EN ISO 16264:2004

• Abstract:

  This International Standard specifies two methods, i.e. flow injection analysis (FIA) and continuous flow analysis (CFA), for the determination of soluble silicate ions in various types of water (such as ground, drinking, surface, leachate and waste water). Both methods are applicable to the determination of a mass concentration of silicate (SiO 2) ranging from 0,2 mg/l to 20 mg/l (with working ranges 0,2 mg/l to 2,0 mg/l and 2,0 mg/l to 20 mg/l). Other mass concentration ranges are applicable, provided they cover exactly one decade of concentration units (e.g. 0,02 mg/l to 0,2 mg/l in SiO2).; These methods can be made applicable to seawater by changing the sensitivity and by adapting the reagent and calibration solutions to the salinity of the samples.

• Status: Published
• Publication Date: 17-Feb-2004
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: CEN/TC 230 - Water analysis
• Drafting Committee: CEN/TC 230/WG 1 - Physical and biochemical methods
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 14-May-2009
• Completion Date: 14-May-2009
• Directive: Not Harmonized2000/60/EC - Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (substitutes Directive Reference 01/991 - Common Position on WFD)
• Ref Project: SIST EN ISO 16264:2004 - Water quality - Determination of soluble silicates by flow analysis (FIA and CFA) and photometric detection (ISO 16264:2002)

• Refers: ISO 5725-2:1994 - Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method
• Effective Date: 25-Aug-2026
• Refers: ISO 3696:1987 - Water for analytical laboratory use — Specification and test methods
• Effective Date: 09-Feb-2026
• Refers: ISO 8466-1:1990 - Water quality — Calibration and evaluation of analytical methods and estimation of performance characteristics — Part 1: Statistical evaluation of the linear calibration function
• Effective Date: 09-Feb-2026
• Referred By: EN 14944-1:2023 - Influence of cementitious products on water intended for human consumption - Test methods - Part 1: Influence of factory made cementitious products on organoleptic parameters
• Effective Date: 28-Jan-2026
• Referred By: EN 511:2006 - Protective gloves against cold
• Effective Date: 28-Jan-2026
• Referred By: EN 16781:2018 - Textile child care articles - Safety requirements and test methods for children's sleep bags for use in a cot
• Effective Date: 28-Jan-2026
• Referred By: EN 14944-2:2025 - Influence of cement based products on water intended for human consumption - Test methods - Part 2: Influence of site-applied cement based materials and associated non-cement based products/materials on organoleptic parameters and migration of organic substances (TOC)
• Effective Date: 28-Jan-2026
• Referred By: EN 14058:2004 - Protective clothing - Garments for protection against cool environments
• Effective Date: 28-Jan-2026
• Referred By: CEN/TR 16422:2012 - Classification of thermoregulatory properties
• Effective Date: 28-Jan-2026
• Referred By: EN 16779-1:2018 - Textile child care articles - Safety requirements and test methods for children's cot duvets - Part 1: Duvet (excluding duvet covers)
• Effective Date: 28-Jan-2026
• Referred By: EN 14944-1:2006 - Influence of cementitious products on water intended for human consumption - Test methods - Part 1: Influence of factory made cementitious products on organoleptic parameters
• Effective Date: 28-Jan-2026
• Referred By: ENV 14237:2002 - Textiles in the healthcare system
• Effective Date: 28-Jan-2026

Overview

EN ISO 16264:2004 specifies standardized procedures for the determination of soluble silicates in water using flow injection analysis (FIA) and continuous flow analysis (CFA) combined with photometric detection. Developed by CEN, this European Standard aligns with ISO 16264:2002 and provides a robust framework for laboratories conducting water quality analysis across a variety of water matrices, including ground, drinking, surface, leachate, and waste water. The standard supports the quantification of silicate concentrations (as SiO₂) within a wide range, making it a valuable reference for environmental monitoring, industrial compliance, and water treatment operations.

Key Topics

• Silicate Determination in Water: Focuses on measuring soluble silicate ions using automated, high-throughput methods.
• Analytical Techniques:
  • Flow Injection Analysis (FIA): Automates sample injection into a water carrier, reacts with heptamolybdate, and uses photometric detection.
  • Continuous Flow Analysis (CFA): Introduces reagents continuously for reaction and detection, suitable for larger sample series.
• Photometric Detection: Measures the concentration of the resulting molybdenum blue complex, expressed in mg/L as SiO₂.
• Applicable Concentration Ranges:
  • Typical working ranges: 0.2–2.0 mg/L and 2.0–20 mg/L, adaptable for other ranges covering a single decade (e.g., 0.02–0.2 mg/L).
• Interference and Matrix Adaptation: Addresses issues such as tannins, phosphates, iron, and salinity, with procedures for mitigating potential interferences and adaptations for seawater samples.
• Sampling and Storage Guidance: Outlines best practices for sample filtration, handling, and preservation to ensure result accuracy.

Applications

EN ISO 16264:2004 is widely applicable in:

• Environmental Monitoring: Regular assessment of rivers, lakes, and groundwater for silicate content as part of comprehensive water quality monitoring programs.
• Drinking Water Analysis: Ensures compliance with regulatory standards by accurately quantifying silicate levels in potable water.
• Waste Water and Industrial Effluents: Provides reliable results needed for process control, discharge permitting, and environmental compliance.
• Laboratory Testing: Serves as a reference method for accredited laboratories performing routine chemical analysis of water samples using validated, traceable procedures.
• Research: Used in scientific studies investigating the geochemical cycling of silicon and monitoring industrial impacts on water systems.

The methods outlined allow for high sample throughput, reduced manual intervention, and reproducible results, making them suited for both small-scale and industrial laboratories.

Related Standards

• ISO 3696: Water for analytical laboratory use - Specification and test methods.
• ISO 5725-2: Accuracy (trueness and precision) of measurement methods and results - Basic method for determining repeatability and reproducibility.
• ISO 8466-1: Water quality - Calibration and evaluation of analytical methods and estimation of performance characteristics.

Related standards cover laboratory water quality, method validation, and calibration, supporting the reliable implementation of EN ISO 16264:2004 in analytical settings.

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Keywords: EN ISO 16264:2004, water quality, determination of soluble silicates, flow injection analysis (FIA), continuous flow analysis (CFA), photometric detection, silicate in water, water analysis standard, CEN, ISO, environmental monitoring, laboratory methods.

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Wasserbeschaffenheit - Bestimmung löslicher Silicate mittels Fließanalytik (FIA und CFA) und photometrischer Detektion (ISO 16264:2002)Qualité de l'eau - Dosage des silicates solubles par analyse en flux (FIA et CFA) et détection photométrique (ISO 16264:2002)Water quality - Determination of soluble silicates by flow analysis (FIA and CFA) and photometric detection (ISO 16264:2002)13.060.50VQRYLExamination of water for chemical substancesICS:Ta slovenski standard je istoveten z:EN ISO 16264:2004SIST EN ISO 16264:2004en,fr,de01-junij-2004SIST EN ISO 16264:2004SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN ISO 16264February 2004ICS 13.060.50English versionWater quality - Determination of soluble silicates by flow analysis(FIA and CFA) and photometric detection (ISO 16264:2002)Qualité de l'eau - Dosage des silicates solubles par analyseen flux (FIA et CFA) et détection photométrique (ISO16264:2002)Wasserbeschaffenheit - Bestimmung löslicher Silicatemittels Fließanalytik (FIA und CFA) und photometrischerDetektion (ISO 16264:2002)This European Standard was approved by CEN on 2 January 2004.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2004 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 16264:2004: ESIST EN ISO 16264:2004

Normative references to International Standards are listed in annex ZA (normative).SIST EN ISO 16264:2004

Reference numberISO 16264:2002(E)© ISO 2002
INTERNATIONAL STANDARD ISO16264First edition2002-05-15Water quality — Determination of soluble silicates by flow analysis (FIA and CFA) and photometric detection Qualité de l'eau — Dosage des silicates solubles par analyse en flux (FIA et CFA) et détection photométrique
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ii © ISO 2002 – All rights reserved
ISO 16264:2002(E) © ISO 2002 – All rights reserved iii Contents Page Foreword.iv Introduction.v 1 Scope.1 2 Normative references.1 3 General interferences.1 4 Principle.2 5 Reagents.2 6 Apparatus.4 7 Sampling and sample preparation.7 8 Procedure.7 9 Calculation.9 10 Precision.9 11 Test report.10 Bibliography.11
ISO 16264:2002(E) iv © ISO 2002 – 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 3. 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 International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 16264 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical, chemical, biochemical methods. SIST EN ISO 16264:2004

ISO 16264:2002(E) © ISO 2002 – All rights reserved v Introduction Further investigation will be necessary to determine whether and to what extent particular problems will require the specification of additional minor conditions. It is absolutely essential that tests conducted according to this International Standard be carried out by suitably qualified staff. Differentiation is required 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 into the manifold. The reaction product is determined in a flow detector (e.g. photometer). This detector produces a signal from which the concentration of the parameter can be calculated. Methods using flow analysis automate wet chemical procedures and are particularly suitable for processing many analytes in water in large sample series at a high analysis frequency.
INTERNATIONAL STANDARD ISO 16264:2002(E) © ISO 2002 – All rights reserved 1 Water quality — Determination of soluble silicates by flow analysis (FIA and CFA) and photometric detection WARNING — Persons using this International Standard should be familiar with normal laboratory practice. This International 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. 1 Scope This International Standard specifies two methods, i.e. flow injection analysis (FIA) and continuous flow analysis (CFA), for the determination of soluble silicate ions in various types of water (such as ground, drinking, surface, leachate and waste water). Both methods are applicable to the determination of a mass concentration of silicate (SiO2) ranging from 0,2 mg/l to 20 mg/l (with working ranges 0,2 mg/l to 2,0 mg/l and 2 mg/l to 20 mg/l). Other mass concentration ranges are applicable, provided they cover exactly one decade of concentration units (e.g. 0,02 mg/l to 0,2 mg/l in SiO2). These methods can be made applicable to seawater by changing the sensitivity and by adapting the reagent and calibration solutions to the salinity of the samples. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 3696:1987, Water for analytical laboratory use — Specification and test methods ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method ISO 8466-1:1990, Water quality — Calibration and evaluation of analytical methods and estimation of performance characteristics — Part 1: Statistical evaluation of the linear calibration function 3 General interferences Tannin, large amounts of iron, sulfide and phosphate interfere. The treatment with oxalic acid reduces the interference from tannin and eliminates interference from phosphate provided the mass concentrations are < 20 mg/l. If this value is exceeded, the amount of oxalic acid may not be sufficient to destroy all molybdophosphoric acid being formed. In this case, dilute the sample with water (5.1). When aluminium ions are present in the water sample, the addition of oxalic acid is not completely effective in eliminating phosphate interference. In this case, add 0,2 ml of a 0,1 mol/l sodium cyanide solution per litre of sample prior to analysis. If the sample contains fluoride in concentrations > 150 mg/l, treat the samples with boric acid. High concentrations of oxidizing agents are destroyed by adding 1 mol/l of sodium sulfite solution prior to analysis. If the sample contains large concentrations of sulfide, e.g. > 5 mg/l, special provisions are necessary. SIST EN ISO 16264:2004

ISO 16264:2002(E) 2 © ISO 2002 – All rights reserved
4 Principle 4.1 FIA method The sample is injected into a carrier stream of water by means of a valve. An acidic solution of heptamolybdate is added to the sample and reacts with silicates and phosphates to form molybdosilicate and molybdophosphoric acid. The latter is destroyed by oxalic acid. The molybdosilicate is then reduced to molybdenum blue using a tin(II) chloride solution. The result is expressed in milligrams of SiO2 per litre of water. 4.2 CFA method An acidic solution of heptamolybdate is added to the sample and reacts with silicates and phosphates to form molybdosilicate and molybdophosphoric acid. The latter is destroyed by oxalic acid. The molybdosilicate is then reduced to molybdenum blue using ascorbic acid. The result is expressed in milligrams of SiO2 per litre of water. 5 Reagents Use analytical grade chemicals unless otherwise specified. Check the silicate blank value of the water and of the reagents (8.2.1). Carefully degas all reagent solutions, e.g. by vacuum filtration or by purging with helium (about 1 min). Use only polyethene or polypropene laboratory ware (flasks, beakers and pipettes) for the preparation and storage of the samples (see clause 7), water (5.1) and the solutions 5.8, 5.9 and 5.10. 5.1 Water, complying with purity grade 1 of ISO 3696. 5.2 Sulfuric acid (H2SO4), ρ(H2SO4) = 1,84 g/ml. 5.3 Molybdate solution, (see R1 in Figures 1 and 2). In a 1 000 ml volumetric flask, dissolve (30 ± 0,3) g of hexaammonium heptamolybdate tetrahydrate, (NH4)6Mo7O24⋅4H2O, in about 800 ml of water (5.1). Add 15 ml of sulfuric acid (5.2) and dilute to volume with water. The solution may be stored for up to 3 months at room temperature. Discard the solution if precipitation or coloration occurs. 5.4 Oxalic acid solution, (see R2 in Figures 1 and 2). In a 1 000 ml volumetric flask, dissolve (44 ± 0,4) g of oxalic acid dihydrate, C2H2O4⋅2H2O, in about 800 ml of water (5.1) and dilute to volume with water. The solution may be stored up to 3 months at room temperature. 5.5 Tin(II) chloride reagent, for the determination of silicate by FIA (see R3 in Figure 1). Slowly add 28 ml of sulfuric acid (5.2) to 800 ml water (5.1) in a 1 0
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