E. DEVELOPMENT AND EVALUATION OF METHODS
by Eugene R. Kennedy, Ph.D., Thomas J. Fischbach, Ruiguang Song, Ph.D., Peter M. Eller, Ph.D., Stanley A. Shulman, Ph.D., NIOSH/DPSE and R. DeLon Hull, Ph.D., NIOSH/DSHEFS
| Contents: | Page | |
|---|---|---|
| 1. | Method Development | 36 |
| a. | Preliminary Experimentation | 37 |
| b. | Recovery of Analyte from Medium | 37 |
| c. | Stability of the Analyte on the Medium | 38 |
| 2. | Method Evaluation | 39 |
| a. | Feasibility of Analyte Generation | 39 |
| b. | Capacity of the Sampler and Sampling Rate | 40 |
| c. | Sampling and Analysis Evaluation | 42 |
| d. | Sample Stability | 42 |
| e. | Precision, Bias, and Accuracy | 43 |
| 3. | Field Evaluation | 44 |
| 4. | Documentation | 44 |
| 5. | Appendix - Accuracy and Its Evaluation | 45 |
| 6. | References | 48 |
| Figure 1. | Nomogram Relating Accuracy to Precision and Bias | 50 |
| Table I | Values of the Bias and the Precision Required to | 51 |
| Obtain Designated Accuracy in Percentage Units |
1. METHOD DEVELOPMENT
The development and evaluation of analytical methods that are useful, reliable and accurate for industrial hygiene monitoring problems require the application of some general guidelines and evaluation criteria. The guiding objective in this work requires that, over a specified concentration range, the method provide a result that differs no more than ±25% from the true value 95 times out of 100. The application of consistent evaluation criteria and guidelines is particularly important when methods are developed by different individuals and organizations (e.g., contractors or outside laboratories) and compiled into a single manual. Adherence to guidelines should minimize overlooking potential problems in the methodology during its development, as well as provide cohesiveness and uniformity to the method that is developed. This chapter provides an outline of a generalized set of evaluation criteria prepared by NIOSH researchers for the evaluation of sampling and analytical methodology [1].
In the development of a sampling and analytical method, there is a logical progression of events that cover a search of the literature to gather pertinent information and the preliminary experimentation for selection of analysis technique and sampling medium. To initiate the development of a method, the identity of the analyte must be as fully defined as possible. Physical and chemical properties of the analyte should be defined so that procedures for proper handling and use of the analyte can be prepared. These also aid in establishment of analyte purity. Potential sources of this information include chemical reference books, health hazard evaluation
reports, bulk sample analyses, material safety data sheets, chemical process information, etc.
