ISO/FDIS 8655-8

Piston-operated volumetric apparatus

Appareils volumétriques à piston

General Information

• Status: Published
• ICS: 17.060 - Measurement of volume, mass, density, viscosity
• ICS: 71.040.20 - Laboratory ware and related apparatus
• Technical Committee: ISO/TC 48 - Laboratory equipment
• Drafting Committee: ISO/TC 48/WG 4 - Liquid Handling Devices – Manual and Semi-Automatic
• Current Stage: 5060 - Close of voting Proof returned by Secretariat
• Completion Date: 12-Jan-2022

Standards Content (sample)

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 8655-8
ISO/TC 48
Piston-operated volumetric
Secretariat: DIN
apparatus —
Voting begins on:
2021-11-17
Part 8:
Voting terminates on:
Photometric reference measurement
2022-01-12
procedure for the determination of
volume
Appareils volumétriques à piston —
Partie 8: Méthode photométrique de mesurage de référence pour la
détermination du volume
ISO/CEN PARALLEL PROCESSING
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 SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 8655-8:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2021
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ISO/FDIS 8655-8:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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

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ISO/FDIS 8655-8:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction .............................................................................................................................................................................................................................. vi

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

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 General requirements .................................................................................................................................................................................... 2

5 Test equipment ......................................................................................................................................................................................................2

5.1 General ........................................................................................................................................................................................................... 2

5.2 Spectrophotometer ............................................................................................................................................................................. 2

5.3 Cuvette and mixer ........................................................................................................................................... ..................................... 2

5.4 Measuring devices ............................................................................................................................................................................... 3

5.5 Equipment used for solution preparation ...................................................................................................................... 3

5.6 Balances ........................................................................................................................................................................................................ 3

5.7 Density meter .......................................................................................................................................................................................... 4

5.8 pH meter ....................................................................................................................................................................................................... 4

6 Reagents ........................................................................................................................................................................................................................ 4

6.1 General requirements ...................................................................................................................................................................... 4

6.2 Water ............................................................................................................................................................................................................... 4

6.3 Buffer solution ........................................................................................................................................................................................ 4

6.4 Copper(II) chloride solution ....................................................................................................................................................... 4

6.5 Ponceau S solutions ............................................................................................................................................................................ 4

6.6 Calibrator solutions ............................................................................................................................................................................ 5

6.7 Stability of solutions .......................................................................................................................................................................... 6

6.7.1 General ........................................................................................................................................................................................ 6

6.7.2 Preservatives ......................................................................................................................................................................... 6

6.7.3 Light sensitivity .................................................................................................................................................................. 6

6.7.4 Storage temperature ....................................................................................................................................................... 6

7 Test conditions .......................................................................................................................................................................................................6

7.1 General ........................................................................................................................................................................................................... 6

7.2 Test room ..................................................................................................................................................................................................... 6

7.3 Evaporation ............................................................................................................................................................................................... 7

8 Procedure ....................................................................................................................................................................................................................7

8.1 General ........................................................................................................................................................................................................... 7

8.1.1 Summary ................................................................................................................................................................................... 7

8.1.2 Test conditions ..................................................................................................................................................................... 7

8.1.3 Test volume ............................................................................................................................................................................. 7

8.1.4 Number of measurements per volume to be tested ............................................................................ 8

8.2 System calibration ............................................................................................................................................................................... 8

8.2.1 General ........................................................................................................................................................................................ 8

8.2.2 System calibration procedure ................................................................................................................................ 8

8.2.3 Previous calibration ........................................................................................................................................................ 8

8.3 Photometric procedure ................................................................................................................................................................... 8

8.3.1 Preparation of cuvettes ................................................................................................................................................ 8

8.3.2 Zero of the spectrophotometer ............................................................................................................................. 9

8.3.3 Starting absorbances ...................................................................................................................................................... 9

8.3.4 Dispensing of samples ................................................................................................................................................... 9

8.3.5 Absorbance of the chromophore mixture.................................................................................................... 9

8.3.6 Calculation of the delivered test volume ....................................................................................................... 9

8.4 Preparation ................................................................................................................................................................................................ 9

8.5 Single-channel air displacement pipettes (in accordance with ISO 8655-2) ............................... 10

8.5.1 General ..................................................................................................................................................................................... 10

iii
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ISO/FDIS 8655-8:2021(E)

8.5.2 Test cycle ................................................................................................................................................................................ 10

8.6 Multi-channel pipettes (in accordance with ISO 8655-2) ............................................................................. 11

8.7 Positive displacement pipettes (in accordance with ISO 8655-2) ......................................................... 11

8.8 Burettes (in accordance with ISO 8655-3) ................................................................................................................. 11

8.9 Dispensers (in accordance with ISO 8655-5) ...........................................................................................................12

8.10 Syringes (in accordance with ISO 8655-9) .................................................................................................................12

8.10.1 General .....................................................................................................................................................................................12

8.10.2 Test cycle ................................................................................................................................................................................12

9 Evaluation ................................................................................................................................................................................................................13

9.1 Calculation of volume .................................................................................................................................................................... 13

9.1.1 Calibration constant .....................................................................................................................................................13

9.1.2 Volume of test liquid .....................................................................................................................................................13

9.1.3 Temperature correction ........................................................................................................................................... 14

9.1.4 Mean volume ....................................................................................................................................................................... 14

9.2 Systematic error of measurement ...................................................................................................................................... 14

9.3 Random error of measurement ............................................................................................................................................ 15

9.4 Uncertainty of measurement ..................................................................................................................................................15

10 Reporting of results .......................................................................................................................................................................................15

Annex A (normative) Calculation of volumes from balance readings ...........................................................................17

Bibliography .............................................................................................................................................................................................................................18

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ISO/FDIS 8655-8:2021(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 48, Laboratory equipment, in collaboration

with the European Committee for Standardization (CEN) Technical Committee CEN/TC 332, Laboratory

equipment, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna

Agreement).
A list of all parts in the ISO 8655 series can be found on the ISO website.

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.
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ISO/FDIS 8655-8:2021(E)
Introduction
The ISO 8655 series addresses the needs of:

— manufacturers, as a basis for quality control including, where appropriate, the issuance of

manufacturer’s declarations;

— calibration laboratories, test houses, users of the equipment and other bodies as a basis for

independent calibration, testing, verification, and routine tests.

The tests specified in the ISO 8655 series are intended to be carried out by trained personnel.

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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 8655-8:2021(E)
Piston-operated volumetric apparatus —
Part 8:
Photometric reference measurement procedure for the
determination of volume
1 Scope

This document specifies the photometric reference measurement procedure for the determination

of volume of piston-operated volumetric apparatus (POVA). The procedure is applicable to complete

systems comprising the basic apparatus with a maximum nominal volume of 5 000 µl and all parts

selected for use with the apparatus, disposable or reusable, involved in the measurement by delivery

(Ex).
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 1042, Laboratory glassware — One-mark volumetric flasks

ISO 3696:1987, Water for analytical laboratory use — Specification and test methods

ISO 8655-1:— , Piston-operated volumetric apparatus — Part 1: Terminology, general requirements and

user recommendations
ISO 8655-2, Piston-operated volumetric apparatus — Part 2: Pipettes
ISO 8655-3, Piston-operated volumetric apparatus — Part 3: Burettes
ISO 8655-5, Piston-operated volumetric apparatus — Part 5: Dispensers

ISO 8655-9, Piston-operated volumetric apparatus — Part 9: Manually operated precision laboratory

syringes
ISO/IEC Guide 2, Standardization and related activities — General vocabulary

ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and

associated terms (VIM)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in in ISO 8655-1, ISO/IEC Guide 2,

and ISO/IEC Guide 99 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 https:// www .electropedia .org/
1) Under preparation. Stage at the time of publication: ISO/FDIS 8655-1.
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ISO/FDIS 8655-8:2021(E)
4 General requirements

When performing calibrations according to the reference measurement procedure described in

this document, all provisions and requirements of this document shall be followed or exceeded (e.g.,

performing 30 instead of 10 replicates per volume). If one or more of those requirements is not followed,

conformity to this document shall not be claimed.
5 Test equipment
5.1 General

Measurement equipment for spectrophotometry, weighing, temperature, density, pH, humidity, and

barometric pressure shall be traceable to the international system of units (SI) and shall meet the

uncertainty requirements of this document.

NOTE An example of the calculation of the expanded uncertainty of the photometric reference procedure is

[1]
given in ISO/TR 16153 .
5.2 Spectrophotometer

The visible range spectrophotometer shall meet the performance requirements specified in Table 1 at

520 nm and 730 nm.
Table 1 — Performance requirements of the spectrophotometric system
Parameter Requirement
Photometric repeatability at A = 0,0 AU 0,000 05 AU
Photometric repeatability at A = 0,5 AU 0,000 05 AU
Photometric repeatability at A = 1,0 AU 0,000 10 AU
Photometric repeatability at A = 1,5 AU 0,000 15 AU
Centre wavelength reproducibility 0,025 nm
Bandwidth reproducibility 0,050 nm
Reproducibility of cuvette attenuance 0,000 10 AU
ND glass calibration standards
Uncertainty at A = 0,5 AU 0,001 5 AU
Uncertainty at A = 1,0 AU 0,002 5 AU
Uncertainty at A = 1,5 AU 0,003 0 AU

Repeatability to be measured as standard deviation using the same reading procedures, settings and conditions as

are used during the photometric volume determination. Adjusting integration time (sample averaging time), bandpass (slit

width), and the number of replicate readings are acceptable means of improving the spectrophotometer’s repeatability.

Wavelength and bandwidth reproducibility applies to instruments where wavelength and bandwidth are adjustable. It

does not apply to fixed-wavelength interference filter instruments.

Cuvette attenuance reproducibility applies to the spectrophotometer and cuvette tested together. An example is given

[1]
in ISO/TR 16153 .
Applicable when use of ND glass standard is specified by the manufacturer.
5.3 Cuvette and mixer

The cuvette shall be made of a material with at least 99 % internal optical transmittance at 520 nm and

730 nm. The cuvette shall have an optical path length of 20 mm ± 2 mm. If multiple cuvettes are used,

each cuvette shall have a path length within ± 0,2 mm of the chosen nominal.

A mixing mechanism shall be fitted to the cuvette holder of the spectrophotometer, such that the

cuvette’s contents can be mixed while the cuvette remains seated in the spectrophotometer. Mixing

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ISO/FDIS 8655-8:2021(E)

shall ensure that the liquid contents are mixed to within 0,010 % of complete mixing. Mixing speed

shall be sufficient to wash down dye solution deposited on the cuvette side wall.

Mixing mechanisms, such as orbital mixing, a glass-covered magnetic stir bar or a PTFE-covered

(Polytetrafluoroethylene, PTFE) magnetic stir bar may be used and shall be verified to meet this

requirement.

NOTE Complete mixing is achieved when re-mixing and re-measuring the absorbance produces a systematic

change no larger than the required value.
5.4 Measuring devices

The minimum requirements for each relevant measuring device are specified in Table 2.

Table 2 — Minimum requirements for measuring devices
Device Resolution Expanded uncertainty of meas-
urement (k = 2)
Thermometer for liquids 0,01 °C 0,2 °C
Thermometer for room air 0,1 °C 0,3 °C
Hygrometer 1 % relative humidity 5 % relative humidity
Barometer 0,1 kPa 1 kPa
Timing device 1 s not applicable

NOTE Acceptable means of measuring the temperature of a solution in a cuvette include a thermistor bead

probe immersed in the solution within the cuvette; a suitable contact thermometer on the outside of the cuvette;

or a suitable infrared thermometer.
5.5 Equipment used for solution preparation
Solutions shall be prepared by gravimetric or volumetric means.

The liquid components of solutions may be weighed using balances, which shall meet the requirements

of Table 3.

For volumetric preparations, class A glassware meeting the maximum permissible errors for narrow

neck flasks of ISO 1042 shall be used.
5.6 Balances

Balances used for accurate weighing of dry reagents, preparation of calibrator solutions, and filling of

cuvettes shall meet the requirements specified in Table 3.
Table 3 — Minimum requirements for balances
Minimum mass to be Resolution Repeatability Expanded uncertainty in
weighed use (k = 2)
(d) (s)
g mg mg mg
1,0 0,01 0,02 0,04
10 0,1 0,2 0,4
100 1 2 4
1 000 10 20 40

Uncertainty in use is determined according to Reference [2] at the minimum mass listed in the table.

Weighing results for liquids shall be corrected for density, temperature and air buoyancy when

determining volume, see Annex A.
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ISO/FDIS 8655-8:2021(E)
5.7 Density meter

Densities of the chromophore solutions shall be measured for each lot of solutions using a temperature-

controlled density meter with an uncertainty of 0,000 05 g/ml (k = 2) or better.
5.8 pH meter

The pH meter is used for the preparation of the solutions in 6.3, 6.4, 6.5, and 6.6. It shall be calibrated

with reference buffer solutions over a range from pH 4 to pH 7 including pH 6,00 according to

manufacturer’s instructions. A reference material having a certified value in the range of pH 6,00 ± 0,05

and an uncertainty (k = 2) of 0,02 pH units, or better is required for comparison.

6 Reagents
6.1 General requirements

All components used in the preparation of reagent solutions shall be of at least 99 % analytical purity

unless otherwise stated.

NaOH (CAS No. 1310-73-2) and HCl (CAS No. 7647-01-0) solutions may be used for adjustment of pH.

The measured pH value of the reagent solutions in 6.3, 6.4, 6.5 and 6.6 shall be compared to the pH 6,00

certified reference material in 5.8.
6.2 Water

Water (CAS No. 7732-18-5) used for preparing chromophore solutions shall comply with Grade 1 in

accordance with ISO 3696:1987.
6.3 Buffer solution

Dissolve 4,08 g of potassium hydrogen phthalate (CAS No. 877-24-7) and 3,81 g of tetrasodium

ethylenediaminetetraacetic acid dihydrate (EDTA, CAS No. 10378-23-1) per litre of water, adjust to pH

6,0 ± 0,1, and filter through a 0,2 µm filter.
6.4 Copper(II) chloride solution

Dissolve 1,12 g/l of copper(II) chloride dihydrate (CuCl ·2H O) (CAS No. 10125-13-0) in the phthalate/

2 2

EDTA buffer and adjust to pH 6,0 ± 0,1. Filter the resulting solution through a 0,2 µm filter.

6.5 Ponceau S solutions

Dissolve Ponceau S (CAS No. 6226-79-5) in water, adjust to pH 6,0 ± 0,1, and then filter the dye solution

through a 0,2 µm filter. Table 4 indicates the amount of Ponceau S dye (which can contain up to 15 %

water) per litre of solution. These Ponceau S solutions are used for the preparation of calibrator

solutions (see 6.6) and as test liquids.

NOTE 1 Ponceau S solutions prepared according to Table 4 are suitable to measure test volumes from 0,1 µl to

5 000 µl in cuvettes as specified in 5.3.

NOTE 2 When prepared as described in this subclause, the solutions will fulfil the density and viscosity

requirements listed in Table 4.
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ISO/FDIS 8655-8:2021(E)
Table 4 — Ponceau S solutions
Ponceau S Test volume V Ponceau S dye Relative density Viscosity at
solution 20 °C
No. µl g/1 000 ml (vs. H O) mPa · s
1 200 ≤ V ≤ 5 000 0,024 1,000 to 1,004 0,9 to 1,1
2 50 ≤ V < 200 0,052 1,000 to 1,004 0,9 to 1,1
3 10 ≤ V < 50 0,165 1,000 to 1,004 0,9 to 1,1
4 2 ≤ V < 10 0,745 1,000 to 1,004 0,9 to 1,1
5 0,5 ≤ V < 2 3,72 1,000 to 1,004 0,9 to 1,1
6 0,1 ≤ V < 0,5 14,9 1,000 to 1,016 0,9 to 1,1

Amounts listed in this table are target values. Actual amounts may vary up to ± 5 % from the target value, provided the

same batch of solutions is used for the preparation of calibrator solutions (6.6) and as test liquids (8.3).

6.6 Calibrator solutions

Prepare a calibrator solution for each selected volume V to be tested. Mix a measured volume of

Ponceau S solution (see Table 4) with a measured volume of copper(II) chloride solution. Determine the

volumes of each solution as follows:

Ponceau S solution: use a 10-fold amount of the desired test volume V (for n = 10 replicates) and

multiply it by the preparation factor given in Table 5.

Copper(II) solution: multiply the volume V of copper(II) chloride solution in the cuvette by the

preparation factor given in Table 5.
NOTE V is de
...