Method for synchronously measuring multiple elements in geochemical sample based on ICP-OES

Abstract

The invention provides a method for synchronously measuring multiple elements in a geochemical sample based on ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer), which comprises the following specific steps: crushing, grinding and drying a sample, and digesting the sample at 280 DEG C by using hydrofluoric acid-nitric acid-perchloric acid (5: 4: 1) mixed acid; subsequently extracting with 1: 1 aqua regia; preparing a standard solution matched with the acidity of the sample, synchronously measuring the spectral intensity of constant and characteristic elements by utilizing ICP-OES, and quantitatively calculating the element concentration through a standard curve. According to the method, the sample pretreatment and ICP-OES detection conditions and the sample pretreatment process are optimized, the detection efficiency is remarkably improved, multi-element analysis can be completed through a single test, and efficient multi-element synchronous analysis is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of determination method of geochemical sample elements, and particularly relates to a method for synchronously determining multiple elements in a geochemical sample based on ICP-OES. BACKGROUND

[0002] A geochemical sample refers to a material sample collected from various geological bodies (such as rocks, soil, sediments, water system sediments, etc.) on the earth surface, and used for analyzing the chemical composition and element distribution characteristics thereof. Accurate determination of constant elements (such as aluminum, iron, titanium, calcium, magnesium, sodium, potassium, etc.) and characteristic elements (such as copper, lead, zinc, etc.) in the geochemical sample is the basis for understanding the geological evolution process, mineral resource exploration and environmental monitoring. The content and distribution characteristics of these elements can not only reveal the physical and chemical conditions of rock formation, but also provide key data support for mineral resource evaluation and ecological environment assessment. With the deepening of regional geochemical survey work, higher requirements are put forward for the efficiency, accuracy and multi-element simultaneous determination capability of the analysis method. The traditional analysis method has obvious limitations: flame atomic absorption spectrometry (FAAS) needs to be measured element by element, which is difficult to meet the high-throughput analysis demand, and the high-concentration sample needs to be diluted multiple times; X-ray fluorescence spectrometry can realize multi-element analysis, but the sensitivity for light elements is insufficient; and inductively coupled plasma mass spectrometry (ICP-MS) is limited by the total dissolved solids (TDS) tolerance ability (usually <0.2%), which is difficult to adapt to the complex matrix interference in the geochemical sample. In addition, the classical chemical methods such as gravimetric method, titration method and colorimetric method have the problems of complicated operation, long analysis period and inability to simultaneously analyze multiple elements, which cannot meet the timeliness requirements of modern geochemical research.

[0003] With the continuous development of modern analysis technology, inductively coupled plasma optical emission spectrometry (ICP-OES) has been increasingly widely applied in the field of geochemical sample analysis due to its technical advantages such as simultaneous determination of multiple elements (tens of elements can be synchronously analyzed), wide linear range (usually up to 5-6 orders of magnitude), fast analysis speed (only about one minute is needed for single sample multi-element determination), excellent accuracy and precision, etc. This method can effectively overcome the shortcomings of traditional analysis methods and provides an efficient and reliable technical means for the determination of multiple elements. For example, in the national standard method, GB / T 14506.32-2019 'Silicate rock chemical analysis method Part 32: Determination of 20 components such as aluminum oxide by inductively coupled plasma atomic emission spectrometry' clearly specifies ICP-OES as one of the standard methods for the determination of multiple elements in silicate rocks, providing an authoritative basis for the standardized application of the method; GB / T 3286.1-2022 'Limestone and dolomite chemical analysis method Part 1: Determination of calcium oxide and magnesium oxide content' uses ICP-OES as an important means for the determination of calcium and magnesium constant elements in limestone and dolomite; GB / T 16399-2021 'Clay chemical analysis method' also uses ICP-OES to determine multiple elements such as Fe2O3, MgO, TiO2, K2O, Na2O in clay. At present, many researchers have used ICP-OES to analyze and determine different types of samples and have achieved good results. However, for large quantities of geochemical samples of complex nature (such as minerals, soils, stream sediments, etc.), a quick and applicable universal method is needed to simplify the process, improve efficiency, and promote the upgrading of detection technology.

[0004] Therefore, there is an urgent need for a method for simultaneous determination of multiple elements in geochemical samples based on ICP-OES to achieve rapid and accurate detection of multiple constant and characteristic elements in the same system and provide efficient technical support for geochemical analysis. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a method for rapid and accurate detection of multiple constant and characteristic elements in the same system.

[0006] The purpose of the present application is achieved by the following technical solutions: The method for simultaneous determination of multiple elements in geochemical samples based on ICP-OES comprises the following steps: S1. Sample preparation: crush and grind the geochemical sample, dry and cool to obtain sample powder; S2. Sample pretreatment: weigh the sample powder into a crucible, add a mixture of hydrofluoric acid, nitric acid and perchloric acid with a volume ratio of 5:4:1, digest on an electric hot plate until high perchloric acid smoke is generated and only a few yellow bean-sized liquid beads remain, and cool; S3. Leaching: Add aqua regia to the crucible, leach on the hot plate, and after cooling, dilute to volume to obtain the test solution; S4. Standard curve preparation: Prepare a series of standard solutions using a single-element standard stock solution, with the same matrix acidity as the test solution, to obtain standard solutions; S5. Measurement: Measure the spectral intensity of the standard solution, blank solution, and test solution, calculate the element concentration from the standard curve, and when the linear range is exceeded, dilute and re-measure; S6. Result calculation: Calculate the element content in the geochemical sample.

[0007] Preferably, the geochemical sample in S1 is ground to a particle size of less than 0.075 mm, the drying temperature is 100-105°C, and the drying time is not less than 2 h; Preferably, the ratio of the mass of the sample powder to the volume of the mixed acid of hydrofluoric acid-nitric acid-perchloric acid in S2 is 0.1-0.2:15-20; the crucible includes a polytetrafluoroethylene crucible; Specifically, the preparation method of the aqua regia in S3 includes: adding 3 parts of hydrochloric acid and 1 part of nitric acid to 4 parts of water, and mixing and stirring to obtain the aqua regia; the volume ratio of the hydrochloric acid, the nitric acid, and water in the 1:1 aqua regia is 3:1:4; Preferably, the temperature of the hot plate in S3 is 280°C-289°C, and the leaching time is not less than 15 min until the solution is clear; When the temperature of the hot plate is greater than or equal to 290°C, the polytetrafluoroethylene crucible is prone to deformation, so to protect the crucible and prevent solution leakage, the optimal temperature should be maintained at about 280°C.

[0008] Preferably, the range of the series of standard solutions in S4 includes 0.00-100.0 mg / L; Preferably, the series of standard solutions in S4 includes 0.00, 1.00, 5.00, 10.00, 25.00, 50.00, and 100.0 mg / L; Specifically, the measuring instrument in S5 includes an inductively coupled plasma optical emission spectrometer (ICP-OES); Specifically, the working parameters of the ICP-OES are as follows: Radio frequency power: 1300 W; Plasma gas flow rate: 12 L / min; Atomizing gas flow rate: 0.56 L / min; Auxiliary gas flow rate: 0.2 L / min; Peristaltic pump flow rate: 1.50 mL / min; Observation mode: radial observation; Specifically, the calculation formula in S6 is: The content of the element i to be detected in the sample is in percentage (10 -2 ) ; The mass concentration of the element i to be detected in the sample solution is in mg / L (mg / L) ; The mass concentration of the element to be detected in the blank test solution is in mg / L (mg / L) ; V is the volume of the sample solution, in L (L) ; m is the mass of the sample for testing, in g (g) ; n is the dilution multiple, and is 1 when not diluted; K is the oxide conversion coefficient (applied to the calculation of the results related to the oxide, and no conversion is required if the calculation is for an elemental substance).

[0009] Specifically, the element analysis wavelength is: Na 589.592 nm, Mg 285.213 nm, Al 396.153 nm, P 213.617 nm, K 766.490 nm, Ca 317.933 nm, Ti 334.940 nm, Mn 257.610 nm, Fe 238.204 nm, Cu 327.393 nm, Zn 206.200 nm, Pb 220.353 nm, and Sr 407.771 nm.

[0010] Specifically, the sample detection limit of the present application includes 0.725-33.53 μg / g; Specifically, the hydrochloric acid, the nitric acid, the hydrofluoric acid and the perchloric acid are all of high purity; Specifically, the multi-element includes elements K, Na, Ca, Mg, Fe, Al, Mn, P, Ti, Cu, Pb, Zn and Sr.

[0011] Part of the standard solution, the standard sample and the obtained results used in the experimental process of the present application are calculated in the form of oxide, including K2O, Na2O, CaO, MgO, Fe2O3 and Al2O3, and the oxide conversion coefficient K is included in the calculation formula; The method of the present application also applies elements Li, Mo, Co, Ni and rare earth elements; Specifically, the geochemical sample includes at least one of rock, ore, soil and stream sediment.

[0012] The present application has the following advantages: (1) The method of the present application can efficiently analyze multiple elements simultaneously. K, Na, Ca, Mg, Al, Fe, Ti, Mn, P, Cu, Pb, Zn, Sr and other multiple constant and characteristic elements can be detected simultaneously in a single determination, significantly improving detection efficiency; (2) The method of the present application optimizes the sample pretreatment process. A mixed acid system of hydrofluoric acid-nitric acid-perchloric acid (5:4:1) is used to digest the sample at about 280°C, and the digestion time is significantly shortened. Subsequently, 1:1 aqua regia is used for leaching, effectively dissolving the insoluble components and ensuring the release of elements; (3) The method of the present application has low cost and universality. The use of ICP-OES has stronger tolerance to total dissolved solids, reducing the requirement for sample dilution and saving reagent consumption. The method has been successfully verified to be applicable to various geochemical samples such as rocks, soils, sediments and polymetallic ores, and has wide applicability; (4) The method of the present application has low detection limit and high sensitivity. The method detection limit of each element is as low as 0.725-33.53 μg / g, meeting the trace analysis requirements of environmental monitoring and mineral resource evaluation, and the detection capability of heavy metals such as Pb and Cu is better than that of some industry standards. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The standard curve fitting graphs of Examples 1-3 and Comparative Examples 1-2 are shown in the following table: Figure 2 The instrument detection limits of Examples 1-3 and Comparative Examples 1-2 are shown in the following table: DETAILED DESCRIPTION

[0014] The technical solutions of the present application will be described in further detail below with reference to the accompanying drawings, but the scope of protection of the present application is not limited to the following description.

[0015] Experimental materials and reagents: Hydrochloric acid (HCl), nitric acid (HNO3), hydrofluoric acid (HF), perchloric acid (HClO 4） , sulfuric acid (H2SO4) are all of high purity, and high purity argon (Ar) has a purity of more than 99.99%. Laboratory water meets the requirements of GB / T 6682-2008 "Water specifications and test methods for analytical laboratories" for secondary water, unless otherwise specified.

[0016] Among them, K, Na, CaO, MgO, Fe2O3, TiO2, Al2O3, Mn, P, Cu, Pb, Zn, Sr and other single-element standard stock solutions (1000 mg / L, National Non-ferrous Metals and Electronic Materials Analysis and Testing Center); all national standard materials come from the Standard Material and Standard Sample Information Center.

[0017] Instrument and working conditions: inductively coupled plasma spectrometer (Avio-550, PerkinElmer); Table 1 ICP-OES detection working conditions Example 1 The contents of K2O, Na2O, CaO, MgO, Fe2O3, Ti, Al2O3, Mn, P, Cu, Pb, Zn, and Sr in geochemical samples were simultaneously determined based on ICP-OES, and the specific method was as follows: 1) Sample preparation: the ore samples (originated from the wood lithium mine, and 3 samples were taken during the beneficiation process, marked as I, II, and III) were crushed and ground to a particle size of less than 0.075 mm, and then dried in an electric hot air drying oven at 100-105°C for 2 h, and then cooled to room temperature.

[0018] 2) Sample pretreatment and preparation of the solution to be tested: 0.1000 g of ore powder A was accurately weighed on an analytical balance in a polytetrafluoroethylene crucible, 15 mL of mixed acid prepared by hydrogen fluoride, nitric acid, and perchloric acid (5:4:1, V / V) was added, and the sample was dissolved on a 280°C hot plate until the perchloric acid fumed and there was about a soybean-sized liquid bead left, and then the sample was removed and cooled. 20 mL of 1:1 aqua regia was added, and the polytetrafluoroethylene crucible was placed on a 280°C hot plate for 15 min. After removal, the sample was cooled and diluted to a 100 mL volumetric flask, and then shaken to obtain the sample solution to be tested.

[0019] 3) Preparation of standard solution: an appropriate amount of standard stock solution was taken, 1:1 aqua regia was added to make it consistent with the acidity of the sample, and distilled water was added to the volume, and 0.00, 1.00, 5.00, 10.00, 25.00, 50.00, and 100.0 mg / L were configured as standard working solutions; 4) Sample determination and calculation: the standard curve was obtained by determining the prepared standard solution of each element using an inductively coupled plasma spectrometer, and then the blank sample solution and the sample solution to be tested were respectively introduced into the ICP-OES, and the concentration values of each element were determined according to the standard curve. If the measured concentration value exceeds the range of the standard curve, then the dilution liquid concentration is determined by diluting 2-5 times, and the content of each element in the sample is calculated by formula 1.

[0020] Among them, the preparation method of the blank sample solution is that no sample powder is added in step 2), and the other steps are the same.

[0021] Formula 1 The content of the element i to be tested in the sample is calculated by formula 1, and the value is calculated in percentage (10 -2 ); The value of the mass concentration of the element i to be detected in the sample solution, in milligrams per liter (mg / L); The value of the mass concentration of the element to be detected in the blank test solution, in milligrams per liter (mg / L); V The value of the volume of the sample solution, in liters (L); m The value of the mass of the sample for testing, in grams (g); n The dilution multiple, which is 1 for no dilution; K The oxide conversion coefficient.

[0022] The fitting of the standard curve is shown in Figure 1 All the curve configuration concentrations are 0.00, 1.00, 5.00, 10.00, 25.00, 50.00, and 100.0 mg / L, and the series curves are well fitted, with R 2 > 0.99995.

[0023] The detection limits of the elements based on the present application are shown in Figure 2 .

[0024] Comparative Example 1 Comparative Example 1 is used to compare the digestion times of different mixed acids on different temperature hot plates, as follows: 0.1000 g of each of the national primary standard materials GSR-1, GSD-1a, and GSS-1 was weighed, 15 mL of three kinds of mixed acids were used, namely mixed acid A: hydrofluoric acid: nitric acid: perchloric acid = 5:4:1; mixed acid B: hydrofluoric acid: nitric acid: sulfuric acid (1:1) = 5:4:1; and mixed acid C: hydrofluoric acid: nitric acid: perchloric acid: sulfuric acid (1:1) = 5:4:1:0.5, and dissolution was performed in a 50 mL polytetrafluoroethylene beaker on different temperature hot plates, and the time required for the solution to smoke and form liquid beads the size of soybeans is shown in Table 2: Table 2 Digestion times of different mixed acids As can be seen from the test results, the addition of sulfuric acid can greatly increase the digestion time required, and therefore, if the digestion effect is consistent, sulfuric acid can be selected not to be added to save digestion time. In addition, when the hot plate is greater than or equal to 290°C, the polytetrafluoroethylene crucible is prone to deformation, and therefore, to protect the crucible and prevent solution leakage, the optimal temperature should be maintained at about 280°C.

[0025] Comparative Example 2 Comparative Example 2 is used to compare the leaching effects of different leaching solutions on silicate minerals, stream sediments and soil samples in the determination of Al2O3, Fe2O3, CaO, MgO, K2O, Na2O, Ti, Mn, P and other common elements, as follows: Randomly select one sample from each of the national primary standard materials GSR (rock), GSD (stream sediment) and GSS (soil) series (the selected samples are GSD-17, GSR-11 and GSS-20), weigh 0.1000 g, add 15 mL of mixed acid (hydrofluoric acid: nitric acid: perchloric acid = 5:4:1) in a 50 mL polytetrafluoroethylene beaker, and dissolve on a 280°C hot plate. When the solution is smoked and there is about a soybean-sized liquid bead left, remove the cooling. Add 20 mL of leaching solution (1:1 nitric acid, 1:1 hydrochloric acid, 1:1 aqua regia, 1:1 sulfuric acid), and then place the polytetrafluoroethylene crucible on a 250°C hot plate and leach for 15 min until the solution is clear. Remove it, and after cooling, dilute to 100 mL in a volumetric flask, shake well, and obtain the sample solution to be tested. Use ICP-OES to determine the standard curve of the prepared standard solution of each element, and then sample the blank sample solution and the sample solution to be tested into the ICP-OES, and according to the standard curve, the concentration values of each element are determined by the instrument. Each sample is tested in triplicate, and the data obtained are as follows: Table 3 Effect of leaching acid on element determination (unit: 10 -2 ) From the test results, it can be seen that the leaching effect of sulfuric acid is the worst, and it is significantly lower than the standard value in almost all element determinations. The nitric acid leaching solution tends to be high in the determination of P, and the differences between hydrochloric acid, nitric acid and aqua regia in the determination of the remaining elements are not obvious, and the test results are consistent with the standard values.

[0026] Example 2 This example is used to verify the determination effect of the method on Al2O3, Fe2O3, CaO, MgO, K2O, Na2O, Mn and other common elements in polymetallic minerals, as well as characteristic elements Cu, Pb and Zn, as follows: Select GBW07162-GBW07165, a total of 4 national primary standard materials of polymetallic minerals, and perform three parallel experiments for each sample according to the method described in the patent, and the measured values and standard values are as follows: Table 4 Determination of polymetallic minerals (unit: 10 -2 ) From the test results, the contents of Al2O3, Fe2O3, CaO, MgO, K2O, Na2O, Mn, Cu, Pb, Zn and other elements measured by the method are consistent with the standard values, indicating that the method is also applicable to the analysis of constant elements of non-ferrous metal minerals.

[0027] Example 3 The accuracy of the determination results of the method was verified, as shown in Tables 5 and 6: Table 5 Element contents in various geochemical samples of GSR-11, GSS-2 and GSD-12 Table 6 Element contents in various geochemical samples of geological survey mineral samples By repeatedly determining the contents of various constant elements in national primary standard materials GSR-11, GSS-2, GSD-12 and geological survey mineral samples I (silicate mineral), II (lithium ore) and III (copper ore), it can be known that the detection precision of the detection method provided by the application is reliable, and the detection method is suitable for simultaneously determining the contents of elements in various geochemical samples by ICP-OES method.

[0028] The above only describes the preferred embodiments of the present application, and it should be understood that the present application is not limited to the forms disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concepts described herein by the above teachings or related technical or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the appended claims of the present application.

Claims

1. A method for simultaneous determination of multiple elements in geochemical samples based on ICP-OES, characterized in that, Includes the following steps: S1. Sample preparation: The geochemical sample is crushed and ground, dried and cooled to obtain sample powder; S2. Sample pretreatment: Weigh the sample powder into a crucible, add a mixed acid of hydrofluoric acid-nitric acid-perchloric acid in a volume ratio of 5:4:1, digest it on a hot plate until it emits thick perchloric acid fumes and leaves liquid droplets the size of soybeans, then cool it. S3. Extraction: Add aqua regia to the crucible, extract on the hot plate, cool and bring to a final volume to obtain the solution to be tested; S4. Preparation of standard curve: Prepare a series of standard solutions using single-element standard stock solutions, with the matrix acidity consistent with the solution to be tested, to obtain standard solutions; S5. Measurement: Measure the spectral intensity of the standard solution, blank solution and the test solution, calculate the elemental concentration through the standard curve, and dilute and measure again if the concentration exceeds the linear range; S6. Result Calculation: Calculate the elemental content in the geochemical sample.

2. The determination method according to claim 1, characterized in that: The geochemical sample described in S1 is crushed and ground to a particle size of less than 0.075 mm, and the drying temperature is 100~105℃, with a drying time of not less than 2 h.

3. The determination method according to claim 1, characterized in that: The mass ratio of the sample powder to the volume of the hydrofluoric acid-nitric acid-perchloric acid mixed acid in S2 is 0.1~0.2:15~20; the crucible includes a polytetrafluoroethylene crucible.

4. The determination method according to claim 1, characterized in that: The method for preparing aqua regia described in S3 includes: Add 3 parts hydrochloric acid and 1 part nitric acid to 4 parts water, mix and stir to obtain the aqua regia. The volume ratio of hydrochloric acid, nitric acid and water in the 1:1 aqua regia is 3:1:

4. The hydrochloric acid, nitric acid, hydrofluoric acid, and perchloric acid are all of analytical grade.

5. The determination method according to claim 1, characterized in that: The temperature of the heating plate in S3 is 280℃~289℃, and the extraction time is not less than 15 minutes until the solution is clear.

6. The determination method according to claim 1, characterized in that: The series of standard solutions described in S4 ranges from 0.00 to 100.0 mg / L.

7. The determination method according to claim 1, characterized in that: The measuring instruments described in S5 include an inductively coupled plasma optically spectroscopy (ICP-OES) instrument.

8. The determination method according to claim 1, characterized in that: The limits of detection for samples in this application range from 0.725 to 33.53 μg / g.

9. The determination method according to claim 1, characterized in that: The multi-element composition includes the elements K, Na, Ca, Mg, Fe, Al, Mn, P, Ti, Cu, Pb, Zn, and Sr.

10. The determination method according to claim 1, characterized in that: The geochemical samples include at least one of rocks, ores, soils, and stream sediments.

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