Overview - ISO 9174:1998 (Water quality - Determination of chromium)
ISO 9174:1998 specifies two atomic absorption spectrometric (AAS) methods for determining total chromium in water, wastewater, sludges and sediments. The standard covers:
- Flame AAS (nitrous oxide/acetylene flame, wavelength 357.9 nm) for routine determinations in the nominal range 0.5 mg/l to 20 mg/l (with concentration-concentration preconcentration options for lower levels).
- Electrothermal (graphite furnace) AAS (same analytical wavelength, 357.9 nm) for lower concentration work and higher sensitivity; clause 4 is applicable for nominal ranges 5 mg/l to 100 mg/l using a 20 µl–20 ml injection strategy depending on instrumentation.
Annex A gives guidance on pretreatment/digestion of sludge and sediment samples; Annex B provides precision data.
Key topics and technical requirements
- Analytical principle: measurement of chromium absorbance at 357.9 nm using a chromium hollow-cathode lamp.
- Flame AAS specifics:
- Use nitrous oxide/acetylene flame.
- Add lanthanum chloride as a matrix modifier to reduce interferences.
- Sample pretreatment: acidify to pH 1–2, oxidize/digest with hydrogen peroxide and nitric acid, avoid drying to dryness; filtrations for water‑soluble chromium.
- Calibration: at least five standards across the working range; blank tests required.
- Electrothermal AAS specifics:
- Use pyrolytically coated graphite tubes (L'vov platform permissible).
- Autosampler or microsyringe recommended for precision.
- Use direct measurement or standard additions when matrix interferences are suspected.
- Quality and contamination control:
- Clean glassware by soaking in nitric acid; avoid glassware cleaned with chromic acid.
- Follow ISO 5667-2 and ISO 5667-3 for sampling, preservation and handling.
- Interferences: standard lists of ions tested for no interference up to specific concentrations (e.g., sulfate, chloride, common cations); total dissolved solids and conductivity limits are specified.
Applications and users
ISO 9174 is relevant for:
- Environmental testing laboratories conducting water quality and wastewater chromium monitoring.
- Regulatory compliance monitoring for effluent and ambient waters.
- Industrial labs monitoring process streams, sludge and sediment chromium content.
- Research groups assessing chromium contamination or remediation effectiveness.
Users include chemists, environmental analysts, laboratory managers and regulatory bodies requiring harmonized chromium determination methods.
Related standards
- ISO 5667-2: Sampling - guidance on sampling techniques
- ISO 5667-3: Sampling - preservation and handling of samples
Keywords: ISO 9174, chromium determination, water quality, atomic absorption spectrometry, flame AAS, graphite furnace AAS, sample digestion, lanthanum chloride, standard additions, environmental monitoring.