ISO/TS 17951-1:2016

TECHNICAL ISO/TS
SPECIFICATION 17951-1
First edition
2016-07-01
Water quality — Determination of
fluoride using flow analysis (FIA and
CFA) —
Part 1:
Method using flow injection analysis
(FIA) and spectrometric detection
after off-line distillation
Qualité de l’eau — Dosage des fluorures par analyse en flux (FIA et
CFA) —
Partie 1: Méthode par analyse avec injection en flux (FIA) et détection
spectrométrique
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
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ii © ISO 2016 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Interferences . 2
5 Reagents . 2
6 Apparatus . 4
7 Sampling and sample preparation . 4
8 Procedure. 5
8.1 Distillation . . 5
8.2 Setting up the system . 5
8.3 Reagent blank measurement . 5
8.4 Adjustment of sensitivity . 5
8.5 Confirmation of repeatability . 5
8.6 Calibration . 5
8.7 Measurement of samples . 6
9 Calculation . 6
10 Expression of results . 6
11 Test report . 7
Annex A (informative) Example of flow injection analysis (FIA) system .8
Annex B (informative) Example of a distillation apparatus and procedure .9
Annex C (informative) Results of the interlaboratory trial .11
Bibliography .12
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical methods.
ISO 17951 consists of the following parts, under the general title Water quality — Determination of
fluoride using flow analysis (FIA and CFA):
— Part 1: Method using flow injection analysis (FIA) and spectrometric detection after off-line distillation
[Technical Specification]
— Part 2: Method using continuous flow analysis (CFA) with automated in-line distillation [Technical
Specification]
iv © ISO 2016 – All rights reserved

Introduction
Fluorine compounds in waters and effluents exist in various chemical forms, such as fluoride ion,
complexes of iron, aluminium, boron and etc., as well as insoluble forms, such as calcium and magnesium
fluorides. Excess fluoride can cause bone damage and fluorosis. The manual steam distillation method
can be troublesome because of its complexity. It is necessary to ensure conversion of any insoluble
fluorides into soluble fluoride for measurement.
Flow analysis with colourimetric detection is a rapid cost-effective method of determining of soluble
(dissolved) fluoride in the method distillate.
This part of ISO 17951 describes FIA methods for flow analysis of fluoride.
TECHNICAL SPECIFICATION ISO/TS 17951-1:2016(E)
Water quality — Determination of fluoride using flow
analysis (FIA and CFA) —
Part 1:
Method using flow injection analysis (FIA) and
spectrometric detection after off-line distillation
WARNING — Persons using this part of ISO 17951 should be familiar with normal laboratory
practice. This part of ISO 17951 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 part of
ISO 17951 be carried out by suitably qualified staff.
1 Scope
This part of ISO 17951 specifies a method for the determination of fluoride in waters, waste waters and
effluents by flow injection analysis (FIA). Any insoluble or complexed fluoride is converted to fluoride
ion by a manual distillation procedure from sulfuric/phosphoric acid. Fluoride ion in the distillate is
measured using flow analysis with lanthanum alizarin complexone and spectrometric detection. This
method is applicable to industrial waste waters, effluents, surface waters, ground waters, leachates.
It is not recommended for drinking waters where a distillation step is not required. In this part of
ISO 17951, two working ranges are described:
— working range I: 0,1 mg/l to 1 mg/l;
— working range II: 1 mg/l to 10 mg/l.
The specification of the calibration solutions are to be adapted accordingly.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of
performance characteristics — Part 1: Statistical evaluation of the linear calibration function
ISO 8466-2, Water quality — Calibration and evaluation of analytical methods and estimation of
performance characteristics — Part 2: Calibration strategy for non-linear second-order calibration
functions
3 Principle
Prior to the introduction of sample solution into the FIA system, the sample solution is manually
distilled (see Annex B). Then, the distillate is introduced into a continuous carrier stream (water)
by means of injection valve and is mixed with a continuously streaming flow of lanthanum alizarin
complexone solution. The formed blue colour is measured by spectrometric detection around 620 nm.
Without the distillation, fluoride ion in water samples is determined.
4 Interferences
Without distillation, lanthanum alizarin complexone spectrometric method suffers from the
interferences by aluminium, cadmium, cobalt, iron, nickel, beryllium, lead, etc. However, these
interferences are removed by the distillation.
5 Reagents
Use only reagents of recognized analytical grade. The prepared solution is degassed, if necessary.
5.1 Water, grade 1, as specified in ISO 3696.
5.2 1,2-Dihydroxyanthraquinonyl-3-methylamine-N,N-diacetic acid dihydrate (alizarin
complexone), C H NO ·2H O.
19 15 8 2
5.3 Ammonia solution I, c(NH ) = 15 mol/l, as specified in ISO 6353-2.
5.4 Hydrochloric acid I, c(HCl) = 12 mol/l, as specified in ISO 6353-2.
5.5 Ammonium acetate, C H NO , as specified in ISO 6353-2.
2 7 2
5.6 Sodium acetate trihydrate, C H O Na·3H O, as specified in ISO 6353-2.
2 3 2 2
5.7 Acetic acid, C H O , as specified in ISO 6353-2.
2 4 2
5.8 Lanthanum(III) oxide, La O .
2 3
5.9 Acetone, C H O, as specified in ISO 6353-2.
3 6
5.10 Sodium fluoride, NaF.
5.11 Sulfuric acid, c(H SO ) = 18 mol/l.
2 4
5.12 Phosphoric acid, c(H PO ) = 14,6 mol/l.
3 4
5.13 Carrier solution, water (5.1).
5.14 Ammonia solution II.
Mix 10 ml of ammonia solution I (5.3) and 100 ml of water (5.1).
5.15 Ammonium acetate solution, ρ(C H NO ) = 200 g/l.
2 7 2
Dissolve 200 g of ammonium acetate (5.5) in about 800 ml of water (5.1). Make up to 1 000 ml with
water (5.1).
5.16 Sodium acetate solution.
Dissolve 41 g of sodium acetate trihydrate (5.6) in 400 ml of water (5.1) and add 24 ml of acetic acid (5.7).
2 © ISO 2016 – All rights reserved

5.17 Hydrochloric acid II, c(HCl) = 2 mol/l.
Mix 20 ml of hydrochloric acid (5.4) and 100 ml of water (5.1).
5.18 Lanthanum(III) solution, c(La(III)) = 0,1 mol/l.
Add 0,163 g of lanthanum(III) oxide (5.8) to 10 ml of hydrochloric acid II (5.17) and dissolve it by heating
of the solution.
5.19 Lanthanum-alizarin complexone solution.
Dissolve 0,192 g of alizarin complexone (5.2) to 4 ml of ammonia solution II (5.14) and 4 ml of ammonium
acetate solution (200 g/l) (5.15). Add this solution into 425 ml of sodium acetate solution (5.16) with
stirring, and add 400 ml of acetone (5.9) gradually. Then, add 10 ml of lanthanum(III) solution (5.18)
to the solution and mix it. After cooling, adjust the pH of the solution to 4,7 with acetic acid (5.7) or
ammonia solution I (5.3), then make it up to 1 000 ml with water (5.1).
1)
Lanthanum-alizarin complexone solution (5.19) can be prepared by using alfusone. In that case,
after dissolving 1,2 g of alfusone to small amount of water (5.1), add 90 ml of acetone (5.9) and mix the
solution. Make up the solution to 300 ml with water (5.1). The solution shall be prepared at the time of
analysis.
5.20 Fluoride stock solution ion, ρ(F‾) = 100 mg/l.
Take sodium fluoride (5.10) in a platinum plate and dry at 105 °C at least 1 h. Then coo
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