ASTM D6689-01(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D6689–01 (Reapproved 2006)
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 ments for the Competence of Calibration and Testing
Laboratories
1.1 This guide describes a protocol for optimizing, control-
ling, and reporting test method uncertainties from multiple
3. Terminology
workstations in the same laboratory organization. It does not
3.1 Definitions—For definitions of terms used in this Guide,
apply when different test methods, dissimilar instruments, or
refer to Terminology E135 and D1129.
different parts of the same laboratory organization function
3.2 Defintions of Terms Specific to This Standard:
independently to validate or verify the accuracy of a specific
3.2.1 laboratory organization—a business entity that pro-
analytical measurement.
vides similar types of measurements from more than one
1.2 This standard does not purport to address all of the
workstation located in one or more laboratories, all of which
safety concerns, if any, associated with its use. It is the
operate under the same quality system.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
NOTE 1—KeyaspectsofaqualitysystemarecoveredinISO 17025and
bility of regulatory requirements prior to use. include documenting procedures, application of statistical control to
measurement processes and participation in proficiency testing.
2. Referenced Documents
3.2.2 maximum deviation—the maximum error associated
2.1 ASTM Standards:
with a report value, at a specified confidence level, for a given
D1129 Terminology Relating to Water
concentration of a given element, determined by a specific
D6091 Practice for 99 %/95 % Interlaboratory Detection
method, throughout a laboratory organization.
Estimate (IDE) for Analytical Methods with Negligible
3.2.3 measurement quality objectives—a model used by the
Calibration Error
laboratory organization to specify the maximum error associ-
D6512 Practice for Interlaboratory Quantitation Estimate
ated with a report value, at a specified confidence level.
E135 Terminology Relating to Analytical Chemistry for
3.2.4 workstation—a combination of people and equipment
Metals, Ores, and Related Materials
that executes a specific test method using a single specified
E415 Test Method for Atomic Emission Vacuum Spectro-
measuring device to quantify one or more parameters, with
metric Analysis of Carbon and Low-Alloy Steel
each report value having an established estimated uncertainty
E1763 Guide for Interpretation and Use of Results from
that complies with the measurement quality objectives of the
Interlaboratory Testing of Chemical Analysis Methods
laboratory organization.
STP 15D ASTM Manual on Presentation of Data and
4. Significance and Use
Control Chart Analysis, Prepared by Committee E11 on
Statistical Methods
4.1 Many analytical laboratories comply with accepted
2.2 Other Documents:
quality system requirements such as NELAC chapter 5 (see
ISO 17025 (previously ISO Guide 25) General Require-
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,
estimates are generated during the standardization process as
Technical Resources, and Statistical Methods.
part of the interlaboratory studies (ILS). Many laboratories
Current edition approved Aug. 15, 2006. Published August 2006. Originally
approved in 2001. Last previous edition approved in 2001 as D6689 – 01. DOI: participate in proficiency tests to confirm that they perform
10.1520/D6689-01R06.
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, 25 West 43rd St., 4th
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 (2006)
consistently over time. In both ILS and proficiency testing 5. Summary
protocols, it is generally assumed that only one workstation is
5.1 Identify the Test Method and establish the required
used to generate the data (see 6.5.1).
measurement quality objectives to be met throughout the
laboratory organization.
NOTE 2—NELAC chapter 5 allows the use of a Work Cell where
5.2 Identify the workstations to be included in the protocol
multiple instruments/operators are treated as one unit: the performance of
and harmonize their experimental procedures, calibrations and
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 control strategies to be identical, so they will be statistically
monitoring workstations independently. comparable.
5.3 Tabulate performance data for each workstation and
4.2 Many laboratories have workloads and/or logistical
ensure that each workstation complies with the laboratory
requirements that dictate the use of multiple workstations.
organization’s measurement quality objectives.
Some have multiple stations in the same area (central labora-
5.4 Document items covered in 5.1-5.3.
toryformat).Others’stationsarescatteredthroughoutafacility
5.5 Establish and document a laboratory organization-wide
(at-line laboratory format). Often, analysis reports do not
Proficiency Test Policy that provides traceability to all work-
identify the workstation used for the testing, even if worksta-
stations.
tions differ in their testing uncertainties. Problems can arise if
5.6 Operate each workstation independently as described in
clientsmistakenlyattributevariationinreportvaluestoprocess
its associated documentation. If any changes are made to any
rather then workstation variability. These problems can be
workstation or its performance levels, document the changes
minimized if the laboratory organization sets, complies with,
and ensure compliance with the laboratory organization’s
and reports a unified set of measurement quality objectives
measurement quality objectives.
throughout.
4.3 This guide can be used to harmonize calibration and
6. Procedure
control protocols for all workstations, thereby providing the
6.1 Identify the Test Method and establish the measurement
same level of measurement traceability and control. It stream-
quality objectives to be met throughout the laboratory organi-
lines documentation and training requirements, thereby facili-
zation.
tating flexibility in personnel assignments. Finally, it offers an
6.1.1 Multi-element test methods can be handled concur-
opportunity to claim traceability of proficiency test measure-
rently, if all elements are measured using common technology,
ments to all included workstations, regardless on which work-
and the parameters that influence data quality are tabulated and
station the proficiency test sample was tested. The potential
evaluated for each element individually. An example is Test
benefits of utilizing this protocol increase with the number of
Method E415 that covers the analysis of plain carbon and low
workstations included in the laboratory organization.
alloy steel by optical emission vacuum spectrometry. Worksta-
4.4 This guide can be used to identify and quantify benefits
tions can be under manual or robotic control, as long as the
derived from corrective actions relating to under-performing estimated uncertainties are within the specified measurement
workstations. It also provides means to track improved perfor- quality objectives. Avoid handling multi-element test methods
mance after improvements have been made. that concurrently use different measurement technologies.
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-
responsibility for ensuring the accuracy of the measurements
stations are directly statistically comparable.
madebytheworkstationstobeoperatedunderthisprotocol.In
6.2.1 For each workstation, list the parameters (personnel,
addition to the checks mentioned in 6.2.3, laboratories are
equipment, etc.) that significantly influence data quality. Each
encouraged to use other techniques, including, but not limited
component of each workstation does not have to be identical
to, analyzing some materials by independent methods, either
(such as from the same manufacturer or model number).
within the same laboratory or in collaboration with other
However, each workstation must perform the functions de-
equally competent laboratories. The risks associated with scribed in the test method.
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 (2006)
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 proce
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