ISO 7393-2-2017 PDF

Full title and description

Water quality — Determination of free chlorine and total chlorine — Part 2: Colorimetric method using N,N-dialkyl-1,4-phenylenediamine (DPD) for routine control purposes. The standard specifies a portable and laboratory-applicable colorimetric procedure (photometer or visual comparators) for measuring the red DPD colour complex produced by free and total chlorine in water samples.

Abstract

ISO 7393-2:2017 defines a routine DPD colorimetric method to determine free and total chlorine in drinking and other low-pollution waters. It covers use of calibrated photometers or visual scales, required reagents and buffers (pH adjustment to a measurement range around 6.2–6.5), applicable concentration ranges (practically ~0.0004 mmol/L to 0.07 mmol/L, ≈0.03 mg/L to 5 mg/L Cl2), interference considerations and procedures for differentiating combined-chlorine species (monochloramine, dichloramine, nitrogen trichloride). Annexes include special procedures and a mesofluidic disposable-cuvette option.

General information

• Status: Published (International Standard).
• Publication date: December 2017.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 13.060.50 — Examination and analysis of water.
• Edition / version: 2nd edition (2017-12).
• Number of pages: 19 pages.

(General information and lifecycle details based on ISO bibliographic record and regional adoptions.)

Scope

Specifies a routine colorimetric test for determination of free and total chlorine in drinking water and other low-pollution waters using N,N-dialkyl-1,4-phenylenediamine (DPD). The method is intended for both field and laboratory use; it is appropriate where bromine, iodine and other oxidizing agents are negligible. The standard notes special-procedure requirements for seawater or waters containing appreciable bromide/iodide and gives dilution guidance for concentrations above the practical working range.

Key topics and requirements

• Analytical principle: formation of a red DPD colour complex proportional to free or total chlorine; measurement by absorbance (photometer) or visual comparison with calibrated standards.
• Target analytes: free chlorine (HOCl/OCl–/dissolved Cl2) and total chlorine (including combined-chlorine species such as monochloramine, dichloramine and nitrogen trichloride).
• Applicable concentration range: typically ~0.0004 mmol/L to 0.07 mmol/L (≈0.03–5 mg/L Cl2); dilute samples with higher concentrations.
• Reagents and pH control: use commercially available DPD reagents and a buffering system to set measurement solution pH (typically ~6.2–6.5); sample pH should be checked/adjusted if outside pH 4–8.
• Interferences and limitations: advises on interferences from bromide/iodide, oxidized manganese, turbidity and coloured samples and provides mitigation/alternative procedures.
• Apparatus and sampling: describes required glassware/cuvettes, portable photometers or visual comparators, sampling and test-portion handling suitable for routine and field control.
• Annexes: includes a procedure to differentiate combined-chlorine types (Annex A) and an option for disposable planar reagent-filled cuvettes with mesofluidic pump/colorimeter (Annex C).

These technical points are summarized from the ISO document and widely used regional adoptions.

Typical use and users

Used by municipal and industrial water laboratories, distribution-system operators, pool and recreational-water operators, environmental monitoring teams, regulatory bodies and manufacturers of portable photometers and reagent kits. Typical applications include routine monitoring of drinking-water disinfection, distribution system residual checks, swimming-pool control and on-site field verifications.

Related standards

ISO 7393 is a multipart series addressing chlorine determination. Relevant related parts include ISO 7393-1 (titrimetric DPD/titration procedures; original 1985 edition, maintained) and ISO 7393-3 (iodometric titration method for total chlorine; 1990 edition). Other regional/adopted versions (EN ISO) provide harmonized regional texts. Users often consult these parts when choosing titrimetric vs colorimetric or iodometric approaches for different concentration ranges or interfering matrixes.

Keywords

DPD, colorimetric method, free chlorine, total chlorine, water quality, photometer, visual comparator, buffer, pH adjustment, combined chlorine, monochloramine, dichloramine, nitrogen trichloride, ISO 7393 series.

FAQ

Q: What is this standard?

A: ISO 7393-2:2017 is an international standard that specifies a routine colorimetric (DPD) method for measuring free and total chlorine in water using photometric or visual techniques.

Q: What does it cover?

A: It covers the analytical principle (DPD colour development), reagents and buffering requirements, sample handling, instrument/visual comparison, applicable concentration ranges, known interferences and special procedures (e.g., differentiation of combined-chlorine forms and procedures for waters with bromide/iodide).

Q: Who typically uses it?

A: Water-treatment laboratories, field technicians, utilities, pool operators, environmental regulators, and manufacturers of test kits and portable photometers for routine monitoring and control of water disinfection.

Q: Is it current or superseded?

A: The 2017 second edition (ISO 7393-2:2017) is the published current edition (confirmed in ISO records). Users should check national adoption/confirmation status periodically; ISO standards are subject to 5-year systematic review cycles.

Q: Is it part of a series?

A: Yes — ISO 7393 is a multipart series. Part 1 (titrimetric method) and Part 3 (iodometric titration for total chlorine) are the most relevant companion parts; users select the part best suited to concentration range and sample matrix.

Q: What are the key keywords?

A: DPD, free chlorine, total chlorine, colorimetric, photometer, visual comparator, buffer, pH adjustment, combined chlorine, monochloramine, dichloramine.