EN ISO 16265:2012

Water quality - Determination of the methylene blue active substances (MBAS) index - Method using continuous flow analysis (CFA) (ISO 16265:2009)

ISO 16265:2009 specifies a procedure for the determination of the methylene blue active substances (MBAS) index, in the ranges 0,05 mg/l to 0,5 mg/l and 0,5 mg/l to 5,0 mg/l, in various water samples (e.g. ground water, drinking water, surface water, waste water and leachates). Anionic surfactants are the most important substances showing methylene blue activity. This method is therefore useful for estimating the anionic surfactant content [including anionic surfactants with carboxylate groups (e.g. soaps)] of water. Other types of substance may also show methylene blue activity and contribute to the result. On a case-by-case basis, the range of the analysis may be changed and the method used for other concentration ranges provided they cover exactly one decade of concentration units.

Wasserbeschaffenheit - Bestimmung des Indexes von methylenblauaktiven Substanzen (MBAS) - Verfahren mittels kontinuierlicher Durchflussanalyse (CFA) (ISO 16265:2009)

Diese Internationale Norm legt ein Verfahren für die Bestimmung des MBAS Indexes in den Bereichen von 0,05 mg/l bis 0,5 mg/l und 0,5 mg/l bis 5,0 mg/l in verschiedenen Wasserproben (z. B. Grund , Trink , Oberflächen , Abwasser, Sickerwasser) fest. Anionische grenzflächenaktive Substanzen sind die wichtigsten methylenblauaktiven Substanzen. Dieses Verfahren ist daher geeignet, den Gehalt an anionischen grenz-flächenaktiven Substanzen (eingeschlossen anionischer grenzflächenaktiver Substanzen mit Carboxylgruppen (z. B. Seifen)) von Wässern abzuschätzen. Andere Substanzen können ebenfalls methylenblauaktiv sein und zum Ergebnis beitragen. Im Einzelfall kann der Analysenbereich angepasst und für andere Konzentrationsbereiche verwendet werden, vorrausgesetzt sie decken genau eine Dekade ab.

Qualité de l'eau - Mesurage de l'indice des substances actives au bleu de méthylène (SABM) - Méthode par analyse en flux continu (CFA) (ISO 16265:2009)

L'ISO 16265:2009 spécifie un mode opératoire pour le mesurage de l'indice des substances actives au bleu de méthylène (SABM), dans les plages de 0,05 mg/l à 0,5 mg/l et de 0,5 mg/l à 5,0 mg/l, dans différents échantillons d'eau (par exemple, eau souterraine, eau potable, eaux de ruissellement, eau résiduaire et percolats). Les agents de surface anioniques sont les substances les plus importantes présentant une activité vis-à-vis du bleu de méthylène. Cette méthode est donc utile pour évaluer la teneur des eaux en agents de surface anioniques [y compris les agents de surface anioniques contenant des groupes carboxylates (par exemple, savons)]. D'autres types de substances peuvent également présenter une activité vis-à-vis du bleu de méthylène et contribuer au résultat. Dans des cas particuliers, l'étendue de l'analyse peut être modifiée et la méthode peut être utilisée pour d'autres plages de concentration à condition qu'elles couvrent exactement une décade d'unités de concentration.

Kakovost vode - Določevanje indeksa anionskih površinsko aktivnih snovi z metilen modrim (MBAS) - Metoda s kontinuirano pretočno analizo (CFA) (ISO 16265:2009)

Ta mednarodni standard določa postopek za določevanje indeksa anionskih površinsko aktivnih snovi z metilen modrim (MBAS) v območjih od 0,05 mg/l do 0,5 mg/l in od 0,5 mg/l do 5,0 mg/l v različnih vzorcih vode (npr. podtalnica, pitna voda, površinska voda, odpadna voda in izcedne vode). Anionske površinsko aktivne snovi so najpomembnejše snovi, ki aktivirajo metilen modro. Ta metoda je uporabna za ocenjevanje vsebnosti anionskih površinsko aktivnih snovi [vključno z anionskimi površinsko aktivnimi snovmi s karboksilatnimi skupinami (npr. mila)] v vodi. Druge vrste snovi lahko prav tako aktivirajo metilen modro in prispevajo k rezultatu. Obseg analize in metoda, ki se uporablja za druga območja koncentracije, se lahko odvisno od primera spremenita, če zajemata natanko eno dekado koncentracijskih enot.

General Information

• Status: Published
• Publication Date: 14-Feb-2012
• Withdrawal Date: 30-Aug-2012
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: CEN/TC 230 - Water analysis
• Drafting Committee: CEN/TC 230 - Water analysis
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 15-Feb-2012
• Due Date: 26-May-2012
• Completion Date: 15-Feb-2012
• Ref Project: SIST EN ISO 16265:2012 - Water quality - Determination of the methylene blue active substances (MBAS) index - Method using continuous flow analysis (CFA) (ISO 16265:2009)

Relations

• Refers: ISO 3696:1987 - Water for analytical laboratory use - Specification and test methods
• Effective Date: 09-Feb-2026
• Refers: ISO 648:2008 - Laboratory glassware - Single-volume pipettes
• Effective Date: 09-Feb-2026
• Refers: EN 15649-3:2009 - Floating leisure articles for use on and in the water - Part 3: Additional specific safety requirements and test methods for Class A devices
• Effective Date: 28-Jan-2026

Overview

EN ISO 16265:2012 (ISO 16265:2009 adopted by CEN) defines a laboratory method for measuring the methylene blue active substances (MBAS) index in water using continuous flow analysis (CFA). The standard covers MBAS determination in a variety of waters (groundwater, drinking water, surface water, wastewater, leachates) in the ranges 0.05–0.5 mg/L and 0.5–5.0 mg/L (results expressed as sodium dodecyl sulfate, SDS, equivalents). MBAS is a method‑defined indicator commonly used to estimate anionic surfactant content.

Key topics and technical requirements

• Principle: Sample mixed in a continuous flow with alkaline methylene blue to form ion‑pairs with MBAS; ion‑pairs extracted to trichloromethane (CHCl3), acidified and measured photometrically at 650 nm ± 10 nm. Results reported as SDS concentration.
• Analytical scope: Intended ranges 0.05–0.5 mg/L and 0.5–5.0 mg/L; other one‑decade ranges may be used case‑by‑case.
• Reagents & apparatus: Standard requires specific reagents (e.g., methylene blue, alkaline/acidified reagent solutions, trichloromethane) and CFA equipment; use reagent‑grade water and follow recommended degassing and preparation steps.
• Sampling and pretreatment: Filtration recommended for particles >100 µm; samples >5 mg/L MBAS must be diluted. Blank compensations are used to correct sample colour.
• Interferences: Cationic compounds, high humic acid (>20 mg/L), non‑MBAS surfactants at high concentration (>50 mg/L), strong reducing agents (e.g., sulfide/thiosulfate/hypochlorite), and high inorganic anions can bias results. Some interferences require removal (e.g., oxidation) before analysis.
• Performance & safety: CFA supports high throughput (many samples, up to ~100/h). The standard includes precision data and warns on hazardous wastes (trichloromethane, methanol) and the need for trained personnel.

Applications

• Routine monitoring of anionic surfactants in drinking water, surface water and wastewater
• Environmental compliance and process control at wastewater treatment plants and industrial effluents
• Screening of leachates and groundwater for surfactant contamination
• High‑throughput laboratory workflows using continuous flow analysis (CFA)

Who uses this standard

• Environmental and public‑health water testing laboratories
• Wastewater treatment operators and industrial environmental teams
• Regulatory authorities and compliance laboratories
• Contract testing labs and research institutions studying surfactant pollution

Related standards

• Normative references in EN ISO 16265: ISO 648, ISO 1042, ISO 3696 (laboratory glassware and water quality for analytical use).
• MBAS is a method‑defined parameter; users should consider complementary surfactant-specific methods when detailed compound identification is required.

Keywords: EN ISO 16265:2012, MBAS, methylene blue active substances, continuous flow analysis, CFA, water quality, anionic surfactants, sodium dodecyl sulfate, SDS, environmental monitoring.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Wasserbeschaffenheit - Bestimmung des Index von methylenblau-aktiven Substanzen (MBAS) - Verfahren mittels kontinuierlicher Durchflussanalyse (CFA) (ISO 16265:2009)Qualité de l'eau - Mesurage de l'indice des substances actives au bleu de méthylène (SABM) - Méthode par analyse en flux continu (CFA) (ISO 16265:2009)Water quality - Determination of the methylene blue active substances (MBAS) index - Method using continuous flow analysis (CFA) (ISO 16265:2009)13.060.50VQRYLExamination of water for chemical substancesICS:Ta slovenski standard je istoveten z:EN ISO 16265:2012SIST EN ISO 16265:2012en,fr,de01-junij-2012SIST EN ISO 16265:2012SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN ISO 16265
February 2012 ICS 13.060.50 English Version
Water quality - Determination of the methylene blue active substances (MBAS) index - Method using continuous flow analysis (CFA) (ISO 16265:2009)
Qualité de l'eau - Mesurage de l'indice des substances actives au bleu de méthylène (SABM) - Méthode par analyse en flux continu (CFA) (ISO 16265:2009)
Wasserbeschaffenheit - Bestimmung des Indexes von methylenblauaktiven Substanzen (MBAS) - Verfahren mittels kontinuierlicher Durchflussanalyse (CFA) (ISO 16265:2009) This European Standard was approved by CEN on 15 January 2012.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
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B-1000 Brussels © 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 16265:2012: ESIST EN ISO 16265:2012

Reference numberISO 16265:2009(E)© ISO 2009
INTERNATIONAL STANDARD ISO16265First edition2009-03-01Water quality — Determination of the methylene blue active substances (MBAS) index — Method using continuous flow analysis (CFA) Qualité de l'eau —Mesurage de l'indice des substances actives au bleu de méthylène (SABM) — Méthode par analyse en flux continu (CFA)
ISO 16265:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
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ISO 2009 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel.
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ii © ISO 2009 – All rights reserved
ISO 16265:2009(E) © ISO 2009 – All rights reserved iiiContents Page Foreword.iv Introduction.v 1 Scope.1 2 Normative references.1 3 Interferences.1 4 Principle.2 5 Reagents.2 6 Apparatus.4 7 Sampling and sample pretreatment.5 8 Procedure.5 9 Calculation of the results.7 10 Expression of results.8 11 Precision.8 12 Test report.8 Annex A (informative)
Example of a flow diagram for the determination of MBAS index by continuous flow analysis (CFA).9 Annex B (informative)
Precision data.10 Bibliography.11
ISO 16265:2009(E) iv © ISO 2009 – All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 16265 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical, chemical and biochemical methods. SIST EN ISO 16265:2012

ISO 16265:2009(E) © ISO 2009 – All rights reserved vIntroduction Methods using flow analysis automate wet chemical procedures and are particularly suitable for the processing of many analytes in water in large numbers of samples at a high analysis frequency (up to 100 samples per hour). A differentiation is made between flow injection analysis (FIA) [1], [2] and continuous flow analysis (CFA) [3]. Both methods share the feature of an automatic dosage of the sample into a flow system (manifold) where the analytes in the sample react with the reagent solutions on their way through the manifold. The sample preparation may be integrated in the manifold. The reaction product is measured in a flow detector (e.g. a photometer). The detector produces a signal from which the concentration of the parameter is calculated. The MBAS (methylene blue active substances) index is an analytical convention (a method-defined parameter) used for water quality control purposes. It measures surfactants and other substances that react with methylene blue under specified conditions. The user should be aware that particular problems could require the specification of additional conditions.
INTERNATIONAL STANDARD ISO 16265:2009(E) © ISO 2009 – All rights reserved 1Water quality — Determination of the methylene blue active substances (MBAS) index — Method using continuous flow analysis (CFA) WARNING — Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. IMPORTANT — It is absolutely essential that tests conducted in accordance with this International Standard be carried out by suitably trained staff. Trichloromethane and methanol waste solutions should be disposed of properly. 1 Scope This International Standard specifies a procedure for the determination of the methylene blue active substances (MBAS) index, in the ranges 0,05 mg/l to 0,5 mg/l and 0,5 mg/l to 5,0 mg/l, in various water samples (e.g. ground water, drinking water, surface water, waste water and leachates). Anionic surfactants are the most important substances showing methylene blue activity. This method is therefore useful for estimating the anionic surfactant content [including anionic surfactants with carboxylate groups (e.g. soaps)] of water. Other types of substance may also show methylene blue activity and contribute to the result. On a case-by-case basis, the range of the analysis may be changed and the method used for other concentration ranges provided they cover exactly one decade of concentration units. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the reference document (including any amendments) applies. ISO 648, Laboratory glassware — Single-volume pipettes ISO 1042, Laboratory glassware — One-mark volumetric flasks ISO 3696, Water for analytical laboratory use — Specification and test methods 3 Interferences The following substances can interfere with the analysis: ⎯ Cationic compounds able to form strong ion-pairs with the active substances in methylene blue. ⎯ Humic acids in concentrations > 20 mg/l. ⎯ Chemicals with a high surface activity (e.g. non methylene blue active surfactants in concentrations > 50 mg/l). SIST EN ISO 16265:2012

ISO 16265:2009(E) 2 © ISO 2009 – All rights reserved ⎯ Chemicals with a strong reductive potential for the oxidation of methylene blue (e.g. S2−, 23SO−, 223SO,−=OCl−). These chemicals shall be removed (e.g. with H2O2) prior to analysis. ⎯ High concentrations of inorganic anions (e.g. nitrate, chloride, bromide) may cause positive bias. ⎯ Chemicals which react with any of the reagents used to form a coloured compound soluble in trichloromethane (CHCl3) (excluded are methylene blue active substances). Filtration of the sample before analysis is advisable for samples containing particles larger than 100 µm in size. Otherwise the particles in the sample may clog the transport tubes. If filtration is necessary, significant losses of anionic surfactants due to adsorbance effects are possible. The absorbance due to the colour of the sample can be compensated for by a blank analysis which omits the methylene blue from the reagents. The responses of the sample with and without reagent addition are determined. The difference between the two responses is used in Equations (3) and (4). Samples with an MBAS index concentration > 5 mg/l shall be diluted before analysis. 4 Principle The sample is mixed, in a continuously flowing stream, with an alkaline methylene blue solution, forming coloured ion-pairs with certain types of organic substance (e.g. anionic surfactants) contained in the sample. The ion-pairs are extracted with trichloromethane. The organic phase is treated with an acidic methylene blue solution and its absorbance determined photometrically at a wavelength of 650 nm ± 10 nm. The result is expressed in terms of sodium dodecyl sulfate concentration. 5 Reagents Unless otherwise stated, use only reagents of recognized analytical grade. Degas reagents if air bubbles appear spontaneously. Unless otherwise specified, degas by passing helium gas at 20 l/h through the reagent for 15 min. Add detergent after degassing. Avoid using reagents showing any turbidity, filtering them if necessary. 5.1 Water, complying with grade 1 as defined in ISO 3696. 5.2 Sodium hydroxide, NaOH. 5.3 Sodium tetraborate decahydrate, Na2B4O7·10H2O. 5.4 Sodium dihydrogen phosphate monohydrate, NaH2PO4·H2O. 5.5 Potassium dihydrogen phosphate monohydrate, KH2PO4·H2O. 5.6 Sulfuric acid, H2SO4, ρ(H2SO4) = 1,84 g/ml. 5.7 Hydrochloric acid, HCl, ρ(HCl) = 1,18 g/ml. 5.8 Methylene blue, C16H18N3SCl·2H2O. 5.9 Methanol, CH3OH. 5.10 Ethanol, C2H5OH, w (C2H5OH) ≈ 96 %. 5.11 Trichloromethane, CHCl3. Trichloromethane is stable for 3 months if stored in a dark place. SIST EN ISO 16265:2012

ISO 16265:2009(E) © ISO 2009 – All rights reserved 3Before use, degas the trichloromethane for 30 min by purging with a stream of He or by using an ultrasonic bath. 5.12 Sodium dodecyl sulfate (sodium lauryl sulfate), CH3(CH2)11OSO3Na. 5.13 Petroleum ether. 5.14 Poly(ethylene glycol) dodecyl ether, HO(CH2CH2O)nC12H25, aqueous solution, w = 30 %. 5.15 Alkaline bora
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