Determination of Total Boron in Soil by Alkali Fusion and Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
I. Overview of the Method
Alkali fusion combined with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is an efficient and sensitive analytical method for determining total boron in soil. This method involves the complete release of boron from soil samples using alkali fusion, followed by high-sensitivity quantitative analysis using ICP-MS. It effectively avoids matrix interferences in the samples, improving the accuracy and precision of the measurements.
II. Sample Preparation and Digestion
Sample Preparation
Air-dried soil samples are ground to a particle size smaller than 0.147 mm and stored for analysis.
Alkali Fusion
Weigh 0.5 g of air-dried soil sample, accurate to 0.0001 g, into a platinum crucible. Add 3 g of anhydrous sodium carbonate, mix thoroughly, and then fuse at 950°C for 30 minutes. After fusion, remove the crucible, allow it to cool slightly, and transfer the melt into a 200 mL quartz beaker. Add 50 mL of water and dissolve the melt with 4 mol/L sulfuric acid, adjusting the solution pH to between 6.0 and 6.8. Finally, transfer the solution to a 100 mL quartz volumetric flask, dilute to the mark, and mix well for subsequent analysis.
III. Analysis Procedure
Instrument and Reagent Preparation
Instrument: Inductively Coupled Plasma Mass Spectrometer (ICP-MS).
Reagents: Anhydrous sodium carbonate, 4 mol/L sulfuric acid, boron standard solution (100 µg/mL).
Standard Curve Preparation
Dilute the boron standard solution to prepare a series of standard solutions with different concentrations. Treat these standards following the same procedure as the samples and measure their absorbance to construct a calibration curve.
Sample Analysis
Take 5.0 mL of the prepared sample solution and process it following the same steps used for the standard curve preparation. Measure the absorbance and calculate the boron content in the sample based on the calibration curve.
IV. Considerations
Color Development Conditions
During the color development process, strictly control the evaporation time, temperature, and rate. Avoid interruptions, especially after adding curcumin, to ensure accurate results.
Instrument Calibration
Before analysis, calibrate the ICP-MS to ensure the instrument is operating optimally.
Matrix Effect Mitigation
Since soil samples may contain various matrix components, it is recommended to use internal standards or matrix-matched calibration methods during analysis to eliminate matrix interferences.
V. Results and Discussion
This method offers high sensitivity and accuracy, making it suitable for determining total boron in soil. Experimental results indicate that the alkali fusion-ICP-MS method can rapidly and accurately determine boron content in soil, meeting the needs of modern agricultural soil quality monitoring.
By employing this method, total boron in soil can be effectively measured, providing a scientific basis for soil fertility assessment and rational fertilization practices.
