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This standard specifies the method for the determination of trace elements in imported chemical fertilizers — copper, zinc, iron, manganese, and magnesium. The detection method is as follows:
1. Atomic absorption spectrometer square detection method summary:
The sample is dissolved in nitric acid or hydrochloric acid. In the medium of 2% nitric acid or hydrochloric acid, the atomic absorption spectrometer is used at the wavelengths of 324.7nm, 213.9nm, 248.3nm, 279.5nm and 285.2nm. Determination of iron, manganese and magnesium.
2. Description of instruments such as atomic absorption spectrometer:
Atomic absorption spectrometer: attached with air-acetylene burner, and copper, zinc, iron, manganese, magnesium hollow cathode lamp, metal sleeve glass high-efficiency atomizer.
The atomic absorption spectrometer used shall meet the following indicators:
Minimum sensitivity: The absorbance reading of the highest concentration standard in the equal concentration standard solution is not less than 0.5.
Working curve linearity: the difference between the absorbance readings of the two highest concentration standard solutions in the equal concentration standard solution is not less than 0.7 times the difference between the absorbance readings of the lowest concentration standard solution and the zero concentration solution.
Minimum stability: The absorbance readings obtained from multiple measurements of the highest concentration standard solution and the zero concentration solution are not greater than 1.5% and 0.6%, respectively, with respect to the average coefficient of variation of the highest concentration standard solution absorbance readings.
3. Atomic absorption spectrometer reagents and detection process:
3.1 Hydrochloric acid (11).
3.2 Nitric acid (1 1).
3.3 Lanthanum chloride solution (0.1%): Weigh 0.1g of lanthanum chloride in 100mL of water.
3.4 Zinc standard stock solution (1mg / mL): Accurately weigh 1.000g of metal zinc (99.95% or more) in a 400mL beaker, add 30mL hydrochloric acid (3.1), dissolve by heating, move the solution into a 1L volumetric flask, and dilute to the standard with water Line, mix well and store in plastic bottles. This solution 1mL contains 1mg zinc.
3.5 Zinc standard solution (10? G / mL): Pipette 5mL zinc standard stock solution (3.4) into a 500mL volumetric flask, dilute to the mark with water, and mix well. 1mL of this solution contains 10? G of zinc.
3.6 Copper standard stock solution: Accurately weigh 1.000g of copper metal (above 99.95%), place it in a 400mL beaker, add 50mL of nitric acid (3.2) to heat and dissolve, and after cooling, transfer the solution to a 1L volumetric flask and dilute to the mark with water , Mix well and store in a plastic bottle. This solution 1mL contains 1mg copper.
3.7 Copper standard solution (10? G / mL): Pipette 5mL copper standard stock solution (3.6) into a 500mL volumetric flask, dilute with water to the mark, and mix well. This solution 1mL contains 10? G copper.
3.8 Iron standard stock solution (1mg / mL): accurately weigh 1.000g of metallic iron (more than 99.9%) into a 400mL beaker, add 50mL of nitric acid (3.2), dissolve by heating, and after cooling, transfer the solution to a 1L volumetric flask and use water Dilute to the mark and mix well. Store in plastic bottles. This solution 1mL contains 1mg iron.
3.9 Iron standard solution (100? G / mL): Pipette 50mL iron standard stock solution (3.8) into a 500mL volumetric flask, dilute to the mark with water, and mix well. This solution 1mL contains 100? G iron.
3.10 Manganese standard stock solution: Accurately weigh 1.000g of metal manganese (99.9%), place it in a 400mL beaker, add 50mL hydrochloric acid (3.1) to heat to dissolve, and after cooling, transfer the solution to a 1L volumetric flask, dilute to the mark with water Evenly, store in a plastic bottle, this solution 1mL contains 1mg manganese.
3.11 Manganese standard solution (10? G / mL): Pipette 5mL manganese standard stock solution (3.10) into a 500mL volumetric flask, dilute to the mark with water, and mix well. 1mL of this solution contains 10? G manganese.
3.12 Magnesium standard stock solution (1mg / mL): accurately weigh the spectrally pure magnesium oxide 1.6584g, place it in a 400mL beaker, add 20mL hydrochloric acid (3.1) to heat to dissolve, after cooling, move this solution into a 1L volumetric flask and dilute with water To the mark, mix well and store in a plastic bottle. This solution 1mL contains 1mg magnesium.
3.13 Magnesium standard solution (10? G / mL): Pipette 5mL magnesium standard stock solution (3.12) into a 500mL volumetric flask, dilute to the mark with water, and mix well. 1mL of this solution contains 10? G magnesium.
4. Operation procedure of atomic absorption spectrometer:
4.1 Preparation of test solution
Weigh 1g of the sample into a 100mL beaker, add 15mL hydrochloric acid (3.1) to heat and boil, steam to 2 ~ 4mL, cool, transfer to a 100mL volumetric flask, dilute to the mark with water, and mix well.
4.2 Measurement of absorbance of zinc, copper, iron, manganese
Put the above solution (4.1) on the atomic absorption spectrometer at the wavelengths of 213.9nm, 324.7nm, 248.3nm, 279.5nm, in the air-acetylene flame, and zero with water at the same time with various corresponding standard solution series. The absorbance of zinc, copper, iron, and manganese can be found from the working curve respectively.
4.3 Measurement of absorbance of magnesium
Pipette 10 mL of the above solution (4.1) into a 100 mL volumetric flask, add 4 mL of lanthanum chloride (3.3) and 2 mL of hydrochloric acid (3.1), dilute with water to the mark, and mix well. On the atomic absorption spectrometer, at a wavelength of 285.2nm, in the air-acetylene flame, the water is zeroed with the magnesium standard series at the same time, the absorbance of magnesium is measured, and the corresponding amount of magnesium is found from the working curve.
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