ASTM E1154-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E1154 − 14 E1154 − 23
Standard Specification for
Piston or Plunger Operated Volumetric Apparatus and
Operator Qualification
This standard is issued under the fixed designation E1154; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers requirements, operating conditions, and test methodsprocedures for piston or plunger operated
volumetric apparatus (POVA).(POVA), as well as requirements for pipette operator training and qualification.
1.2 This specification includes specifications applicable foris applicable to all types of POVA or those given by the
manufacturer. POVA. The following precautionary caveat pertains only to the test methodprocedure portion, SectionAnnex A1 and
13Annex A2, of this specification: This standard does not purport to address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to establish appropriate safety and healthsafety, health, and environmental
practices and determine the applicability of regulatory limitations prior to use.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E288 Specification for Laboratory Glass Volumetric Flasks
E456 Terminology Relating to Quality and Statistics
E542 Practice for Gravimetric Calibration of Laboratory Volumetric Instruments
E617 Specification for Laboratory Weights and Precision Mass Standards
E898 Practice for Calibration of Non-Automatic Weighing Instruments
E969 Specification for Glass Volumetric (Transfer) Pipets
2.2 ISO Documents:Standard:
ISO 3534 Statistics—Vocabulary and Symbols
ISO 653 Long Solid-Stem Thermometers for Precision Use
ISO 655 Long Enclosed-Scale Thermometers for Precision Use
ISO 4787ISO 3696 Laboratory Glassware—Volumetric Glassware—Methods for Testing and UseWater For Analytical
Laboratory Use – Specification And Test Methods
This specification is under the jurisdiction of ASTM Committee E41 on Laboratory Apparatus and is the direct responsibility of Subcommittee E41.06 on Laboratory
Instruments and Equipment.
Current edition approved Dec. 1, 2014Jan. 1, 2023. Published January 2015February 2023. Originally approved in 1987. Last previous edition approved in 20082014 as
E1154 – 89 (2008).E1154 – 14. DOI: 10.1520/E1154-14.10.1520/E1154-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.International Organization for
Standardization (ISO), ISO Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland, https://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1154 − 23
2.3 Other DocumentsDocuments:
OIML R 111-1 Weights of classes E , E , F , F , M , M , M , M and and M : Part 1: Metrological and technical
1 2 1 2 1 1–2 2 2–3 3
requirementsTechnical Requirements
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 accuracy —the accuracy of an instrument a volumetric apparatus is the closeness of agreement between the nominalselected
volume and the mean volume, obtained by applying one of the test procedureprocedures specified in Section 13 of this
specification.Specification. It is quantified by the inaccuracy of the mean.
3.1.2 dead volume—the dead volume is that part of the total liquid volume, held in the operational part of the device, which is
not delivered.
3.1.2.1 Discussion—
The dead volume should not be confused with the dead air space of an air displacement instrument.apparatus. The dead air space
is the air gap between the piston and sample liquid in air-displacement devices and is sometimes referred to as air cushion.
3.1.3 disposable—those parts of an instrument a volumetric apparatus that are intended to be used once only and then discarded.
Disposable parts are generally intended for use in applications where sample carryover is intolerable.
3.1.4 maximum error—the maximum difference between the nominalselected volume and any single individual volume obtained
by applying one of the test procedureprocedures specified in Section 13 of this Specification.
3.1.5 maximum expectable error—with more than 95 % probability, the maximum expectable error (MEE) is calculated as
follows:according to Eq 1:
6~1E 112s! (1)
T
MEE 56 E 12s (1)
~ !
? t? r
where:
E = inaccuracy of the mean, and
T
s = standard deviation from the repeatability test in Section 13.
MEE = maximum expectable error,
E = inaccuracy of the mean, and
t
s = standard deviation of repeatability, see A1.4.8 and A2.5.7.
r
3.1.6 nominal volume(s)—the stated volume(s) for which performance is specified.
3.1.6 piston or plungerpiston- or plunger- operated volumetric apparatus (POVA)—the volume of liquid to be measured with
POVA is defined by one or more strokes of one or more pistons or plungers. POVA may be operated manually or mechanically
(for example, electrically, pneumatically or by hydrostatic pressure).
3.1.6.1 Discussion—
In the following text the word ‘piston’ means ‘piston or plunger.’
3.1.7 precision —the closeness of agreement between the individual volumes obtained by applying one of the test procedure-
procedures specified in this specification. It is quantified by the imprecision. coefficient of variation (CV).
3.1.7.1 Discussion—
The test procedure specified gives only specified test procedures give a measure of the repeatability (see ISO 3534) under
controlled conditions. conditions (see E456).
3.1.8 reference temperature—the temperature at which the instrumentapparatus is designed to deliver its nominalselected
volume(s).
Available from International Organization of Legal Metrology, 11 rue Turgot, 75009 Paris, France. www.oilm.org/en/
These definitions apply only in the cases where the distributions are Gaussian.
E1154 − 23
3.1.8.1 Discussion—
At that temperature the closest agreement between manufacturer’s performance claims and test results may be expected.
3.1.9 reference temperature range—thatthe temperature range for which the tolerances for accuracy and precision are specified.
3.1.10 reusable—those parts of an instrumentapparatus that are meant to be used more than once. As the reusability of some parts
can rarely be quantified, any institution or individual who reuses a reusable part must see to its safety and effectiveness. Reusable
parts are generally intended for use in applications where sample carryover is tolerable, or can be adequately prevented.
3.1.11 sample carryover—thatthe portion of the sample that is retained in the instrumentapparatus and that may affect subsequent
samples.
3.1.12 selected volume(s)—the volume setting(s) at which performance is tested.
3.1.13 stated feature—any feature claimed by the manufacturer.
3.1.14 unit of volume—the millilitremilliliter or the microlitre, thatmicroliter, which are accepted substitutes for the cubic
centimetrecentimeter or cubic millimetre.millimeter.
3.1.14.1 Discussion—
It is recommended that volumes Volumes should be specified in microlitresmicroliters up to 999 μL, and in millilitresmilliliters
from 1 mL.
3.1.15 working range—thatthe part (of the total range) for which manufacturer’s performance specifications are given.
3.1.16 working temperature range—thatthe range of temperatures for which manufacturer’s performance specifications are given.
4. Classification
4.1 Types of POVA—Piston or plunger operated volumetric apparatus (POVA) are classified as follows:
4.1.1 Pipette—A measuring instrumentapparatus for the transfer of a predetermined volume of liquid from one vessel to another.
It is not connected to a reservoir.
4.1.2 Dispenser—A measuring instrumentapparatus for delivering predetermined volumes of liquid from a reservoir. The reservoir
may be integrated with the instrumentapparatus or connected externally.
4.1.3 Dilutor—A measuring instrumentapparatus for taking up different liquids (for example, sample and diluent) and delivering
them in combination so as to comprise a predetermined ratio, or predetermined volumes, or both. The reservoir of diluent may be
integrated with the instrumentapparatus or connected externally.
4.1.4 Displacement Buret—Burette—A measuring instrumentapparatus from which the volume delivered is determined by an
external indicator. The volume delivered can then be read.
4.2 Types of Displacement:
4.2.1 Displacement with an air interface (“air displacement”). The delivered liquid is displaced by an air interface (indirect action),
(seesee Figs. 1 and 2Fig. 1).
4.2.2 Displacement without an air interface (“positive displacement”). The delivered liquid is displaced either by a liquid interface
(indirect action) or by actual contact with the piston (direct action), (seeor Fig. 3 andby a Fig. 4). liquid interface (indirect action)
see Fig. 2.
5. Performance Requirements
5.1 Performance Tolerances:
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FIG. 1 Displacement With an Air Interface (Air Displacement)
FIG. 2 Displacement Without an Air Interface (Positive Displacement)
FIG. 3 PipetterForward Mode of Operation (Forward Mode)Pipette Operation
FIG. 4 PipetterReverse Mode of Operation (Reverse Mode)Pipette Operation
5.1.1 Performance tolerances specified for POVA are meant to include any thermal drift effect upon the accuracy and precision
attributable to hand-transmitted heat heat, either hand-transmitted or from electric components, during normal use. It is, therefore,
important that the instrumentapparatus being evaluated according to the referenced procedure not be preconditioned (warmed) by
recent handling, handling or use, nor isolated from normal handwarmingwarming during the test series (30 or 10 cycles).
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5.1.2 Volumetric performance tolerances are not specified in this specification.standard. The manufacturer or user shall specify the
performance tolerances in terms of the accuracyinaccuracy of the mean (E¯E in volume units, or η , in %) and coefficient of
Cc c
variation (CV %)., in %). Values shall be given for the minimum and maximum volumes of the working range, as well as for
c
any intermediate volumes in the series 1, 2, 5, 10 .
5.2 The reference temperature recommended for all POVA is 21.5°C, which is the mid-point of the reference temperature range,
(see section 20.0 °C. 3.1.10). The use of another reference temperature must be stated by the manufacturer.
5.2.1 Reference Temperature Range—The reference temperature range for all POVA shall be 19 to 24°C,20 °C to 25 °C, (see
section 3.1.93.1.8 and section 3.1.103.1.9).
5.3 Removable Parts:
5.3.1 The volumetric performance of POVA to be used with removable parts can depend to a large extent on the design, material,
and workmanship of those parts. The test procedures described can give information only about the performance of the
instrumentsapparatus together with the removable parts actually used. Removable parts used during testing shall be identified in
the test report to the extent possible and necessary (e.g., by manufacturer, model/type, size, batch number, etc.).
5.3.2 Single-MeasurementSingle-Delivery Test—The single-measurementsingle-delivery
ment test requires either 30 or 10 randomly selected removable parts, one for each sample of the series. This test evaluates the
instrument’sapparatus’ performance and component of imprecision due to the variation of these parts.
5.3.3 Replicate-Delivery Test—The replicate delivery test uses one removable part for the 30 or 10 sample series. This test
evaluates the instrument’sapparatus’ performance and the component of imprecision due to the reuse of this part.
5.4 Durability—Any claim by a manufacturer that an instrumentapparatus is resistant to any defined conditions (for example,
sterilization and chemical exposure) shall be understood in such a way that even long term or repeated exposure to those conditions
(as specified by the manufacturer) will not affect the rated performance of the instrument.apparatus.
6. General Operating Conditions
6.1 Relationship to Performance—The specification of operating procedures is critical to the proper functioning of the
instruments, volumetric apparatus, and determines their ability to perform within specified tolerances. Changes in the operating
mode can dramatically alter the results of analyses. Most instrumentsdelivered volume. Most apparatus are calibrated for certain
operating modes; another manner of use may result in a change in the accuracy or precision, or both.
6.2 Delineation—It is the manufacturer’s responsibility to delineate the modes of operation in instruction manuals and to state for
which of the modes the instrumentapparatus is calibrated.
6.3 Preparation—The manufacturer shall provide instructions necessary for the preparation of the instrumentapparatus for use in
particular operating modes (for example, mounting of removable parts, method of volume adjustment, temperature equation,
isothermal requirements, testing of piston action, lubrication, priming, purging or prerinsing information, etc.).
7. Operating Conditions for PipettersPipettes
7.1 Two common modes of operation are in use, the forward mode (sometimes referred to as normal mode), and the reverse mode
(usable with two-component stroke mechanism systems only), (seesee Fig. 3 and Fig. 4).
7.1.1 In general, the precision of the repetitive use of the forward mode relies upon the precise draining by air pressure (in the
case of air displacement pipetters)pipettes) or internal wiping of the pipetpipette barrel or tip (in the case of positive displacement
pipetters).pipettes). As compared to the reverse mode, the forward mode is relatively insensitive to variations in the speed of the
piston or plunger in the dispensing action. Positive displacement instrumentspipettes with relatively small delivery orifices are
generally less sensitive to change in accuracy when handling liquids with high wetability characteristics.which wet plastic tips.
7.1.2 Air displacement pipetterspipettes with two-component stroke mechanisms are generally less sensitive than air displacement
pipetterspipettes with one-stroke mechanisms and positive displacement pipetterspipettes to errors introduced by slight variations
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of the dynamics of the liquid interface break at the end of the pipet or pipetpipette or pipette tip during the dispensing action, due
to the purging action of the air “blow-out” stroke potential.
7.1.3 The use of the reverse mode with two-component stroke mechanism pipetterspipettes may be more advantageous when
liquids that are difficult to handle in the forward mode are encountered.
7.2 Forward Mode, General Format:
7.2.1 Preparation—PipetterPipette and environment shall be isothermal. Volume settings and the mounting of removable or
disposable pipetpipette tips shall be accomplished according to the manufacturer’s directions.
7.2.2 Aspiration:
7.2.2.1 Hold the instrumentpipette in a vertical position, or as prescribed by the manufacturer.
7.2.2.2 In the case of two-component stroke systems, depress the push button smoothly to the intermediate stop position.
7.2.2.3 In the case of one-component stroke systems, depress the push-button smoothly to the bottom stop position.
7.2.2.4 Immerse the pipet or pipetpipette or pipette tip into the liquid to be pipetted to, and maintain it at the following depth:depth
(see Table 1):
TABLE 1 Immersion Depth of Pipette Tip
Volume, μL Immersion Depth, mm
< 1 1 to 2
1 to 100 2 to 3
101 to 1000 2 to 4
1.1 to 10 mL 3 to 6
7.2.2.5 Allow the push-button to move up to the top stop position slowly and smoothly.
7.2.2.6 For air displacement pipetters,pipettes, observe a wait of 1 s.1 second.
7.2.2.7 Withdraw the pipet or pipetpipette or pipette tip smoothly by lifting straight up either from the center of the liquid surface
in the vessel, or up the sidewall of the vessel.
NOTE 1—No further liquid contact of the pipet or pipetpipette or pipette tip is allowed once the liquid interface is broken.
7.2.2.8 Wipe the pipet or pipetpipette or pipette tip only if there are extraneous droplets. Contact with the orifice of the pipet or
pipetpipette or pipette tip, especially with absorbent material, must be avoided, as large components of random or systematic error
may be introduced.
7.2.3 Delivery—Place the pipet or pipetpipette or pipette tip at an angle (10(10° to 45°, or as prescribed by the manufacturer)
against the inside wall of the receiving vessel.
7.2.3.1 For two-component stroke systems, depress the push-button smoothly to the intermediate stop position. After a wait of 1
s,second, depress the push-button to the bottom stop position as the pipet or pipetpipette or pipette tip end is removed from the
sidewall by either a sliding action up the wall or a movement away from the wall (“touching off”).
7.2.3.2 For one-component stroke systems, depress the push-button smoothly to the bottom stop position as the pipet or
pipetpipette or pipette tip end is removed from the sidewall by either a sliding action up the wall, or a movement away from the
wall.
7.2.3.3 Allow the push-button to move up to the top stop position.
7.3 Reverse Mode, General Format:
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7.3.1 Preparation—Prepare in accordance with 7.2.1, forward mode.
7.3.2 Aspiration—Aspirate in accordance with 7.2.2, except that the push-button is depressed to the bottom stop position prior to
pipetpipette tip immersion.
7.3.3 Delivery:
7.3.3.1 Place the pipet or pipetpipette or pipette tip at an angle (10(10° to 45°, or as prescribed by the manufacturer) against the
inside wall of the receiving vessel.
7.3.3.2 Depress the push-button smoothly to the intermediate stop position.
7.3.3.3 After a 1-s 1 second wait, remove the pipet or pipetpipette or pipette tip from the sidewall, in accordance with 7.2.3.
7.3.3.4 In the case of the pipetpipette tip being reused, allow the push-button to remain in the intermediate stop position for
subsequent immersion for the next pipetting cycle. In the case of the pipetpipette tip to be changed, allow the push-button to return
to the top stop position.
NOTE 2—Top and bottom stop positions, as described in the procedures above, are not meant to include auxiliary stroke positions (for example, for tip
ejection).
7.4 Prerinsing (Forward Mode):
7.4.1 Prerinsing is the action of precoating the inside of the liquid contracting part(s) with a thin film of the same liquid to be
pipetted. pipetted, and for increasing the humidity in the air cushion (air displacement pipettes only). It is accomplished by
duplicating the exact motion of a forward mode pipetting cycle, except that the liquid is dispensed back into the original vessel,
or preferably discarded.
7.4.2 Prerinsing in the forward mode is advantageous when reusing (the same liquid and volume setting only) the pipet or
pipetpipette or pipette tip for subsequent immediate pipettings. Eliminating the dispensed amount from the first wetting from the
sample group formed by subsequent wettings and thus the removal of its value from the calculation of a precision statistic for the
group, will result in a more precise distribution.
7.4.3 Prerinsing may also be practiced when a removable pipetpipette tip is to be used only once (for example, when pipetting
different liquids), but the increase in time required to accommodate prerinsing each tip reserves this practice for pipetting different
liquids which may be especially difficult to handle (for example, different patient sera). The need for prerinsing is also related to
the surface properties of the pipetpipette tip as well as due to the physical characteristics of the liquid(s).
7.5 Positioning the Residual Volume (Reverse Mode)—Positioning the residual volume for the reverse mode is the functional
equivalent of prerinsing for the forward mode. It is accomplished by duplicating the exact motion of a reverse mode pipetting
cycle, except that the liquid is dispensed back into the original vessel, or preferably discarded, and the push-button kept at the
intermediate stop position instead of being allowed to return to the top stop position, when reusing the pipetpipette tip.
7.6 Disposable PipetPipette Tips—Discarded pipetpipette tips contain liquid residues, particularly when used in the reverse mode.
Suitable precautions should be taken with their disposal.
8. Operating Conditions for Dispensers
8.1 Dispensers with Valves(s)—The aspiration tube must be immersed in the reservoir for operation. When the system is filled (free
of air bubbles, according to manufacturer’s instructions), the movement of the piston in one direction aspirates liquid. While
moving in the opposite direction, the adjusted volume of liquid is dispensed, (seesee Fig. 5).
8.2 Dispensers Without Valve—When the system is filled (free of air bubbles, according to manufacturer’s instructions), the
movement of the piston in one direction aspirates liquid. While moving in the opposite directions, the adjusted volume of liquid
is dispensed, (seesee Fig. 6).
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FIG. 5 Dispenser With Valve
FIG. 6 Dispenser Without Valve
9. Operating Conditions for Dilutors
9.1 During operation the entire system, except the end of the probe tube, is filled with diluent. Any movement of the piston (V)
in the direction (A) aspirates diluent. The diluent is aspirated as follows:
9.1.1 In the case of dilutors with valve(s), through the aspiration tube, (seesee Fig. 7),, and
9.1.2 In the case of dilutors without valve, through the probe tube, (seesee Fig. 8).
9.2 Any movement of the piston (P) in the direction (A) aspirates sample liquid through the probe tube.
9.3 A movement of the pistons (V ) and (P) in the direction (B) expels diluent and sample liquids in the adjusted ratio. Fig. 7 and
Fig. 8 show dilutors with two separate pistons. Dilutors may also operate with one piston or with telescopic pistons. For the
functioning of a dilutor it is irrelevant whether the pistons operate in the same direction, and simultaneously, or in opposite
directions at different times.
10. Operating Conditions for Displacement BuretsBurettes
10.1 BuretsBurettes with Valves(s)—The aspiration tube must be immersed in the reservoir for operation. When the system is filled
(free of air bubbles, according to manufacturer’s instructions), the movement of the piston in one direction aspirates liquid. The
movement of the piston in the opposite direction expels liquid, after which a reading can be taken, (seesee Fig. 9).
FIG. 7 Dilutor With Valve
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FIG. 8 Dilutor Without Valve
FIG. 9 Burette With Valve
10.2 BuretsBurettes Without Valve—When the system is filled (free of air bubbles, according to manufacturer’s instructions), the
movement of the piston in one direction aspiratesliquid. aspirates liquid. The movement of the piston in the opposite direction
expels liquid, after which a reading can be taken, (seesee Fig. 10).
11. Number of Tests and Retests
11.1 Functional Test—A functional test (for example, tests for leakage, broken parts, existence of air bubbles, contamination) shall
be performed daily.
11.2 Volumetric Tests:
11.2.1 An appropriate single or replicate measurement test should also be performed following a change in the source of any
removable parts of the delivery system (for example, as indicated by control or lot numbers of pipetpipette tips, or change in
dispensing cannulae).
11.2.2 A quick check four sample test measuring accuracy and roughly estimating precision should be performed at least monthly,
or more frequently as indicated by the physical condition or extent of use of the apparatus.
11.2.3 A ten sample test measuring both accuracy and precision should be performed on all delivery systems upon introduction
to service, following routine and other maintenance, and as otherwise necessary to provide a comprehensive evaluation on at least
a quarterly basis.
FIG. 10 Burette Without Valve
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12. Sample Size
12.1 For purposes of specifying or testing the volumetric performances of a single instrument establishing volumetric performance
specifications of a POVA by the manufacturer, supplier, or testing agent, the procedures specified in Section 1313 shall be repeated
at least 30 times.
12.2 For control purposes calibration and verification of accuracy and precision, ten replicate measurements may be sufficient.
12.3 For quick checks of accuracy, four replicate measurements are sufficient.
13. Test Procedures
13.1 Scope—These test procedures cover the testing of POVA under prescribed conditions.
13.2 Significance and Use—These test procedures are intended to provide uniform reference procedures that can be used by
anyone to assess the errors of POVA. These test procedures are recommended for use in establishing performance claims, in quality
control procedures, as well as in quick checks throughout the working life of a POVA.
13.3 Summary of the Gravimetric Procedure—The gravimetric test procedure is based upon the determination of the weighing
result of water samples delivered by the POVA. The values are corrected for evaporation, then true mass and volume are calculated
simultaneously, based upon the knowledge of the density of water at specific temperatures and corrections for air buoyancy (see
E542). The gravimetric test procedure is described in Annex A1.
13.4 Summary of the Photometric Procedure—The dual-dye ratiometric photometric test procedure is based on the Beer-Lambert
Law, which correlates the concentration of a chromophore in solution with its absorbance. The unknown volume of a test solution
(of known Ponceau S concentration) is added to a known amount of copper(II) chloride solution of known concentration.
Ratiometric application of the Beer-Lambert Law allows the calculation of the delivered volume of test solution. The photometric
test procedure is described in Annex A2.
14. Gravimetric Test Method Dispense Procedures:
14.1 Scope—General—These test methods cover the testing of POVA under prescribed conditions.Ensure that all equipment and
materials, including a sufficient number of removable parts, are properly selected and conditioned, the desired volume is set (if
applicable) and the electronic balance (if used) or spectrophotometer (if used) has had the warm-up time specified by the
manufacturer.
13.2 Summary of Method—The general procedure is based upon the determination of the weighing result of water samples
delivered by the instrument. The values are corrected for evaporation, then true mass and volume are calculated simultaneously,
based upon the knowledge of the density of water at specific temperatures and corrections for air buoyancy (see ISO 4787).
13.3 Significance and Use—These test methods are intended to provide uniform reference procedures that can be used by anyone
to assess the errors of instruments. These test methods are recommended for use in the establishing performance claims, in quality
control procedures during manufacture, as well as in control checks throughout the working life of an instrument.
13.4 Apparatus:
13.4.1 The resolution requirement of the weighing equipment shall be to one tenth of one percent of the water sample weight. The
imprecision requirement of the weighing equipment is determined as the standard deviation of at least ten repeated weighings of
a metal weight of a mass similar to the mass of the water sample. The minimum requirements for the balance are as shown in Table
1. Balances shall be calibrated and maintained at least annually, and re-calibrated after being moved. Balance calibration shall be
checked at least daily. (See Test Method E898 for balance calibration and OIML R 111-1 or Specification E617 for weight
requirements.)
13.4.2 Weighing Vessel, shall be such that the instrument can be operated according to the manufacturer’s instructions. The total
volume of the weighing vessel shall be as small as practicable and preferably smaller than 50 times the volume to be tested. In
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the case of test volumes smaller than 100 μL, the weighing vessel shall be covered with a cap to avoid excessive errors due to the
evaporation of water during weighing, unless conditions such as high ambient relative humidity make this unnecessary. The cap
must not come into contact with the liquid.
13.4.2.1 The vessel and cover shall be made of nonporous material.
13.4.2.2 The opening shall be as small as possible. The top edge angle shall be such as not to affect the normal operation of the
instrument under test.
+
13.4.3 Thermometer, used for measuring the ambient and water temperature shall show a maximum permissible error of 0.1°C,
for example, thermometer STL/0.1/−5/ + 25 in accordance with ISO 653, or thermometer EL/0.1/−5/ + 25 in accordance with
ISO 655.
13.5 Materials and Environment:
13.5.1 Water shall be distilled and reasonably free of dissolved air.
13.5.2 Ambient Test Conditions—The instruments shall be tested under referenced ambient conditions. The ambient conditions for
the tests shall be as follows:
13.5.2.1 The temperatures of the test environment, including the analytical equipment, material, test water, instrument to be
+
evaluated (including removable parts) should be identical, and as stable as possible ( 0.5°C) at least 2 h prior to and throughout
the evaluation period.
13.5.2.2 The relative humidity should be maintained at 45 to 75 %, in order to reduce the evaporation rate and control the buildup
of electrostatic potentials. In the immediate weighing area the relative humidity may be increased, but care should then be taken
against condensation of water.
13.5.2.3 The balance area shall be reasonably free of vibration and air currents.
13.5.2.4 The ambient air shall be reasonably clean.
13.5.2.5 The lighting shall be of necessary intensity, and glare-free. Diffused light is preferred (direct sunlight must be avoided).
13.5.2.6 The working surface directly in front of the balance should be a dark color and glare-free.
+
13.5.2.7 The average barometric pressure in the test laboratory shall be known to 25 m bar.
14.2 Procedures: Pipettes—
13.6.1 General—Ensure that all equipment and materials including a sufficient number of removable parts are properly selected
and conditioned, the desired volume is set (if applicable) and the electronic balance (if used) has had the warm-up time specified
by the manufacturer. Select the following test conditions: pipetting operating mode, option regarding prerinsing or not, whether
to reuse or dispose of pipette tips, and a cycle time for the procedure.
NOTE 3—The cycle time shall be consistent throughout a series of measurements.
14.2.1 Pipetters—Select the following test conditions: pipetting operating mode, option regarding prerinsing or not, whether to
reuse or dispose of pipet tips, and a cycle time for procedure. Mount removable pipette tip.
NOTE 3—The cycle time shall be consistent throughout a series of measurements.
13.6.2.1 Mount removable pipet tip.
13.6.2.2 Measure the temperature of the water to ≤0.1°C and record it.
13.6.2.3 Place a small amount of water in the weighing vessel (between 2 and 30 sample amounts, or a minimum of 0.5 mL).
E1154 − 23
13.6.2.4 Place the cap on the weighing vessel, if necessary, and the weighing vessel on the balance pan.
13.6.2.5 While the balance is equilibrating the pipet tip may be prerinsed, and the sample aspirated, according to the operating
mode selected.
13.6.2.6 Tare the weighing vessel and record the value, if necessary.
13.6.2.7 Note the time.
13.6.2.8 Deliver the sample according to the operating mode selected and replace the cap, if used.
13.6.2.9 Weigh the weighing vessel and record the time and weighing result.
13.6.2.10 If a series of measurements shall be carried out: repeat 13.6.2.5 through 13.6.2.9 until the desired number of
measurements is achieved.
13.6.2.11 Perform a control blank for estimation of evaporation by repeating 13.6.2.6 through 13.6.2.9 exactly as in a normal
sample weighing but without actually delivering any liquid to the weighing vessel.
NOTE 4—It is suggested that this evaporation control check be performed at the beginning and end of each series of measurements, and between each
group of 10 samples in larger series.
13.6.2.12 Measure the temperature of the water and record a second time.
13.6.2.13 The procedure in 13.6.2.5 through 13.6.2.9 should be performed as quickly as practicable but without compromise to
the integrity of the liquid delivery, precision of the technique of the operator, or time intervals.
14.2.2 Measure the temperature of the test liquid to ≤0.1 °C and record it.
14.2.3 Follow the respective test procedure in Annex A1 or Annex A2 for preparing the balance and weighing vessel, or
spectrophotometer and cuvettes, and for the measurement of delivered test liquid volumes.
14.2.4 Prerinse the pipette tip, if desired.
14.2.5 Dispensers: Aspirate the test liquid and deliver the sample according to the operating mode selected against the side wall
of the weighing vessel or cuvette.
13.6.3.1 Measure the temperature of the water to ≤0.1°C and record.
13.6.3.2 Connect or fill the reservoir and prime the dispenser according to the manufacturer’s instructions before equilibrating it
for normal use.
13.6.3.3 Place a small amount of water in the weighing vessel (between 2 and 30 sample amounts, or a minimum of 0.5 mL).
13.6.3.4 Place the cap on the weighing vessel, if necessary, and the weighing vessel on the balance pan. Equilibrate the dispenser
to normal operation by actuating at least one complete cycle and discarding the first dispensing.
13.6.3.5 Tare the weighing vessel and record the value, if necessary.
13.6.3.6 Note the time.
13.6.3.7 Actuate a complete dispensing cycle to deliver the sample into the weighing vessel and replace the cap, if used.
13.6.3.8 Weigh the weighing vessel and record the time and weighing result.
13.6.3.9 If a series of measurements shall be carried out, the procedure in 13.6.3.5 – 13.6.3.8 are to be repeated until the desired
number of measurements is achieved.
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13.6.3.10 Perform a control blank for estimation of evaporation by repeating 13.6.3.5 – 13.6.3.8 exactly as in a normal sample
weighing but without actually delivering any liquid to the weighing vessel.
NOTE 5—It is suggested that this evaporation control check be performed at the beginning and end of each series of measurements, and between each
group of 10 samples in larger series.
13.6.3.11 Measure the temperature of the water and record a second time.
13.6.3.12 The procedure in 13.6.3.5 – 13.6.3.10 should be performed as quickly as possible, but without compromise to the
integrity of the liquid delivery, precision of technique of the operator, or time intervals.
13.6.4 Dilutors:
13.6.4.1 In the case of dilutors, parameters to be tested can be as follows: the sample volume, the diluent volume, and the total
volume or the dilution ratio, or both.
13.6.4.2 Dilutors can be tested gravimetrically only if there is no interdependence between the sample and diluent volume(s). In
this case follow the procedures described for dispensers or pipetters, as appropriate.
13.6.5 Displacement Burets—When the buret is filled (free of air bubbles, according to manufacturer’s instruction(s)), deliver an
amount of liquid which is approximately as large as the volume to be tested into a weighing vessel. Compare the volume(s) actually
delivered with the indication(s) of the buret and use the resulting deviation(s) for the calculation(s).
14.3 Calculations:Dispensers:
14.3.1 General—The mean volume at the test temperature (Measure the temperature of the test liquid V¯ ) shall be calculated from
t
the mean weighing result (W¯) by addition of the mean evaporation (e¯), and conversion of the sum by an appropriate factor
incorporating density and buoyancy corrections for water when weighed in air, at the test temperature and pressure, at standard
humidity (see Table 2). This calculation need only be performed once in order to calculate the performance statistics.to ≤0.1 °C
and record.
13.7.2 Individual Weighings—The individual weighing result (W ) in air shall be calculated by subtracting the tare reading from
i
the sample reading.
13.7.3 Evaporation—The evaporation (e ) shall be estimated by subtracting the appropriate balance reading after the control
i
blanks from the reading before each blank (these values should be positive). The mean evaporation (e) shall be calculated as
follows from the number of determinations (n ):
e
e 5 εe /n (2)
i e
13.7.4 Test Temperature—The test temperature (t) shall be the average of the two measurements of water temperature, rounded
to the nearest 0.5°C.
13.7.5 Mean Weighing Result—The mean weighing result (W¯) shall be calculated from the n individual weighings (W ):
i
¯
W 5 εW /n (3)
i
13.7.6 Mean Volume—The mean volume of the liquid samples (V ) shall be calculated as follows from the mean weighing result
t
(W) as follows:
¯
V 5 W1e ·Z (4)
~ !
t
where:
e¯ = mean evaporation loss (mg), and
Z = conversion factor (μL/mg) incorporating the density of water when buoyed in air, at the test temperature and pressure.
Values of Z for water at various test temperatures are listed in Table 2.
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14.3.2 Inaccuracy of the Mean—The accuracy of the mean (Connect or fill the reservoir andE %) of the apparatus at the test
t
temperature ( prime the dispenser according to t) shall be calculated from the nominal volume of the apparatus (the manufacturer’s
instructions before equilibrating it forV ) and the calculated mean volume ( normal use.V ) as
o t
E %5 V 2 V /V ×100 (5)
t t o o
14.3.3 Imprecision—The imprecision, expressed as a percentage (coefficient of variation) shall be calculated from the distribution
of individual weighing results (W ) about their mean (W), which is then corrected for error due to evaporation, as
i
CV %5 s·100/W1e (6)
where:
e = mean evaporation
¯
s =
ε W 2W
~ !
i
n21
n = 30 or 10, and
CV = coefficient of variation.
This statistic measures the total sources of imprecision, includingFollow the respective test procedure in Annex A1 thator Annex
A2of the operator, mode of operation and test method, and is thus best used for comparison purposes. for preparing the balance
and weighing vessel, or spectrophotometer and cuvettes, and for the measurement of delivered test liquid volumes.
NOTE 6—Volume may be calculated for each weighing result if data processing equipment is available.
14.3.4 Actuate a complete dispensing cycle to deliver the sample into the weighing vessel or cuvette and replace the cap, if used.
14.4 Precision and Bias: Dilutors:
13.8.1 Analytical Error—The tolerances permitted in this test method for parameters involved in the calculation of V (see below)
t
are as follows:
Maximum
Maximum Volume
Parameter Deviation Deviation
water temperature ±0.25°C 0.005 %
air pressure ±27 m bar 0.003 %
air temperature ±2.5°C 0.001 %
relative humidity ±25, − 5 % r.h. 0.0003 %
Total = 0.01 %
14.4.1 Hypothesis Test (Bias): In the case of dilutors, parameters to be tested can be as follows: the sample volume, the diluent
volume, and the total volume or the dilution ratio, or both.
13.8.2.1 If the critical value of the test result exceeds the values listed below, the instrument evaluated is considered significantly
acceptable or rejectable at the listed confidence levels.
13.8.2.2 If the critical value is smaller than the indicated value at the confidence level required, the instrument should be
reevaluated after giving careful consideration to the test conditions, method requirements, selection of operating mode, removable
parts and competence of the operator, before a final decision is made.
Confidence Level for
(+) Acceptance/ Critical Value
(−) Rejection (Fraction of Tests, CV % value)
n = 30 n = 10
50 % 0 0
90 % ±0.24 ±0.43
95 % ±0.31 ±0.57
99 % ±0.45 ±0.87
99.9 % ±0.62 ±1.31
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Critical values for other confidence levels can be calculated as follows:
6~t/=n! CV % (7)
where:
t = critical value of Student’s for one-tailed test at the significance value desired (commonly available from statistical tables)
and
n = 30 or 10.
d % E %2E %
c T
Critical Value 5 5 (8)
CV % CV %
T T
where:
E % = inaccuracy of the mean, %,
T
E % = claimed inaccuracy of the mean, %, and
c
CV % = imprecision, %, (see Figs. 11 and 12).
t
14.4.2 Hypothesis Test (Precision)—If the ratio of the test result value to the specified tolerance for the precision (CV %) exceeds
c
the limits listed below, the combined precisions of the instrument, operator and test method are considered significantly rejectable
at the confidence levels listed below. The figures are based upon the assumption that the specification requires 30 samples. Figs.
11 and 12.
Confidence
Level for
Acceptance/ Critical Value of Ratio
Rejection Acceptance/Rejection Acceptance/Rejection
n = 30 n = 10
50 % 1.00 1.00 1.00 1.00
90 % 0.73 1.37 0.67 1.49
95 % 0.69 1.46 0.62 1.61
98 % 0.64 1.57 0.57 1.76
99 % 0.61 1.65 0.53 1.87
Critical values for other confidence levels can be calculated Dilutors can be tested gravimetrically only if there is no
interdependence between the sample and diluent volume(s). In this case follow the procedures described for dispensers or pipettes,
as 22.=1/Fappropriate. The photometric procedure in Annex A2for acceptance or is not suitable for testing dilutors.22
.= F for rejection.
where:
F = critical value for F for one-tailed test (see accuracy test regarding reevaluation considerations).
14.5 Displacement Burettes—When the burette is filled (free of air bubbles, according to manufacturer’s instruction(s)), deliver
an amount of test liquid, which is approximately as large as the volume to be tested, into the weighing vessel or cuvette. Compare
the volume(s) actually delivered with the indication(s) of the burette and use the resulting deviation(s) for the calculation(s).
15. Precision and Bias:
15.1 Hypothesis Test (Bias):
15.1.1 If the critical value of the test result exceeds the values listed below, the POVA evaluated is considered significantly
acceptable or rejectable at the listed confidence levels.
15.1.2 To determine pass/fail status, a simple decision rule may be applied. Under the simple decision rule, if the test results are
within tolerance limits, the instrument is considered to have passed. When test results are near the tolerance limits, a simple
decision rule will run the risk of making incorrect pass/fail decisions. For greater confidence in the pass/fail status, the following
procedure may be used to evaluate accuracy tolerances.
(a) Calculate a test statistic for bias according to Eq 2:
E ?2 E
? t ? c?
TSB 5 (2)
s
t
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where:
TSB = Test Statistic for Bias,
E = measured test inaccuracy E (absolute value),
t
E = tolerance for inaccuracy (absolute value and assuming symmetric tolerances), and
c
s = measured test standard deviation.
t
(b) Determine the critical value for this bias test using Eq 3:
t
inv
CrVB 5 (3)
=n
where:
CrVB = Critical Value for the Bias test,
t = left-tailed inverse of the Studen
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