ISO 7393-2:2017
Water quality — Determination of free chlorine and total chlorine — Part 2: Colorimetric method using N,N-dialkyl-1,4-phenylenediamine, for routine control purposes
Water quality — Determination of free chlorine and total chlorine — Part 2: Colorimetric method using N,N-dialkyl-1,4-phenylenediamine, for routine control purposes
- Статус документа:
- Действующий
- Формат:
- Электронный (PDF)
- Количество страниц:
- 19
- Дата публикации:
- 13 декабря 2017 г.
- Издание:
- ISO IS 7393 edition 2 version 1
- ICS:
- 13.060.50
ISO 7393-2:2017 specifies a method for the determination of free chlorine and total chlorine in water, readily applicable to lab- and field-testing. It is based on measurement of the absorption, the red DPD colour complex in a photometer or the colour intensity by visual comparison of the colour with a scale of standards that is regularly calibrated. This method is appropriate for drinking water and other waters, where additional halogens like bromine, iodine and other oxidizing agents are present in almost negligible amounts. Seawater and waters containing bromides and iodides comprise a group for which special procedures are to be carried out. This method is in practice applicable to concentrations, in terms of chlorine (Cl2), from, for example, 0,000 4 mmol/l to 0,07 mmol/l (e.g. 0,03 mg/l to 5 mg/l) total chlorine. For higher concentrations, the test portion is diluted. Commonly, the method is applied as a field method with mobile photometers and commercially available ready-for-use reagents (liquid reagents, powders and tablets). It is essential that those reagents comply with minimum requirements and contain the essential reagents and a buffer system suitable to adjust the measurement solution to a pH range of typically 6,2 to 6,5. If there is doubt that water samples have uncommon pH values and/or buffer capacities, the user has to check and, if necessary, to adjust the sample pH to the required range. The pH of the sample is within the range of pH 4 and 8. Adjust, if necessary, with sodium hydroxide solution or sulfuric acid before the test. A procedure for the differentiation of combined chlorine of the monochloramine type, combined chlorine of the dichloramine type and combined chlorine in the form of nitrogen trichloride is presented in Annex A. In Annex C, a procedure is presented for the determination of free and total chlorine in drinking and other low polluted waters, for disposable planar reagent-filled cuvettes using a mesofluidic channel pump/colorimeter.
Abstract
Overview
ISO 7393-2:2017 specifies a routine, field- and laboratory-applicable colorimetric method (DPD) for the determination of free chlorine and total chlorine in water. The method uses N,N-dialkyl-1,4-phenylenediamine (DPD) to form a red colour complex that is measured by photometer or by visual comparison to calibrated standards. It is designed primarily for drinking water and other low-pollution waters and covers practical concentration ranges (about 0.0004–0.07 mmol/L, approx. 0.03–5 mg/L Cl2). Special procedures are required for seawater and waters with significant bromides/iodides.
Key topics and requirements
- Principle: Direct DPD reaction for free chlorine; DPD + excess potassium iodide for total chlorine.
- Measurement: Photometric absorbance or visual comparator against regularly calibrated standards.
- Reagents and buffering: Ready-to-use reagents (liquids, powders, tablets) must contain essential reagents and a buffer system to achieve a measurement pH typically 6.2–6.5. Sample pH should be within 4–8; adjust with sodium hydroxide or sulfuric acid if necessary.
- Interferences: Guidance on common interferences (bromine, iodine, chlorine dioxide, ozone, hydrogen peroxide, oxidized manganese, Cu(II), Fe(III), coloured/turbid samples). Some interferences are suppressed by disodium EDTA in reagents; oxidized manganese can be quantified using arsenite or thioacetamide treatment.
- Sampling and calibration: Applicable to both laboratory and field testing with mobile photometers; calibration and measurement procedures are specified (including dilution for higher concentrations).
- Annexes:
- Annex A - differentiation of combined chlorine species (monochloramine, dichloramine, nitrogen trichloride).
- Annex C - procedure for disposable planar reagent-filled cuvettes using a mesofluidic channel pump / colorimeter.
Applications and users
ISO 7393-2:2017 is intended for routine control and monitoring where reliable chlorine measurement is required:
- Drinking water utilities and treatment plant operators
- Field technicians using portable photometers and comparator kits
- Laboratories performing regulatory compliance or routine quality control
- Pool and spa operators, cooling-water monitoring, and environmental monitoring teams (with caution for complex matrices)
The standard supports rapid on-site decisions and laboratory confirmation of residual disinfectant levels.
Related standards
- ISO 3696 - Water for analytical laboratory use
- ISO 5667-3 - Sampling: preservation and handling of water samples
- ISO 8466-1 - Calibration and evaluation of analytical methods (statistical treatment)
Keywords: ISO 7393-2, DPD colorimetric method, free chlorine, total chlorine, water quality, photometer, field testing, drinking water, chloramines, routine control.
Технические детали
- Технический комитет
- ISO/TC 147/SC 2 - Physical, chemical and biochemical methods
- SKU
- ISO 7393-2:2017
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