Environmental Protection Agency calibration

The U.S. Environmental Protection Agency publishes sets of Series Methods that describe procedures for detecting and estimating the quantity of environmentally hazardous substances. There are strict requirements for accuracy, reproducibility, and for calibration of mass spectrometers. 

U.S. Environmental Protection Agency, "Transfer Standards for Calibration of Air Monitoring Analyzers for Ozone," EPA-600/4-79-056. Office of Air Quality Planning and Standards, Research Triangle Park, NC, 1979. 

Rehme, K. A., B. E. Martin, and J. A. Hodgeson. Tentative Method for the Calibration of Nitric Oxide, Nitrogen Dioxide, and Ozone Analyzers hy Gas Phase lltration. EPA-R2-73-246. Research Triangje Park, N.C. U.S. Environmental Protection Agency, 1974. 16 pp. 

Government agencies such as the U.S. Environmental Protection Agency set requirements for quality assurance for their own labs and for certification of other labs. Published standard methods specify precision, accuracy, numbers of blanks, replicates, and calibration checks. To monitor drinking water, regulations state how often and how many samples are to be taken. Documentation is necessary to demonstrate that all requirements have been met. Table 5-1 summarizes the quality assurance process. 

J. R. Troost and E. Y. Olavasen [ Gas Chromatographic/Mass Spectrometric Calibration Bias, Anal. Chem. 1996,68, 708] discovered that a chromatography procedure from the U.S. Environmental Protection Agency had a nonlinear response on a variety of instruments. The assumption of constant response factor led to errors as great as 40%. 

We can estimate the pH of an aqueous solution very quickly by using a strip of universal indicator paper, which turns different colors at different pH values. More precise measurements are made with a pH meter (Fig. 10.10). This instrument consists of a voltmeter connected to two electrodes that dip into the solution. The difference in electrical potential across the electrodes is proportional to the pH (as will be explained in Section 12.11) so once the scale on the meter has been calibrated, the pH can be read directly. In the United States, the Environmental Protection Agency (EPA) defines waste as corrosive if its pH is either lower than... 

Coal containing 5.0 wt% S is burned at a rate of 1250 Ibm/min in a boiler furnace. All of the sulfur in the coal is oxidized to SO2. The product gas is sent to a scrubber in which most of the SO2 is removed, and the scrubbed gas then passes out of a stack. An Environmental Protection Agency regulation requires that the gas in the stack must contain no more than 0.018 Ibm SCh/lbm coal burned. To test compliance with this regulation a flowmeter and an SO analyzer are mounted in the stack. The volumetric flow rale of the scrubbed gas is found to be 2867 ft /s, and the SO analyzer reading is 37. Calibration data for the analyzer are given in the table below. 

When a problem of contamination or interference is encountered in an interlaboratory study, it is easier to detect. Figure 1 shows the results of a very old study done by Taft Sanitary Engineering Center, a forerunner of the U. S. Environmental Protection Agency, when they sent portions of a sample of aluminum ion to a number of different laboratories. Each laboratory calibrated its procedure for aluminum ion against a primary standard and did the analysis in triplicate. The fact that a variety of methods was used suggests that the high result for the mean was not due to an interference in a particular method but. Instead, due to contamination of the entire lot or the presence of an interference from the walls of the sample containers. 

The Root Mean Square Error (RMSE) method, recommended by the US Environmental Protection Agency, involves generation of a calibration curve and calculating the RMSE. The steps involved are as follows ... 

EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards, revised Sept. 1993, U.S. Environmental Protection Agency, Quality Assurance and Technical Support Division, Research Triangle Park, NC 27711. 

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