SIST EN ISO 7393-2:2018 PDF

Overview

EN ISO 7393-2:2018 (ISO 7393-2:2017) specifies a routine colorimetric method for the determination of free chlorine and total chlorine in water using N,N-dialkyl-1,4-phenylenediamine (DPD). The method is suitable for both laboratory and field testing and is based on measuring the red DPD colour complex either with a photometer (portable or benchtop) or by visual comparison against calibrated colour standards.

Key topics and technical requirements

• Analytical principle: Formation of a red DPD colour complex proportional to free or total chlorine; measurement by absorbance or visual scale.
• Target analytes: Free chlorine (hypochlorous acid, hypochlorite ion, dissolved Cl2) and total chlorine (including combined chlorine species).
• Applicable concentration range: Practically from about 0.0004 mmol/L to 0.07 mmol/L (approximately 0.03 mg/L to 5 mg/L Cl2); higher concentrations require dilution of the test portion.
• Reagents and buffers: Use commercially available ready-for-use reagents (liquids, powders, tablets) that meet minimum requirements and include a buffer to set the measurement solution pH to typically 6.2–6.5.
• Sample pH limits: Samples should have pH within 4 to 8; adjust with sodium hydroxide or sulfuric acid if necessary before testing.
• Interferences: Method is appropriate where bromine, iodine and other oxidants are negligible; seawater and waters with significant bromide/iodide require special procedures. Turbidity, coloured samples, oxidized manganese and non-chlorine oxidants can interfere.
• Differentiation of combined chlorine: Annex A provides procedures to distinguish monochloramine, dichloramine and nitrogen trichloride.
• Mesofluidic cuvettes: Annex C describes procedures for disposable planar reagent-filled cuvettes using a mesofluidic channel pump/colorimeter (suitable for low-pollution drinking waters).
• Normative references: ISO 3696, ISO 5667-3, ISO 8466-1 for laboratory water, sampling, and calibration/statistics.

Applications and who uses this standard

• Water utilities and treatment plants for drinking water compliance and process control
• Field technicians and environmental monitoring teams using portable photometers
• Laboratories performing routine chlorine testing for distribution systems, reservoirs, and surface waters
• Pool operators, food and beverage facilities, and industrial process control where chlorine disinfection is used
• Regulators and auditors referencing standardized methods for monitoring and reporting water quality

Related standards

• ISO 3696 - Water for analytical laboratory use
• ISO 5667-3 - Sampling: preservation and handling
• ISO 8466-1 - Calibration and evaluation of analytical methods

EN ISO 7393-2:2018 is a practical, widely adopted standard for routine chlorine monitoring that balances field usability (mobile photometers, ready reagents) with clear guidance on interferences, pH control and differentiation of combined chlorine species.