Overview - ISO 14402:1999 (phenol index by flow analysis, FIA & CFA)
ISO 14402:1999 specifies two automated flow-analysis methods for the determination of the phenol index in waters (groundwater, surface water, seep water, waste water) in the mass concentration range 0.01 mg/L to 1 mg/L. The standard covers:
- Flow Injection Analysis (FIA) and Continuous Flow Analysis (CFA) implementations.
- Two procedural variants: determination without distillation after extraction (flow extraction into chloroform) and determination after distillation (without extraction).
- Reagent, apparatus and calibration requirements, sample handling, interferences, calculation, precision and reporting.
The phenol index is an analytical convention: a set of aromatic compounds that under the method’s reaction conditions form coloured condensation products whose response is expressed as phenol concentration.
Key topics and technical requirements
- Analytical principle: oxidation of phenolic compounds with potassium peroxodisulfate and coupling with 4‑aminoantipyrine to form coloured products; measurement of the organic phase absorbance at 470–475 nm.
- Reagents: 4‑aminoantipyrine, potassium peroxodisulfate, buffer (pH ≈ 10.3), chloroform for extraction; degassed solutions recommended; stock and calibration solutions (examples provided for working ranges 0.01–0.1 mg/L and 0.1–1.0 mg/L).
- Instrumentation:
- FIA system components: low-pulsation pump, injector (example injection volumes 200 µL or 600 µL), extraction cell, phase separator (PTFE membrane examples), detector (optical path 10 mm).
- CFA system components: autosampler, manifold with segmentation, phase separator, detector (optical pathlength 0.5–5 cm).
- Typical tubing and coil dimensions are given to minimise dead volume and ensure reproducible reactions.
- Interferences & sample handling:
- Aromatic amines give positive bias; pH must reach 10.0–10.5 after reagent addition (acidic/strongly buffered samples may need pH adjustment).
- Turbidity can be managed; coloured sample blanks and detergents (foaming) can affect extraction/phase separation-detergent-rich wastewaters may limit applicability below 0.1 mg/L.
- Safety note: phenol and chloroform are hazardous; handle and dispose of wastes appropriately.
- Quality control: daily reagent preparation, reagent blanks, multi-point calibration (minimum five standards), precision/accuracy data and interlaboratory statistics referenced in annex A.
Applications - who uses ISO 14402
- Environmental and public‑health water testing laboratories performing routine monitoring and high-throughput analysis.
- Water utilities and wastewater treatment plants for process control and compliance screening.
- Regulatory agencies and consultants investigating pollution incidents involving phenolic compounds.
- Instrument manufacturers and service providers implementing FIA/CFA analysers for phenol index determination.
Related standards
- ISO 6439 - phenol index by 4‑aminoantipyrine spectrometric methods after distillation.
- ISO 3696 - water for analytical laboratory use.
- ISO 5667-3 - sampling guidance for water quality.
Keywords: ISO 14402, phenol index, flow analysis, FIA, CFA, water quality, phenol determination, 4‑aminoantipyrine, potassium peroxodisulfate, chloroform.