, 2016, 196: 673-681. [百度学术]
徐怀洲, 王智志, 张圣虎, 等. 有机磷酸酯类阻燃剂毒性效应研究进展[J]. 生态毒理学报, 2018, 13(3): 19-30. [百度学术]
XU H Z, WANG Z Z, ZHANG S H, et al. Research progress on toxicity effects of organophosphate flame retardants[J]. Asian Journal of Ecotoxicology, 2018, 13(3): 19-30. [百度学术]
HOU R,XU Y,WANG Z. Review of OPFRs in animals and humans: Absorption, bioaccumulation, metabolism, and internal exposure research[J]. Chemosphere, 2016, 153: 78-90. [百度学术]
刘世龙, 张华, 胡晓辉, 等. 气相色谱-串联质谱法测定沉积物中有机磷酸酯[J]. 分析化学, 2016, 44(2): 192-197. [百度学术]
LIU S L, ZHANG H, HU X H, et al. Analysis of organophosphate esters in sediment samples using gas chromatography-tandem mass spectrometry[J]. Chinese Journal of Analytical Chemistry, 2016, 44(2): 192-197. [百度学术]
LIU Y E, HUANG L Q, LUO X J . Determination of organophosphorus flame retardants in fish by freezing-lipid precipitation, solid-phase extraction and gas chromatography-mass spectrometry[J]. Journal of Chromatography A, 2018, 1532: 68-73. [百度学术]
王成云, 谢堂堂, 肖来龙, 等. 微波辅助萃取-气相色谱法同时测定纺织品中6种禁用有机磷阻燃剂[J]. 分析试验室, 2011, 30(12): 38-41. [百度学术]
WANG C Y, XIE T T, XIAO L L, et al. Simultaneous determination of six banned organophosphorous flame retardants in textiles by gas chromatography combined with microwave-assisted extraction[J]. Chinese Journal of Analysis Laboratory, 2011, 30(12): 38-41. [百度学术]
董政, 马玉龙, 李珺琪, 等. 潍坊滨海经济技术开发区饮用水中有机磷酸酯的水平及人体暴露风险评估[J]. 环境科学, 2017, 38(10): 4212-4219. [百度学术]
DONG Z, MA Y L, LI J Q, et al. Occurrence and human exposure risk assessment of organophosphate esters in drinking water in the Weifang Binhai economic-technological development area[J]. Environmental Science, 2017, 38(10): 4212-4219. [百度学术]
DING J, DENG T, XU M. Residuals of organophosphate esters in foodstuffs and implication for human exposure[J]. Environmental Pollution, 2018, 233: 986-991. [百度学术]
张晓利, 麦晓霞, 周长征. 纺织品中磷酸三酯类化合物的超声提取-GC/MS检测[J]. 印染, 2017, 43(6): 39-45. [百度学术]
ZHANG X L, MAI X X, ZHOU C Z. Determination of several organophosphate esters in textiles by ultrasonic extraction combined with GC/MS[J]. Dyeing & Finishing, 2017, 43(6): 39-45. [百度学术]
YANG X, ZHANG H, LIU Y. Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography-mass spectrometry: Determination of 88 pesticides in berries using SPE and GC-MS[J]. Food Chemistry, 2011, 127(2): 855-865. [百度学术]
MIYAKE Y, TOKUMURA M, WANG Q, et al. Identification of novel phosphorus-based flame retardants in curtains purchased in Japan using orbitrap mass spectrometry[J]. Environmental Science & Technology Letters, 2018, 5(7): 448-455. [百度学术]
LI S H, CHEN D W, LV B, et al. One-step cold-induced aqueous two-phase system for the simultaneous determination of fipronil and its metabolites in dietary samples by liquid chromatography-high resolution mass spectrometry and the application in Total Diet Study[J]. Food Chemistry, 2020, 309: 125748. [百度学术]
LI S H, REN J, ZHANG Y P, et al. A highly-efficient and cost-effective pretreatment method for selective extraction and detection of perchlorate in tea and dairy products[J]. Food Chemistry, 2020, 328: 127113. [百度学术]
张恒, 郭昌胜, 吕佳佩, 等. 在线固相萃取-超高效液相色谱法检测水中14种有机磷酸酯[J]. 环境化学, 2020, 39(4): 1047-1054. [百度学术]
ZHANG H, GUO C S, LYU J P, et al. Determination of 14 organic phosphate esters in water by high performance liquid chromatography coupled with online solid phase extraction[J]. Environmental Chemistry, 2020, 39(4): 1047-1054. [百度学术]
TOLLBACK J, TAMBURRO D, CRESCENZI C, et al. Air sampling with Empore solid phase extraction membranes and online single-channel desorption/liquid chromatography/mass spectrometry analysis: Determination of volatile and semi-volatile organophosphate esters[J]. Journal of Chromatography A, 2006, 1129(1): 1-8. [百度学术]
彭凌峰, 赵芳, 申长鑫, 等. 超高效液相色谱-串联质谱法检测小龙虾中7种有机磷酸酯类阻燃剂. 食品安全质量检测学报, 2022, 13(8): 2405-2412. [百度学术]
PENG L F, ZHAO F, SHEN C X, et al. Determination of 7 kinds of organophosphate flame retardants in Procambarus clarkii by ultra performance liquid chromatography-tandem mass spectrometry[J]. Journal of Food Safety & Quality, 2022, 13(8): 2405-2412. [百度学术]
GU T, GU Y, ZHENG Y, et al. Phase separation of acetonitrile-water mixture in protein purification[J]. Separations Technology, 1994, 4(4): 258-260. [百度学术]