Fertilizers and soil conditioners -- Determination of monosilicic acid concentrations in nonliquid fertilizer materials

This document establishes a method for the determination of monosilicic acid concentrations in nonliquid fertilizer materials. Monosilicic acid is reported as silicon (Si). This extraction method is applicable to the detection of monosilicic acid in nonliquid fertilizer products, blended products, and beneficial substances at silicon (Si) concentrations of 2 to 84 g/kg, with a limit of detection (LOD) of 0,6 g/kg Si, and a limit of quantification (LOQ) of 2 g/kg correlating well with plant uptake. This method is not applicable to liquid silicon fertilizer sources due to an expected low bias of Si recovery and low correlation with plant uptake.

Détermination des concentrations en silicium soluble dans les matières fertilisantes non liquides

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Publication Date
28-Oct-2020
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INTERNATIONAL ISO
STANDARD 19747
First edition
2020-10
Fertilizers and soil conditioners —
Determination of monosilicic acid
concentrations in nonliquid fertilizer
materials
Détermination des concentrations en silicium soluble dans les
matières fertilisantes non liquides
Reference number
ISO 19747:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 19747:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 19747:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative References ..................................................................................................................................................................................... 1

3 Terms and Definitions .................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Safety ................................................................................................................................................................................................................................ 1

6 Reagents ........................................................................................................................................................................................................................ 2

7 Calibration standards ...................................................................................................................................................................................... 3

8 Apparatus ..................................................................................................................................................................................................................... 3

9 Procedure..................................................................................................................................................................................................................... 5

9.1 Sample preparation ............................................................................................................................................................................ 5

9.2 Extraction .................................................................................................................................................................................................... 5

9.3 Heteropoly blue analyses ............................................................................................................................................................... 5

9.4 Manual spectrophotometer analyses .................................................................................................................................. 5

9.5 Calculations ................................................................................................................................................................................................ 6

9.6 Precision ....................................................................................................................................................................................................... 6

9.7 Statistical analysis ................................................................................................................................................................................ 7

9.8 Ring study .................................................................................................................................................................................................... 7

Annex A (Informative) Report of the international laboratories ring study ............................................................... 8

Bibliography ................................................................................................................................................................................................................................ 9

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 19747:2020(E)
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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

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).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 134, Fertilizers, soil conditioners and

beneficial substances.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 19747:2020(E)
Introduction
[3]

Although silicon is ubiquitous in nature, making up a quarter of the earth's crust , not all forms of

[4],[5]

silicon found in soils or fertilizer products are soluble and plant-available . The form of silicon in

soils that is soluble and available for plant uptake is monosilicic acid. Worldwide, it has been estimated

that annual removal of silicon from soils during crop production can amount to 239-255 mega tons

annually, based on FAO 1998 global crop production estimates, and a conservative annual increase of

[6]

1 % through 2012. Although the first US patent on a solid Si fertilizer was issued in 1881 , fertilizer

manufacturers, governmental regulators and consumers had no means of evaluating nonliquid silicon

fertilizer materials for their monosilicic acid supplying capacity to meet and replace plant uptake needs.

[7]

The first research into the use of silicon fertilizers was reported in 1840 . Additionally, increased

plant silicon concentrations were first associated with reductions in rice (Oryza sativa L.) blast disease

[8]

(Magnaporthe grisea M.E. Barr) over a century ago in Japan . Since then, research has extended to

[9] [10]

other grasses and grains (e.g. barley (Hordeum vulgare L.) , corn (Zea mays L.) , oats (Avena sativa

[11] [12] [13] [14]

L.) , wheat (Triticum aestivum L.) , sugar cane (Saccharum officinarum L.) , pasture , turf

[15] [16]

grasses , and to dicotyledonous crops (e.g. cucumber (Cucumis sativus L.) , grapes (Vitis vinifera

[17] [18] [19] [20]

L.) , pepper (Capsicum L.) , pumpkin (Curcubita pepo L.) , soybean (Glycine max (L.) Merr.) ,

[21]

tomato (Solanum lycopersicum L.) . Beneficial effects from silicon fertility have included increased

stress tolerance (disease, insect, drought, salt, nutrient imbalance, UV-rays, low and high temperature)

[4]

and yield increases with or without stress . Other benefits from silicon supplements to soils have

[22] [23]

included CO sequestration , reductions in metals toxicity , and reduced phosphorus run-off while

[24]
increasing phosphorus use efficiency .

Considering the extensive research, a growing market, and the potential benefits from silicon fertility

to global agriculture; it is important that a standard method exists to enable regulation of nonliquid

silicon fertilizer materials based on their monosilicic acid supplying capacity. This is the first method

developed which correlates well with plant silicon uptake while using commonly available laboratory

equipment at a reasonable cost for the analysis. Reference the peer reviewed published version, single

[25]
lab validated AOAC method .
© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 19747:2020(E)
Fertilizers and soil conditioners — Determination of
monosilicic acid concentrations in nonliquid fertilizer
materials
1 Scope

This document establishes a method for the determination of monosilicic acid concentrations in

nonliquid fertilizer materials. Monosilicic acid is reported as silicon (Si).

This extraction method is applicable to the detection of monosilicic acid in nonliquid fertilizer products,

blended products, and beneficial substances at silicon (Si) concentrations of 2 to 84 g/kg, with a limit

of detection (LOD) of 0,6 g/kg Si, and a limit of quantification (LOQ) of 2 g/kg correlating well with

plant uptake.

This method is not applicable to liquid silicon fertilizer sources due to an expected low bias of Si

recovery and low correlation with plant uptake.
2 Normative References

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 8157, Fertilizers and soil conditioners — Vocabulary
3 Terms and Definitions

For the purposes of this document, the terms and definitions given in ISO 8157 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
monosilicic acid

inorganic molecule that is soluble in soil solution and is the form of silicon available for plant uptake

4 Principle

Monosilicic acid (reported as Si) from nonliquid Si fertilizer sources is extracted at ambient room

temperature using a dilute Na CO -NH NO extractant. The extractant solution is analysed by manual

2 3 4 3
[26]
spectrophotometry at 660 nm using the heteropoly blue method .
5 Safety

General requirements: A minimum of standard laboratory personal protective equipment including

safety glasses, gloves, and lab coats should be worn always. Consult individual SDS for chemicals listed

and follow safety and handling conditions per individual SDS instructions.
© ISO 2020 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 19747:2020(E)
6 Reagents

6.1 General requirements: Protect from sunlight. Store all reagents in a manner consistent with general

laboratory practices. Store in temperatures between 20 and 24 °C unless otherwise noted.

6.2 Sodium carbonate solution, 0,094 M — fill a 19 l plastic dispensing bottle with 18 l water. Add

180 g anhydrous Na CO . Stir to dissolve.
2 3

6.3 Ammonium nitrate solution, 0,20 M — fill a 19 l plastic dispensing bottle with 18 l water. Add

288 g NH NO . Stir to dissolve.
4 3

Ammonium nitrate (NH NO ): Is a strong oxidizing agent and should not be used near flames, heating

4 3

or ignition sources, combustible materials, or reducing agents to avoid the potential for combustion or

explosion hazards. NH NO shall be separated from all organic materials present within the laboratory.

4 3

Check with governmental agencies for any additional regulatory licensing requirements before

obtaining or using NH NO .
4 3

6.4 Sodium carbonate-ammonium nitrate extractant solution, 9,4 pH — add 50 ml of each solution

(6.2 and 6.3) to a plastic beaker, stir, and verify that the pH of the mixed solution is 9,4 using a pH meter.

Mixing of sodium carbonate and ammonium nitrate: Flexible vinyl gloves are to be worn when mixing

Na CO and NH NO , due to the caustic nature of this extractant. Care shall be taken to avoid eye or

2 3 4 3

skin contact. If contact is made with eyes or skin, flush immediately with clean tap water and seek

medical attention. Clean up any spills immediately.

6.5 Silicon 1000 mg/l stock solution, silicon standard — this solution, preferably 20 g/kg sodium

hydroxide, is commercially available from numerous sources. Follow specific manufacturer’s SDS for

proper storage and shelf life.

6.6 Silicon spike solution, 500 mg/l — pipette 50 ml of a stock 1000 mg/l silicon standard into a

100 ml volumetric flask. Dilute to 100 ml with water.

6.7 Ammonium Molybdate solution, 0,42 M — add 75 g ammonium molybdate [(NH ) Mo O ·

4 6 7 24

4H O] to a 1 l beaker. Add 500 ml water. Dissolve. Slowly add 100 ml concentrated (18,4 M) sulfuric acid

(H SO ). Cool. Transfer to a 1 l volumetric flask. Dilute to 1 l with water.
2 4

WARNING — Handling of concentrated sulfuric acid: gloves, safety goggles, face shields, and lab

coats should always be worn when handling concentrated sulfuric acid. Sulfuric acid is extremely

corrosive and dehydrating, causing severe burns. Care shall be taken to avoid eye or skin contact.

If contact is made with eyes or skin, flush immediately with clean tap water and seek immediate

medical attention. To avoid the potential for fuming and spattering of concentrated sulfuric acid

during dilution, always add sulfuric acid to water and do not add water to sulfuric acid.

6.8 Tartaric acid solution, 1,33 M — add 200 g tartaric acid (C H O )to a 1 l beaker. Add 700 ml

4 6 6
water. Stir. Transfer to a 1 l volumetric flask. Dilute to 1 l with water.

6.9 Ascorbic acid solution, 0,017 M — add 3 g ascorbic acid (C H O )to 1 l volumetric flask. Dilute to

6 8 6

1 l with water. Stopper the flask and mix by inverting 10 times. Transfer to a plastic storage bottle. Cap

tightly and refrigerate.

6.10 Intermediate silicon standard solution, 50 mg/l — dilute 5 ml of a stock 1000 mg/l silicon

standard to 100 ml in a volumetric flask. Transfer immediately to a plastic storage bottle.

6.11 Cleaning solution for glassware, dilute 4 ml/l of Nitric Acid with de-ionized water (HNO ).

2 © ISO 2020 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 19747:2020(E)

6.12 Cleaning solution for flow cell, dilute 100 ml/l of HCl with de-ionized water.

7 Calibration standards

7.1 Blank: 0 mg/l Si — add 10 ml sodium carbonate–ammonium nitrate extractant solution (6.4) to a

1 l volumetric flask. Dilute to 1 l with water. Stopper the flask and mix by inverting 10 times.

7.2 Standard 1: 0,25 mg/l Si — add 10 ml sodium carbonate–ammonium nitrate extractant solution

(6.4) to a 1 L volumetric flask. Add 5 ml intermediate silicon standard solution (6.10). Dilute to 1 l with

water. Stopper the flask and mix by inverting 10 times.

7.3 Standard 2: 0,50 mg/l Si — add 10 ml sodium carbonate–ammonium nitrate extractant solution

(6.4) to a 1 l volumetric flask. Add 10 ml intermediate silicon standard solution (6.10). Dilute to 1 l with

water. Stopper the flask and mix well by inverting 10 times.
7.4 Standard 3: 1,0 mg/l Si — add 10 ml sodium carbonate–ammo
...

DRAFT INTERNATIONAL STANDARD
ISO/DIS 19747
ISO/TC 134 Secretariat: ISIRI
Voting begins on: Voting terminates on:
2020-01-09 2020-04-02
Fertilizers and soil conditioners — Determination of
monosilicic acid concentrations in nonliquid fertilizer
materials

Détermination des concentrations en silicium soluble dans les matières fertilisantes non liquides

ICS: 65.080
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 19747:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020
---------------------- Page: 1 ----------------------
ISO/DIS 19747:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DIS 19747:2020(E)
Contents Page

Introduction ................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative References ..................................................................................................................................................................................... 1

3 Terms and Definitions .................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Safety ................................................................................................................................................................................................................................ 2

6 Reagents ........................................................................................................................................................................................................................ 2

7 Calibration standards ...................................................................................................................................................................................... 3

8 Apparatus ..................................................................................................................................................................................................................... 3

9 Procedure..................................................................................................................................................................................................................... 4

9.1 Sample preparation ............................................................................................................................................................................ 4

9.2 Extraction .................................................................................................................................................................................................... 5

9.3 Heteropoly blue analyses ............................................................................................................................................................... 5

9.4 Manual spectrophotometer analyses .................................................................................................................................. 5

9.5 Calculations ................................................................................................................................................................................................ 5

9.6 Precision ....................................................................................................................................................................................................... 6

9.7 Statistical analysis ................................................................................................................................................................................ 6

9.8 Ring study .................................................................................................................................................................................................... 6

Annex A (Informative) Report of the international laboratories Ring Study .............................................................7

Bibliography ................................................................................................................................................................................................................................ 8

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/DIS 19747:2020(E)
Introduction
[1]

Although Silicon is ubiquitous in nature, making up a quarter of the earth's crust , not all forms of

[2,3]

silicon found in soils or fertilizer products are soluble and plant-available . The form of silicon in

soils that is soluble and available for plant uptake is monosilicic acid. Worldwide, it has been estimated

that annual removal of silicon from soils during crop production can amount to 239-255 mega tons

annually based on FAO 1998 global crop production estimates and a conservative annual increase of

[4]

1 % through 2012. Although the first U.S. patent on a solid Si fertilizer was issued in 1881 , fertilizer

manufacturers, governmental regulators and consumers had no means of evaluating nonliquid silicon

fertilizer materials for their monosilicic acid supplying capacity to meet and replace plant uptake needs.

[5]

The first research into the use of silicon fertilizers was reported in 1840 . Additionally, increased

plant silicon concentrations were first associated with reductions in rice (Oryza sativa L.) blast disease

[6]

(Magnaporthe grisea M.E. Barr) over a century ago in Japan . Since then, research has extended to

[7] [8]

other grasses and grains (e.g. barley (Hordeum vulgare L.) , corn (Zea mays L.) , oats (Avena sativa

[9] [10] [11] [12]

L.) , wheat (Triticum aestivum L.) , sugarcane (Saccharum officinarum L.) , pasture , turf

[13] [14]

grasses , and to dicotyledonous crops (e.g. cucumber (Cucumis sativus L.) , grapes (Vitis vinifera

[15] [16] [17] [18]

L.) , pepper (Capsicum L.) , pumpkin (Curcubita pepo L.) , soybean (Glycine max (L.) Merr.) ,

[19]

tomato (Solanum lycopersicum L.) . Beneficial effects from silicon fertility have included increased

stress tolerance (disease, insect, drought, salt, nutrient imbalance, UV-rays, low and high temperature)

[2]

and yield increases with or without stress . Other benefits from silicon supplements to soils have

[20] [21]

included CO sequestration , reductions in metals toxicity , and reduced phosphorus run-off while

[22]
increasing phosphorus use efficiency .

Considering the extensive research, a growing market, and the potential benefits from silicon fertility

to global agriculture; it is important that a standard method exist to enable regulation of nonliquid

silicon fertilizer materials based on their monosilicic acid supplying capacity. This is the first method

developed which correlates well with plant silicon uptake while using commonly available laboratory

equipment at a reasonable cost for the analysis.
iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
DRAFT INTERNATIONAL STANDARD ISO/DIS 19747:2020(E)
Fertilizers and soil conditioners — Determination of
monosilicic acid concentrations in nonliquid fertilizer
materials
1 Scope

This document establishes a method for the determination of monosilicic acid concentrations in

nonliquid fertilizer materials. Monosilicic acid is reported as % Si.

This extraction method is applicable to the detection of monosilicic acid in nonliquid fertilizer products,

blended products, and beneficial substances at silicon (Si) concentrations of 0,2 to 8,4 %, with a Limit

of Detection (LOD) of 0.06 % Si, and a Limit of Quantification (LOQ) of 0,20 % correlating well with

plant uptake.

This method is not applicable to liquid silicon fertilizer sources due to an expected low bias of Si

recovery and low correlation with plant uptake.
2 Normative References

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any amendments)

[23]
applies .
ISO 8157:—, Fertilizers and Soil Conditioners — Vocabulary
3 Terms and Definitions

For the purposes of this document, the terms and definitions given in ISO 8157and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
Monosilicic acid

inorganic molecule that is soluble in soil solution and is the form of silicon available for plant uptake

4 Principle

Monosilicic acid (reported as % Si) from nonliquid Si fertilizer sources is extracted at ambient room

temperature using a dilute Na CO -NH NO extractant. The extractant solution is analyzed by manual

2 3 4 3
spectrophotometry at 660 nm using the heteropoly blue method.
1) Under preparation.
© ISO 2020 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO/DIS 19747:2020(E)
5 Safety

5.1 General requirements: A minimum of standard laboratory personal protective equipment including

safety glasses, gloves, and lab coats should be worn always. Consult individual SDS for chemicals listed

and follow safety and handling conditions per individual SDS instructions.
6 Reagents

6.1 General requirements: Protect from sunlight. Store all reagents in a manner consistent with general

laboratory practices. Store in temperatures between 20-24 °C unless otherwise noted.

6.2 Sodium Carbonate solution, 0,094 M- Fill a 19 l plastic dispensing bottle with 18 l water. Add

180 g anhydrous Na CO . Stir to dissolve.
2 3

6.3 Ammonium Nitrate solution, 0,20 M- Fill a 19 l plastic dispensing bottle with 18 l water. Add

288 g NH NO . Stir to dissolve.
4 3

Ammonium Nitrate (NH NO ): Is a strong oxidizing agent and should not be used near flames, heating

4 3

or ignition sources, combustible materials, or reducing agents to avoid the potential for combustion or

explosion hazards. NH NO shall be separated from all organic materials present within the laboratory.

4 3

Check with governmental agencies for any additional regulatory licensing requirements before

obtaining or using NH NO .
4 3

6.4 Sodium Carbonate-Ammonium Nitrate extractant solution, 9,4 pH - Add 50 ml of each solution

(6.1 & 6.2) to a plastic beaker, stir, and verify a pH of 9.4 for the mixed solution using a pH meter.

Mixing of Sodium Carbonate and Ammonium Nitrate: Flexible vinyl gloves are to be worn when mixing

Na CO and NH NO , due to the caustic nature of this extractant. Care shall be taken to avoid eye or

2 3 4 3

skin contact. If contact is made with eyes or skin, flush immediately with clean tap water and seek

medical attention. Clean up any spills immediately.

6.5 Silicon 1000 mg/l stock solution, Silicon Standard - This solution preferably 2 % Sodium

Hydroxide is commercially available from numerous sources. Follow specific manufacturer’s SDS for

proper storage and shelf life.

6.6 Silicon spike solution, 500 mg/l- Pipette 50 ml of a stock 1000 mg/l Silicon standard into a

100 ml volumetric flask. Dilute to 100 ml with water.

6.7 Ammonium Molybdate solution, 0,42 M- Add 75 g ammonium molybdate [(NH ) Mo O ·

4 6 7 24

4H O] to a 1 l beaker. Add 500 ml water. Dissolve. Slowly add 100 ml concentrated (18.4 M) sulfuric acid

(H SO ). Cool. Transfer to a 1 l volumetric flask. Dilute to 1 l with water.
2 4

Handling of Concentrated Sulfuric Acid: Gloves, safety goggles, face shields, and lab coats should

always be worn when handling concentrated sulfuric acid. Sulfuric acid is extremely corrosive and

dehydrating, causing severe burns. Care shall be taken to avoid eye or skin contact. If contact is made

with eyes or skin, flush immediately with clean tap water and seek immediate medical attention. To

avoid the potential for fuming and spattering of concentrated sulfuric acid during dilution, always add

sulfuric acid to water and do not add water to sulfuric acid.

6.8 Tartaric Acid solution, 1,33 M-M- Add 200 g tartaric acid to a 1 l beaker. Add 700 ml water. Stir.

Transfer to a 1 l volumetric flask. Dilute to 1 l with water.

6.9 Ascorbic Acid solution, 0,017 M- Add 3 g ascorbic acid to 1 l volumetric flask. Dilute to 1 l with

water. Stopper the flask and mix by inverting 10 times. Transfer to a plastic storage bottle. Cap tightly and

refrigerate.
2 © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/DIS 19747:2020(E)

6.10 Intermediate Silicon standard solution, 50 mg/l- Dilute 5 ml of a stock 1000 mg/l Silicon

standard to 100 ml in a volumetric flask. Transfer immediately to a plastic storage bottle.

7 Calibration standards

7.1 Blank: 0 mg Si/l- Add 10 ml sodium carbonate–ammonium nitrate extractant solution (6.4) to a 1 l

volumetric flask. Dilute to 1 l with water. Stopper the flask and mix by inverting 10 times.

7.2 Standard 1: 0,25 mg Si/l- Add 10 ml sodium carbonate–ammonium nitrate extractant solution

(6.4) to a 1 L volumetric flask. Add 5 ml intermediate silicon standard solution (6.9). Dilute to 1 l with

water. Stopper the flask and mix by inverting 10 times.

7.3 Standard 2: 0,50 mg Si/l- Add 10 ml sodium carbonate–ammonium nitrate extractant solution

(6.4) to a 1 l volumetric flask. Add 10 ml intermediate silicon standard solution (6.9). Dilute to 1 l with

water. Stopper the flask and mix well by inverting 10 times.

7.4 Standard 3: 1,0 mg Si/l- Add 10 ml sodium carbonate–ammonium nitrate extractant solution (6.4)

to a 1 l volumetric flask. Add 20 ml intermediate silicon standard solution (6.9). Dilute to 1 l with water.

Stopper the flask and mix by inverting 10 times.
7.5 Standard 4: 2.0 mg S
...

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