A method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry

Abstract

The invention discloses a method for determining boron in soil by acid-soluble inductively coupled plasma mass spectrometry. The method comprises the following steps: decomposing a soil boron detection sample by hydrochloric acid, hydrofluoric acid and nitric acid, adding ammonium chloride and mannitol to protect B, evaporating to remove a large amount of hydrofluoric acid, dissolving soluble salts by aqua regia, adding an internal standard solution, shaking well, taking a portion of the clarified solution, diluting, and determining by plasma mass spectrometry. The method adopts the joint protective effect of ammonium chloride and mannitol, avoids the volatilization loss of B, removes hydrofluoric acid, effectively reduces the detection limit of B, and improves the accuracy. The detection limit of B is 0.7 μg / g.

Description

Technical Field

[0001] The invention relates to the technical field of chemical element determination, in particular to a method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry. Background Art

[0002] At present, the boron (B) in soil and water sediments in China is mainly determined by emission spectroscopy, inductively coupled plasma emission spectroscopy or inductively coupled plasma mass spectrometry. Since emission spectroscopy uses AC or DC arc to excite powder samples, the introduced reagent blank is low, which is extremely beneficial for the detection of low-content samples, but the linear range is narrow. In addition, for organic matter, sulfide, and carbonate samples, due to easy splashing, large injection fluctuations, and limited applicable sample types. Inductively coupled plasma emission spectroscopy is affected by interference from elements such as iron and cobalt, and even with mathematical correction, it is still difficult to meet the detection needs of low-content samples. The actual detection limit is greater than 5μg / g, which does not meet the minimum requirement (<1μg / g) of the Quality Management Specification for Laboratory Testing of Geological Mineral Resources (DZT0130-2006). Inductively coupled plasma mass spectrometry has the characteristics of high sensitivity, less interference and fast detection speed. In recent years, many workers have tried to use inductively coupled plasma mass spectrometry to determine B in regional geochemical samples. According to sample digestion, it is divided into two methods: acid dissolution or alkaline fusion. When alkaline fusion is used, the sampling system of inductively coupled plasma mass spectrometry is limited by salt, and a large amount of salt needs to be removed by cation exchange resin to obtain the ideal detection effect. The procedure is complicated and the cost is high when it is determined alone. When the acid dissolution method is used, in order to avoid the volatilization loss of B during evaporation, phosphoric acid or direct hydrofluoric acid medium needs to be added for direct sampling. Both methods have certain defects (phosphoric acid introduces a high blank and causes greater damage to the interceptor cone, hydrofluoric acid is highly corrosive, the working environment is not conducive to the protection of personnel, and a dedicated set of hydrofluoric acid-resistant sampling system is required), and they are rarely used in large-scale detection. Although the acid dissolution method is simple and easy to master, it is inevitable to use hydrofluoric acid. How to remove hydrofluoric acid and avoid the volatilization loss of B in the future is the key link of the method. Summary of the invention

[0003] The present invention aims at the above problems and provides a method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry. The method of the present invention adopts the joint protective effect of ammonium chloride and mannitol, avoids the volatilization loss of B and the addition of phosphoric acid when volatilizing and removing hydrofluoric acid, effectively reduces the detection limit of B, and the method is easier to master and mass produce.

[0004] In order to achieve the above purpose, the technical solution adopted in the present invention is as follows:

[0005] A method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry comprises the following steps:

[0006] S1: Weigh 0.1500g of boron test sample into a 30mL polytetrafluoroethylene crucible, add 0.1g of ammonium chloride, then add 3-5mL of a mixed acid consisting of HCl and HF, and then add 0.3-0.5mL of HNO 3 , cover the lid, heat to 130-150℃ on a perforated electric hot plate, keep warm for 3-4h, cool to 100℃, open the lid, add 1-2mL mannitol, heat to 150℃ until the solution evaporates, keep warm for 10-15min, add 5-6mL aqua regia to extract, add 10.00mL of germanium internal standard solution after the soluble salt is dissolved, remove and shake well. Take 0.5mL of the clear solution in a 10mL plastic tube, add 5mL of dilute HNO 3 , obtaining a sample solution to be tested;

[0007] S2: In a polytetrafluoroethylene crucible, add a certain amount of B standard solution, prepare the corresponding standard solution according to step S1, shake well, and obtain a series of standard solutions with different concentrations;

[0008] S3: using inductively coupled plasma mass spectrometry to measure the signal response value of B using standard solutions of different concentrations, and then drawing a working curve according to the signal response value;

[0009] S4: Using inductively coupled plasma mass spectrometry to measure the signal response value of B in the sample solution obtained in step S1, substituting the obtained signal response value into the working curve, and calculating the content of B in the sample.

[0010] As a preferred technical solution of the present invention: the amount of germanium added to the mixed internal standard is 50 μg.

[0011] As a preferred technical solution of the present invention: the volume ratio of HCl to HF in the mixed acid is 1:1.

[0012] As a preferred technical solution of the present invention: the concentration of mannitol is 5%-10%.

[0013] As a preferred technical solution of the present invention: the working conditions of the inductively coupled plasma mass spectrometry are:

[0014] name Technical Parameters name Technical Parameters Plasma power 1500W Nebulizer flow rate 0.8-0.95L / min Cooling gas (Ar) 13L / min Injection pump speed 30rpm Auxiliary gas (Ar) 0.9L / min Injection time 15S Ф sampling cone (Ni) 1.1mm Scanning method Peak Jump Ф Skimmer Cone (Ni) 0.7mm Measurement mode pulse B mass number 10 Channel dwell time 100ms Ge mass number 74 Sampling depth / step 60

[0015] As a preferred technical solution of the present invention: the particle size of the test sample should be less than 0.097 mm, dried at 105° C. for 2 h, and then placed in a ground-mouth small glass bottle for later use after cooling.

[0016] As a preferred technical solution of the present invention: the method also includes verification and comparison of the working curve, specifically, selecting 3 to 5 geochemical primary standard substances, preparing corresponding solutions according to step S1, and preparing a sample blank solution at the same time, and measuring them by inductively coupled plasma mass spectrometry under the same conditions, and then verifying and comparing the measurement results with the standard values ​​of each standard substance.

[0017] As a preferred technical solution of the present invention: the boron detection sample includes the detection of B in water system sediment or soil.

[0018] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0019] 1. The method of the present invention decomposes the sample with hydrochloric acid, hydrofluoric acid and nitric acid, adds ammonium chloride and mannitol to protect B, evaporates to remove a large amount of hydrofluoric acid, dissolves soluble salts with aqua regia, adds germanium internal standard solution, dilutes to obtain a test solution, and then determines the boron content by inductively coupled plasma mass spectrometry. The method has the advantages of low detection limit, high accuracy, simple operation, and easy batch detection.

[0020] 2. The method of the present invention adopts the joint protective effect of ammonium chloride and mannitol to avoid the volatilization loss of B and the addition of phosphoric acid, effectively reducing the detection limit of B and improving the accuracy. The detection limit of B is 0.7 μg / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the standard curve of B. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 work are within the scope of protection of the present invention.

[0023] Example 1

[0024] A method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry comprises the following steps:

[0025] S1: Weigh 0.1500g of the test sample into a 30mL polytetrafluoroethylene crucible, add 0.1g of ammonium chloride, then add 3-5mL of a mixed acid consisting of HCl and HF, and then add 0.3-0.5mL of HNO 3, cover the lid, heat to 130-150℃ on a perforated electric hot plate, keep warm for 3-4h, cool to 100℃, open the lid, add 1-2mL mannitol, heat to 150℃ until the solution evaporates, keep warm for 10-15min, add 5-6mL aqua regia to extract, add 10.00mL of germanium internal standard solution after the soluble salt is dissolved, remove and shake well. Take 0.5mL of the clear solution in a 10mL plastic tube, add 5mL of dilute HNO 3 , obtaining a sample solution to be tested;

[0026] S2: In a polytetrafluoroethylene crucible, add a certain amount of B standard solution, prepare the corresponding standard solution according to step S1, shake well, and obtain a series of standard solutions with different concentrations (as shown in Table 1);

[0027] S3: Using the instrument parameters of Table 2 of the standard solutions with different concentrations to measure the signal response value of B on the inductively coupled plasma mass spectrometer, and then drawing a working curve according to the signal response value. The drawn working curve is as follows: Figure 1 :

[0028] Table 1: Standard curve of B element

[0029] Mass (ug) Signal response value 0 520 2 4673 5 10895 10 21233 20 42131 50 104362 75 155653

[0030] Table 2: Recommended instrument parameters

[0031] name Technical Parameters name Technical Parameters Plasma power 1500W Nebulizer flow rate 0.8-0.95L / min Cooling gas (Ar) 13L / min Injection pump speed 30rpm Auxiliary gas (Ar) 0.9L / min Injection time 15S Ф sampling cone (Ni) 1.1mm Scanning method Peak Jump Ф Skimmer Cone (Ni) 0.7mm Measurement mode pulse B mass number 10 Channel dwell time 100ms Ge mass number 74 Sampling depth / step 60

[0032] S4: The working curve of B obtained from step S3 is: Y=2070.31712X+582.23236, R 2 =0.99999, the sample solution obtained in step S1 is used to determine the signal response value of B by inductively coupled plasma mass spectrometry, the obtained signal response value is substituted into the working curve, and the content of B in the sample is calculated.

[0033] Accuracy analysis of this method

[0034] Select multiple geochemical primary standard substances (washed sediments, soil), prepare the corresponding solutions according to step S1, and prepare a sample blank solution at the same time. Use inductively coupled plasma mass spectrometry to measure under the same working conditions, and verify and compare with the standard values ​​of each standard substance. The test results are shown in the following table.

[0035]

[0036]

[0037]

[0038] It can be seen from the table that among the national primary standard substances measured, the accuracy ΔlogC≤± 0.1, which meets the testing requirements of the Quality Management Standards for Laboratory Testing of Geology and Mineral Resources (DZT0130-2006), and the method has a high accuracy.

[0039] Method precision determination

[0040] Three soil and two stream sediment samples of national primary standard materials were selected, 12 portions of each were weighed, and the corresponding solutions were prepared according to step S1. At the same time, a sample blank solution was prepared. The inductively coupled plasma mass spectrometry was used for determination under the same working conditions, and the relative standard deviations were calculated. The test results are shown in the following table.

[0041] GSS-5 GSS-8 GSS-17 GSD-5a GSD-18 1 54.1 57 21.4 98.4 5.83 2 55.5 56.3 22.1 97.1 5.1 3 53.2 55.9 23.3 96.8 5.93 4 55.5 58.1 21.5 97.1 5.61 5 56.7 58.8 23.2 98.2 5.15 6 57.2 57.1 21.8 99.2 5.49 7 56.1 56.7 20.7 95.4 5.54 8 56.3 58.2 22.2 94.9 5.81 9 55.2 55.4 22.7 96.3 6.16 10 53.8 58.6 21.7 96.5 5.49 11 53.8 54.9 22.6 98.2 5.95 12 54.6 53.9 21.6 99.4 6.03 Average value (ug / g) 55.17 56.74 22.07 97.29 5.67 Standard value (ug / g) 53 54 24 96 5.5 Standard Deviation 1.28 1.54 0.77 1.42 0.34 Relative standard deviation 2.31 2.71 3.50 1.46 5.92

[0042] As can be seen from the table, the relative standard deviations of the five national standard substances are between 2.31% and 6%, which meets the requirement of less than 8% in the Quality Management Standard for Laboratory Testing of Geological and Mineral Resources (DZT0130-2006) and has better measurement precision.

[0043] Method detection limit

[0044] In 12 polytetrafluoroethylene crucibles, 12 process blank solutions were prepared according to step S1, except that no samples were weighed. The solutions were measured by inductively coupled plasma mass spectrometry under the same working conditions. The standard deviation was calculated and 3 times the standard deviation was the detection limit. The test results are shown in the following table.

[0045]

[0046]

[0047] As can be seen from the table, the detection limit is much lower than the minimum detection limit (1ug / g) required by the Quality Management Standards for Laboratory Testing of Geological and Mineral Resources (DZT 0130-2006), and the method is more advanced.

[0048] The above contents are further detailed descriptions of the present invention in combination with specific / preferred implementations, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can also make several substitutions or modifications to these described embodiments without departing from the concept of the present invention, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry, characterized in that: The steps include: S1: Weigh 0.1500 g of boron test sample into a 30 mL polytetrafluoroethylene crucible, add 0.1 g of ammonium chloride, then add 3-5 mL of a mixed acid composed of HCl and HF, and then add 0.3-0.5 mL of HNO3, cover the lid, heat to 130-150°C on a perforated electric hot plate, keep warm for 3-4 hours, cool to 100°C, open the lid, add 1-2 mL of mannitol, heat to 150°C until the solution is evaporated, keep warm for 10-15 minutes, add 5-6 mL of aqua regia to extract, add 10.00 mL of germanium internal standard solution after the soluble salt is dissolved, remove and shake well, take 0.5 mL of the clear solution into a 10 mL plastic tube, add 5 mL of dilute HNO3, and obtain the sample solution to be tested; S2: In a polytetrafluoroethylene crucible, add a certain amount of B standard solution, prepare the corresponding standard solution according to step S1, shake well, and obtain a series of standard solutions with different concentrations; S3: using inductively coupled plasma mass spectrometry to measure the signal response value of B using standard solutions of different concentrations, and then drawing a working curve according to the signal response value; S4: Using inductively coupled plasma mass spectrometry to measure the signal response value of B in the sample solution obtained in step S1, substituting the obtained signal response value into the working curve, and calculating the content of B in the sample.

2. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to claim 1, characterized in that: The amount of germanium added in the internal standard is 50 μg.

3. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to claim 1, characterized in that: The volume ratio of HCl to HF in the mixed acid is 1:

1.

4. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to claim 1, characterized in that: The concentration of the mannitol is 5%-10%.

5. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to claim 1, characterized in that: The working conditions of the inductively coupled plasma mass spectrometry determination are: 。 6. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to claim 1, characterized in that: The particle size of the test sample should be less than 0.097 mm and dried at 105°C for 2 hours.

7. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to claim 1, characterized in that: The aqua regia is composed of hydrochloric acid and nitric acid in a volume ratio of 3:

1.

8. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to claim 1, characterized in that: The method also includes drawing and comparing working curves, specifically selecting 3 to 5 geochemical primary standard substances, preparing corresponding solutions according to step S1, and preparing a sample blank solution at the same time, and measuring them by inductively coupled plasma mass spectrometry under the same conditions, and then verifying and comparing the measurement results with the standard values ​​of each standard substance.

9. The method for determining boron in soil by acid dissolution-inductively coupled plasma mass spectrometry according to any one of claims 1 to 8, characterized in that: The soil sample is suitable for detecting water system sediments.

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