Separation of Sr, Nd, and U from Geological Samples Using Tandem Resin Column
-
摘要:
Sr、Nd、U等同位素体系被广泛应用于地球表生过程中年代测定及物源示踪等研究, 高效地分离这些同位素体系，对于推广这些同位素方法的应用具有重要现实意义。若要同时分析地质样品中Sr、Nd、U三种元素的同位素，现有方法往往需要消解两份样品，一份用于Sr-Nd而另一份用于U的分离提纯。这种方法不但增加了样品用量，而且需要多次蒸干溶液转换介质，既延长了分离流程也增加了样品被污染的风险。为了提高样品利用率和分析效率，本文通过将树脂柱串联改进了分离流程，提出一种仅需消解一份样品，便可同时提取Sr、Nd、U三种元素的新方法。本方法中Sr的分离采用Sr特效树脂，包含Nd在内的稀土元素(REE)的分离采用AG50W-X8树脂，U的分离采用UTEVA特效树脂。实验中将三种树脂柱串联，采用3mol/L硝酸淋洗液淋洗，同步进行平衡树脂、上样、洗杂志，避免了蒸干操作。分离后的淋出液使用电感耦合等离子体质谱仪(ICP-MS)测试元素含量。结果表明：U的回收率接近99.9%，Sr的回收率超过90%，Nd的回收率超过80%；同时三种树脂柱串联的分离流程，主要基体元素(K、Ca、Na、Ba、Fe、Rb等)的去除率均超过99%，降低了对Sr、Nd、U高精度同位素分析的干扰；REE中的Sm则可以通过后续使用Ln树脂等进一步去除。此外，本文还交换了Sr特效树脂和UTEVA树脂的位置，比对两种不同串联顺序对分离结果的影响，结果表明两种树脂柱串联顺序对目标元素的分离并无显著影响。使用该方法可以有效地实现Sr、Nd、U的分离，在减少操作步骤的同时节省约一半的样品用量，提高了同位素分析效率。
要点(1) 将树脂柱串联，采用相同淋洗液同步进行平衡树脂、上样、洗杂质，避免了蒸干操作。
(2) UTEVA特效树脂和Sr特效树脂的上下串联顺序，对Sr、Nd、U元素的回收率并无显著影响。
(3) 多次重复回收利用树脂可能导致树脂柱失效，影响对目标元素的吸附能力，需要及时更换新树脂。
HIGHLIGHTS(1) The resin columns are connected in series, and the same eluent is used to balance the resin, load the sample, and wash the impurities simultaneously, avoiding the operation of evaporation to dryness.
(2) Reversing the column positions, UTEVA column and Sr column, has no effect on Sr, Nd and U separation and the column recovery.
(3) Multiple reuse of resin can lead to resin column lapse, affecting the adsorption capacity of the target element, thus new resins should be used in a timely manner.
Abstract:BACKGROUNDUranium-series nuclides are one of the three major radioactive decay systems, which are suitable for studying various geological processes at different time scales. In addition, 87Sr/86Sr and 143Nd/144Nd isotopes (Sr-Nd isotopes for short) are two commonly used isotopes, for rock dating, chemical weathering assessment and tracing sediment sources. In this case, the combination of Sr-Nd-U isotopes can provide more comprehensively knowledge of the element cycle on the earth's surface and deepen our understanding of the sediment "Source to Sink"processes.
Most previous studies involving the Sr-Nd-U isotopes have been established by separating Sr-Nd and U isotopes respectively. In this way, the digestion operation must be performed twice, one for separating Sr-Nd and the other for separating U. Alternatively, if only one sample is digested for measuring all three isotopes, between each element separation, the residue must be dried and dissolved in another solution so as to start a new column work. The former increases the amount of samples, which is not conducive to analysis of precious and trace samples; the latter adds additional drying operation, which is time consuming and increases the risk of sample loss and contamination.
OBJECTIVESTo establish a new Sr-Nd-U combined separation scheme. In this method, only one sample is dissolved, avoiding solution transfer between each separation, so as to reduce sample amount and improve the efficiency of separation and purification of Sr-Nd-U isotopes.
METHODSA new chromatographic scheme of separating Sr-Nd-U with one sample digestion using a tandem column scheme is presented. Three columns were overlain sequentially to separate Sr in Sr Spec column, Nd in AG50W-X8 column and U in UTEVA column. 3mol/L HNO3 was used to pre-condition, load the sample, and rinse the matrix. After rinsing the matrix, the tandem column was separated to 3 independent columns to elute the target elements (Sr, Nd, U) respectively.
As the connection sequence of different resin columns may interfere with the recovery of target elements, two different chromatographic schemes were compared. In Scheme 1, U column was placed on top of Sr column, while in Scheme 2 the positions of U column and Sr resin column were exchanged. In both schemes, the AG50W-X8 resin column was set at the bottom as the cationic resin can adsorb the most complex elements.
All separated elution was tested for element concentration using inductively coupled plasma-mass spectrometry (ICP-MS). The basalt standard sample (BCR-2) was used to examine the behavior and recovery of each element in the separation procedure.
RESULTSA total of 10 fractions were recovered from the tandem column scheme, among which fraction 1 represented the leachate recovered by loading samples and rinsing matrix from the tandem three columns. Fraction 2, 5 and 8 represented the leachate recovered by Sr Spec resin, AG50W-X8 resin and UTEVA resin respectively rinsing matrix after separation of the three columns. Fraction 3, 6 and 9 represented the leachate recovered by Sr, REE and U columns, which was Sr, Nd and U collection. Fraction 4, 7 and 10 represented the leachate from each resin recycle stage.
In either Scheme 1 or Scheme 2, most matrix elements (high content of K, Ca, Na, Mg, Al, Fe, Ti and P and low content of Rb, Hf and Th) were mainly concentrated in fraction 1. The elution rate of Na, Ti, Rb and Hf was up to 99%. The elution rate of K and Ca was slightly lower at about 85% and the elution rate of Fe was about 56%. Sr was mainly concentrated in fraction 3, which contained only a small amount of P and Ba. Nd was mainly concentrated in fraction 6, which also contained both Sm and Ce. U was mainly concentrated in fraction 9, which only contained a very small amount of P and Pb. The column recovery was almost 99.9% for U, 90% for Sr and over 80% for Nd.
The removal rate of major matrix elements (K, Ca, Na, Ba, Fe, Rb, etc.) exceeded 99%, which reduced interference with high-precision isotope analysis of Sr, Nd, and U. The recovery and purity of Sr, Nd, U were all quite high. A very small amount of P and Ba in fraction 3 had no interference with Sr isotopes (87Sr/86Sr). The Rb which was isomorphism of Sr was removed completely. With regard to Sm and Ce in fraction 6, previous studies had shown that 142Ce could not interfere with Nd isotope (143Nd/144Nd), and Sm could be further separated by Ln resin, so as not to affect Nd isotopic test. Fraction 9 contained nearly 100% U with no other elements.
The sequence of resin column splicing is a crucial consideration which may impact the element separation. Hence, the position of Sr Spec column and UTEVA column was exchanged to compare the influence of different column sequences on eluting target elements. Both Scheme 1 and Scheme 2 can effectively wash off most of the matrix elements, and the target elements Sr, Nd and U can be efficiently adsorbed on the resin. There is no significant difference on target element separation between the two different column sequences. This indicates that Sr Spec and UTEVA resins do not interfere with each other on the target elements.
CONCLUSIONSThe new chromatographic scheme of separating Sr-Nd-U with one sample digestion using a tandem column scheme can be used to quickly and efficiently separate Sr, Nd and U elements from silicate rock samples. The recovery rate for U, Sr and Nd is 99.9%, 92.5% and 82.1%, respectively, which meet the requirements of subsequent isotope analysis. This Sr-Nd-U combined separation method can be used to reduce the sample consumption by about 50%, which is beneficial to the analysis of precious and trace samples. Meanwhile, as no solution transfer is needed between each column separation, this method can also save time for column work and increase the efficiency of chemical separation. A new idea for Sr-Nd-U multi-isotope separation is provided. If the recovery of Pb in the fraction 4 of this chromatographic scheme can be improved in further studies, the application of this new method may be expanded to more fields in the future.
-
Keywords:
- Sr /
- Nd /
- U /
- tandem resin column /
- column recovery /
- isotopic separation /
- inductively coupled plasma-mass spectrometry
-
多环芳烃(PAHs)是一种自然界中广泛分布的半挥发性有机污染物，该类化合物由两个及以上的苯环结构组成，其主要来源是化石燃料的不完全燃烧[1]。该类污染物对动物体具有较大的致癌、致畸、致突变的危害，其中致癌性最大的是4~6环的稠环PAHs[2]。该类化合物在环境中分布广泛，但由于环境基体复杂且其含量较低，很难直接、快速地对样品中PAHs进行分析[3-4]，常常需要结合样品前处理技术进行富集。常规的样品前处理方法，如索氏提取、加速溶剂提取、液液萃取等方式耗时长，且使用大量有机溶剂，容易对环境造成二次污染，因此有必要建立一种样品前处理过程高效绿色、分析检测快速灵敏的新方法。
固相微萃取(SPME)是一种集分离、富集、进样于一体的样品前处理技术[5-6]，在操作过程中避免了大量有机试剂的使用，在保证绿色环保的基础上具有提高目标物富集效率[7-10]的优点。已有很多研究者将SPME技术应用于PAHs的检测中并取得了较好的萃取效果[4, 11]。对于SPME技术而言，涂层的性能是制约萃取效率和目标分析物种类的关键因素[12-14]，是目前SPME技术研究的热点问题。金属有机骨架化合物(MOFs)是一类独特的多孔材料[15-16]，其永久性纳米孔隙率、高比表面积、均匀且可调节的孔径、易于功能化和表面改性[17]的特点，使MOFs材料在分离、气体储存、分子传感、富集和催化等方面具有广阔的应用前景[18-22]。然而，包括MOF-5和HKUST-1在内的MOFs材料在水溶液中稳定性较差，一定程度上了限制了它的实际应用。研究得到MIL-53(M=Al，Cr，Fe)是一种常见的金属骨架有机化合物，其中心金属离子可以是三价铁、铝或铬离子，配体为对苯二甲酸，是一类合成简便、性能优良、化学稳定性较好的MOFs材料，且在吸附水时其孔隙率没有明显变化[23]。Chen等[24]采用中性硅酮胶黏接法制备了MIL-53(Al，Cr，Fe)SPME涂层纤维，进行了浸入式萃取研究，并结合GC-MS/MS检测，结果显示三种MIL-53(M)涂层对PAHs都具有较好的萃取效率。该研究结果表明，该类水稳定性MOFs材料的SPME涂层对水样中芳香族化合物的富集和检测具有很好的应用前景，特别是对于浸入式萃取模式下萃取环境水样中难挥发的PAHs类物质具有较大的优势。传统的MOFs涂层制作方式，如水热原位沉积法、溶胶-凝胶法(sol-gel)、黏合固定法等往往存在步骤复杂、涂层机械强度较差等不足[21, 25-26]。
本研究在MOFs材料优良的吸附性能以及较好的水稳定性的基础上，采用金属基质材料原位自转化的方式[27]，在铁丝基质上直接生长MOFs涂层，该过程使得金属丝不仅作为支撑吸附剂的基质材料，而且还作为铁源参与MOFs材料的形成，不需要再添加金属盐，一定程度上节约了成本，避免重金属离子对环境的二次污染。将该涂层应用于环境水体中PAHs的萃取，并结合GC-MS进行检测，建立了环境水样中7种PAHs的SPME检测方法，以期为高效SPME涂层的简单、快速制备提供新思路。
1. 实验部分
1.1 材料和主要试剂
铁丝(直径为0.2mm，纯度99.9%，赛维精密金属材料有限公司)。
苯并(a)蒽(BaA，99.8%)；䓛(CHR，99.8%)；苯并(b)荧蒽(BbF，99.7%)；苯并(k)荧蒽(BKF，100%)；苯并(a)芘(BaP，99.8%)；茚苯(1, 2, 3-cd)芘(IPY，98.8%)；二苯并(a, n)蒽(DBA，98.3%)；苯并(ghi)芘(二萘嵌苯)(BPE，98.4%，美国AccuStandard公司)；100μm PDMS聚二甲基硅氧烷涂层(美国Supelco公司)。
对苯二甲酸(H2BDC，98%)、六水氯化铁(FeCl3·6H2O，麦克林生化科技有限公司)；三乙胺(TEA，国药集团)；超纯水；N, N-二甲基甲酰胺(DMF，国药集团)；乙醇(国药集团)。丙酮(美国Tedia公司)；甲醇(美国Tedia公司)。
上述试剂除丙酮和甲醇为色谱纯，其余试剂为分析纯。
1.2 仪器及工作条件
气相色谱-质谱仪(GCMS-QP2010plus，日本岛津公司)。该仪器测试PAHs条件：载气为高纯氦(99.999%)；色谱柱为Rtx-1MS(30m×0.25mm×0.25μm)；流量1.2mL/min，不分流进样；进样口260℃；离子源温度250℃；接口温度260℃；升温程序：初始温度50℃，保持2min，以20℃/min升至230℃，再以2.5℃/min升至250℃，保持2min。检测方式特征离子扫描(SIM)。
X射线粉晶衍射仪(D8-FOCUS，德国布鲁克科技有限公司)；傅里叶变换红外光谱仪(Nicolet 6700，美国ThermoFisher公司)；高分辨率场发射扫描电子显微镜(SU8010，日本日立公司)；全自动进样装置(MPS，德国Gerstel科技有限公司)。
1.3 实验方法
1.3.1 固相微萃取涂层IW@MIL-53(Fe)的制作
将直径为0.2mm的铁丝截为3cm的一段，置于10mol/L盐酸中反应15min，待反应至合适尺寸后取出铁丝，随后将其依次置于丙酮、甲醇、超纯水的条件下超声处理30min，取出铁丝于65℃烘箱中干燥12h备用。取0.65g对苯二甲酸溶于50mL N, N-二甲基甲酰胺中，加入5mL三乙胺，室温下搅拌15min；将反应液置于100mL高压反应釜中，将处理好的铁丝放入反应液中，并将密封好的高压反应釜置于180℃的条件下反应12h。将制作好的涂层置于100℃的真空烘箱中12h。将自制涂层在GC进样口280℃老化2h用以去除多余的溶剂。
1.3.2 金属有机骨架化合物多孔膜MIL-53(Fe)水热合成
将810mg六水氯化铁和498mg对苯二甲酸溶于15mL N, N-二甲基甲酰胺中，常温搅拌10min，置于50mL反应釜中150℃保持6h，带溶液冷却至室温后，超纯水清洗，转移至600mL超纯水中分散24h后，过滤，60℃烘干24h[23, 28-29]。
1.3.3 浸入式SPME过程
将制好的样品溶液转移到MPS自动进样平台特定区域，由自动进样器控制自制涂层装置在设定的萃取温度、萃取时间的条件下完成对PAHs的萃取，接着萃取了目标物的涂层被转移到GC-MS的进样口进行解吸分析。
1.3.4 实际样品采集和制备
样品一采自东湖(武汉)；样品二采自长江(武汉)。采集时间均为同一天的上午8:00~10:00。将采集的环境水样放置在25℃的室温下静置1h后经0.45μm微孔滤膜过滤，将处理好的水样取10mL于20mL顶空瓶中并放置在4℃的条件下备用。
2. 结果与讨论
2.1 自制IW@MIL-53(Fe)涂层表征
自制IW@MIL涂层通过扫描电子显微镜进行表征(图 1)。图 1a为经盐酸蚀刻的铁丝，可以看出经盐酸处理后铁丝表面呈“鳞片状”，该表面形状与光滑的铁丝表面相比，可以增大铁丝表面与反应液的接触面积；图 1b为经过水热反应后铁丝表面的变化，一层均匀的“树皮褶皱”材料覆盖在铁丝表面，铁丝反应前后直径无明显变化，由161μm变为163μm，局部放大(图 1c)可以看出该层状物质是由小的片状颗粒堆积而成；图 1d为该涂层的截面图，从该图中可以得出涂层平均厚度为10μm；为保护涂层外侧的吸附材料，避免在浸入式萃取过程中脱落和污染，涂层外涂覆了一层薄薄的中性硅酮胶加以固定，如图 1e、1f所示，通过与图 1b的对比，可以看出中性硅酮胶将吸附材料紧紧地包覆在胶层内部，其厚度约为15μm。
![]()
图 1 自制IW@MIL-53(Fe)涂层扫描电子显微镜图像a—铁丝；b—涂层表面；c—涂层表面细节放大图；d—涂层横截面；e—胶层包裹的涂层表面；f—胶层包裹的涂层横截面。Figure 1. SEM diagrams of self-made IW@MIL-53(Fe) coating从X射线衍射图谱(图 2a)可以看出，水热合成的MIL-53(Fe)与原位转化的材料在衍射峰的位置上对应良好，可以证明为同一种物质，表明铁丝上已原位转化出一层MIL-53(Fe)的薄膜。通过红外光谱图(图 2b)可以看出，红外光谱的所有振动带与水热合成的MIL-53(Fe)的数据吻合良好。红外光谱在近1645cm-1处表现出羧基的强烈伸缩振动，证明了对苯二甲酸中的—COOH基团与Fe金属离子成功结合。
![]()
图 2 水热合成MIL-53(Fe)与原位转化涂层的对比：(a)X射线衍射谱图对比; (b)红外光谱谱图对比Figure 2. Comparison between hydrothermal synthesis MIL-53(Fe) and self-made IW@MIL-53(Fe) coating: (a) X-ray diffraction diagrams; (b) infrared spectra2.2 自制IW@MIL-53(Fe)涂层萃取条件的优化
2.2.1 萃取温度
SPME在萃取的过程温度可以促进待测物在基质中的扩散以及扩大待测物的分配系数，加快与涂层之间的分配平衡，从而缩短达到平衡所需的时间。但随着温度的升高，涂层本身萃取相的分配系数也会下降，导致涂层灵敏度的降低[30-32]。为获取最佳的萃取温度以发挥SPME涂层最佳的萃取性能，实验中在萃取时间为50min，解吸温度为280℃，解吸时间为4min的条件下对萃取温度进行优化。图 3a结果表明，随着温度的升高，涂层的萃取性能也随之增强，直到80℃达到最佳性能，随之性能略有下降。因此该自制涂层的最佳萃取温度为80℃。
![]()
图 3 自制IW@MIL-53(Fe)涂层萃取条件的优化a—萃取温度；b—萃取时间；c—解吸时间；d—解吸温度。Figure 3. Optimization of extraction performance self-made IW@MIL-53(Fe) coating2.2.2 萃取时间
由于SPME技术是建立在平衡吸附基础上的样品前处理技术，需要使待测组分与萃取相达到平衡状态时，才能够保证测试数据的准确性和萃取过程的重现性。为保证在最短的时间内完成有效的萃取过程，实验设置了自制涂层在萃取温度为80℃，解吸温度为280℃，解吸时间为4min的条件下分别萃取5、10、20、25、30、40、50、60min。图 3b结果表明，随着时间的增加，自制涂层在萃取50min后逐渐达到萃取平衡。因此选取的最佳萃取时间为50min。
2.2.3 解吸时间
为确定一个最佳的解吸时间，实验在萃取温度为80℃，萃取时间为50min，解吸温度为280℃的条件下设置了1、2、3、4、5min五个解吸时间。图 3c结果表明，解吸4min后，涂层上的目标分析物已经解吸完全。因此该自制涂层的最佳解吸时间为4min。
2.2.4 解吸温度
SPME进样的解吸温度需要稍高于直接进样的温度，温度越高，涂层上的物质解吸得越完全，但这也存在着目标分析物分解以及高温降低涂层使用寿命的问题，因此解吸时不宜使用过高的温度。为确定一个合适的解吸温度，实验在萃取温度为80℃，萃取时间为50min，解吸时间为4min的条件下设置了240℃、250℃、260℃、270℃、280℃、290℃六个解吸温度进行测试。图 3d结果表明，解吸温度在280℃的条件下，测试性能最佳。因此该自制涂层的最佳解吸温度为280℃。
2.2.5 离子强度
无机盐的加入一方面可以改变样品溶液中的相界面性质，进而影响组分之间的分配系数；另一方面，加入无机盐之后样品溶液的离子强度增强，产生盐析效应，降低了目标分析物在溶液中的溶解度，有利于涂层的萃取。为了确定加入无机盐的用量，实验设计了萃取温度为80℃，萃取时间为50min，解吸温度为280℃，解吸时间为4min，以饱和食盐水为盐溶液的最大浓度，将其稀释为0%、15%、30%、50%、65%、80%、100%的氯化钠溶液。图 4结果表明，在氯化钠浓度为50%的条件下萃取效率达到最佳。因此该自制涂层的最佳盐浓度为50%的饱和氯化钠溶液。
2.3 自制IW@MIL-53(Fe)涂层性能评价
为了考察自制涂层的萃取性能，实验选取性能稳定的商用PDMS涂层为参照，以7种多环芳烃为目标分析物，在最优萃取条件下与商用100μm PDMS涂层萃取多环芳烃的性能进行了比较，对比结果如图 5a所示。实验结果表明，自制涂层的萃取性能略优于商用涂层1~2倍，表现出良好的萃取性能。同时比较了外涂的硅酮胶的吸附能力，得到IW@MIL-53(Fe)涂层的吸附性能主要是来自MIL-53(Fe)材料。
![]()
图 5 自制IW@MIL-53(Fe)涂层与商用100μm PDMS的(a)萃取性能和(b)使用寿命对比优化的实验条件：萃取温度80℃，萃取时间50min，解吸温度280℃，解吸时间4min，盐浓度50%。Figure 5. Comparison of (a) the extraction performance and (b) service life of self-made IW@MIL-53(Fe) coating with commercial 100μm PDMS为了测试涂层的使用次数，实验比较了涂层使用1次、60次、90次、120次萃取目标分析物的萃取性能，对比结果如图 5b所示。从图中可以看出，该涂层在使用120次之后萃取性能并没有明显下降，因此，该自制涂层具有较长的使用寿命，使用次数大于120次，显著优越于商用涂层的有效使用次数(< 80次)[33]。自制涂层良好的稳定性，是由于MIL-53(Fe)本身具有良好的水稳定性，此外外涂的硅酮胶也起到了很好的保护作用，避免了外层涂层材料的脱落，提高了涂层的重复使用次数。
在最佳的实验条件下，考察了IW@MIL-53(Fe)涂层结合GC-MS测定7种多环芳烃的分析性能(表 1)，得到该方法的检出限(LOD)为0.03~2.25ng/L，定量限(LOQ)为0.10~7.50ng/L，线性范围为250~10000ng/L，相关系数为0.9903~0.9991；同一根涂层测定结果的相对标准偏差(RSD，n=5)为3.1%~10.4%；不同根涂层测定结果的相对标准偏差(RSD，n=3)为3.0%~9.5%。
表 1 IW@MIL-53(Fe)涂层SPME-GC-MS分析7种PAHs的分析性能Table 1. Analysis performance of 7 kinds of PAHs by IW@MIL-53(Fe) coating with SPME-GC-MS分析物 线性范围(ng/L) R2 LOD (ng/L, S/N=3) LOQ (ng/L, S/N=10) RSD(%) 涂层内(n=5) 涂层间(n=3) BaA 250~10000 0.9991 0.03 0.10 3.1 6.7 CHR 250~10000 0.9922 0.13 0.43 6.2 3.0 BbF 250~10000 0.9922 0.11 0.37 8.9 5.7 BKF 250~10000 0.9903 0.26 0.87 5.2 5.5 BaP 250~10000 0.9933 0.36 1.20 7.7 6.0 IPY 250~10000 0.9962 1.50 5.00 10.4 9.5 BPE 250~10000 0.9982 2.25 7.50 10.4 2.5 2.4 实际样品分析
按照1.3节的实验方法，采用自制IW@MIL-53(Fe)涂层结合GC-MS分析方法对东湖和长江的实际水样进行分析，目标分析物浓度低于检出限，结果未检出。对样品进行加标回收实验，得到该方法的回收率为80.1%~108.5%(表 2)。
表 2 实际水样中PAHs分析结果Table 2. Analytical results of PAHs in actual water samples分析物 东湖水样 长江水样 浓度(ng/L) 加标浓度(ng/L) RSD (%, n=3) 回收率(%) 浓度(ng/L) 加标浓度(ng/L) RSD (%, n=3) 回收率(%) BaA ND 500 11.6 89.3 ND 500 3.5 80.1 CHR ND 500 8.0 102.3 ND 500 7.0 92.5 BbF ND 500 8.8 96.5 ND 500 10.6 84.6 BKF ND 500 5.5 91.1 ND 500 6.4 89.5 BaP ND 500 11.1 90.6 ND 500 9.6 83.0 IPY ND 500 8.6 91.8 ND 500 5.1 108.5 BPE ND 500 4.9 99.7 ND 500 14.4 91.8 注：ND表示未检出。 3. 结论
为了提高固相微萃取涂层的萃取效率和机械强度，本文通过原位自转化的方式在铁丝上生长出一层MIL-53(Fe)的MOFs膜，该方法在转化过程中，铁丝既作为涂层纤维的基质又可以为MIL-53(Fe)的生成提供铁离子，不需要向反应体系中额外添加金属盐。研究结果表明：采用金属基质原位自转化的方式制备固相微萃取涂层，具有涂层制备快速简便、环境友好、性质稳定等优点。
将该新材料用作固相微萃取涂层，以7种PAHs作为目标分析物，以浸入式萃取的模式并结合GC-MS作为检测手段验证了其萃取性能，应用于长江及东湖水样中PAHs的测定，得到加标回收率为80.1%~108.5%。建立的SPME-GC-MS方法实现了有机污染物的快速、灵敏检测，显示出良好的应用前景。
致谢: 感谢同济大学海洋与地球科学学院马松阳硕士对本文撰写提供的指导和建议，同时感谢两位匿名审稿人提出的宝贵意见。 -
![]()
图 1 Sr、Nd、U同位素联合分离流程示意图
步骤1：对三根树脂柱分别进行预清洗，降低本底。步骤2：三柱串联，同步进行平衡树脂、上样、洗杂质。步骤3：三柱分离单独淋洗接取目标元素。
Figure 1. Schematic diagrams of the combined Sr, Nd, U isotopes separation procedure.
![]()
图 2 方案一中Sr-Nd-U在不同馏分中的回收率
Figure 2. Recoveries of Sr-Nd-U in different fractions in procedure Ⅰ. The Sr and U recoveries are over 90%, while the Nd recovery is only 43.6% and need further separation with Sm.
![]()
图 3 方案二中Sr-Nd-U在不同馏分中的回收率
Figure 3. Recoveries of Sr-Nd-U in different fractions in procedure Ⅱ. The Sr and U recoveries are over 90%, while the Nd recovery is only 53.7% and need further separation with Sm.
![]()
图 4 更新AG50W-X8树脂后Nd的回收率
Figure 4. Nd recovery using renewed AG50W-X8 resin. The updated recovery for Nd is increased to 82.1%.
表 1 Sr、Nd、U同位素联合过柱分离流程
Table 1 Procedure of combined Sr, Nd, U isotopes separation
流程 分离步骤 树脂柱 淋洗试剂 试剂总体积
(mL)馏分
编号①
预清洗本底清洗 Sr特效树脂 3mol/L硝酸 6 - 超纯水 6 - 3mol/L硝酸 5 - 超纯水 5 - 3mol/L硝酸 5 - 超纯水 5 - AG50W-X8
树脂6mol/L盐酸 15 - 超纯水 5 - UTEVA特效
树脂3mol/L硝酸 4 - 3mol/L盐酸 4 - 3mol/L盐酸 4 - 超纯水 4 - ②
三柱串联平衡树脂 - 3mol/L硝酸 3 - 上样 3mol/L硝酸 2 1 洗杂质 3mol/L硝酸 6 ③
三柱分离洗杂质 Sr特效
树脂3mol/L硝酸 9 2 收集Sr 超纯水 4 3 回收树脂 6mol/L盐酸+超纯水 11 4 洗杂质 AG50W-X8
树脂2.5mol/L盐酸 4 5 收集REE 6mol/L盐酸 10 6 回收树脂 6mol/L盐酸 5 7 洗杂质 UTEVA特效
树脂3mol/L盐酸 6 8 收集U 1mol/L盐酸 4 9 回收树脂 超纯水+3mol/L硝酸 +3mol/L盐酸 +1mol/L盐酸 20 10 
下载: 导出CSV
-
[1] Bourdon B, Henderson G M, Lundstrom C C, et al. Uranium- series geochemistry[M]. Washington D C: Publisher Mineralogical Society of America, 2003.
[2] Li C, Francois R, Yang S, et al. Constraining the transport time of lithogenic sediments to the Okinawa Trough (East China Sea)[J]. Chemical Geology, 2016, 445: 199-207. doi: 10.1016/j.chemgeo.2016.04.010
[3] Martin A N, Dosseto A, May J H, et al. Sediment residence times in catchments draining to the Gulf of Carpentaria, northern Australia, inferred by uranium comminution dating[J]. Geochimica et Cosmochimica Acta, 2019, 244: 264-291. doi: 10.1016/j.gca.2018.09.031
[4] Li L, Liu X J, Li T, et al. Uranium comminution age tested by the eolian deposits on the Chinese Loess Plateau[J]. Earth and Planetary Science Letters, 2017, 467: 64-71. doi: 10.1016/j.epsl.2017.03.014
[5] Cogez A, Herman F, Pelt É, et al. U-Th and 10Be con-straints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia[J]. Earth Surface Dynamics, 2018, 6(1): 121-140. doi: 10.5194/esurf-6-121-2018
[6] Banner J L. Radiogenic isotopes: Systematics and appli-cations to earth surface processes and chemical stratigraphy[J]. Earth-Science Reviews, 2004, 65(3-4): 141-194. doi: 10.1016/S0012-8252(03)00086-2
[7] Tripathy G R, Singh S K, Krishnaswami S. Sr and Nd isotopes as tracers of chemical and physical erosion[M]//Handbook of environmental isotope geochemistry. Springer, 2012: 521-552.
[8] Anderson F S, Levine J, Whitaker T J. Rb-Sr resonance ionization geochronology of the Duluth Gabbro: A proof of concept for in situ dating on the Moon[J]. Rapid Communications in Mass Spectrometry, 2015, 29(16): 1457-1464. doi: 10.1002/rcm.7253
[9] Cao J Y, Yang X Y, Lu Y Y, et al. Zircon U-Pb and Sm-Nd geochronology and geochemistry of the Sn-W deposits in the northern Guposhan ore field, Nanling Range, southern China[J]. Ore Geology Reviews, 2020, 118: 103323. doi: 10.1016/j.oregeorev.2020.103323
[10] Xu Z K, Li T G, Clift P D, et al. Bathyal records of enhanced silicate erosion and weathering on the exposed Luzon shelf during glacial lowstands and their significance for atmospheric CO2 sink[J]. Chemical Geology, 2018, 476: 302-315. doi: 10.1016/j.chemgeo.2017.11.027
[11] Dou Y G, Yang S Y, Shi X F, et al. Provenance weathering and erosion records in southern Okinawa Trough sediments since 28ka: Geochemical and Sr-Nd-Pb isotopic evidences[J]. Chemical Geology, 2016, 425: 93-109. doi: 10.1016/j.chemgeo.2016.01.029
[12] Li J R, Liu S F, Shi X F, et al. Clay minerals and Sr-Nd isotopic composition of the Bay of Bengal sediments: Implications for sediment provenance and climate control since 40ka[J]. Quaternary International, 2018, 493: 50-58. doi: 10.1016/j.quaint.2018.06.044
[13] Hu S Y, Zeng Z G, Fang X, et al. Increasing terrigenous sediment supply from Taiwan to the southern Okinawa Trough over the last 3000 years evidenced by Sr-Nd isotopes and geochemistry[J]. Sedimentary Geology, 2020, 406: 105725. doi: 10.1016/j.sedgeo.2020.105725
[14] Li C, Yang S Y, Lian E G, et al. A review of com-minution age method and its potential application in the East China Sea to constrain the time scale of sediment source-to-sink process[J]. Journal of Ocean University of China, 2015, 14(3): 399-406. doi: 10.1007/s11802-015-2769-8
[15] Li L, Chen J, Chen Y, et al. Uranium isotopic constraints on the provenance of dust on the Chinese Loess Plateau[J]. Geology, 2018, 46(9): 747-750. doi: 10.1130/G45130.1
[16] Guéguen F, Stille P, Dietze V, et al. Chemical and isotopic properties and origin of coarse airborne particles collected by passive samplers in industrial, urban, and rural environments[J]. Atmospheric Environment, 2012, 62: 631-645. doi: 10.1016/j.atmosenv.2012.08.044
[17] 刘文刚, 刘卉, 李国占, 等. 离子交换树脂在地质样品Sr-Nd同位素测定中的应用[J]. 地质学报, 2017, 91(11): 2584-2592. doi: 10.3969/j.issn.0001-5717.2017.11.013 Liu W G, Liu H, Li G Z, et al. The application of ion exchange resins in Sr-Nd isotopic assay of geological samples[J]. Acta Geologica Sinica, 2017, 91(11): 2584-2592. doi: 10.3969/j.issn.0001-5717.2017.11.013
[18] 何连花, 张俊, 高晶晶, 等. 地质样品Sr和Nd同位素的化学分离方法改进[J]. 海洋科学进展, 2014, 32(1): 78-83. doi: 10.3969/j.issn.1671-6647.2014.01.009 He L H, Zhang J, Gao J J, et al. Improvement of the method for chemical separations of Sr and Nd in geological samples[J]. Advances in Marine Science, 2014, 32(1): 78-83. doi: 10.3969/j.issn.1671-6647.2014.01.009
[19] Rovan L, Štrok M. Optimization of the sample preparation and measurement protocol for the analysis of uranium isotopes by MC-ICP-MS without spike addition[J]. Journal of Analytical Atomic Spectrometry, 2019, 34(9): 1882-1891. doi: 10.1039/C9JA00144A
[20] Granet M, Chabaux F, Stille P, et al. U-series disequilibria in suspended river sediments and implication for sediment transfer time in alluvial plains: The case of the Himalayan Rivers[J]. Geochimica et Cosmochimica Acta, 2010, 74(10): 2851-2865. doi: 10.1016/j.gca.2010.02.016
[21] 廖泽波, 邵庆丰, 李春华, 等. MC-ICP-MS标样-样品交叉测试法测定石笋样品的230Th/U年龄[J]. 质谱学报, 2018, 39(3): 295-309. https://www.cnki.com.cn/Article/CJFDTOTAL-ZPXB201803005.htm Liao Z B, Shao Q F, Li C H, et al. Measurement of U/Th isotopic compositions in stalagmites for 230Th/U geochro-nology using MC-ICP-MS by standard-sample bracketing method[J]. Journal of Chinese Mass Spectrometry Society, 2018, 39(3): 295-309. https://www.cnki.com.cn/Article/CJFDTOTAL-ZPXB201803005.htm
[22] Pin C, Gannoun A, Dupont A. Rapid, simultaneous separation of Sr, Pb, and Nd by extraction chromatography prior to isotope ratios determination by TIMS and MC-ICP-MS[J]. Journal of Analytical and Atomic Spectrometry, 2014, 29(10): 1858-1870. doi: 10.1039/C4JA00169A
[23] Bast R, Scherer E, Sprung P, et al. A rapid and efficient ion-exchange chromatography for Lu-Hf, Sm-Nd, and Rb-Sr geochronology and the routine isotope analysis of sub-ng amounts of Hf by MC-ICP-MS[J]. Journal of Analytical and Atomic Spectrometry, 2015, 30(11): 2323-2333. doi: 10.1039/C5JA00283D
[24] Li C F, Wang X C, Guo J H, et al. Rapid separation scheme of Sr, Nd, Pb, and Hf from a single rock digest using a tandem chromatography column prior to isotope ratio measurements by mass spectrometry[J]. Journal of Analytical Atomic Spectrometry, 2016, 31(5): 1150-1159. doi: 10.1039/C5JA00477B
[25] Moragues-Quiroga C, Juilleret J, Gourdol L, et al. Ge-nesis and evolution of regoliths: Evidence from trace and major elements and Sr-Nd-Pb-U isotopes[J]. Catena, 2017, 149: 185-198. doi: 10.1016/j.catena.2016.09.015
[26] Aciego S M, Bourdon B, Lupker M, et al. A new proce-dure for separating and measuring radiogenic isotopes (U, Th, Pa, Ra, Sr, Nd, Hf) in ice cores[J]. Chemical Geology, 2009, 266(3-4): 194-204. doi: 10.1016/j.chemgeo.2009.06.003
[27] 韦刚健, 刘颖, 涂湘林, 等. 利用选择性特效树脂富集分离岩石样品中的锶钐和钕[J]. 岩矿测试, 2004, 23(1): 11-14. doi: 10.3969/j.issn.0254-5357.2004.01.003 Wei G J, Liu Y, Tu X L, et al. Separation of Sr, Sm and Nd in mineral and rock samples using selective specific resins[J]. Rock and Mineral Analysis, 2004, 23(1): 11-14. doi: 10.3969/j.issn.0254-5357.2004.01.003
[28] Wang R M, You C F. Precise determination of U isotopic compositions in low concentration carbonate samples by MC-ICP-MS[J]. Talanta, 2013, 107: 67-73. doi: 10.1016/j.talanta.2012.12.044
[29] Shao Q F, Pons Branchu E, Zhu Q P, et al. High precision U/Th dating of the rock paintings at Mt. Huashan, Guangxi, southern China[J]. Quaternary Research, 2017, 88(1): 1-13. doi: 10.1017/qua.2017.24
[30] 马松阳, 李超, 王晨羽, 等. 两种硅酸盐碎屑组分234U/238U测试前处理方法的比较及启示[J]. 矿物岩石地球化学通报, 2022, 41(1): 127-134. https://www.cnki.com.cn/Article/CJFDTOTAL-KYDH202201008.htm Ma S Y, Li C, Wang C Y, et al. The comparison of two pre-treatment methods for the 234U/238U measurement of silicate detrital fractions and its enlightment significance[J]. Bulletin of Mineralogy, Petrology and Geochemistry, 2022, 41(1): 127-134. https://www.cnki.com.cn/Article/CJFDTOTAL-KYDH202201008.htm
[31] Deng K, Yang S Y, Bi L, et al. Small dynamic moun-tainous rivers in Taiwan exhibit large sedimentary geochemical and provenance heterogeneity over multi-spatial scales[J]. Earth and Planetary Science Letters, 2019, 505: 96-109. doi: 10.1016/j.epsl.2018.10.012
[32] Xu J, Yang S Y, Yang Y H, et al. Determination of stable strontium isotopic compositions by MC-ICP-MS[J]. Atomic Spectroscopy, 2020, 41(2): 64-73. doi: 10.46770/AS.2020.02.003
[33] Misawa K, Yamazaki F, Ihira N, et al. Separation of rare earth elements and strontium from chondritic meteorites by miniaturized extraction chromatography for elemental and isotopic analyses[J]. Geochemical Journal, 2000, 34(1): 11-21. doi: 10.2343/geochemj.34.11
[34] Deniel C, Pin C. Single-stage method for the simultaneous isolation of lead and strontium from silicate samples for isotopic measurements[J]. Analytica Chimica Acta, 2001, 426(1): 95-103. doi: 10.1016/S0003-2670(00)01185-5
[35] 尹鹏, 何倩, 何会军, 等. 离子交换树脂法分离沉积物中锶和钕的影响因素研究[J]. 岩矿测试, 2018, 37(4): 379-387. doi: 10.15898/j.cnki.11-2131/td.201804170046 Yin P, He Q, He H J, et al. Study on the factors influencing the separation of Sr and Nd in sediments by ion exchange resin[J]. Rock and Mineral Analysis, 2018, 37(4): 379-387. doi: 10.15898/j.cnki.11-2131/td.201804170046
[36] 宗春蕾, 袁洪林, 戴梦宁. 一次溶样分离地质样品中Pb-Sr-Nd方法的可行性研究[J]. 岩矿测试, 2012, 31(6): 945-949. doi: 10.3969/j.issn.0254-5357.2012.06.005 Zong C L, Yuan H L, Dai M N. A feasibility study on chemical separation of Pb, Sr and Nd from the same single dissolution of geological sample[J]. Rock and Mineral Analysis, 2012, 31(6): 945-949. doi: 10.3969/j.issn.0254-5357.2012.06.005
[37] 刘婉, 李丹丹, 刘盛遨. 多接收器电感耦合等离子体质谱法测定土壤标准物质铜同位素组成[J]. 岩矿测试, 2021, 40(4): 561-569. doi: 10.15898/j.cnki.11-2131/td.202012130163 Liu W, Li D D, Liu S A. Determination of copper isotope composition of soil reference materials by MC-ICP-MS[J]. Rock and Mineral Analysis, 2021, 40(4): 561-569. doi: 10.15898/j.cnki.11-2131/td.202012130163
[38] Pin C, Gannoun A. A triple tandem columns extraction chromatography method for isolation of highly purified neodymium prior to 143Nd/144Nd and 142Nd/144Nd isotope ratios determinations[J]. Journal of Analytical Atomic Spectrometry, 2019, 34(2): 310-318. doi: 10.1039/C8JA00360B
[39] 朱志勇, 潘辰旭, 朱祥坤. 利用套柱法快速分离提纯Sr和Nd元素[J]. 岩矿测试, 2020, 39(4): 515-524. doi: 10.15898/j.cnki.11-2131/td.201908120126 Zhu Z Y, Pan C X, Zhu X K. Rapid purification of Sr and Nd for isotope analysis with multiple-column method[J]. Rock and Mineral Analysis, 2020, 39(4): 515-524. doi: 10.15898/j.cnki.11-2131/td.201908120126
[40] 杨岳衡, 张宏福, 谢烈文, 等. 多接收器电感耦合等离子质谱精确测定钕同位素组成[J]. 分析化学, 2007, 35(1): 71-74. doi: 10.3321/j.issn:0253-3820.2007.01.013 Yang Y H, Zhang H F, Xie L W, et al. Accurate measurement of neodymium isotopic composition using neptune multiple collector inductively coupled plasma mass spectrometry[J]. Chinese Journal of Analytical Chemistry, 2007, 35(1): 71-74. doi: 10.3321/j.issn:0253-3820.2007.01.013
[41] Li C F, Chu Z Y, Guo J H, et al. A rapid single column separation scheme for high-precision Sr-Nd-Pb isotopic analysis in geological samples using thermal ionization mass spectrometry[J]. Analytical Methods, 2015, 7(11): 4793-4802. doi: 10.1039/C4AY02896A
[42] Lin J, Liu Y S, Yang Y H, et al. Calibration and correction of LA-ICP-MS and LA-MC-ICP-MS analyses for element contents and isotopic ratios[J]. Solid Earth Sciences, 2016, 1(1): 5-27. doi: 10.1016/j.sesci.2016.04.002
[43] Pin C, Briot D, Bassin C, et al. Concomitant separation of strontium and samarium-neodymium for isotopic analysis in silicate samples, based on specific extraction chromatography[J]. Analytica Chimica Acta, 1994, 298(2): 209-217. doi: 10.1016/0003-2670(94)00274-6
[44] 袁永海, 杨锋, 余红霞, 等. 微波消解-多接收电感耦合等离子体质谱高精度测定锶钕同位素组成[J]. 岩矿测试, 2018, 37(4): 356-363. doi: 10.15898/j.cnki.11-2131/td.201707290122 Yuan Y H, Yang F, Yu H X, et al. High-precision measurement of strontium and neodymium isotopic composition by multi-collector inductively coupled plasma-mass spectrometry with microwave digestion[J]. Rock and Mineral Analysis, 2018, 37(4): 356-363. doi: 10.15898/j.cnki.11-2131/td.201707290122
[45] Zhu J M, Wu G L, Wang X L, et al. An improved method of Cr purification for high precision measurement of Cr isotopes by double spike MC-ICP-MS[J]. Journal of Analytical Atomic Spectrometry, 2018, 33(5): 809-821.
[46] Li X Q, Han G L, Zhang Q, et al. An optimal separation method for high-precision K isotope analysis by using MC-ICP-MS with a dummy bucket[J]. Journal of Analytical Atomic Spectrometry, 2020, 35(7): 1330-1339.
[47] Zhang Z Y, Ma J L, Zhang L, et al. Rubidium purification via a single chemical column and its isotope measurement on geological standard materials by MC-ICP-MS[J]. Journal of Analytical Atomic Spectrometry, 2018, 33(2): 322-328.
-
期刊类型引用(2)
1. 李丙阳，陈佳，邱洪灯. 骨架材料在固相微萃取方面的应用研究进展. 分析测试学报. 2025(02): 195-210 . 
百度学术
2. 乔淞汾，秦冲，刘爱琴，安彩秀，刘安，杨利娟，孙凯茜，冉卓. 超声萃取-高效液相色谱-串联质谱法测定土壤中三种硝基酚类化合物. 岩矿测试. 2024(03): 501-508 . 本站查看
其他类型引用(0)
计量
- 文章访问数: 162
- HTML全文浏览量: 54
- PDF下载量: 31
- 被引次数: 2
京公网安备 11010202008159号