ASTM D6689-01(2011)
(Guide)Standard Guide for Optimizing, Controlling and Reporting Test Method Uncertainties from Multiple Workstations in the Same Laboratory Organization
Standard Guide for Optimizing, Controlling and Reporting Test Method Uncertainties from Multiple Workstations in the Same Laboratory Organization
SIGNIFICANCE AND USE
Many analytical laboratories comply with accepted 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 estimates (R2) published in the standard. Reproducibility estimates are generated during the standardization process as part of the interlaboratory studies (ILS). Many laboratories participate in proficiency tests to confirm that they perform consistently over time. In both ILS and proficiency testing protocols, it is generally assumed that only one workstation is used to generate the data (see 6.5.1).
Note 2—NELAC chapter 5 allows the use of a Work Cell where multiple instruments/operators are treated as one unit: the performance of the Work Cell is tracked rather than each workstation independently. This guide is intended to go beyond the Work Cell to achieve the benefits of monitoring workstations independently.
Many laboratories have workloads and/or logistical requirements that dictate the use of multiple workstations. Some have multiple stations in the same area (central laboratory format). Others' stations are scattered throughout a facility (at-line laboratory format). Often, analysis reports do not identify the workstation used for the testing, even if workstations differ in their testing uncertainties. Problems can arise if clients mistakenly attribute variation in report values to process rather then workstation variability. These problems can be minimized if the laboratory organization sets, complies with, and reports a unified set of measurement quality objectives throughout.
This guide can be used to harmonize calibration and control protocols for all workstations, thereby providing the same level of measurement traceability and control. It streamlines documentation and training requirements, thereby facilitating flexibility in personnel assignments. Finally, it off...
SCOPE
1.1 This guide describes a protocol for optimizing, controlling, and reporting test method uncertainties from multiple workstations in the same laboratory organization. It does not apply when different test methods, dissimilar instruments, or different parts of the same laboratory organization function independently to validate or verify the accuracy of a specific analytical measurement.
1.2 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 health practices and determine the applicability of regulatory requirements prior to use.
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Designation: D6689 − 01 (Reapproved 2011)
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 D6689; 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 2.2 Other Documents:
ISO 17025 (previously ISO Guide 25) General Require-
1.1 This guide describes a protocol for optimizing,
ments for the Competence of Calibration and Testing
controlling, and reporting test method uncertainties from mul-
Laboratories
tiple workstations in the same laboratory organization. It does
not apply when different test methods, dissimilar instruments,
3. Terminology
or 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 E135 and D1129.
analytical measurement.
3.2 Definitions 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.
NOTE1—KeyaspectsofaqualitysystemarecoveredinISO17025and
2. Referenced Documents include documenting procedures, application of statistical control to
measurement processes and participation in proficiency testing.
2.1 ASTM Standards:
3.2.2 maximum deviation—the maximum error associated
D1129 Terminology Relating to Water
with a report value, at a specified confidence level, for a given
D6091 Practice for 99 %/95 % Interlaboratory Detection
concentration of a given element, determined by a specific
Estimate (IDE) for Analytical Methods with Negligible
method, throughout a laboratory organization.
Calibration Error
3.2.3 measurement quality objectives—a model used by the
D6512 Practice for Interlaboratory Quantitation Estimate
laboratory organization to specify the maximum error associ-
E135 Terminology Relating to Analytical Chemistry for
ated with a report value, at a specified confidence level.
Metals, Ores, and Related Materials
E415 Test Method for Analysis of Carbon and Low-Alloy
3.2.4 workstation—a combination of people and equipment
Steel by Spark Atomic Emission Spectrometry
that executes a specific test method using a single specified
E1763 Guide for Interpretation and Use of Results from
measuring device to quantify one or more parameters, with
Interlaboratory Testing of Chemical Analysis Methods
each report value having an established estimated uncertainty
STP 15D ASTM Manual on Presentation of Data and
that complies with the measurement quality objectives of the
Control Chart Analysis, Prepared by Committee E11 on
laboratory organization.
Statistical Methods
4. Significance and Use
4.1 Many analytical laboratories comply with accepted
1 quality system requirements such as NELAC chapter 5 (see
This guide is under the jurisdiction ofASTM Committee D19 on Water and is
thedirectresponsibilityofSubcommitteeD19.02onQualitySystems,Specification, Note 2) and ISO 17025. When using standard test methods,
and Statistics.
their test results on the same sample should agree with those
Current edition approved May 1, 2011. Published June 2011. Originally
from other similar laboratories within the reproducibility
approved in 2001. Last previous edition approved in 2006 as D6689 – 01 (2006).
estimates (R2) published in the standard. Reproducibility
DOI: 10.1520/D6689-01R11.
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 fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6689 − 01 (2011)
estimates are generated during the standardization process as generating large volumes of data from carefully harmonized,
part of the interlaboratory studies (ILS). Many laboratories but incorrectly calibrated multiple workstations are obvious
participate in proficiency tests to confirm that they perform and must be avoided.
consistently over time. In both ILS and proficiency testing
protocols, it is generally assumed that only one workstation is
5. Summary
used to generate the data (see 6.5.1).
5.1 Identify the Test Method and establish the required
measurement quality objectives to be met throughout the
NOTE 2—NELAC chapter 5 allows the use of a Work Cell where
multiple instruments/operators are treated as one unit: the performance of laboratory organization.
the Work Cell is tracked rather than each workstation independently. This
5.2 Identify the workstations to be included in the protocol
guide is intended to go beyond the Work Cell to achieve the benefits of
and harmonize their experimental procedures, calibrations and
monitoring workstations independently.
control strategies to be identical, so they will be statistically
4.2 Many laboratories have workloads and/or logistical
comparable.
requirements that dictate the use of multiple workstations.
5.3 Tabulate performance data for each workstation and
Some have multiple stations in the same area (central labora-
ensure that each workstation complies with the laboratory
toryformat).Others’stationsarescatteredthroughoutafacility
organization’s measurement quality objectives.
(at-line laboratory format). Often, analysis reports do not
identify the workstation used for the testing, even if worksta-
5.4 Document items covered in 5.1 – 5.3.
tions differ in their testing uncertainties. Problems can arise if
5.5 Establish and document a laboratory organization-wide
clientsmistakenlyattributevariationinreportvaluestoprocess
Proficiency Test Policy that provides traceability to all work-
rather then workstation variability. These problems can be
stations.
minimized if the laboratory organization sets, complies with,
5.6 Operate each workstation independently as described in
and reports a unified set of measurement quality objectives
its associated documentation. If any changes are made to any
throughout.
workstation or its performance levels, document the changes
4.3 This guide can be used to harmonize calibration and
and ensure compliance with the laboratory organization’s
control protocols for all workstations, thereby providing the
measurement quality objectives.
same level of measurement traceability and control. It stream-
lines documentation and training requirements, thereby facili-
6. Procedure
tating flexibility in personnel assignments. Finally, it offers an
6.1 Identify the Test Method and establish the measurement
opportunity to claim traceability of proficiency test measure-
quality objectives to be met throughout the laboratory organi-
ments to all included workstations, regardless on which work-
zation.
station the proficiency test sample was tested. The potential
6.1.1 Multi-element test methods can be handled
benefits of utilizing this protocol increase with the number of
concurrently, if all elements are measured using common
workstations included in the laboratory organization.
technology, and the parameters that influence data quality are
4.4 This guide can be used to identify and quantify benefits
tabulated and evaluated for each element individually. An
derived from corrective actions relating to under-performing
example is Test Method E415 that covers the analysis of plain
workstations. It also provides means to track improved perfor-
carbon and low alloy steel by optical emission vacuum
mance after improvements have been made.
spectrometry. Workstations can be under manual or robotic
control, as long as the estimated uncertainties are within the
4.5 It is a prerequisite that all users of this guide comply
specified measurement quality objectives. Avoid handling
with ISO 17025, especially including the use of documented
multi-element test methods that concurrently use different
procedures, the application of statistical control of measure-
measurement technologies. Their procedures and error evalu-
ment processes, and participation in proficiency testing.
ations are too diverse to be incorporated into one easy-to-
4.6 The general principles of this protocol can be adapted to
manage package.
other types of measurements, such as mechanical testing and
6.1.2 Set the measurement quality objectives for the use of
on-line process control measurements such as temperature and
the Test Method throughout the laboratory organization, using
thickness gauging. In these areas, users will likely need to
customer requirements and available performance data. At the
establish their own models for defining measurement quality
conclusion of this effort, the laboratory organization will know
objectives. Proficiency testing may not be available or appli-
the maximum deviation allowable for any report value, at any
cable.
concentrationlevel,usingthemethodofchoice.Anexampleof
a possible method for establishing measurement quality objec-
4.7 It is especially important that users of this guide take
tives is given in Appendix X1.
responsibility for ensuring the accuracy of the measurements
madebytheworkstationstobeoperatedunderthisprotocol.In 6.2 Identify the workstations to be included in the protocol
addition to the checks mentioned in 6.2.3, laboratories are and harmonize their experimental procedures, calibrations and
encouraged to use other techniques, including, but not limited control strategies so that all performance data from all work-
to, analyzing some materials by independent methods, either stations are directly statistically comparable.
within the same laboratory or in collaboration with other 6.2.1 For each workstation, list the parameters (personnel,
equally competent laboratories. The risks associated with equipment, etc.) that significantly influence data quality. Each
D6689 − 01 (2011)
TABLE 1 Continued
component of each workstation does not have to be identical
Assumed
(such as from the same manufacturer or model number).
Std.
ERM True WS Av. UCL LCL
Dev.
However, each workstation must perform the functions de-
Conc.
scribed in the test method.
2 0.08722 0.08941 0.08503 0.00073
3 0.08696 0.09011 0.08381 0.00105
6.2.2 Harmonize the experimental procedures associated
V 638 0.02107 1 0.02076 0.02184 0.01968 0.00036
with each workstation to ensure that all stations are capable of
2 0.02114 0.02219 0.02009 0.00035
3 0.02132 0.02231 0.02033 0.00033
generatingstatisticallycomparabledatathatcanbeexpectedto
648 0.06937 1 0.06892 0.07123 0.06661 0.00077
fall within the maximum allowable limits for the laboratory
2 0.06949 0.07219 0.06679 0.00090
organization. Ideally, all workstations within the laboratory 3 0.06969 0.07233 0.06705 0.00088
Ti 638 0.00224 1 0.00272 0.00296 0.00248 0.00008
organization will have essentially the same experimental pro-
2 0.00200 0.00200 0.00200 0.00000
cedures.
3 0.00200 0.00200 0.00200 0.00000
648 0.04279 1 0.04285 0.04726 0.03844 0.00147
TABLE 1 Sample SPC Control Parameter Tabulation
2 0.04285 0.04684 0.03886 0.00133
Assumed
Std. 3 0.04268 0.04688 0.03848 0.00140
ERM True WS Av. UCL LCL
Dev.
Al 638 0.02346 1 0.02373 0.02964 0.01782 0.00197
Conc.
2 0.02343 0.02646 0.02040 0.00101
C 638 0.06014 1 0.05996 0.06764 0.05228 0.00256
3 0.02323 0.02584 0.02062 0.00087
2 0.06040 0.06364 0.05716 0.00108
648 0.06268 1 0.06268 0.06721 0.05815 0.00151
3 0.06005 0.06308 0.05702 0.00101
2 0.06198 0.06633 0.05763 0.00145
648 0.25665 1 0.25212 0.27069 0.23355 0.00619
3 0.06222 0.06576 0.05868 0.00118
2 0.25923 0.27402 0.24444 0.00493
3 0.25861 0.27283 0.24439 0.00474
E = Element determined
Mn 638 0.29832 1 0.29620 0.30304 0.28936 0.00228
RM = Reference material used for SPC control
2 0.29967 0.30567 0.29367 0.00200
Assumed True Conc. = Concentration of E in the RM
3 0.29908 0.30643 0.29173 0.00245
WS = Work Station
648 0.90328 1 0.90408 0.92088 0.88728 0.00564
Av. = Grand Mean from the SPC chart
2 0.90408 0.92385 0.88431 0.00659
UCL = Upper control limit from the SPC chart
3 0.90168 0.92664 0.87672 0.00832
LCL = Lower control limit from the SPC chart
P 638 0.00563 1 0.00543 0.00600 0.00486 0.00019
Std. Dev. = Standard Deviation from the SPC chart {(UCL-LCL)/6}
2 0.00575 0.00605 0.00545 0.00010
6.2.3 Harmonize calibration protocols so that equivalent
3 0.00571 0.00601 0.00541 0.00010
648 0.03431 1 0.03413 0.03674 0.03152 0.00087 calibrants (i.e. same material source, same stock solutions) are
2 0.03447 0.03702 0.03192 0.00085
usedtocoverthesamecalibrationrangesforthesameelements
3 0.03434 0.03689 0.03179 0.00085
on all instruments (see Note 3). Avoid the use of different
S 638 0.01820 1 0.01702 0.02146 0.01258 0.00148
2 0.01868 0.02153 0.01583 0.00095
calibrants on different instruments that may lead to calibration
3 0.01891 0.02128 0.01654 0.00079
biases and uncertainties that are larger than necessary. Make
648 0.02424 1 0.02330 0.02771 0.01889 0.00147
sure that all interferences and matrix effects are accounted for.
2 0.02475 0.02940 0.02010 0.00155
3 0.02467 0.02884 0.02050 0.00139
Verify the calibrations with certified reference materials not
Si 638 0.01688 1 0.01565 0.01718 0.01412 0.00051
used in the calibration, when possible. Record the findings for
2 0.01755 0.01863 0.01647 0.00036
each workstation.
3 0.01743 0.01830 0.01656 0.00029
648 0.23283 1 0.22900 0.23911 0.21889 0.00337
NOTE 3—It is recommended that the same calibrants are used for each
2 0.23240 0.24404 0.22076 0.00388
instrument, i.e. same material source, same stock solution, etc. when
3 0.23710 0.24619 0.22801 0.00303
practical. Calibrations on all Workstations must be performed within a
Cu 638 0.26588 1 0.26685 0.27555 0.25815 0.00290
2 0.26569 0.27295 0.25843 0.00242 time period such that the stability of the calibration standards are not a
3 0.26511 0.27276 0.25746 0.00255
concern, if applicable.
648 0.10700 1 0.10654 0.11089 0.10219 0.00145
6.2.4 Use the same Statistical Process Control (SPC) mate-
2 0.10753 0.11086 0.10420 0.00111
...
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