1、Designation: E882 10Standard Guide forAccountability and Quality Control in the Chemical AnalysisLaboratory1This standard is issued under the fixed designation E882; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the essential aspects of an account-ability and quality control program for a chemical analysislaboratory
3、. The reasons for establishing and operating such aprogram are discussed.2. Referenced Documents2.1 ASTM Standards:2E135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE1329 Practice for Verification and Use of Control Charts inSpectrochemical AnalysisMNL 7A Manua
4、l on Presentation of Data and Control ChartAnalysis32.2 ASQC Document:4ASQC Standard A1 Definitions, Symbols, Formulas, andTables for Control Charts3. Terminology3.1 DefinitionsFor definitions of terms used in this guide,refer to Terminology E135.4. Significance and Use4.1 An accountability and qual
5、ity control system is estab-lished by laboratory management to improve the quality of itsresults. It provides documented records which serve to assureusers of the laboratorys services that a specified level ofprecision is achieved in the routine performance of its mea-surements and that the data rep
6、orted were obtained from thesamples submitted. The system also provides for: early warn-ing to analysts when methods or equipment begin to develop abias or show deterioration of precision; the protection andretrievability of data (results); traceability and control ofsamples as they are processed th
7、rough the laboratory; goodcommunication of sample information between submitters,analysts, and supervision; and information on sample process-ing history. This guide describes such a system. Other account-ability and quality control programs can be developed. Suchprograms can be equivalent to the pr
8、ogram in this guide if theyprovide all of the benefits mentioned above.5. Accountability5.1 Accountability means assurance that the results reportedrefer directly to the samples submitted.5.2 Prior to submitting samples to the laboratory, the pro-spective user should consult with laboratory personne
9、l con-cerning his needs and the capability of the laboratory to satisfythem. It is the responsibility of the originator of the samples toselect and identify proper samples for submission to thelaboratory, to decide what information is required, and, afterconsulting with laboratory personnel, to subm
10、it the samples insuitable containers, properly labeled, and accompanied bywritten instructions identifying the samples, their nature, andthe information sought through chemical analysis. This shouldbe done formally, using a well-defined document for informa-tion transfer to initiate work in the labo
11、ratory.5.3 Laboratory management establishes a written account-ability system to be used throughout the laboratory at all times.This implies traceability and documentation of all reportedresults through the laboratory back to the submitted sample.This system should have the following general charact
12、eristics:5.3.1 Each testing request submitted by a user of thelaboratorys services is assigned an internal laboratory identi-fication number (ID), which is used to correlate all samples,work, time, and cost accounting, consultation, and reports andother paperwork associated with that request. The fi
13、nal reportthat is returned to the originator will always bear the number(ID) for future reference. Moreover, it is convenient forlaboratory data to be filed according to sequential ID numbers.For example, “86/0428” might identify the associated work asthe 428th request submitted in the year 1986. Th
14、e Data Recordshould provide all data generated during the analyses, names ofpersons performing the analyses, dates the analyses were1This guide is under the jurisdiction of ASTM Committee E01 on AnalyticalChemistry for Metals, Ores, and Related Materials and is the direct responsibility ofSubcommitt
15、ee E01.22 on Laboratory Quality.Current edition approved Oct. 1, 2010. Published December 2010. Originallyapproved in 1982. Last previous edition approved in 2003 as E882 98 (2003).DOI: 10.1520/E0882-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Ser
16、vice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3ASTM Manual Series, ASTM, 7th Edition, 2002.4Available from American Society for Quality (ASQ), 600 N. Plankinton Ave.,Milwaukee, WI 53203, http:/www.asq.org
17、.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.performed, and any unusual occurrences that happened duringthe analyses. Accountability for production control samples isnormally maintained separately from the other testing recordsbe
18、cause results from production control samples are usuallyreported on routine report forms, the samples being identifiedwith the day, shift, run, or lot from which they were taken.5.3.2 Each sample, specimen, sample site, or other uniquepiece of material or container identified as a separate sample b
19、ythe originator should be assigned a sequential item number(NN) for internal laboratory use. As soon as the samples areaccepted by the laboratory, laboratory personnel will markeach sample or sample container with its own laboratorysample number (ID-NN) in such manner that the label is notlikely to
20、become separated from its sample or renderedunreadable during its residence in the laboratory. For example,the fifth sample on the above-mentioned request might beidentified as “86/0428-05.”5.3.3 All laboratory work records, intermediate samplecontainers, data, and reports for a specific sample will
21、 beidentified by the same laboratory identification and itemnumber to avoid any opportunity for samples or data to be lostor intermixed within or between requests.5.3.4 The first and last steps in the accountability procedureare functions of technical supervision. Before any work isperformed, the co
22、mpatibility of the work requested with thephysical condition of the samples and the capabilities of thelaboratory must be verified. When the analysts have completedtheir work, the results must be reviewed to be certain that allinformation requested has been determined and that the workhas been perfo
23、rmed with the required care and precision. Inthis latter regard, quality control procedures prove invaluableboth to the analysts performing the work and the reviewingsupervisor. The supervisor also verifies that the results arecalculated in units that are most meaningful to the submitterand that the
24、 units and basis on which the results are calculatedare clearly stated.5.3.5 Except for the most routine work, the original ana-lysts data book, a serial listing of laboratory identificationnumbers and descriptions, and a copy of each job report areretained in the laboratorys records for the periods
25、 of timeestablished by laboratory policy. Intermediate calculations andsamples are normally discarded after the submitter has had areasonable opportunity to submit questions concerning theresults and request return of his samples. In some cases,customer specifications may dictate the records that mu
26、st beretained and the retention times for both analytical records andlaboratory samples.6. Quality Control6.1 Quality control of analytical methods provides theinformation needed to ensure that procedures, equipment, andpersonnel are performing at the levels of precision and accu-racy required by th
27、e intended use of the data.6.2 General CharacteristicsThe following factors havebeen found helpful in maximizing the effectiveness and mini-mizing the cost of quality control procedures:6.2.1 Involve the operators or analysts who actually performthe work to the greatest possible extent.6.2.2 Use the
28、 simplest, most direct statistical proceduresthat will provide the necessary degree of control. This meansthat graphical or simplified arithmetic procedures are preferred.6.2.3 Perform the quality control measurements as early inthe measurement process as possible. This prevents waste ofanalytical e
29、ffort if the method is not initially in control.However, when a prolonged series of measurements is made, itis also necessary to verify that the method remains in controlthroughout the run.6.2.4 Provide specific action limits and describe exactlywhat must be done when these limits are exceeded.6.2.5
30、 For each method (for each sample type), choose acontrol material that is known to be stable, homogeneous andhas measured values within the range of interest. Any inhomo-geneity in the control sample will add to the variance of theresults. Any increase in variability that is not related to themeasur
31、ement process will reduce the sensitivity of the qualitycontrol procedure to detect changes in the measurementprocess. Where possible, the control material should be similarto the samples to be analyzed. Obtain as large an amount ofcontrol material as can be prepared in a homogeneous statebecause co
32、nsiderable effort is required to prepare a newcontrol.Always prepare a new control material well in advanceof exhausting the old one so that the new supply is ready whenneeded. In situations where satisfactory control material cannotbe obtained, alternative techniques (such as, retest by a seniorana
33、lyst) may be substituted for the control material approach.6.2.6 Give analysts specific instructions concerning theirresponse to an out-of-control condition. Supervision maydecide that, if the analyst can correct the problem so that thecontrol sample results are again within limits, the process mayc
34、ontinue without immediate contact with the supervisor. Inother situations, the supervisor may need to become involvedwith each out-of-control incident. In either case, adjustments tothe process should be recorded to explain each shift in thecontrol measurements.6.2.7 Provide for a periodic in-depth
35、review by supervisionand management of the overall effectiveness of the laboratoryquality control system. Operating experience may indicate thatmethods should be added to, or dropped from the program, thatthe frequency of specific control samples should be increasedor decreased, or that a different
36、strategy might be moreappropriate for control of a specific method. The interval forsuch reviews should be determined by the uniformity of theprocesses that generate the samples. Any anticipated or ob-served change in the character of the samples being analyzedshould initiate at least a cursory revi
37、ew of the control proce-dures for the methods that apply to those samples.6.3 Laboratory Quality Control StrategiesControl chartmethods are suitable for laboratory quality control programs.The choice of which control strategy to use depends oncircumstances: the type of instrument or laboratory proce
38、dure,the number of samples and frequency of the analyses, and thecloseness of control required. The following are appropriate:6.3.1 The X- and R-chart method is most frequently used.The control sample is run two or more times during the run,batch, or shift. The average is plotted on the X-chart and
39、theabsolute value of the difference between the high and lowE882 102values, the range, is plotted on the R-chart. If the average fallsbetween the upper and lower control limits and the range fallsbelow the upper control limit, the process is considered to be incontrol. Fig. 1 shows the essential fea
40、tures of charts foraverages and ranges.6.3.2 The X-chart method (often called the control chart forindividuals) is useful for measurements that are made on afrequent or continual basis. It is appropriate for methods orinstruments for which the usual mode of failure producesrelatively large shifts in
41、 results and the cost of a determinationprecludes performing replicate analyses of control samples. Itsmain characteristic is that it responds rapidly to suddenrelatively large changes in the analytical process, but it is notas sensitive to small changes as the X- and R-chart method.Each time the co
42、ntrol material is analyzed, its value is plottedon the X-chart. If the point plots between the upper and lowercontrol limits, the analytical process is considered to be incontrol. Fig. 3 shows the essential features of charts forindividuals.6.3.3 A combination of the above two methods constitutes au
43、seful strategy. A fixed number of control sample runs aremade during a period that samples are being analyzed (suchperiod could, for example, be a shift or a day in a continuousanalysis process). Each individual value is plotted on theX-chart as the measurement is completed. Their average valueand r
44、ange are plotted on the X- and R-charts. The additionaleffort to prepare and maintain both types of control charts maybe justified in situations where erroneous assays would causelarge economic losses. Other control chart techniques that maybe appropriate for special circumstances may be found in th
45、eASQC Standard A1 document.6.3.4 Comparison with certified reference materials (CRMs)is frequently the only strategy that can be employed forinfrequently used analytical methods or for non-routine sampletypes. If a CRM (from the National Institute of Standards andTechnology or other CRM producer) si
46、milar to the samples incomposition is tested with the samples, comparison of themeasured value to the assigned value of the CRM provides ameasure of confidence in the sample assays. Lacking a CRM,any previously analyzed material may be used. In all cases, itis important to retain as large a portion
47、of such a material aspossible and to tabulate the results, the method used, the date,and the analyst. Materials and data thus obtained may haveimportant future statistical or control chart use.6.4 Definitions:6.4.1 mean:X5 X11 X21 . . Xn! / n (1)where:n = the number of analytical values.6.4.2 grand
48、mean:X55 X11 X21 . Xk! / k (2)where:k = the number of individual means.6.4.3 range:R 5 Xh2 Xl(3)where:Xh= highest observed value, andXl= lowest observed value in the data.6.4.4 average range:R5 R11 R21 . Rk! / k (4)FIG. 1 Control Chart for AveragesE882 1036.4.5 estimated standard deviation:s 5(Xi2 X
49、!2n 1(5)where:xi= the individual values of successive observations,X= the mean of the values, andn = the number of values.6.5 Control Chart ConstructionCalculate the centralvalue and control limits. Prepare the control chart with thevertical scale labeled so that the central value is approximatelymidway on the graph. Select a scale factor to permit the resultsto be plotted accurately and easily. The horizontal axis islabeled by shift, day, run number, or run date, as appropriate.Draw and label the central line and the lines representing theupper and l
