Determination and analysis method of high-field strength elements in diorite for reducing equipment damage

Abstract

The present invention belongs to the technical fields of geological survey and ICP-MS application, and discloses a method for determining and analyzing high-field-strength elements in diorite to reduce equipment damage. Aiming at the occurrence state of high-field-strength elements, firstly, a pre-digestion process is added. Secondly, a conditional experiment of three factors and three levels is designed for the reagent addition amounts (hydrofluoric acid, nitric acid) required for dissolving the sample and the digestion time, so as to obtain the optimal reagent addition amounts as: 2 mL of hydrofluoric acid and 1 mL of nitric acid, and the digestion time is 36 h. The most important factor affecting the dissolution rate of high-field-strength elements is hydrofluoric acid. Dissolve the sample under the optimal pretreatment experimental scheme, and add hydrochloric acid with a concentration of 0.1% (volume ratio) to the completely dissolved solution medium to ensure the stability of high-field-strength elements in the solution; test the dissolved GBW07111 on ICP-MS according to this method, and calculate the detection limit, quantification limit, precision, and relative standard deviation of this method. The present invention utilizes ICP-MS to achieve accurate analysis of high-field-strength elements in diorite.

Description

Technical Field

[0001] The present invention belongs to the technical fields of geological survey and ICP-MS application, and particularly relates to a method for determining and analyzing high-field-strength elements, rare earth elements and other trace elements in diorite to reduce damage to ICP-MS equipment. Background Art

[0002] At present, trace zircon in granodiorite is determined by the method of high-pressure closed acid digestion - inductively coupled plasma mass spectrometry. However, in this method, there are few design factors in the selection of the best experimental conditions, few experimental groups, and the main factors affecting the dissolution rate are not analyzed. Moreover, hydrofluoric acid is added to the finally dissolved solution, and hydrofluoric acid will corrode the sample introduction system (nebulizer, spray chamber, torch tube) in ICP-MS. For GB / T 14506.30-2010 (Methods for chemical analysis of silicate rocks - Determination of 44 elements), since high-field-strength elements in diorite are mainly hosted in refractory accessory minerals, they cannot be completely dissolved when analyzing high-field-strength elements in diorite by the experimental method of this standard. In addition, alkali fusion can achieve the purpose of dissolving high-field-strength elements, but it has the disadvantages of high background and serious matrix effect, and is not suitable for the simultaneous determination of other trace elements.

[0003] In summary, the problems existing in the prior art are as follows:

[0004] (1) In the prior art, the method of high-pressure closed acid digestion - inductively coupled plasma mass spectrometry is used to determine trace zircon in granodiorite. There are few design factors in the scheme, few experimental groups, insufficient representativeness, the main influencing factors are not pointed out, and the addition of hydrofluoric acid to the solution will corrode the ICP-MS sample introduction system.

[0005] (2) When using GB / T14506.30-2010 to analyze trace elements in diorite, the digestion time and reagent addition amount are not sufficient to completely dissolve high-field-strength elements.

[0006] (3) Although alkali fusion can completely dissolve high-field-strength elements, other trace elements cannot be analyzed simultaneously.

[0007] (4) High-field-strength elements are unstable in nitric acid medium.

[0008] The difficulty in solving the above technical problems: How to quickly find the best experimental scheme and the main influencing factors among multiple pretreatment influencing factors, achieve the complete digestion of refractory accessory minerals (zircon, rutile) in diorite, so that high-field-strength elements are completely dissolved, and at the same time analyze other trace elements in diorite. In addition, ensure the stability of elements such as high-field-strength elements in the solution to be measured without causing damage to the equipment. Summary of the Invention

[0009] A method for determining and analyzing high-field-strength elements in diorite to reduce equipment damage, aiming at the problems existing in the prior art.

[0010] The present invention is implemented as follows. A method for determining and analyzing high-field-strength elements in diorite to reduce equipment damage, the method for determining and analyzing high-field-strength elements in diorite to reduce equipment damage includes:

[0011] Consult the literature and analyze the occurrence state of high-field-strength elements in diorite;

[0012] For the occurrence state of high-field-strength elements, add a little hydrofluoric acid for pre-digestion, then add a pre-digestion process for high-field-strength elements, and then determine the best determination and analysis conditions by selecting three factors of digestion time, hydrofluoric acid addition amount, and nitric acid addition amount and the corresponding three-level values of each factor, obtain the main factors affecting the dissolution rate of high-field-strength elements, and determine the main factors affecting the dissolution rate of high-field-strength elements;

[0013] After dissolving the sample using the best experimental method, add hydrochloric acid with a concentration of 0.1% (volume ratio);

[0014] Calculate the detection limit and quantification limit of the method. Secondly, digest 7 samples of the sample (GBW07111) with this method, conduct ICP-MS tests, and calculate the precision RSD. Thirdly, calculate the average value obtained from the determination of 7 samples (GBW07111), and calculate the relative standard deviation RE from the true value.

[0015] Taking the diorite national standard substance GBW07111 as the analysis object, consult the literature and analyze the occurrence state of high-field-strength elements in diorite.

[0016] Perform ICP-MS tests on the diorite samples (GBW07111) digested under the best experimental conditions obtained from the above-mentioned condition tests, determine the blank values of high-field-strength elements according to the process blank (n = 7 times), and calculate the average value of the determination and the standard deviation (s), then calculate the method detection limit according to MDL = t(n - 1, 0.99)×S, take 4 times the detection limit as the determination lower limit (if the number of determinations n is 7 and the confidence level is 99%, then t = 3.143), and calculate the detection limit and determination lower limit of high-field-strength elements. Calculate the average value according to the determination results of diorite samples (GBW07111) (n = 7 times) and the standard deviation (s) to obtain the precision According to the average value Divide by the accurate value of the diorite sample (GBW07111) to calculate the relative standard deviation RE.

[0017] Furthermore, the pretreatment for the occurrence state of high-field-strength elements includes:

[0018] First, add a pre-digestion process. Add 1 - 1.5 mL of hydrofluoric acid and place it on a hot plate to evaporate to dryness at 150 °C. Secondly, conduct a conditional experiment with three factors and three levels on the reagent addition amounts (hydrofluoric acid, nitric acid) and digestion time required to dissolve the sample. Arrange the experiment according to the L9(3 4 ) orthogonal array (see Tables 1 and 2).

[0019] Table 1 Conditional experiment with three factors and three levels

[0020]

[0021] Table 2 Data table of conditional experiment

[0022]

[0023] Among them, K1, K2, and K3 are the total results of the level experiments, k1, k2, and k3 are the average results of the level experiments, and R is the range.

[0024] From Table 2, it can be obtained that among the 9 experimental results, the dissolution rate of Experiment 9 is the best. Arranged by factors, its level combination is A3, B3, C2, which are the levels with the greatest influence among the respective factors. Therefore, it can be seen that the optimal experimental conditions of this method are a digestion time of 36 h, a hydrofluoric acid addition amount of 2 mL, and a nitric acid addition amount of 1 mL. And through the magnitude of the R value, it can be seen that there is a significant order among the factors of this method, and their primary and secondary relationship is B > A > C, that is, the most important factor affecting the dissolution rate of high-field-strength elements is the hydrofluoric acid addition amount.

[0025] Furthermore, after calculating the detection limit, method quantification limit, precision RSD, n = 7, and relative standard deviation RE, it is also necessary to: take an unknown diorite sample for analysis.

[0026] Another object of the present invention is to provide a determination and analysis method for high-field-strength elements in diorite that implements the reduction of ICP-MS equipment damage, and an analysis device for determining trace elements in diorite based on ICP-MS.

[0027] To sum up, the advantages and positive effects of the present invention are as follows:

[0028] High-field-strength elements are hosted in refractory accessory minerals. The purpose of the present invention is to establish a diorite ore-dissolving method to achieve accurate analysis and reduce the damage of ICP-MS equipment;

[0029] The present invention uses ICP-MS to improve the national standard method, so that the dissolution rates of high-field-strength elements are all increased from about 75% to about 95%. Accurate analysis of rare earth elements, trace elements, especially high-field-strength elements in diorite is achieved.

[0030] The detection limits of titanium provided by the present invention are: 2.54 μg / g, the quantification limit is 10.2 μg / g; the detection limit of niobium is 0.012 μg / g, the quantification limit is 0.048 μg / g; the detection limit of tantalum is 0.0044 μg / g, the quantification limit is 0.018 μg / g; the detection limit of zirconium is 0.044 μg / g, the quantification limit is 0.18 μg / g; the detection limit of hafnium is 0.006 μg / g, the quantification limit is 0.024 μg / g. The precision RSD of titanium is 0.36% (n = 7), and the relative standard deviation is 1.04%; the precision RSD of niobium is 1.93% (n = 7), and the relative standard deviation is 4.72%; the precision RSD of tantalum is 2.28% (n = 7), and the relative standard deviation is 4.84%; the precision RSD of zirconium is 1.93% (n = 7), and the relative standard deviation is 4.02%; the precision RSD of hafnium is 2.08% (n = 7), and the relative standard deviation is 2.69%. A determination and analysis method for high-field strength elements in diorite by ICP-MS is established, which has the characteristics of low detection limit and high accuracy. It is of great significance for analyzing the origin of diorite.

[0031] The method provided by the present invention aims at the phenomenon of low dissolution rate of high-field strength elements in diorite analyzed by the existing analytical technique ICP-MS, and in view of the difficulty of dissolving accessory minerals containing high-field strength elements, a pre-digestion step is added, and a three-factor and three-level condition experiment is designed. The optimal experimental conditions are obtained as follows: the digestion time is 36 h, the addition amount of hydrofluoric acid is 2 mL, and the addition amount of nitric acid is 1 mL. The most important factor affecting the dissolution rate of high-field strength elements is hydrofluoric acid, which increases the dissolution rate of high-field strength elements to about 95%.

[0032] Because high-field strength elements are unstable in nitric acid medium, and in the prior art, a little hydrofluoric acid is added for reference. However, the injection system (nebulizer, spray chamber, torch tube) of the ICP-MS equipment is made of quartz material, and the introduction of hydrofluoric acid will cause corrosion of the injection system, resulting in equipment damage. The present invention introduces 0.1% hydrochloric acid (volume ratio) into the prepared solution, which not only ensures the stability of high-field strength elements but also does not cause damage to the ICP-MS equipment.

[0033] The accurate analysis of trace elements in diorite by the present invention is of great significance in the research of the petrogenesis, tectonic evolution, geochemistry and other geological environments of diorite. Description of the Drawings

[0034] Figure 1 It is a flow chart of the determination and analysis method for high-field strength elements in diorite provided by the embodiment of the present invention to reduce equipment damage. Detailed Embodiments

[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] In the prior art, (1) the high-pressure closed acid digestion-inductively coupled plasma mass spectrometry method is used to determine trace zircon in granodiorite. There are few design factors in the scheme, few experimental groups, insufficient representativeness, and the main influencing factors are not pointed out. Moreover, the addition of hydrofluoric acid to the solution will corrode the ICP-MS injection system.

[0037] (2) When analyzing the trace elements of diorite by GB / T14506.30-2010, the sample digestion time and reagent addition amount are not sufficient to achieve the purpose of complete dissolution of high-field strength elements.

[0038] (3) Although alkali fusion can completely dissolve high-field strength elements, other trace elements cannot be analyzed simultaneously.

[0039] (4) High-field strength elements such as high-field strength elements are unstable in nitric acid medium.

[0040] To solve the above problems, the present invention will be described in detail below in conjunction with specific solutions.

[0041] As Figure 1 shown, the determination and analysis method for high-field strength elements in diorite that reduces the damage of ICP-MS equipment provided by the embodiment of the present invention includes:

[0042] S101, taking the diorite national standard substance GBW07111 as the analysis object, consulting the literature, and analyzing the occurrence state of high-field strength elements in diorite.

[0043] S102, adding a pre-digestion process to the high-field strength elements, and then determining the best determination and analysis conditions by selecting three factors of digestion time, hydrofluoric acid addition amount, and nitric acid addition amount and the values of three levels corresponding to each factor, and obtaining the main factors affecting the dissolution rate of high-field strength elements;

[0044] Specifically: According to the occurrence state of high-field strength elements, a pre-digestion process is added, and then a three-factor and three-level condition experiment is designed for the sample digestion pretreatment conditions, so as to obtain the best experimental conditions: 2 mL of hydrofluoric acid and 1 mL of nitric acid, the digestion time is 36 h, and the main factor affecting the dissolution rate of high-field strength elements is hydrofluoric acid.

[0045] S103, digesting the sample under the best pretreatment experimental scheme, and adding hydrochloric acid with a concentration of 0.1% (volume ratio) to the completely dissolved solution medium to ensure the stability of high-field strength elements in the solution.

[0046] S104. Perform ICP-MS testing on GBW07111 dissolved according to this method, and calculate the detection limit, quantification limit, precision (RSD, n = 7), and relative error (RE) of this method.

[0047] S105. Take unknown diorite samples, analyze them using this method and sodium peroxide alkali fusion respectively, and compare the results to verify the accuracy of this method.

[0048] S106. Perform testing on rare earth elements and other trace elements on GBW07111 dissolved according to this method on the instrument.

[0049] Table 3 Detection limit and quantification limit of high field strength elements

[0050]

[0051] Calculate the method detection limit according to the formula MDL = t (n-1,0.99) ×S, and take 4 times the detection limit as the determination lower limit. (If the number of determinations n is 7 and the confidence level is 99%, then t = 3.143)

[0052] Table 4 Precision of high field strength elements

[0053]

[0054] Table 5 Trueness of high field strength elements

[0055]

[0056] Table 6 Determination results of rare earth elements and trace elements in the reference material GBW07111 analyzed by this method

[0057]

[0058] To sum up, for the analysis of high field strength elements, rare earth elements, and other trace elements in diorite, first add 1 - 1.5 ml of hydrofluoric acid to pre-digest the diorite sample, then sequentially add 2 mL of hydrofluoric acid and 1 mL of nitric acid, place it in a high-pressure sealed reaction vessel, heat it in an oven at 180 °C for 36 h, take it out and cool it, evaporate the solution to dryness on a hot plate, add 3 ml of 50% nitric acid (by volume), re-dissolve it for 6 h, add 0.1% hydrochloric acid (by volume), and make up the volume to 50 ml in a volumetric flask for ICP-MS determination. When measuring, the external standard method is used. Different series of standard curves are configured for high field strength elements, rare earth elements, and other trace elements respectively. For rare earth elements, hafnium, tantalum in high field strength elements, and trace elements with mass numbers greater than 135, Re is selected as the internal standard, and for zirconium, niobium, titanium, and trace elements with mass numbers less than or equal to 135, Rh is selected as the internal standard.

[0059] The method provided by the embodiments of the present invention aims at the phenomenon of low dissolution rate of high-field-strength elements in diorite analyzed by the existing analytical technique ICP-MS, and in view of the difficulty in dissolving accessory minerals containing high-field-strength elements, a pre-digestion step is added, and a three-factor and three-level conditional experiment is designed. The optimal experimental conditions are obtained as follows: digestion time is 36 h, the addition amount of hydrofluoric acid is 2 mL, and the addition amount of nitric acid is 1 mL. The main factor affecting the dissolution rate of high-field-strength elements is hydrofluoric acid, which increases the dissolution rate of high-field-strength elements to about 95%. The detection limit of titanium by this method is 2.54 μg / g, the quantification limit is 10.2 μg / g, the detection limit of niobium is 0.012 μg / g, the quantification limit is 0.048 μg / g, the detection limit of tantalum is 0.0044 μg / g, the quantification limit is 0.018 μg / g, the detection limit of zircon is 0.044 μg / g, the quantification limit is 0.18 μg / g, the detection limit of hafnium is 0.006 μg / g, and the quantification limit is 0.024 μg / g. The precision RSD of titanium is 0.36% (n = 7), the relative standard deviation is 1.04%, the precision RSD of niobium is 1.93% (n = 7), the relative standard deviation is 4.72%, the precision RSD of tantalum is 2.28% (n = 7), the relative standard deviation is 4.84%, the precision RSD of zircon is 1.93% (n = 7), the relative standard deviation is 4.02%, and the precision RSD of hafnium is 2.08% (n = 7), the relative standard deviation is 2.69%. A determination and analysis method for hafnium in diorite by ICP-MS is established, which has the characteristics of low detection limit and high accuracy. It is of great significance for analyzing the origin of diorite.

[0060] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining and analyzing high-field strength elements in diorite to reduce equipment damage, characterized in that Including: A pre-digestion process is added for high-field-strength elements, and then by selecting three factors: digestion time, hydrofluoric acid addition amount, and nitric acid addition amount, as well as the numerical values of three levels corresponding to each factor, the optimal determination and analysis conditions are determined to obtain the main factors affecting the dissolution rate of high-field-strength elements; After dissolution, the sample is dissolved. To ensure the stability of high-field-strength elements, hydrochloric acid with a concentration of 0.1% by volume ratio is added to avoid damage to the injection system of the ICP-MS device caused by the addition of hydrofluoric acid; The dissolved sample is subjected to ICP-MS testing, and the detection limit, quantification limit, precision RSD, n = 7, and relative standard deviation RE are calculated; The samples dissolved according to the optimal conditions are analyzed for rare earth elements and other trace elements simultaneously, and the relative standard deviation RE is calculated.

2. The method for determining and analyzing high-field strength elements in diorite for reducing equipment damage according to claim 1, characterized in that, The said determination and analysis method includes: First, add 1 - 1.5 ml of hydrofluoric acid to pre-digest the diorite sample; Then, add 2 ml of hydrofluoric acid and 1 ml of nitric acid in sequence, place it in a high-pressure closed reaction vessel, heat it in an oven at 180 °C for 36 h, take it out and cool it, evaporate the solution to dryness on a hot plate, add 3 ml of nitric acid with a volume ratio of 50%, re-dissolve it for 6 h, add hydrochloric acid with a volume ratio of 0.1%, and make up the volume to 50 ml in a volumetric flask for ICP-MS determination.

3. The method for determining and analyzing high field strength elements in diorite for reducing equipment damage according to claim 2, wherein, During determination, the external standard method is used. Different series of standard curves are prepared for high-field-strength elements, rare earth elements, and other trace elements respectively. For rare earth elements, hafnium, tantalum, and trace elements with a mass number greater than 135 in high-field-strength elements, Re is selected as the internal standard, and for zirconium, niobium, titanium, and trace elements with a mass number less than or equal to 135, Rh is selected as the internal standard.

4. The method for determining and analyzing high-field strength elements in diorite for reducing equipment damage according to claim 1, characterized in that, Regarding the occurrence state of high-field-strength elements, add 1 - 1.5 ml of hydrofluoric acid to pre-digest the diorite sample, and then design a three-level and three-factor conditional experiment to obtain the optimal experimental conditions for digestion time, hydrofluoric acid, and nitric acid addition amounts to achieve the purpose of accurate analysis of high-field-strength elements and obtain the main factors affecting the dissolution rate of high-field strength.

5. The method for determining and analyzing high-field strength elements in diorite for reducing equipment damage according to claim 1, characterized in that, The digested diorite samples were tested by ICP-MS. According to the process blank, n = 7 times, the blank values of high field strength elements were measured, and the average value of the measurement was calculated. and the standard deviation s, and then according to MDL = t(n - 1, 0.99) × S Calculate the method detection limit, take 4 times the detection limit as the determination lower limit, and calculate the detection limit and determination lower limit of elements such as high-field strength elements; according to the determination results of diorite samples, n = 7 times, calculate the average value and the standard deviation s to obtain the precision RSD; according to the average value Divide by the accurate value of the diorite sample to calculate the relative standard deviation RE.

6. The method for determining and analyzing high-field strength elements in diorite for reducing equipment damage according to claim 1, wherein The said method further includes: Select diorite samples, compare them with sodium peroxide alkali fusion and this determination and analysis method to determine the accuracy of the determination and analysis values.

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