SIST EN ISO 8655-7:2022

SLOVENSKI STANDARD
01-julij-2022
Nadomešča:
SIST EN ISO 8655-7:2006
SIST EN ISO 8655-7:2006/AC:2009
Volumetrične naprave, delujoče na bat - 7. del: Nadomestni merilni postopki za
določanje prostornine (ISO 8655-7:2022)
Piston-operated volumetric apparatus - Part 7: Alternative measurement procedures for
the determination of volume (ISO 8655-7:2022)
Volumenmessgeräte mit Hubkolben - Teil 7: Alternatives Prüfverfahren zur Bestimmung
des Volumens (ISO 8655-7:2022)
Appareils volumétriques à piston - Partie 7: Modes opératoires de mesure alternatifs
pour la détermination de volumes (ISO 8655-7:2022)
Ta slovenski standard je istoveten z: EN ISO 8655-7:2022
ICS:
17.060 Merjenje prostornine, mase, Measurement of volume,
gostote, viskoznosti mass, density, viscosity
71.040.20 Laboratorijska posoda in Laboratory ware and related
aparati apparatus
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 8655-7
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2022
EUROPÄISCHE NORM
ICS 17.060 Supersedes EN ISO 8655-7:2005, EN ISO 8655-
7:2005/AC:2009
English Version
Piston-operated volumetric apparatus - Part 7: Alternative
measurement procedures for the determination of volume
(ISO 8655-7:2022)
Appareils volumétriques à piston - Partie 7: Modes Volumenmessgeräte mit Hubkolben - Teil 7:
opératoires de mesure alternatifs pour la Alternatives Prüfverfahren zur Bestimmung des
détermination de volumes (ISO 8655-7:2022) Volumens (ISO 8655-7:2022)
This European Standard was approved by CEN on 13 February 2022.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 8655-7:2022 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 8655-7:2022) has been prepared by Technical Committee ISO/TC 48
"Laboratory equipment" in collaboration with Technical Committee CEN/TC 332 “Laboratory
equipment” the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by November 2022, and conflicting national standards
shall be withdrawn at the latest by November 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 8655-7:2005, EN ISO 8655-7:2005/AC:2009.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 8655-7:2022 has been approved by CEN as EN ISO 8655-7:2022 without any
modification.
INTERNATIONAL ISO
STANDARD 8655-7
Second edition
2022-04
Piston-operated volumetric
apparatus —
Part 7:
Alternative measurement procedures
for the determination of volume
Appareils volumétriques à piston —
Partie 7: Modes opératoires de mesure alternatifs pour la
détermination de volumes
Reference number
ISO 8655-7:2022(E)
ISO 8655-7:2022(E)
© ISO 2022
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 8655-7:2022(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General requirements . 2
4.1 Metrological confirmation . 2
4.2 Uncertainty of measurement . 2
4.3 Operator qualification . 2
5 Performance requirements . .3
5.1 Performance tolerances . 3
5.2 Operator impact . 3
6 Test conditions .3
6.1 General . 3
6.2 Test equipment . 3
6.3 Test room, environmental conditions . 3
6.4 Test volumes . 4
6.4.1 Fixed volume POVA. 4
6.4.2 Adjustable volume POVA . 4
6.5 Number of measurements per test volume . 4
6.6 Test liquids . 5
7 Evaluation . 5
7.1 Mean volume . 5
7.2 Systematic error of measurement . 5
7.3 Random error of measurement . 6
8 Test methods . 6
8.1 General . 6
8.2 Gravimetric method . . 7
8.3 Dual-dye ratiometric photometric method . 7
8.4 Single dye photometric method . 8
8.5 Hybrid photometric/gravimetric method for multichannel POVA . 8
8.6 Titration method . 8
8.7 Batch testing . 8
9 Dispense procedures .8
9.1 General . 8
9.2 Preparation . 9
9.3 Single-channel air displacement pipettes (in accordance with ISO 8655-2) . 9
9.3.1 General . 9
9.3.2 Test cycle . 9
9.4 Multi-channel pipettes (in accordance with ISO 8655-2) . 10
9.5 Positive displacement pipettes (in accordance with ISO 8655-2) . 11
9.6 Burettes (in accordance with ISO 8655-3) . 11
9.7 Dilutors (in accordance with ISO 8655-4) .12
9.7.1 General .12
9.7.2 Test cycle . 12
9.8 Dispensers (in accordance with ISO 8655-5) . 13
9.9 Syringes (in accordance with ISO 8655-9) . 13
9.9.1 General .13
9.9.2 Test cycle .13
10 Reporting of results .14
iii
ISO 8655-7:2022(E)
Annex A (normative) Gravimetric procedure .16
Annex B (normative) Dual-dye ratiometric photometric procedure .21
Annex C (normative) Single dye photometric procedure .29
Annex D (normative) Photometric/gravimetric hybrid procedure .33
Annex E (normative) Titrimetric procedure.41
Annex F (normative) Conversion of liquid mass to volume .45
Bibliography .48
iv
ISO 8655-7:2022(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).
This second edition cancels and replaces the first edition (ISO 8655-7:2005), which has been technically
revised. It also incorporates the Technical Corrigendum ISO 8655-7:2005/Cor.1:2008.
The main changes are as follows:
— a gravimetric test method was added (see 8.2);
— a photometric/gravimetric hybrid test method was added (see 8.5);
— a batch testing method was added (see 8.7);
— measurement procedures for all methods are given in normative Annexes A to E;
— standard dispense procedures for POVA described in ISO 8655-2, ISO 8655−3, ISO 8655−4,
ISO 8655−5, and ISO 8655−9 were added (see Clause 9);
— requirements for operator qualification have been added (see 4.3);
— requirements for testing of multi-channel POVA is described in more detail, with specific procedures
given for these apparatus (see 8.5, and Annex D);
— Annexes A, B, and C of the first edition have been deleted and replaced.
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.
v
ISO 8655-7:2022(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.
vi
INTERNATIONAL STANDARD ISO 8655-7:2022(E)
Piston-operated volumetric apparatus —
Part 7:
Alternative measurement procedures for the
determination of volume
1 Scope
This document specifies alternative measurement procedures for the determination of volume of
piston-operated volumetric apparatus.
The procedures are applicable to complete systems comprising the basic apparatus and all parts
selected for use with the apparatus, disposable or reusable, involved in the measurement by delivery
process (Ex). Methods described in this document are suitable for various maximum nominal volumes
of piston-operated volumetric apparatus. It is the responsibility of the user to select the appropriate
method.
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 2859-1, Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by
acceptance quality limit (AQL) for lot-by-lot inspection
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 3951-1, Sampling procedures for inspection by variables — Part 1: Specification for single sampling
plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristic
and a single AQL
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 8655-4, Piston-operated volumetric apparatus — Part 4: Dilutors
ISO 8655-5, Piston-operated volumetric apparatus — Part 5: Dispensers
ISO 8655-6, Piston-operated volumetric apparatus — Part 6: Gravimetric reference measurement
procedure for the determination of volume
ISO 8655-8, Piston-operated volumetric apparatus — Part 8: Photometric reference measurement
procedure for the determination of volume
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 8655-7:2022(E)
ISO/IEC Guide 99, 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 ISO 8655-1, ISO/IEC Guide 2,
ISO/IEC Guide 99 and the following apply.
ISO and IEC maintain terminology 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/
3.1
acceptance quality limit
AQL
worst tolerable quality level
Note 1 to entry: This concept only applies when a sampling scheme with rules for switching and for
discontinuation, such as in ISO 2859-1, ISO 3951-1 or ISO 3951-5 is used.
Note 2 to entry: Although individual lots with quality as bad as the acceptance quality limit may be accepted
with fairly high probability, the designation of an acceptance quality limit does not suggest that this is a desirable
quality level. Sampling schemes found in International Standards such as ISO 2859-1, ISO 3951-1 or ISO 3951-5,
with their rules for switching and for discontinuation of sampling inspection, are designed to encourage suppliers
to have process averages consistently better than the AQL.
4 General requirements
4.1 Metrological confirmation
Metrological confirmation of all POVA shall be performed on a regular basis to ensure the apparatus
conforms to requirements for its intended use. The requirements of the methods and procedures
described in this document are suitable to be used in the metrological confirmation of POVA. For
calibrations and testing, no less than ten replicate measurements per selected volume shall be
performed and the measurement procedures in this document shall be validated by comparison to one
of the reference measurement procedures described in ISO 8655-6 or ISO 8655-8.
4.2 Uncertainty of measurement
When performing calibrations (ISO 8655-1:2022, 6.4) according to measurement procedures described
in this document, the expanded measurement uncertainty of the mean delivered volume for each
selected volume shall be estimated and reported (see Clause 10 (m)).
When performing testing (ISO 8655-1:2022, 6.4) or routine tests (ISO 8655-1:2022, 6.5), it is optional to
estimate and report the expanded measurement uncertainty.
NOTE For further information on uncertainty for the photometric and gravimetric methods, refer to
[1] [2]
ISO/TR 16153 and ISO/TR 20461 respectively.
4.3 Operator qualification
An operator who uses POVA for volumetric transfers, performs metrological confirmation or routine
tests of POVA shall be adequately trained on the use of the type of POVA under test. Operator training
and competence should be documented.
NOTE 1 Previously calibrated POVA can be used for the qualification of operators.
ISO 8655-7:2022(E)
NOTE 2 Training and qualification requirements for operators of POVA are intended to be included in
ISO 8655-10.
5 Performance requirements
5.1 Performance tolerances
Calibration, testing, and routine test results may be reported without comparison to performance
tolerances. If the results are verified against performance tolerances, these tolerances shall be stated
on the test report/certificate.
Performance tolerances may be based on the user’s liquid handling process tolerances or the product
tolerances given in the part of ISO 8655 corresponding to the type of POVA under test or the tolerances
specified by the manufacturer, subject to them being fit for purpose.
5.2 Operator impact
Measurement of volumetric performance includes random and systematic errors of the POVA, as well as
errors introduced by the device’s operator. The performance of a hand-held pipette is inseparable from
the performance of its operator.
NOTE More information about operator impact is given in ISO 8655-10.
6 Test conditions
6.1 General
Test conditions described in this clause shall be validated for their suitability for the selected test
method and procedure. Test conditions, together with the test equipment and detailed test procedure,
impact the uncertainty of measurement. Examples for the calculation of the expanded uncertainty of
[1]
the mean volume and of the uncertainty in use of a single delivered volume are given in ISO/TR 16153
[2]
and ISO/TR 20461 .
6.2 Test equipment
All equipment used for the testing of POVA, including for the preparation of test solutions, shall be
chosen such that the required uncertainty of measurement can be obtained.
All test equipment used shall be of suitable readability, accuracy, reproducibility and stability, consistent
with the required expanded uncertainty of measurement.
Deviations from the test equipment given in this document shall be taken into account when calculating
the expanded measurement uncertainty and shall be proven to yield measurement results fit for the
intended purpose.
6.3 Test room, environmental conditions
The following applies:
a) The test room should be kept at a steady temperature throughout the entirety of the equilibration
time for the test equipment and POVA (±1 °C), and throughout the POVA testing time (±0,5 °C). All
test equipment, POVA, exchangeable parts (e. g. pipette tips), and reagents used shall be equilibrated
to the test room temperature.
b) The air temperature, relative humidity, and barometric pressure at the time of the test shall be
recorded. At the start and at the end of the n replicate measurements, the temperature of the test
liquid shall be recorded.
ISO 8655-7:2022(E)
NOTE 1 Air temperature and barometric pressure are necessary for the conversion of liquid mass to
volume (see Annex F); the relative humidity is necessary for the stability of the room conditions and is
necessary for documentation in the test report.
c) To aid evaluation of a POVA’s fitness for purpose, the test room conditions (temperature, relative
humidity, and barometric pressure) should reflect the environmental conditions under which the
POVA is used, within the constraints mentioned in a). This can be achieved when a POVA is tested
within the laboratory in which it is used. Other environmental and non-environmental factors can
influence a POVA’s fitness for purpose.
d) The test environment should be draft free.
e) Prior to the test, the apparatus to be tested, all test equipment, and test solutions shall have stood
in the test room conditions for a sufficient time to reach equilibrium with the test room conditions.
f) The environmental conditions, air temperature and air humidity, shall be within the specified
limits for the test room for at least 2 h before starting the test (minimum equilibration time) and
during the test itself.
NOTE 2 It is unlikely that this minimum equilibration time will be less than 2 h and can be considerably
longer.
NOTE 3 Calibration laboratories at test houses or pipette manufacturer’s quality control laboratories can
often precisely control environmental conditions to achieve a desired standard condition. It can be very
challenging to reproduce such results under different environmental conditions.
6.4 Test volumes
6.4.1 Fixed volume POVA
In the case of a fixed-volume POVA, the selected volume V is the nominal volume V and is the only
S Nom
test volume.
6.4.2 Adjustable volume POVA
a) For calibrations and testing, adjustable volume POVA shall be tested at least at three volumes:
— nominal volume;
— 50 % of the nominal volume, or the closest possible (if equidistant, use the higher value);
— the lower limit of the useable volume range or 10 % of the nominal volume (whichever is the
greater).
Measurement of further volumes is optional.
b) For routine tests, fewer than three volumes may be tested.
In case the POVA is to be tested at only two volumes, the nominal volume and the lower limit of the
useable volume range, or 10 % of the nominal volume (whichever is the greater), shall be tested.
NOTE The linearity of delivered volumes between these two test points is unknown and is likely to increase
the risk for volumetric errors as compared to a test at three volumes.
In case the POVA is tested only at one volume, it shall be tested at its nominal volume, or at the volume
at which it will be used.
6.5 Number of measurements per test volume
The confidence of metrological confirmation increases with the number of replicate measurements
for each test volume. A minimum of 10 measurements per volume is required by the reference
ISO 8655-7:2022(E)
measurement procedures specified in ISO 8655-6 and ISO 8655-8. For routine tests, 10 measurements
are recommended, but fewer replicate measurements may be made if the expanded uncertainty of
measurement for the POVA is fit for the intended purpose. The number of replicates shall not be less
than 4.
After repair or adjustment of the POVA, a minimum of 10 measurements shall be performed.
The replicate volume measurements shall be used to calculate the systematic and the random errors of
measurement in accordance with Clause 8. When applicable, the reported uncertainty shall be based on
the number of replicates.
6.6 Test liquids
POVA are typically supplied with adjustments using water. Calibrations or routine tests may be
performed using other liquids or solutions. For the purpose of this document, the term “test liquid”
is used for pure solvents, as well as for prepared chromophore or other solutions. The test liquid used
shall be described in sufficient detail to allow replication of the test and interpretation of the results.
The following characteristics of the test liquid shall be taken into account when determining the
measured volume: Z-factor when weighing, absorbances of the chromophore when using photometric
methods, and conductivity and reactivity when performing potentiometric titration.
Depending on the type of POVA, the following parameters can influence the amount of liquid aspirated
and/or dispensed: viscosity, density, chemical composition, and surface tension.
The stability of each test liquid shall be known if it is to be stored for any length of time. Refer to the
specific procedure for the preparation and storage of reagent solutions.
The test liquid used shall be reported. The influence of the test liquid on the expanded uncertainty of
measurement shall be accounted for during calibrations.
7 Evaluation
7.1 Mean volume
Add together the n test volumes delivered V (i) (where i = 1 to n) and divide the sum by n to provide the
T
mean volume V delivered at the test temperature, as shown in Formula (1). This value can be expressed
in microlitres or millilitres:
n
V= Vi() (1)
∑
T
n
i=1
where
is the mean volume;
V
n is the number of replicate deliveries of the test volume;
V (i) is the volume of test liquid delivered by each replicate, i = 1 to n.
T
7.2 Systematic error of measurement
Calculate the systematic error of measurement e of the piston-operated volumetric apparatus using
S
Formula (2):
eV=−V (2)
ss
ISO 8655-7:2022(E)
where
e is the absolute systematic error of measurement, expressed in units of volume;
S
V is the selected test volume at the POVA under test.
S
This systematic error of measurement may be expressed in percent using Formula (3):
()VV−
S
η = ×100 % (3)
S
V
S
where η is the relative systematic error of measurement, expressed in percent.
S
In the case of fixed volume POVA, the selected test volume V is the nominal volume.
S
The systematic error of measurement in the ISO 8655 series is based on historic convention within the
pipetting industry and is reversed in sign compared to the definition described in ISO guide 99:2007,
2.17, for more information see ISO 8655-1:2022, 6.2.
7.3 Random error of measurement
Calculate the random error of the POVA as repeatability or standard deviation s using Formula (4):
r
n
((Vi))−V
∑ T
i=1
s = (4)
r
n−1
where s is the standard deviation, expressed in units of volume.
r
This random error may also be expressed as a percentage by the coefficient of variation, C , using
V
Formula (5).
s
r
C =×100 % (5)
V
V
where C is the coefficient of variation, expressed in percent.
V
8 Test methods
8.1 General
This document describes five test methods and the corresponding test procedures: gravimetry, dual-
dye ratiometric photometry, single dye photometry, hybrid method using photometry and gravimetry,
and titration.
The test liquids and receiving vessels depend on the selected method. Test procedures corresponding
to the selected methods are described in Annex A to Annex E, respectively, and shall be followed for the
preparation of test liquids. Receiving vessels for the test liquid shall conform to those specified in the
respective test procedure.
Chemicals used in the preparation of the test liquids and their corresponding CAS registration numbers
are listed in Table 1.
Table 1 — CAS registration numbers
Chemical CAS No.
copper(II) chloride dihydrate 10125–13–0
ISO 8655-7:2022(E)
Table 1 (continued)
Chemical CAS No.
disodium hydrogen phosphate dihydrate 10028–24–7
hydrochloric acid 7647–01–0
nitric acid 7697–37–2
4-nitrophenol 100–02–7
Orange G 1936–15–8
Ponceau S 6226–79–5
potassium chloride 7447–40–7
potassium hydrogen phthalate 877–24–7
potassium nitrate 7757–79–1
silver nitrate 7761–88–8
sodium chloride 7647–14–5
sodium hydroxide 1310–73–2
sulfuric acid 7664–93–9
Tartrazine 1934–21–0
tetrasodium ethylenediaminetetraacetic 10378–23–1
acid dihydrate (EDTA)
water 7732–18–5
8.2 Gravimetric method
This method uses a balance to measure the mass of the delivered test volume. It can be used to evaluate
the volumetric performance of a POVA for a variety of test liquids, provided that the specific density of
the test liquid is known.
The gravimetric procedure is described in Annex A.
This method may be adapted for the use of multi-channel balances, which allow the simultaneous
delivery of test liquid from multi-channel POVA.
When following the gravimetric reference measurement procedure specified in ISO 8655-6 but
deviating from any of its requirements, A.2 applies.
8.3 Dual-dye ratiometric photometric method
This method uses two chromophore solutions: the test solution containing Ponceau S is delivered
into copper(II) chloride solution, and the degree of dilution of both chromophores is calculated from
photometric measurements at 520 nm and 730 nm.
The ratiometric photometric procedure described in Annex B is suitable for test volumes between 0,1 µl
and 5 000 µl.
An adaptation of this method is suitable for testing multi-channel POVA by delivering the chromophore
solutions from all channels simultaneously into 96-well or 384-well micro plates (see Reference [3]
5.2.1 and Annex B).
When following the photometric reference measurement procedure specified in ISO 8655-8 but
deviating from any of its requirements, B.2 applies.
ISO 8655-7:2022(E)
8.4 Single dye photometric method
In this method, the dilution of a chromophore solution (test solution) is calculated from the measured
absorbance of the delivered test solution. The following chromophores may be used for this method:
Ponceau S, Orange G, Tartrazine, and 4-nitrophenol.
The photometric procedure described in Annex C is based on the use of Ponceau S as chromophore and
is suitable for test volumes between 2 µl and 200 µl.
8.5 Hybrid photometric/gravimetric method for multichannel POVA
This method allows the evaluation of the volumetric performance of multichannel POVA by combining
a gravimetric measurement with subsequent photometric measurement. Test liquid containing either
Tartrazine, Orange G, or 4-nitrophenol as chromophore is delivered by all channels in parallel into 96-
well or 384-well microplates.
The procedure described in Annex D is generally suitable for test volumes between 1 µl and 100 µl in
96-well plates, and between 1 µl and 50 µl in 384-well plates.
8.6 Titration method
This method is suitable for testing volumes larger than 500 µl, using sodium chloride (NaCl) solution as
test liquid, which is titrated with silver nitrate (AgNO ) solution. The equivalence point is determined
by potentiometric detection, e. g. with a silver electrode.
The potentiometric titration procedure is described in Annex E.
8.7 Batch testing
Statistical approaches based on random testing and sample inspection may be used to aid in batch
testing of POVA if all provisions of this subclause are fulfilled. Those utilising this analysis shall
maintain full control over all volume determining components of the POVA, including the tolerances
and assembly process. The production of these components shall have series maturity.
The complete performance and production history of a full batch of POVA of a product line with the
same volumetric characteristics (e.g. same nominal volume, fixed or variable volume device, number of
channels) shall be maintained.
Additionally, the performance homogeneity of the POVA shall be ensured within the specified
performance limits. The performance of volume-determining components shall be determined through
measurements according to one of the reference measurement procedures specified in ISO 8655-6 or
[4]
ISO 8655-8 in a technically competent laboratory .
POVA subject to batch testing according to this document shall be manufactured by an organization
[5] [6]
with a quality management system such as ISO 9001 or ISO 13485 . The sampling plan for this
method shall follow ISO 2859-1 or ISO 3951-1, with an appropriate acceptance quality limit (AQL).
Details of the selected sampling plan and AQL, including reference to the corresponding ISO standard,
shall be reported.
9 Dispense procedures
9.1 General
The test liquid shall be delivered into the receiving vessel following the specific procedures described
in 9.2 to 9.9 unless the POVA manufacturer's instructions specify a different volume delivery procedure,
in which case this procedure (manufacturer's instructions) may be used. If the manufacturer's
ISO 8655-7:2022(E)
instructions are used, this procedure shall be documented in the test report in sufficient detail to allow
the test to be replicated.
9.2 Preparation
Prepare the test equipment, test liquid, and test liquid receiving vessel according to the selected
procedure.
Leave the POVA under test, test equipment, exchangeable parts, and test liquids to reach thermal
equilibrium.
If using a variable volume POVA, select the test volume; this setting shall not be altered during the test
cycle of all replicate measurements.
If testing a burette, dilutor, or dispenser, place the POVA under test, with its reservoir already filled
with test liquid, in such a manner that delivery of the test liquid directly into the receiving vessel is
possible. Prime the POVA under test according to the manufacturer’s instructions in order to remove
any air bubbles inside the tubes and valves. Set the delivery velocity according to the manufacturer’s
instructions. The first drops of liquid might need to be discarded before starting the calibration, if
indicated by the manufacturer.
9.3 Single-channel air displacement pipettes (in accordance with ISO 8655-2)
9.3.1 General
In the case of electronic motorised pipettes, the aspiration and delivery of test liquid are automatic. The
remainder of the procedure is carried out following the steps described in 9.3.2. The user should refer
to the operation manual for speed settings of aspiration and delivery.
NOTE More information regarding this type of piston pipette can be found in ISO 8655-2:2022, Annex B.
9.3.2 Test cycle
Perform the test cycle as follows:
a) Fit the selected tip on the piston pipette;
b) Pre-wet pipette tip five times by aspirating the test solution and expelling to waste to reach a
humidity equilibriu
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