A method for testing rare earth elements in marine sediment pore water

Abstract

This invention discloses a method for testing rare earth elements in marine sediment pore water. This method, belonging to the field of chemical analysis technology, specifically comprises the following steps: treating the pore water using iron co-precipitation and simultaneously detecting it using laser ablation coupled with inductively coupled plasma mass spectrometry. This method provides an effective testing solution for situations where pore water samples are insufficient. The reagents involved are conventional and inexpensive, eliminating the need for expensive pretreatment equipment and offering good economic benefits. Furthermore, the miniaturized sample pretreatment and analysis model employed in this invention exhibits environmentally friendly, low-consumption, and low-pollution characteristics.

Description

Technical Field

[0001] The present invention relates to the field of chemical analysis, and in particular to a method for testing rare earth elements in marine sediment pore water. Background Art

[0002] Pore water, also known as interstitial water, is the bottom water that is entrained into the gaps between particles when sediments settle. The rare earth elements (REE, La~Lu, also known as lanthanides) in it have similar physical and chemical properties to each other, and the variable valence characteristics of Ce and Eu have long been considered to be important indicators for exploring early diagenetic processes. In particular, the profile changes of rare earth elements at sedimentary depths and the distribution pattern of rare earth elements can provide important information for processes such as sedimentary environment, source input, and sediment-water exchange reactions. The difficulty in testing rare earth elements in marine sediment pore water lies mainly in: 1) The content of rare earth elements is extremely low, usually around 10 -12 Level; 2) The salinity is extremely high, with a salinity close to that of seawater, about 35‰;

[0003] 3) Due to the relatively high difficulty in sampling pore water, the amount of sample that can be used is usually very small, and the available volume of a single sample is often less than 10 ml.

[0004] Currently, rare earth elements in pore water are often analyzed using inductively coupled plasma mass spectrometry (ICP-MS). However, due to the low content of the target analytes and the high salinity content in the matrix, the sample still needs to be pre-enriched and the matrix separated before it can be tested on the instrument. Otherwise, the test signal is likely to be lower than the detection limit, and the injection system and the cone hole are easily blocked. Conventional separation and enrichment methods include solid phase extraction and co-precipitation. In the existing technology, when using the co-precipitation method for pre-enrichment treatment, at least 25 mL is required for each analysis. Such a large sample volume is a huge drawback for pore water testing. In addition, in the pore water sample rare earth element testing method based on co-precipitation as a pre-treatment, the co-precipitation has limited ability to remove the sample matrix. The residual Ba in the sample finally used for instrument testing is very likely to interfere with the analysis of medium and heavy rare earth elements; the oxide and hydroxide ions of the light rare earth itself may also affect the testing of medium and heavy rare earth elements.

[0005] Therefore, how to reduce the sample demand during ICP-MS testing of pore water samples and maintain good detection accuracy is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for testing rare earth elements in marine sediment pore water to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A method for testing rare earth elements in marine sediment pore water uses iron co-precipitation to treat the pore water and laser ablation coupled with inductively coupled plasma mass spectrometry for detection.

[0009] Preferably, the method specifically includes the following steps:

[0010] (1) Take pore water, treat it with iron coprecipitation, and dissolve the coprecipitation product with dilute nitric acid to obtain mixture A. Then take 60 μL of mixture A and inject it into the liquid sample target (see Figure 2 );

[0011] (2) After coating the mixture A, move it into a laser ablation cell to ablate a liquid sample target, introduce nitrogen into the aerosol pipeline downstream of the laser ablation cell, and then use inductively coupled plasma mass spectrometry to detect it, and calculate the rare earth element content based on the standard curve established by the standard solution.

[0012] Beneficial effects: The present invention removes the matrix and enriches rare earth elements in pore water through iron co-precipitation, and then uses the trace characteristics of LA sampling to achieve ultra-low sample consumption testing of rare earth elements in marine sediment pore water through ICP-MS. At the same time, by introducing nitrogen as an auxiliary means, the present invention controls the interference yield of oxides and hydroxides during ICP-MS solution sample testing to an extremely low level, greatly reducing the possibility of such interference affecting the test. The present invention provides an effective testing solution for situations where the amount of pore water samples is insufficient, and the reagents involved are conventional and inexpensive, and do not require other expensive pre-treatment equipment, with good economy. In addition, the miniaturized sample pretreatment and analysis mode in the present invention exhibits green and environmentally friendly characteristics of low consumption and low pollution.

[0013] Preferably, the pore water volume in step (1) is 2-4 mL;

[0014] The volume of the sample solution obtained by the final dissolution is 100-200 μL.

[0015] Beneficial effect: The target rare earth elements in pore water samples can be enriched 10-40 times.

[0016] Preferably, the iron co-precipitation treatment in step (1) comprises the following steps:

[0017] Adding an iron ion carrier to the pore water, then adjusting the solution pH to 8 with dilute ammonia water, allowing the solution to stand, centrifuging, and washing to obtain a coprecipitated product;

[0018] The iron ion carrier includes ferric nitrate and / or ferric chloride;

[0019] The ratio of the iron ion carrier to pore water addition is (20-30 μg): 1 mL;

[0020] The concentration of the dilute ammonia water is 10%.

[0021] Beneficial Effects: If the coprecipitation carrier concentration is insufficient, complete rare earth recovery cannot occur. Furthermore, the coprecipitation carrier concentration should not be too high, as this wastes reagents and increases the likelihood of contamination and background. The process described in the present invention avoids this technical issue.

[0022] Preferably, the standing temperature is room temperature, and the standing time is 12 hours (overnight);

[0023] The centrifugal speed is 4000 r / min.

[0024] Beneficial effect: High salt matrix (such as Na, Mg, K, Ca, etc.) in pore water samples is removed to a large extent.

[0025] Preferably, before dissolving the precipitate with dilute nitric acid, an In internal standard solution is added to the coprecipitated product;

[0026] The volume of the internal standard solution added was 100 μL;

[0027] The concentration of the In internal standard solution is 10 ng mL -1 ;

[0028] The concentration of the dilute nitric acid is 10%.

[0029] Beneficial effects: The behavior of the In internal standard and rare earth elements during LA-ICP-MS analysis is essentially the same, enabling accurate quantification using the internal standard method.

[0030] Preferably, when the liquid sample target is laser ablated in step (2), the laser ablation beam spot is 60 μm and the frequency is 20-250 Hz; the ablation beam spot and frequency used for the reference standard solution and the sample do not need to be consistent, and are selected based on different signal size requirements.

[0031] Preferably, the nitrogen flow rate introduced in step (2) is 5 mL min -1 .

[0032] Beneficial effect: Compared with the conventional mode without introducing nitrogen, the introduction of nitrogen in the present invention can reduce the yield of oxides from 0.45% to 0.07% at its own optimal carrier gas flow rate.

[0033] Preferably, before performing inductively coupled plasma mass spectrometry detection in step (2), the carrier gas flow rate needs to be optimized to 0.75 L min -1 , slightly lower than the flow rate corresponding to the highest sensitivity;

[0034] Preferably, the inductively coupled plasma mass spectrometry parameters in step (2) are shown in the following table:

[0035]

[0036] Benefits: Laser ablation (LA) coupled with ICP-MS is a well-known and powerful microanalysis method, currently primarily used for the analysis and testing of solid samples. When using LA for solution sample introduction, a single data acquisition requires only 1 μL of sample (laser ablation 50 seconds, beam spot 160 μm, frequency 10 Hz). Due to this micro-injection feature, even if the final sample used for analysis is only a dozen microliters, it can fully meet the sample volume requirements for quantitative analysis.

[0037] The present invention discloses a method for testing rare earth elements in marine sediment pore water, which has the following beneficial effects:

[0038] 1) The present invention can reduce the amount of marine sediment pore water required to 2 mL. Compared with the traditional method of co-precipitation combined with solution atomization ICP-MS analysis for marine sediment pore water analysis, the present invention reduces the sample requirement for pore water by 10 times.

[0039] 2) Due to the trace nature of LA sampling and the nitrogen-assisted plasma effect of the present invention, the yield of solvent-related interfering ions (oxides and hydroxides) generated during the analysis is extremely low. Under typical analytical conditions, the CeO / Ce ratio is 0.05% and the CeOH / Ce ratio is 0.01%. This is 1-2 orders of magnitude lower than traditional solution nebulization ICP-MS analysis methods. This allows rare earth element analysis to be free of solvent-related polyatomic ion interference, especially the interference of Ba oxide and hydroxide ions remaining in the sample after coprecipitation.

[0040] 3) Compared with the traditional co-precipitation combined with solution atomization ICP-MS analysis method, the present invention can reduce the consumption of ultrapure water and reagents by about 10 times, and does not require special reagents, cumbersome processes and expensive pretreatment equipment. It is simple, economical and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is a flow chart of rare earth element testing of marine sediment pore water in Example 1 of the present invention;

[0043] Figure 2 Schematic diagram of a liquid sample target made of Teflon material, where 1 is the solution filling area with a volume of 60 μL;

[0044] Figure 3 is the standard curve of rare earth elements;

[0045] Figure 4 The concentration of rare earth elements in seawater samples was 10, 20, and 30 μg mL -1 Fe 3+ Recovery rate after coprecipitation treatment at the carrier concentration;

[0046] Figure 5 In Example 7, nitrogen (5 mL min -1 ) on (a) rare earth element analysis sensitivity and (b) oxide and hydroxide interference yield; wherein the dotted lines indicate the optimal carrier gas flow rate for each of the two modes;

[0047] Figure 6 It is a rare earth element distribution pattern diagram after normalization of Example 1 and Examples 3-6 by Australian Post-Archaean shale; among them, NASS-7 is the distribution pattern of Example 1, PW1 is the distribution pattern of Example 3, PW2 is the distribution pattern of Example 4, PW3 is the distribution pattern of Example 5, and PW4 is the distribution pattern of Example 6. DETAILED DESCRIPTION

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] The reagents and equipment used in the following examples are as follows:

[0051] Ultrapure water (Millipore-Simplicity personal ultrapure water system, Millipore Corporation, USA, outlet water resistivity 18.2 MΩ·cm);

[0052] Nitric acid (analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd., purified by secondary sub-boiling distillation, high-purity grade for metal-oxide-semiconductors, i.e., MOS grade);

[0053] Ammonia (chromatographically pure, Shanghai Aladdin Biochemical Technology Co., Ltd.);

[0054] Multi-element standard solution (Agilent Technologies, 10 μg ml -1 );

[0055] In internal standard solution (Indium (In) elemental standard solution) (National Iron and Steel Materials Testing Center, 1000 μg ml -1 ).

[0056] Ba single element solution (barium (Ba) single element standard solution) (National Iron and Steel Materials Testing Center, 1000 μg ml -1 ).

[0057] Ce single element solution (cerium (Ce) single element standard solution) (National Iron and Steel Materials Testing Center, 1000 μg ml -1 ).

[0058] Ferric nitrate solution: Fe 3+ Concentration 1000 μg ml -1 , those skilled in the art can prepare it by dissolving iron sheet IRMM-524A (IRMM, Belgium) in dilute nitric acid.

[0059] Seawater Standard Material NASS-7 (National Research Council of Canada):

[0060] Inductively coupled plasma mass spectrometry (7900ICP-MS, Agilent, USA);

[0061] 257 nm femtosecond laser ablation system (NWR-Femto, ESL, USA);

[0062] Centrifuge (TDZ5-WS, Hunan Xiangyi multi-tube rack automatic balancing centrifuge).

[0063] The inductively coupled plasma mass spectrometry parameters of the embodiment of the present invention are shown in Table 1:

[0064] Table 1: ICP-MS instrument parameter settings

[0065]

[0066]

[0067] Example 1

[0068] The object of determination in this example is seawater standard material NASS-7. Since there is no commercial pore water standard sample, the present invention uses seawater with similar properties to replace pore water for method verification. The concentration gradient of rare earth elements in the multi-element standard solution is 0.1, 1, 2, 5 ng mL -1 The concentration of In internal standard solution was 10 ng mL -1 , the medium is 2% HNO3.

[0069] Standard curve determination method:

[0070] (1) The concentration of rare earth elements was 0.1, 1, 2, and 5 ng mL -1 60 μL of each multi-element standard solution was injected into the liquid sample target (see Figure 2 ), and then moved into the laser ablation cell after coating;

[0071] (2) The liquid sample target was ablated by laser with the ablation parameters of 60 μm and 20 Hz to obtain a standard solution aerosol, which was then sprayed downstream of the aerosol line at a rate of 5 mL min -1 Introducing nitrogen;

[0072] (3) The aerosol is introduced into an inductively coupled plasma mass spectrometer together with nitrogen through a carrier gas for detection. The detection parameters are shown in Table 1.

[0073] Then, a standard curve is drawn with the ratio of the concentration of the rare earth element to the internal standard element in the standard solution as the horizontal axis and the ratio of the signal intensity of the rare earth element to the internal standard element In as the vertical axis. Figure 3 shown.

[0074] A method for testing rare earth elements in pore water of marine sediments, such as Figure 1 As shown, the following steps are included:

[0075] Step S1: Take 2 mL of NASS-7 sample, add 50 μL of ferric nitrate solution, shake the solution, add 10 wt% ammonia water, adjust the pH to 8, and let it stand overnight (12 h) at room temperature. Then centrifuge the sample at 4000 r / min, remove the supernatant, rinse the precipitate with ultrapure water twice, add 100 μL of In internal standard solution, and finally add 10 wt% HNO3 at a time of 10 μL to dissolve the precipitate, and add 30 μL in total.

[0076] Step S2: Inject 60 μL of the sample solution obtained by step S1 into the liquid sample target (see Figure 2 ), and then moved into the laser ablation cell after coating;

[0077] Step S3: Use laser to ablate the liquid sample target, where the ablation parameters are 60 μm, 150 Hz, to obtain a sample aerosol, and then aspirate it at a rate of 5 mL min downstream of the aerosol line. -1 Introducing nitrogen; Step S4: introducing the aerosol together with the nitrogen through a carrier gas into an inductively coupled plasma mass spectrometer for detection, wherein the detection parameters are shown in Table 1.

[0078] Reference standard curve ( Figure 3 ), and the rare earth element content is obtained by signal calculation.

[0079] The test results are shown in Table 2, and the rare earth element distribution pattern after normalization of the Australian Post-Archaean shale is shown in Figure 6 .

[0080] Example 2

[0081] The test object of this embodiment is a spiked sample of seawater standard substance NASS-7, and the accuracy of the test method is verified by the recovery rate.

[0082] Step S1: Take 2 mL of NASS-7 sample and add 50 μL of rare earth element standard solution (1 ng mL -1 , 2% HNO3), then add 50 μL of ferric nitrate solution, shake the solution, add 10 wt% ammonia water dropwise, adjust the pH to 8, let it stand at room temperature overnight (12 h), then centrifuge the sample at 4000 r / min, remove the supernatant, rinse the precipitate with ultrapure water twice, and add 100 μL of 10 ng mL -1 In internal standard solution, finally add 10 wt% HNO3 at a time of 10 μL to dissolve the precipitate, and add a total of 30 μL.

[0083] Step S2: Inject 60 μL of the sample solution obtained by step S1 into the liquid sample target (see Figure 2 ), and then moved into the laser ablation cell after coating;

[0084] Step S3: Use laser to ablate the liquid sample target, where the ablation parameters are 60 μm, 150 Hz, to obtain a sample aerosol, and then aerosol is generated in the downstream of the aerosol line at a rate of 5 mL min -1 Introducing nitrogen;

[0085] Step S4: The aerosol is introduced into an inductively coupled plasma mass spectrometer through a carrier gas together with nitrogen for detection. The detection parameters are shown in Table 1.

[0086] Reference standard curve ( Figure 3), and the rare earth element content was obtained by signal calculation. The content value measured by NASS-7 in Example 1 was deducted from the measured value of each element to obtain the spiked recovery rate. The results are shown in Table 2.

[0087] In step S1, when the coprecipitation carrier Fe 3+ Solution 20μL, 40μL, 60μL (i.e. concentration: 10μg mL -1 , 20 μg mL -1 , 30 μg mL -1 ), different levels of spike recovery were obtained (see Figure 4 ), it can be seen that Fe 3+ The carrier concentration must be controlled at 20 μg mL -1 At the same time, the added concentration of the coprecipitation carrier should not be too high, otherwise it will cause reagent waste and face a greater possibility of introducing contamination and increase the process background. Therefore, the present invention recommends that the ratio of the added amount of iron ion carrier to pore water be controlled at (20-30) μg:1mL.

[0088] Example 3

[0089] The object of measurement in this example is the pore water sample PW1, which was collected from the Dongsha Sea area in the northeast of the South China Sea. The concentration gradient of rare earth in the calibration external standard is 0.1, 1, 2, and 5 ng mL -1 The concentration of In internal standard solution was 10 ng mL -1 , the medium is 2% HNO3.

[0090] The method for determining the standard curve is the same as in Example 1.

[0091] A method for testing rare earth elements in marine sediment pore water, comprising the following steps:

[0092] Step S1: Take 2mL of pore water sample PW1, add 40μL of ferric nitrate solution, shake the solution, add 10wt% ammonia water, adjust the pH to 8, and let it stand overnight (12h) at room temperature. Then centrifuge the sample at 4000r / min, remove the supernatant, rinse the precipitate with ultrapure water twice, add 100μL of In internal standard solution, and finally add 10wt% HNO3 in an amount of 10μL each time to dissolve the precipitate, and add 30μL in total.

[0093] Step S2: inject 60 μL of the sample solution obtained by the treatment in step S1 into the liquid sample target, and move it into the laser ablation cell after coating;

[0094] Step S3: Use laser to ablate the liquid sample target. The ablation parameters for the pore water sample are 60 μm and 250 Hz to obtain the sample aerosol. Then, the sample aerosol is ablated at 5 mL min downstream of the aerosol line. -1 Introducing nitrogen;

[0095] Step S4: The aerosol is introduced into an inductively coupled plasma mass spectrometer through a carrier gas together with nitrogen for detection. The detection parameters are shown in Table 1.

[0096] Reference standard curve ( Figure 3 ), and the rare earth element content is obtained by signal calculation.

[0097] The test results are shown in Table 2, and the rare earth element distribution pattern after normalization of the Australian Post-Archaean shale is shown in Figure 6 .

[0098] Example 4

[0099] The object of measurement in this example is the pore water sample PW2, which was collected from the Dongsha Sea area in the northeast of the South China Sea. The concentration gradient of rare earth in the calibration external standard is 0.1, 1, 2, and 5 ng mL -1 The concentration of In internal standard solution was 10 ng mL -1 , the medium is 2% HNO3.

[0100] The method for determining the standard curve is the same as in Example 1.

[0101] A method for testing rare earth elements in marine sediment pore water, comprising the following steps:

[0102] Step S1: Take 2 mL of pore water sample PW2, which was collected from the Dongsha sea area in the northeastern part of the South China Sea, add 50 μL of ferric nitrate solution, shake the solution, add 10 wt% ammonia water, adjust the pH to 8, and let it stand at room temperature for 12 hours. Then, centrifuge the sample at 4000 r / min, remove the supernatant, rinse the precipitate with ultrapure water twice, add 100 μL of 10 ppb In internal standard solution, and finally add 10 wt% HNO3 in an amount of 10 μL each time to dissolve the precipitate, and add 30 μL in total.

[0103] Step S2: Inject 60 μL of the sample solution obtained by step S1 into the liquid sample target ( Figure 2 ), and then moved into the laser ablation cell after coating;

[0104] Step S3: Use laser to ablate the liquid sample target, where the ablation parameters for the pore water sample are 60 μm, 200 Hz, to obtain a sample / standard solution aerosol, and then aerosolize the sample / standard solution at a rate of 5 mL / min downstream of the aerosol pipeline. -1 Introducing nitrogen;

[0105] Step S4: The aerosol is introduced into an inductively coupled plasma mass spectrometer through a carrier gas together with nitrogen for detection. The detection parameters are shown in Table 1.

[0106] Reference standard curve ( Figure 3 ), and the rare earth element content is obtained by signal calculation.

[0107] The test results are shown in Table 2, and the rare earth element distribution pattern after normalization of the Australian Post-Archaean shale is shown in Figure 6 .

[0108] Example 5

[0109] The object of measurement in this example is the pore water sample PW3, which was collected from the Dongsha Sea area in the northeast of the South China Sea. The concentration gradient of rare earth in the calibration external standard is 0.1, 1, 2, and 5 ng mL -1 The concentration of In internal standard solution was 10 ng mL -1 , the medium is 2% HNO3.

[0110] The method for determining the standard curve is the same as in Example 1.

[0111] A method for testing rare earth elements in marine sediment pore water, comprising the following steps:

[0112] Step S1: Take 2 mL of pore water sample PW3 and add 60 μL of Fe 3+ Solution, after shaking the solution, add 10wt% ammonia water thereto, adjust the pH to 8, let it stand at room temperature for 12 hours, then centrifuge the sample at 4000r / min, remove the supernatant, rinse the precipitate with ultrapure water twice, add 100μL of In internal standard solution, and finally add 10wt% HNO3 at a time of 10μL to dissolve the precipitate, and add 30μL in total.

[0113] Step S2: Inject 60 μL of the sample solution obtained by step S1 into the liquid sample target ( Figure 2 ), and then moved into the laser ablation cell after coating;

[0114] Step S3: Use laser to ablate the liquid sample target. The ablation parameters for the pore water sample are 60 μm, 100 Hz, to obtain the sample aerosol. Then, the sample aerosol is ablated in the downstream of the aerosol pipeline at a rate of 5 mL min. -1 Introducing nitrogen;

[0115] Step S4: The aerosol is introduced into an inductively coupled plasma mass spectrometer through a carrier gas together with nitrogen for detection. The detection parameters are shown in Table 1.

[0116] The rare earth element content was obtained by referring to the standard curve and calculating the signal.

[0117] The test results are shown in Table 2, and the rare earth element distribution pattern after normalization of the Australian Post-Archaean shale is shown in Figure 6 .

[0118] Example 6

[0119] The object of measurement in this example is pore water sample PW4, which was collected from the Dongsha Sea area in the northeast of the South China Sea. The concentration gradient of rare earth in the calibration external standard is 0.1, 1, 2, 5 ng mL -1 The concentration of In internal standard solution was 10 ng mL -1 , the medium is 2% HNO3.

[0120] The method for determining the standard curve is the same as in Example 1.

[0121] A method for testing rare earth elements in marine sediment pore water, comprising the following steps:

[0122] Step S1: Take 2mL of pore water sample PW4, add 50μL of ferric nitrate solution, shake the solution, add 10wt% ammonia water, adjust the pH to 8, and let it stand overnight (12h) at room temperature. Then centrifuge the sample at 4000r / min, remove the supernatant, rinse the precipitate with ultrapure water twice, add 100μL of In internal standard solution, and finally add 10wt% HNO3 in an amount of 10μL each time to dissolve the precipitate, and add 30μL in total.

[0123] Step S2: inject 60 μL of the sample solution obtained by the treatment in step S1 into the liquid sample target, and move it into the laser ablation cell after coating;

[0124] Step S3: Use laser to ablate the liquid sample target. The ablation parameters for the pore water sample are 60 μm, 200 Hz, to obtain the sample aerosol. Then, the sample aerosol is ablated at 5 mL min downstream of the aerosol line. -1 Introducing nitrogen;

[0125] Step S4: The aerosol is introduced into an inductively coupled plasma mass spectrometer through a carrier gas together with nitrogen for detection. The detection parameters are shown in Table 1.

[0126] Reference standard curve ( Figure 3 ), and the rare earth element content is obtained by signal calculation.

[0127] The test results are shown in Table 2, and the rare earth element distribution pattern after normalization of the Australian Post-Archaean shale is shown in Figure 6 .

[0128] Example 7

[0129] A method for testing rare earth elements in marine sediment pore water. Unlike the previous example, this example uses a Ce single element solution (1 μg mL -1 , 2% HNO3) as the test object, change the carrier gas flow rate within the range of 0.5-1.1L / min, and record 140 The signal intensity of Ce and the interference yield of oxides and hydroxides were sorted and plotted to obtain Figure 5 .

[0130] Table 2: Test results of seawater standards and pore water samples

[0131]

[0132] Technical Effects

[0133] As can be seen from Table 2, the precision RSDs of the rare earth element test results of the seawater standard material NASS-7 and the four pore water samples are mostly within 10%. The test values of the seawater standard material NASS-7 are basically consistent with the reference values. The spiked recovery of NASS-7 is between 94% and 101%.

[0134] And by Figure 6 It can be seen that the rare earth element distribution patterns of all sample test results after normalization to Australian Post-Archaean shale are smooth, which proves the reliability of the method.

[0135] Figure 6 A significant positive anomaly of Eu can be observed, due to the extremely low oxide and hydroxide yields of this scheme (refer to Figure 5 ), and at the same time, a single standard solution of Ba (10 μg mL -1 , 2% HNO3) monitoring, it can be seen that the oxides and hydroxides of Ba 151 The interference yield generated at Eu (ie: ( 35 Ba 16 O+ 134 Ba 16 O 1 H) / 137 Ba) is only 0.003%, and the signal of Ba remaining in the final dissolved sample solution is usually no more than 10 5 cps, thus confirming that this anomaly is an actual geochemical anomaly rather than caused by interfering ions in the test.

[0136] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for testing rare earth elements in marine sediment pore water, characterized in that: The pore water was treated by iron co-precipitation and detected by laser ablation coupled with inductively coupled plasma mass spectrometry. The specific steps include: (1) Taking pore water, adding an iron ion carrier to the pore water, and then adjusting the solution pH to 8 with dilute ammonia water, standing, centrifuging, and washing to obtain a coprecipitated product; adding dilute nitric acid dropwise to the coprecipitated product until it is completely dissolved to obtain a mixture A, and injecting the liquid sample target; (2) After coating the mixture A, the mixture is moved into a laser ablation cell to ablate a liquid sample target, and then nitrogen is introduced into the aerosol pipeline downstream of the laser ablation cell. The mixture is detected by inductively coupled plasma mass spectrometry, and the rare earth element content is calculated according to a standard curve established by the standard solution; The volume of pore water in step (1) is 2-4 mL.

2. The method for testing rare earth elements in marine sediment pore water according to claim 1, characterized in that: The iron ion carrier in step (1) includes ferric nitrate and / or ferric chloride; The ratio of the iron ion carrier to pore water addition is (20-30) μg:1 mL; The concentration of the dilute ammonia water is 10%.

3. The method for testing rare earth elements in marine sediment pore water according to claim 1, characterized in that: The standing temperature is room temperature, and the standing time is 12 hours.

4. The method for testing rare earth elements in marine sediment pore water according to claim 1, characterized in that: Before dissolving the precipitate with dilute nitric acid in step (1), adding an In internal standard solution to the coprecipitated product; The volume of the internal standard solution added was 100 μL; The concentration of the In internal standard solution is 10 ng mL -1 ; The concentration of the dilute nitric acid is 10%.

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