AOAC Appendix E_Laboratory Quality Assurance
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031BEA0EAF904679B0AAF3CBD88F05E2 |
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0.06 |
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页数： |
6 |
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日期： |
2013-4-11 |
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Appendix E: Laboratory Quality Assurance,For over a century, AOAC INTERNATIONAL has provided the,methods of analysis required for the measurement of analytes of interest,to those government agencies that regulate products associated,with agriculture, public health, and the environment. But during,the past several decades, analysts realized that providing measurements,based on methods validated and approved through collaborative,study was not enough. Analytical results had to be accompanied,by concurrent proof that the measurements were correct. That proof,could be obtained by the application of the concepts of quality assurance,long used in the industrial world, to analytical measurements.,Scope of Laboratory Quality Assurance,A good analytical method is necessary to obtain valid concentration,estimates, but it is not sufficient. The laboratory equipment must,be running in accord with specifications. Analysts must be performing,their work in a professional manner, and a suitable checking process,must be in operation to ensure the quality of analytical results.,The primary reason for performing laboratory analyses is to obtain,information that can be used to make informed decisions. Analytical,data reported by a laboratory must be fit for its intended,purpose and of a sufficient degree of quality, whether the purpose is,to enforce standards, determine economic value, or protect the public,health. Data must be comparable to those generated in other laboratories.,It is no longer sufficient for a laboratory simply to believe or,maintain that it is generating quality data. Laboratories must be able,to demonstrate that their analyses are correct and in statistical control.,Proof of technical competency and comparability is now a requirement,in the global marketplace.,AOAC Official Methods are designed for the measurement of specific,analytes in defined matrixes. An approved AOAC method has,been demonstrated to produce reliable results when applied by a,representative sample of laboratories expected to use it in practice.,Nevertheless, whenever the method is applied subsequently, each,user laboratory must demonstrate that it can produce results comparable,to those attained in the original interlaboratory study. This demonstration,is necessary when a laboratory analyzes for the same analyte,in the same material for which the method was designed, or when it is,necessary to extend the method to additional analytes in the same matrix,or to additional matrixes with the same analyte. For some extensions,itmaybe necessary to conduct further interlaboratory studies.,All analytical results must be traceable to some reference,point—either fundamental units or reference materials certified by,or traceable to, a metrological institution. Only some classical,gravimetric, titrimetric, and electrometric methods can be traced by,any laboratory to fundamental metrological units. Almost all modern,methods are based on an instrumental comparison of the response,of an analyte with the response of a reference standard when,both are stimulated by the same source of energy. This places a great,burden on the authenticity of the standard. But even possession of a,suitable standard is still not sufficient to produce adequate measurements.,All measurements are accompanied by some degree of uncertainty.,This uncertainty is of 2 types: a systematic displacement from,the true or assumed value and a random scatter of values about a,mean or average value. The systematic type affects all measurements,in a system equally and is called “bias.” If known, it can be,corrected for. The random type of uncertainty affects each measurement,in an unpredictable manner, but oddly enough, taken as a group,their behavior is predictable and is called “random error.” The ability,to correct for bias and use the predictability of random error of the,group is the basis for demonstrating the production of measurements,of suitable quality.,The control of bias and random error of analytical measurements is,the formal procedure of laboratory quality control. But quality control,is only the final stage of a management system of quality assurance,which encompasses all aspects of laboratory operations including,housekeeping, supplies, maintenance of records, training personnel,supervision, physical handling of laboratory samples, documentation,and reporting. This chapter reviews only the aspects of quality control,as it pertains to the direct production and documentation of analytical,measurements. Without the essential organizational infrastructure,however, it is impossible to produce quality measurements. The volumes,by Taylor and by Ga……
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