United States Environmental Protection Agency Environmental Monitoring and Sup Laboratory Cincinnati OH 45268 Research and Development EPA/600/S4-85/056 Dec. 1985 Project Summary Choosing Cost-Effective QA/QC Programs for Chemical Analysis Lloyd P. Provost and Robert S. Elder The primary objective of the full report is to provide guidance for choosing cost-effective quality assurance/qual- ity control (QA/QC) programsf or chem- ical laboratories. It describes general principles of QA/QC, the specific tools available, and the information needed to choose appropriate tools for specific needs. The report does not give detailed discussions of how to apply each quality control tool; references are given for more detailed information. The major tasks of this project were: a literature search to identify current QA/QC practices for inorganic and organic chemical methods; an evaluation of ongoing quality as- surance programs; development of a model to determine the type and level of QA/QC effort required for various uses of particular analytical methods. The full report was submitted in fulfill- ment of Contract Number 68-03-2995, by Radian Corporation. The research reported here was conducted under the sponsorship of the U.S. Environmental Protection Agency (USEPA). This Project Summary was developed by EPA's Environmental Monitoring and Support Laboratory, Cincinnati, OH, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). Background The Environmental Monitoring and Support Laboratory, U.S. Environmental Protection Agency {EPA), Cincinnati of- fice, has the responsibility for developing quality control (QC) procedures and lab- oratory quality assurance (QA) programs to support ongoing analytical method development research and monitoring programs. Radian Corporation was con- tracted to review current QA/QC pro- grams* and develop guidelines for QA/QC practices for the USEPA 600 series methods for chemical analysis of toxic organic pollutants. The primary objective of the full report is to provide guidance for choosing cost- effective analytical QA/QC programs. To this end, the full report is organized into five sections, with two appendices. Ref- erences are provided throughout the report for amplification and follow-up by the reader. Introduction This section presents a general over- view of the report organization. Twelve general references are provided. General QA/QC Principles This section discusses general con- cepts and approaches found useful by the quality control profession in over 50 years of accumulated experience. The princi- ples described are qualitative, but serve as guides to quantitative evaluations of QA/QC programs. They also are helpful guides in starting quality programs for new test methods (where information needed for quantitative decisions may be lacking) or for choosing minimal programs for methods whose results are put to many uses. *QA = Quality assurance, the system of activities whose purpose is to provide assurance that the quality-control job is being done effec- tively QC = Qualitycontrol.thesystemof activities whose purpose is to provide a quality of product or service that meets the needs of users ------- The following concepts are discussed in this section: Definition of Quality as FitnessforUse Total Quality Control Resource Allocation Process Control Measures of Analytical Quality Simplicity Seventeen references are provided to the reader for further studies. QA/QC Tools Commonly used QA/QC tools are dis- cussed in this section in terms of- Purposes and potential benefits Information requiredtojudgeeffective- ness Qualitative guidance for effective use Sources of further information Among the possible reasons for using a quality control tool are documentation, appraisal, control or improvement of quality, and prevention of quality prob- lems. Some tools serve more than one of these purposes. The methods available are not all suitable for every job. A brief subsection is devoted to each topic. EPA's QA audit category identifiers for measured values are given where appropriate. References are listed at the end of each subsection for convenience. The following well-referenced discus- sion topics are presented in this section: Blanks (5 references) Calibration (17 references) Control Charts (24 references) Interlaboratory Studies (15 referenc- es) Material Controls (6 references) Method Development (10 references) Performance and System Audits (5 references) Reference Materials (7 references) Replication (11 references) Sampling Procedures (11 references) Spike-Recovery Studies (3 references) Study Planning (5 references) Surrogate Compounds (2 references) Validation (5 references) Measuring QA/QC Cost Effectiveness Measures of analytical quality, such as bias and precision, are useful to the laboratory for evaluating and maintaining its performance. However, since factors in addition to analytical quality often affect the usefulness of results, more comprehensive criteria are needed for measuring end-use effectiveness. The purpose of this section is to present methods for evaluating the cost-effective- ness of particular QA/QC activities. The statistical tools needed to develop a quality control program, based upon data quality objectives (DQO) are presented in the form of 20 equations, eight charts, and two useful nomographs. Each topic is presented with example calculations to illustrate the solutions to quest ions, such as: How many replicate analyses are needed for a single test to reliably detect a bias of specified size? How many replicate analyses are needed for a single test to reliably detect a specified bias? What is the probability of detecting a serious contamination problem in the laboratory in a single method blank analysis? How many sets of duplicate analyses are needed in a specified period to reliably detect a specified increase in standard deviation? Choosing Cost-Effective QA/QC Programs This section begins with the premise that in many laboratories an analytical method may be routinely applied to the analysis of sample lots with different end- uses and data quality objectives. In such a setting, a single QA/QC program cannot be cost-effective for every application. One reasonable way to avoid requiring superfluous efforts is to establish a two-tier program on the following basis: MinimalQC steps needed regardless of use AdditionalQC steps tailored to end- use needs The cost-effectiveness of QA/QC pro- grams can be improved further by basing levels of QC effort in both the minimal and additional phases on reasonable QC targets (as discussed in Section 4). The development of a minimal program is discussed in the first part of Section 5; the selection of additional QA/QC procedures is discussed in the final part of Section 5. The EPA 600 series methods are used to illustrate the principles discussed in these sections Appendices The first appendix to the full report describes the application of skip-lot qual- ity control procedures. The basic idea of skip-lot procedures is that the amount of appraisal effort required in a quality control program depends on the quality being produced A process that produces consistently high quality requires less monitoring than one that frequently ex- periences quality problems. Skip-lot pro- cedures provide objective rules for decid- ing the frequency of appraisal needed. The second appendix addresses the design and analysis of spike-recovery studies In this appendix, statistical prop- erties of percent recovery data, when analytical bias and precision are propor- tional to sample concentration, are des- cribed. The impact of the presence of the analyte of interest in the unspiked sample (i.e., non-zero background concentration) is examined and some of the potential pitfalls in the interpretation of percent recovery data in method development and quality control applications are dis- cussed. ------- L. P. Provost andR. S. Elder are with Radian Corporation, Austin, TX 78766. James E. Longbottom and Stephen Billets are the EPA Project Officers (see below). The complete report, entitled "Choosing Cost-Effective QA/QC Programs for Chemical Analysis," (Order No. PB 85-241 461; Cost: $16.00. subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, V'A 22161 Telephone: 703-487-4650 The EPA Project Officers can be contacted at: Environmental Monitoring and Support Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Official Business Penalty for Private Use $300 EPA/600/S4-85/056 0000329 PS U $ £NVIR PROTECTION AGENCY REGION 5 LIBRARY 230 $ ol*»BO«N ST|pT CHICAGO *L 60604 ------- |