ISO 12020:1997

Overview

ISO 12020:1997 specifies two atomic absorption spectrometric (AAS) methods for the determination of aluminium (Al) in water and wastewater. It covers a flame AAS procedure (nitrous oxide/acetylene flame) and a graphite furnace AAS procedure, including required reagents, sampling and sample-preparation steps, calibration, measurement and expression of results. Key analytical parameters include measurement at 309.3 nm, background correction and procedures to avoid contamination.

Key Topics

• Scope and detection ranges
  • Flame AAS: applicable for 5 mg/L to 100 mg/L (higher by dilution; lower possible with careful evaporation or by using graphite furnace).
  • Graphite furnace AAS: applicable for 10 µg/L to 100 µg/L (with typical injection volumes around 20 µL; working range can be shifted by dilution or sample volume change).
• Reagents & matrix modifiers
  • Common reagents: nitric acid, hydrochloric acid, hydrogen peroxide.
  • Flame AAS: caesium chloride added to measuring solution.
  • Graphite furnace: magnesium nitrate matrix modifier; sulfuric acid injected to compensate fluoride interferences.
• Sampling & sample preparation
  • Filtration (0.45 µm) for dissolved aluminium.
  • Acidification to pH < 2 for stabilization.
  • Optional digestion (HNO3 + H2O2, evaporation to moist residue) for total aluminium-note some silicates/oxide forms may not be fully recovered.
• Interferences & matrix effects
  • Detailed ion threshold concentrations listed for both methods (e.g., sulfate, chloride, silicate, fluoride), with recommendations to use dilution or standard additions where matrix effects are uncertain.
  • Use of background correction and standard additions to compensate nonspecific absorption and matrix bias.
• Instrumentation & calibration
  • Requirements: AAS with background correction, nitrous oxide/acetylene gas supply (flame), argon for furnace; pyrolytically coated tubes and platform preferred for graphite furnace.
  • Prepare multi-point calibration (minimum five levels) and treat blanks and calibration solutions identically to samples.

Applications

ISO 12020:1997 is intended for laboratories performing water quality monitoring and control:

• Environmental and regulatory water testing (surface water, groundwater).
• Drinking water and wastewater laboratories assessing aluminium concentrations.
• Contract testing and environmental consulting firms.
• Instrument manufacturers and method validation teams using flame AAS or graphite furnace AAS for aluminium analysis.

Related standards

• Prepared by ISO/TC 147 (Water quality), Subcommittee SC 2 (physical, chemical and biochemical methods). Consult other ISO water-quality standards from ISO/TC 147 for complementary sampling, handling and method validation guidance.

Keywords: ISO 12020:1997, water quality, aluminium determination, atomic absorption spectrometry, flame AAS, graphite furnace AAS, sample preparation, calibration, matrix modifier, standard additions.