ASTM E882-87(1998)
(Guide)Standard Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
Standard Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
SCOPE
1.1 This guide describes the essential aspects of an accountability and quality control program for a chemical analysis laboratory. The reasons for establishing and operating such a program are discussed.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 882 – 87 (Reapproved 1998)
Standard Guide for
Accountability and Quality Control in the Chemical
Analysis Laboratory
This standard is issued under the fixed designation E 882; 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 4.2 Prior to submitting samples to the laboratory, the pro-
spective user should consult with laboratory personnel con-
1.1 This guide describes the essential aspects of an account-
cerning his needs and the capability of the laboratory to satisfy
ability and quality control program for a chemical analysis
them. It is the responsibility of the originator of the samples to
laboratory. The reasons for establishing and operating such a
select and identify proper samples for submission to the
program are discussed.
laboratory, to decide what information is required (especially,
2. Referenced Documents
to define the use to be made of the information), and, after
consulting with laboratory personnel, to submit the samples in
2.1 ASTM Standards:
suitable containers, properly labeled, and accompanied by
MNL 7 Manual on Presentation of Data and Control Chart
written instructions identifying the samples, their nature, and
Analysis
the information sought through chemical analysis. This should
2.2 ANSI Document:
be done formally, using a well-defined document for informa-
ANSI/ASQC A1 Definitions, Symbols, Formulas, and
tion transfer to initiate work in the laboratory.
Tables for Control Charts
4.3 Laboratory management establishes a written account-
3. Significance and Use
ability system to be used throughout the laboratory at all times.
This implies traceability and documentation of all reported
3.1 An accountability and quality control system is estab-
results through the laboratory back to the submitted sample.
lished by laboratory management to improve the quality of its
This system should have the following general characteristics:
results. It provides documented records which serve to assure
4.3.1 Each nonroutine job submitted by a user of the
users of the laboratory’s services that a specified level of
laboratory’s services is assigned an internal laboratory identi-
precision is achieved in the routine performance of its mea-
fication number (ID), which is used to correlate all samples,
surements and that the data reported were obtained from the
work, time and cost accounting, consultation, and reports and
samples submitted. The system also provides for: early warn-
other paperwork associated with that job. The final report that
ing to analysts when methods or equipment begin to develop a
is returned to the originator will always bear the number (ID)
bias or show deterioration of precision; the protection and
for future reference. Moreover, it is convenient for laboratory
retrievability of data (results); traceability and control of
data to be filed according to sequential ID numbers. For
samples as they are processed through the laboratory; good
example, “86/0428” might identify the associated work as the
communication of sample information between submitters,
428th request submitted in the year 1986. The Data Record
analysts, and supervision, and information on sample process-
should provide all data generated during the analyses, names of
ing history. This guide describes such a system. Other account-
persons performing the analyses, dates the analyses were
ability and quality control programs can be developed. Such
performed, and any unusual occurrences that happened during
programs can be equivalent to the program in this guide if they
the analyses. Accountability for production control samples is
provide all of the benefits mentioned above.
normally maintained separately from the nonroutine records
4. Accountability
because results from production control samples are usually
reported on routine report forms, the samples being identified
4.1 Accountability means assurance that the results reported
with the day, shift, run, or lot from which they were taken.
refer directly to the samples submitted.
4.3.2 Each sample, specimen, sample site, or other unique
piece of material or container identified as a separate sample by
This guide is under the jurisdiction of ASTM Committee E-1 on Analytical
the originator should be assigned a sequential item number
Chemistry for Metals, Ores, and Related Materials and is the direct responsibility of
(NN) for internal laboratory use. As soon as the samples are
Subcommittee E01.22 on Statistics and Quality Control.
Current edition approved April 24, 1987. Published June 1987. Originally
accepted by the laboratory, laboratory personnel will mark
published as E 882 – 82. Last previous edition E 882 – 82.
each sample or sample container with its own laboratory
ASTM Manual Series, ASTM, 6th Edition, 1990.
3 sample number (ID-NN) in such manner that the label is not
Available from American National Standards Institute, 11 West 42nd Street,
13th Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 882
likely to become separated from its sample or rendered inhomogeneity in the control sample will add to the variance of
unreadable during its residence in the laboratory. For example, the results. Any increase in variability that is not related to the
the fifth sample on the above-mentioned request might be measurement process will reduce the sensitivity of the quality
identified as “86/0428-05.” control procedure to detect changes in the measurement
4.3.3 All laboratory work records, intermediate sample process. Where possible, the control material should be similar
containers, data, and reports for a specific sample will be to the samples to be analyzed. Obtain as large an amount of
identified by the same laboratory identification and item control material as can be prepared in a homogeneous state
number to avoid any opportunity for samples or data to be lost because considerable effort is required to prepare a new
or intermixed within or between jobs. control. Always prepare a new control material well in advance
4.3.4 The first and last steps in the accountability procedure of exhausting the old one so that the new chart is ready when
are functions of technical supervision. Before any work is needed. In situations where satisfactory control material cannot
performed, the compatibility of the work requested with the be obtained, alternative techniques (such as, retest by a senior
physical condition of the samples and the capabilities of the analyst) may be substituted for the control chart approach.
laboratory must be verified. When the analysts have completed
5.2.6 Give analysts specific instructions concerning their
their work, the results must be reviewed to be certain that all
response to an out-of-control condition. Supervision may
information requested has been determined and that the work
decide that, if the analyst can correct the problem so that the
has been performed with the required care and precision. In
control sample results again plot within limits, the process may
this latter regard, quality control procedures prove invaluable
continue without immediate contact with the supervisor. In
both to the analysts performing the work and the reviewing
other situations, the supervisor may need to become involved
supervisor. The supervisor also verifies that the results are
with each out-of-control incident. In either case, adjustments to
calculated in units that are most meaningful to the submitter
the process should be recorded to explain each shift in the
and that the units and basis on which the results are calculated
control measurements.
are clearly stated.
5.2.7 Provide for a periodic in-depth review by supervision
4.3.5 Except for the most routine work, the original ana-
and management of the overall effectiveness of the laboratory
lyst’s data book, a serial listing of laboratory identification
quality control system. Operating experience may indicate that
numbers and descriptions, and a copy of each job report sheet
methods should be added to, or dropped from the program, that
are retained in the laboratory’s records for the periods of time
the frequency of specific control samples should be increased
established by laboratory policy. Intermediate calculations and
or decreased, or that a different strategy might be more
samples are normally discarded after the submitter has had a
appropriate for control of a specific method. The interval for
reasonable opportunity to submit questions concerning the
such reviews should be determined by the uniformity of the
results and request return of his samples. In some cases,
processes that generate the samples. Any anticipated or ob-
customer specifications may dictate the records that must be
served change in the character of the samples being analyzed
retained and the retention times for both analytical records and
should initiate at least a cursory review of the control proce-
laboratory samples.
dures for the methods that apply to those samples.
5.3 Laboratory Quality Control Strategies—Control chart
5. Quality Control
methods are suitable for laboratory quality control programs.
5.1 Quality control of analytical methods provides the
The choice of which control strategy to use depends on
information needed to ensure that procedures, equipment, and
circumstances: the type of instrument or laboratory procedure,
personnel are performing at the levels of precision and accu-
the number of samples and frequency of the analyses, and the
racy required by the intended use of the data.
closeness of control required. The following are appropriate:
5.2 General Characteristics—The following factors have
¯
5.3.1 The X- and R-chart method is most frequently used.
been found helpful in maximizing the effectiveness and mini-
The control sample is run two or more times during the run,
mizing the cost of quality control procedures:
¯
batch, or shift. The average is plotted on the X-chart and the
5.2.1 Involve the operators or analysts who actually perform
absolute value of the difference between the high and low
the work to the greatest possible extent.
values, the range, is plotted on the R-chart. If the average falls
5.2.2 Use the simplest, most direct statistical procedures
between the upper and lower control limits and the range falls
that will provide the necessary degree of control. This means
below the upper control limit, the process is considered to be in
that graphical or simplified arithmetic procedures are preferred.
control. Fig. 1 shows the essential features of charts for
5.2.3 Perform the quality control measurements as early in
averages and ranges.
the measurement process as possible. This prevents waste of
5.3.2 The X-chart method (often called the control chart for
analytical effort if the method is not initially in control.
However, when a prolonged series of measurements is made, it individuals) is useful for measurements that are made on a
is also necessary to verify that the method remains in control frequent or continual basis. It is appropriate for methods or
throughout the run. instruments for which the usual mode of failure produces
5.2.4 Provide specific action limits and describe exactly relatively large shifts in results and the cost of a determination
what must be done when these limits are exceeded. precludes performing replicate analyses of control samples. Its
5.2.5 For each method (for each sample type), choose a main characteristic is that it responds rapidly to sudden
control material that is known to be stable and homogeneous relatively large changes in the analytical process, but it is not
¯
and has measured values within the range of interest. Any as sensitive to small changes as the X- and R-chart method.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 882
FIG. 1 Control Chart for Averages
FIG. 2 Control Chart for Ranges
Each time the control material is analyzed, its value is plotted be appropriate for special circumstances may be found in the
on the X-chart. If the point plots between the upper and lower ANSI/ASQC document.
control limits, the analytical process is considered to be in 5.3.4 Comparison with standard reference materials (SRMs)
control. Fig. 3 shows the essential features of charts for is frequently the only strategy that can be employed for
individuals. infrequently used analytical methods or for nonroutine sample
5.3.3 A combination of the above two methods constitutes a types. If an SRM such as one from the National Institute of
useful strategy. A fixed number of control sample runs are Standards and Technology (similar to the samples) is run along
made during a period that samples are being analyzed (such with the samples, comparison of the measured value against
period could, for example, be a shift or a day in a continuous the known value of the standard provides a measure of
analysis process). Each individual value is plotted on the confidence in the sample assays. Lacking an SRM, any
X-chart as the measurement is completed. Their average value previously analyzed material may be used. In all cases, it is
¯
and range are plotted on the X- and R-charts. The additional important to retain as large a portion of such a material as
effort to prepare and maintain both types of control charts may possible and to tabulate the results, the method used, the date,
be justified in situations where erroneous assays would cause and the analyst. Materials and data thus obtained may have
large economic losses. Other control chart techniques that may important future statistical or control chart use.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 882
FIG. 3 Control Chart for Individuals
5.4 Definitions: original data points that were used to calculate the control
5.4.1 mean: limits.
¯
5.5.1 X- and R-Chart—At least two independent measure-
¯
X 5 ~X 1 X 1 . . X !/~n! (1)
1 2 n
ments must be made on the control material during each run.
where n 5 the number of analytical values.
The average of the n values obtained on
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.