Overview of GB/T 17138-1997 Standard

GB/T 17138-1997 is one of the important methods in Chinese national standards for soil quality testing, with the full title "Soil quality - Determination of copper and zinc - Flame atomic absorption spectrophotometry". This standard specifies the technical process for the determination of copper and zinc content in soil using flame atomic absorption spectrophotometry, applicable to environmental monitoring, agricultural soil surveys, and contaminated site assessment.

This standard has the advantages of simple operation, high sensitivity, and fast analysis speed, and is a classic method for routine laboratory detection of soil copper and zinc. When selecting testing schemes, engineering technicians and procurement personnel can prioritize this standard to ensure data compliance.

Method Principle and Scope of Application

Basic Principle

After acid digestion of soil samples, copper and zinc enter the solution in ionic form. The test solution is sprayed into the flame of a flame atomic absorption spectrophotometer. After atomization, copper and zinc atoms absorb light of specific wavelengths, and the absorbance is proportional to the concentration. Quantification is achieved through a standard curve.

  • Copper: measurement wavelength 324.7 nm
  • Zinc: measurement wavelength 213.9 nm
  • Flame type: air-acetylene flame

Scope of Application

This standard is applicable to the determination of copper and zinc content in various soils. The detection limits are copper 1 mg/kg and zinc 0.5 mg/kg (depending on sample treatment). For high-concentration samples, appropriate dilution can be used before measurement.

Reagents and Instrument Preparation

Main Reagents

  • Hydrochloric acid (guaranteed reagent grade)
  • Nitric acid (guaranteed reagent grade)
  • Hydrofluoric acid (guaranteed reagent grade)
  • Perchloric acid (guaranteed reagent grade)
  • Copper and zinc standard stock solutions (1000 mg/L)

Instruments and Equipment

  • Flame atomic absorption spectrophotometer: equipped with copper and zinc hollow cathode lamps
  • Analytical balance: readability 0.0001 g
  • Electric hot plate or microwave digestion instrument
  • Polytetrafluoroethylene crucible
  • Volumetric flasks, pipettes, and other glassware

Analysis Procedure

Sample Pretreatment

  1. Air-dry and grind soil samples, pass through a 100-mesh nylon sieve.
  2. Accurately weigh 0.5 g sample (to the nearest 0.0001 g) into a polytetrafluoroethylene crucible.
  3. Add a small amount of water to moisten, then sequentially add hydrochloric acid, nitric acid, hydrofluoric acid, and perchloric acid, cover and digest.
  4. Heat until white fumes are exhausted, dissolve the residue with 1% nitric acid, and dilute to 25 mL.
  5. Prepare a blank solution simultaneously.

Instrument Measurement

  1. Set the measurement wavelength, lamp current, slit width, and other parameters for copper and zinc according to the instrument manual.
  2. Ignite the air-acetylene flame and preheat for 10-15 minutes.
  3. Draw a standard curve using standard series solutions; the correlation coefficient should be ≥0.999.
  4. Measure the blank and sample solutions, and record the absorbance.

Key Parameters and Interference Elimination

Recommended Instrument Conditions

Element Wavelength (nm) Lamp Current (mA) Slit (nm) Flame Type
Copper 324.7 3-5 0.7 Air-acetylene
Zinc 213.9 5-7 0.7 Air-acetylene

Interferences and Elimination

  • Physical interference: eliminated by matrix matching or standard addition method.
  • Chemical interference: addition of releasing agents (such as lanthanum salts) can eliminate interference from phosphates and silicates on copper.
  • Background absorption: use deuterium lamp or Zeeman effect for background correction.

Result Calculation and Quality Control

Calculation Formula

The content of copper and zinc in soil (mg/kg) is calculated as follows:

w = (ρ - ρ₀) × V × f / m

  • ρ: concentration of sample solution (mg/L)
  • ρ₀: concentration of blank solution (mg/L)
  • V: constant volume (mL)
  • f: dilution factor
  • m: sample weight (g)

Quality Control

  • At least 2 blanks per batch of samples; blank values should be below the detection limit.
  • Use certified reference materials (GBW series) for accuracy control; recovery should be between 90%-110%.
  • The relative deviation of parallel samples should be ≤10%.

To view the original standard, please refer to the following PDF file: