Overview of HJ 737-2015 Standard
HJ 737-2015 is an industry standard issued by the Ministry of Ecology and Environment, with the full title "Soil and Sediment—Determination of Beryllium—Graphite Furnace Atomic Absorption Spectrophotometry." This standard provides a unified technical specification for the determination of beryllium (Be) content in soil and sediments, and is applicable to fields such as environmental monitoring, site investigation, and scientific research analysis.
Beryllium and its compounds are highly toxic and are listed as one of the key controlled pollutants. Accurate determination of beryllium content in soil and sediments is of great significance for environmental risk assessment and contaminated site remediation.
Standard Scope of Application and Detection Limit
Scope of Application
- Applicable to the determination of beryllium in soil and sediments.
- When the sample amount is 0.2 g and the constant volume is 25 mL, the method detection limit is 0.03 mg/kg, and the lower limit of determination is 0.12 mg/kg.
- Applicable to routine analysis in environmental monitoring stations, third-party testing institutions, and scientific research laboratories.
Method Principle
After acid digestion of soil or sediment samples, beryllium enters the solution in ionic form. The test solution is injected into a graphite furnace atomic absorption spectrophotometer, atomized at high temperature, and ground-state beryllium atoms absorb the characteristic spectral line (234.9 nm). Based on the relationship between absorbance and concentration, quantitative analysis is performed using the standard curve method.
Instrument and Reagent Requirements
Main Instruments and Equipment
| Equipment Name | Technical Requirements |
|---|---|
| Graphite furnace atomic absorption spectrophotometer | Equipped with beryllium hollow cathode lamp, wavelength 234.9 nm |
| Graphite tube | Pyrolytically coated graphite tube, platform graphite tube recommended |
| Analytical balance | Readability 0.0001 g |
| Microwave digestion instrument or electric heating plate | Used for sample pretreatment |
Main Reagents
- Nitric acid: Guaranteed reagent grade or higher purity.
- Hydrofluoric acid: Guaranteed reagent grade.
- Perchloric acid: Guaranteed reagent grade.
- Beryllium standard solution: Commercially available certified reference material.
- Matrix modifier: Such as magnesium nitrate or palladium nitrate, used to eliminate matrix interference.
Analysis Operating Procedures
Sample Pretreatment
- Air-dry and grind the soil or sediment sample, and pass through a 100-mesh sieve (0.15 mm).
- Accurately weigh 0.2 g (to the nearest 0.0001 g) of sample into a digestion vessel.
- Add an appropriate amount of nitric acid, hydrofluoric acid, and perchloric acid, and perform digestion according to the digestion procedure specified in the standard.
- After digestion is complete, evaporate the acid to near dryness, and make up to 25 mL with 1% nitric acid solution.
- Filter through a 0.45 μm membrane filter, and the filtrate is ready for measurement.
Instrument Measurement Conditions
The following are typical graphite furnace temperature program parameters, which should be optimized according to the actual instrument model:
| Stage | Temperature (℃) | Time (s) |
|---|---|---|
| Drying | 80–120 | 30 |
| Ashing | 800–1000 | 20 |
| Atomization | 2400–2600 | 5 |
| Cleaning | 2600–2700 | 3 |
The measurement wavelength is set to 234.9 nm, the spectral bandwidth is 0.7 nm, and the lamp current is set according to the instrument manufacturer's recommended value. Background correction is performed using a deuterium lamp or Zeeman effect.
Standard Curve and Quantification
- Prepare a beryllium standard series solution, with a recommended concentration range of 0–20 μg/L.
- Measure the absorbance of the standard solutions in sequence, and draw the standard curve; the correlation coefficient should be ≥0.999.
- Under the same conditions, measure the sample blank and sample test solution, and calculate the beryllium concentration according to the standard curve.
- Results are expressed as dry-basis mass fraction (mg/kg).
Quality Control and Precautions
Quality Control Requirements
- At least 2 blank tests should be performed for each batch of samples, and the blank value should be lower than the detection limit.
- At least 1 reference material should be inserted for every 20 samples for accuracy control, and the recovery rate should be between 90% and 110%.
- 10% parallel samples should be performed for each batch of samples, and the relative deviation should meet the standard requirements.
- The standard curve should be redrawn or verified for each batch of samples.
Common Interferences and Elimination
- Matrix interference: Soil digestion solutions contain high levels of elements such as aluminum and silicon. It is recommended to use a matrix modifier (such as magnesium nitrate) and a platform graphite tube.
- Background absorption: Use deuterium lamp or Zeeman effect background correction.
- Memory effect: Beryllium easily remains; a high-temperature cleaning step should be set after atomization.
- Reagent blank: Hydrofluoric acid and perchloric acid must be thoroughly evaporated to avoid corroding the graphite tube.
Instrument Selection and Procurement Recommendations
For laboratories that need to implement HJ 737-2015, when purchasing a graphite furnace atomic absorption spectrophotometer, the following indicators should be focused on:
- Detection limit: Should meet the method requirement of 0.03 mg/kg; the graphite furnace system needs high sensitivity.
- Background correction method: Zeeman effect or deuterium lamp correction is recommended to ensure accuracy under complex matrices.
- Automatic sampler: Improves batch sample analysis efficiency and reproducibility.
- Graphite tube type: Supports platform graphite tubes and pyrolytically coated tubes to accommodate different matrices.
- Software functions: Capable of standard curve fitting, automatic addition of matrix modifiers, and quality control data management.
During procurement, it is recommended to require suppliers to provide application reports or demonstration data for soil matrices to ensure that the instrument can stably meet the performance indicators specified in the standard.