Overview
ISO 23913:2006 specifies validated methods for the determination of chromium(VI) in water using flow analysis with spectrometric detection. The standard covers both flow injection analysis (FIA) and continuous flow analysis (CFA), providing procedures, reagents and performance considerations for measuring Cr(VI) in drinking water, groundwater, surface water, leachates and wastewater. The method is based on the reaction of chromium(VI) with 1,5‑diphenylcarbazide (DPC) to form a red‑violet complex measured at 544 nm (±10 nm).
Key topics and requirements
- Analytical ranges
- FIA: 20–200 µg/L and 200–2 000 µg/L (surface water, leachates, wastewater)
- CFA: 2–20 µg/L and 20–200 µg/L (drinking water, groundwater, surface water, leachates, wastewater)
- Ranges can be adjusted by changing operating conditions and sensitivity.
- Principle and detection
- Chromate + DPC → chromium‑diphenylcarbazone complex; photometric detection at 544 nm.
- Reagents and calibration
- Use analytical‑grade reagents (DPC, potassium dichromate stock standards, acid mixtures).
- Prepare calibration solutions daily; at least five standards per working range are recommended.
- Instrumentation
- FIA: low‑pulsation pump, manifold tubing (0.5–0.8 mm ID), flow photometer.
- CFA: peristaltic pump, reproducible gas bubble introduction, thermostated reaction coil (for total Cr), flow detector.
- Interferences and limits
- Reducing agents can cause negative bias; nitrite generally not interfering.
- Sulfide > 0.2 mg/L and Fe(III) > 10 mg/L can interfere (Fe(III) may cause up to ~8% negative bias between 10–100 mg/L).
- Common disinfectants tolerated up to specified concentrations (chlorine 0.6 mg/L, chlorine dioxide 0.4 mg/L, H2O2 0.2 mg/L, ozone 0.1 mg/L).
- Sampling and preservation
- Follow ISO 5667‑3 guidance. Samples stored ≤24 h at 2–5 °C; acidify just prior to analysis (add 10 mL of 0.5 mol/L H2SO4 per 1 L to ≈ pH 3). Avoid reductive preservatives that change chromium speciation.
Applications and users
ISO 23913:2006 is intended for:
- Environmental and regulatory laboratories performing water quality testing and chromium(VI) monitoring
- Drinking water utilities and wastewater treatment plants assessing compliance
- Research labs and instrument manufacturers validating FIA/CFA spectrometric detection setups
- Consultants and field laboratories requiring rapid, high‑throughput chromium speciation methods for environmental monitoring
The method supports routine, high‑frequency analysis where automation and throughput are priorities.
Related standards
- ISO 3696 - Water for analytical laboratory use
- ISO 5667‑3 - Water quality - Sampling: preservation and handling
- ISO 8466‑1 - Calibration and evaluation of analytical methods
Keywords: ISO 23913:2006, chromium(VI) determination, flow analysis, FIA, CFA, spectrometric detection, water quality testing, environmental monitoring, drinking water analysis.