ASTM D6689-01

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Designation:D6689–01
Standard Guide for
Optimizing, Controlling and Reporting Test Method
Uncertainties from Multiple Workstations in the Same
Laboratory Organization
This standard is issued under the fixed designation D 6689; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 Other Documents:
ISO 17025 (previously ISO Guide 25) General Require-
1.1 This guide describes a protocol for optimizing, control-
ments for the Competence of Calibration and Testing
ling, and reporting test method uncertainties from multiple
Laboratories
workstations in the same laboratory organization. It does not
apply when different test methods, dissimilar instruments, or
3. Terminology
different parts of the same laboratory organization function
3.1 Definitions—For definitions of terms used in this Guide,
independently to validate or verify the accuracy of a specific
refer to Terminology E 135 and D 1129.
analytical measurement.
3.2 Defintions of Terms Specific to This Standard:
1.2 This standard does not purport to address all of the
3.2.1 laboratory organization—a business entity that pro-
safety concerns, if any, associated with its use. It is the
vides similar types of measurements from more than one
responsibility of the user of this standard to establish appro-
workstation located in one or more laboratories, all of which
priate safety and health practices and determine the applica-
operate under the same quality system.
bility of regulatory requirements prior to use.
NOTE 1—KeyaspectsofaqualitysystemarecoveredinISO 17025and
2. Referenced Documents
include documenting procedures, application of statistical control to
measurement processes and participation in proficiency testing.
2.1 ASTM Standards:
D 1129 Terminology Relating to Water
3.2.2 maximum deviation—the maximum error associated
D 6091 Practice for 99%/95% Interlaboratory Detection
with a report value, at a specified confidence level, for a given
Estimate (IDE) for Analytical Methods with Negligible
concentration of a given element, determined by a specific
Calibration Error
method, throughout a laboratory organization.
D 6512 Practice for an Interlaboratory Quantitation Esti-
3.2.3 measurement quality objectives—a model used by the
mate
laboratory organization to specify the maximum error associ-
E 135 Terminology Relating to Analytical Chemistry for
ated with a report value, at a specified confidence level.
Metals, Ores and Related Materials
3.2.4 workstation—a combination of people and equipment
E 415 Test Method for Optical Emission Vacuum Spectro-
that executes a specific test method using a single specified
metric Analysis of Carbon and Low-Alloy Steel
measuring device to quantify one or more parameters, with
E 1329 Practice for Verification and the Use of Control
each report value having an established estimated uncertainty
Charts in Spectrochemical Analysis
that complies with the measurement quality objectives of the
E 1763 GuidefortheInterpretationandUseofResultsfrom
laboratory organization.
Interlaboratory Testing of Chemical Analytical Methods
4. Significance and Use
STP 15D ASTM Manual on Presentation of Data and Con-
trol ChartAnalysis, Prepared by Committee E11 on Statis-
4.1 Many analytical laboratories comply with accepted
tical Methods
quality system requirements such as NELAC chapter 5 (see
Note 2) and ISO 17025. When using standard test methods,
their test results on the same sample should agree with those
from other similar laboratories within the reproducibility
This guide is under the jurisdiction ofASTM Committee D19 on Water and is
estimates (R2) published in the standard. Reproducibility
the direct responsibility of Subcommittee D19.02 on General Specifications,
Technical Resources, and Statistical Methods. estimates are generated during the standardization process as
Current edition approved June 10, 2001. Published July 2001.
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 Available from American National Standards Institute, 11 West 42nd St., 13th
the ASTM website. Floor, New York, New York, 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6689–01
part of the interlaboratory studies (ILS). Many laboratories 5. Summary
participate in proficiency tests to confirm that they perform
5.1 Identify the Test Method and establish the required
consistently over time. In both ILS and proficiency testing
measurement quality objectives to be met throughout the
protocols, it is generally assumed that only one workstation is
laboratory organization.
used to generate the data (see 6.5.1).
5.2 Identify the workstations to be included in the protocol
and harmonize their experimental procedures, calibrations and
NOTE 2—NELAC chapter 5 allows the use of a Work Cell where
multiple instruments/operators are treated as one unit: the performance of control strategies to be identical, so they will be statistically
the Work Cell is tracked rather than each workstation independently. This
comparable.
guide is intended to go beyond the Work Cell to achieve the benefits of
5.3 Tabulate performance data for each workstation and
monitoring workstations independently.
ensure that each workstation complies with the laboratory
organization’s measurement quality objectives.
4.2 Many laboratories have workloads and/or logistical
5.4 Document items covered in 5.1-5.3.
requirements that dictate the use of multiple workstations.
5.5 Establish and document a laboratory organization-wide
Some have multiple stations in the same area (central labora-
Proficiency Test Policy that provides traceability to all work-
toryformat).Others’stationsarescatteredthroughoutafacility
stations.
(at-line laboratory format). Often, analysis reports do not
5.6 Operate each workstation independently as described in
identify the workstation used for the testing, even if worksta-
its associated documentation. If any changes are made to any
tions differ in their testing uncertainties. Problems can arise if
workstation or its performance levels, document the changes
clientsmistakenlyattributevariationinreportvaluestoprocess
and ensure compliance with the laboratory organization’s
rather then workstation variability. These problems can be
measurement quality objectives.
minimized if the laboratory organization sets, complies with,
and reports a unified set of measurement quality objectives
6. Procedure
throughout.
4.3 This guide can be used to harmonize calibration and
6.1 Identify the Test Method and establish the measurement
control protocols for all workstations, thereby providing the
quality objectives to be met throughout the laboratory organi-
same level of measurement traceability and control. It stream-
zation.
lines documentation and training requirements, thereby facili-
6.1.1 Multi-element test methods can be handled concur-
tating flexibility in personnel assignments. Finally, it offers an
rently, if all elements are measured using common technology,
opportunity to claim traceability of proficiency test measure-
and the parameters that influence data quality are tabulated and
ments to all included workstations, regardless on which work-
evaluated for each element individually. An example is Test
station the proficiency test sample was tested. The potential
Method E 415 that covers the analysis of plain carbon and low
benefits of utilizing this protocol increase with the number of
alloy steel by optical emission vacuum spectrometry. Worksta-
workstations included in the laboratory organization.
tions can be under manual or robotic control, as long as the
4.4 This guide can be used to identify and quantify benefits
estimated uncertainties are within the specified measurement
derived from corrective actions relating to under-performing
quality objectives. Avoid handling multi-element test methods
workstations. It also provides means to track improved perfor-
that concurrently use different measurement technologies.
mance after improvements have been made.
Their procedures and error evaluations are too diverse to be
4.5 It is a prerequisite that all users of this guide comply
incorporated into one easy-to-manage package.
with ISO 17025, especially including the use of documented
6.1.2 Set the measurement quality objectives for the use of
procedures, the application of statistical control of measure-
the Test Method throughout the laboratory organization, using
ment processes, and participation in proficiency testing.
customer requirements and available performance data. At the
4.6 The general principles of this protocol can be adapted to conclusion of this effort, the laboratory organization will know
other types of measurements, such as mechanical testing and the maximum deviation allowable for any report value, at any
on-line process control measurements such as temperature and concentrationlevel,usingthemethodofchoice.Anexampleof
thickness gauging. In these areas, users will likely need to a possible method for establishing measurement quality objec-
establish their own models for defining measurement quality tives is given in Appendix X1.
objectives. Proficiency testing may not be available or appli-
6.2 Identify the workstations to be included in the protocol
cable. and harmonize their experimental procedures, calibrations and
4.7 It is especially important that users of this guide take control strategies so that all performance data from all work-
stations are directly statistically comparable.
responsibility for ensuring the accuracy of the measurements
madebytheworkstationstobeoperatedunderthisprotocol.In 6.2.1 For each workstation, list the parameters (personnel,
equipment, etc.) that significantly influence data quality. Each
addition to the checks mentioned in 6.2.3, laboratories are
encouraged to use other techniques, including, but not limited component of each workstation does not have to be identical
(such as from the same manufacturer or model number).
to, analyzing some materials by independent methods, either
within the same laboratory or in collaboration with other However, each workstation must perform the functions de-
scribed in the test method.
equally competent laboratories. The risks associated with
generating large volumes of data from carefully harmonized, 6.2.2 Harmonize the experimental procedures associated
but incorrectly calibrated multiple workstations are obvious with each workstation to ensure that all stations are capable of
and must be avoided. generatingstatisticallycomparabledatathatcanbeexpectedto
D6689–01
fall within the maximum allowable limits for the laboratory
TABLE 1 Continued
organization. Ideally, all workstations within the laboratory
Assumed
organization will have essentially the same experimental pro- ERM True WS Av. UCL LCL Std. Dev.
Conc.
cedures.
3 0.06969 0.07233 0.06705 0.00088
Ti 638 0.00224 1 0.00272 0.00296 0.00248 0.00008
TABLE 1 Sample SPC Control Parameter Tabulation
2 0.00200 0.00200 0.00200 0.00000
3 0.00200 0.00200 0.00200 0.00000
Assumed
648 0.04279 1 0.04285 0.04726 0.03844 0.00147
ERM True WS Av. UCL LCL Std. Dev.
2 0.04285 0.04684 0.03886 0.00133
Conc.
3 0.04268 0.04688 0.03848 0.00140
Al 638 0.02346 1 0.02373 0.02964 0.01782 0.00197
C 638 0.06014 1 0.05996 0.06764 0.05228 0.00256
2 0.02343 0.02646 0.02040 0.00101
2 0.06040 0.06364 0.05716 0.00108
3 0.02323 0.02584 0.02062 0.00087
3 0.06005 0.06308 0.05702 0.00101
648 0.06268 1 0.06268 0.06721 0.05815 0.00151
648 0.25665 1 0.25212 0.27069 0.23355 0.00619
2 0.06198 0.06633 0.05763 0.00145
2 0.25923 0.27402 0.24444 0.00493
3 0.06222 0.06576 0.05868 0.00118
3 0.25861 0.27283 0.24439 0.00474
Mn 638 0.29832 1 0.29620 0.30304 0.28936 0.00228
2 0.29967 0.30567 0.29367 0.00200
E = Element determined
3 0.29908 0.30643 0.29173 0.00245
RM = Reference material used for SPC control
648 0.90328 1 0.90408 0.92088 0.88728 0.00564
Assumed True Conc. = Concentration of E in the RM
2 0.90408 0.92385 0.88431 0.00659
WS = Work Station
3 0.90168 0.92664 0.87672 0.00832
Av. = Grand Mean from the SPC chart
P 638 0.00563 1 0.00543 0.00600 0.00486 0.00019
UCL = Upper control limit from the SPC chart
2 0.00575 0.00605 0.00545 0.00010
LCL = Lower control limit from the SPC chart
3 0.00571 0.00601 0.00541 0.00010
Std. Dev. = Standard Deviation from the SPC chart {(UCL-LCL)/6}
648 0.03431 1 0.03413 0.03674 0.03152 0.00087
6.2.3 Harmonize calibration protocols so that equivalent
2 0.03447 0.03702 0.03192 0.00085
3 0.03434 0.03689 0.03179 0.00085
calibrants (i.e. same material source, same stock solutions) are
S 638 0.01820 1 0.01702 0.02146 0.01258 0.00148
usedtocoverthesamecalibrationrangesforthesameelements
2 0.01868 0.02153 0.01583 0.00095
on all instruments (see Note 3). Avoid the use of different
3 0.01891 0.02128 0.01654 0.00079
648 0.02424 1 0.02330 0.02771 0.01889 0.00147
calibrants on different instruments that may lead to calibration
2 0.02475 0.02940 0.02010 0.00155
biases and uncertainties that are larger than necessary. Make
3 0.02467 0.02884 0.02050 0.00139
sure that all interferences and matrix effects are accounted for.
Si 638 0.01688 1 0.01565 0.01718 0.01412 0.00051
2 0.01755 0.01863 0.01647 0.00036
Verify the calibrations with certified reference materials not
3 0.01743 0.01830 0.01656 0.00029
used in the calibration, when possible. Record the findings for
648 0.23283 1 0.22900 0.23911 0.21889 0.00337
2 0.23240 0.24404 0.22076 0.00388 each workstation.
3 0.23710 0.24619 0.22801 0.00303
NOTE 3—It is recommended that the same calibrants are used for each
Cu 638 0.26588 1 0.26685 0.27555 0.25815 0.00290
instrument, i.e. same material source, same stock solution, etc. when
2 0.26569 0.27295 0.25843 0.00242
3 0.26511 0.27276 0.25746 0.00255
practical. Calibrations on all Workstations must be performed within a
648 0.10700 1 0.10654 0.11089 0.10219 0.00145
time period such that the stability of the calibration standards are not a
2 0.10753 0.11086 0.10420 0.00111
concern, if applicable.
3 0.10694 0.13784 0.07604 0.01030
Ni 638 0.69005 1 0.70014 0.72516 0.67512 0.00834 6.2.4 Use the same Statistical Process Control (SPC) mate-
2 0.68252 0.69440 0.67064 0.00396
rials and data collection practices on all workstations (see Note
3 0.68750 0.71309 0.66191 0.00853
4). Carry SPC materials through all procedural steps that
648 0.25063 1 0.25174
...