The Multi-Agency Radiological Laboratory Analytical Protocols (MARLAP) Manual


MARLAP-cover.pngThe MARLAP manual is a guidance document for radiochemistry laboratories and for planners of projects that involve radiochemical analysis. The manual was developed by a multi-agency workgroup with representation from the following federal departments and agencies:

  • Environmental Protection Agency (EPA)
  • Nuclear Regulatory Commission (NRC)
  • Department of Energy (DOE)
  • Department of Defense (DoD), with representatives from the Army (and USACE), Navy, and Air Force
  • U.S. Geological Survey (USGS)
  • Food and Drug Administration (FDA)
  • Department of Homeland Security (DHS)
  • National Institute of Standards and Technology (NIST)

There was also representation from the states (Kentucky and California).

The MARLAP manual is a large document, and it is divided conceptually into two parts (although the printed version actually has three volumes). Part I is intended primarily for project planners and deals with data quality objectives (DQOs), measurement quality objectives (MQOs), and analytical issues that project planners should be aware of. MARLAP Part II is intended mainly for laboratory personnel and deals with technical issues at the radiochemistry laboratory including chemistry, nuclear counting instruments, quality control, and uncertainty evaluation.


The workgroup met for the first time in Washington, DC, in August 1995. The first meeting lasted only about two days, and there were no more meetings for several months, partly because of the temporary shutdown of much of the federal bureaucracy in late 1995. The next meeting occurred in Montgomery, AL, in March 1996. The group clearly underestimated the effort that would be required to develop the manual. Subsequent meetings gradually increased in length from two days to five days and became more frequent. Several meetings were held at the headquarters of the Nuclear Regulatory Commission in Rockville, MD. A few meetings were held at the EPA’s National Air and Radiation Environmental Laboratory in Montgomery, AL, and a few were held at the USGS’s National Water Quality Laboratory in Denver, CO. Two meetings were held at DOE’s Environmental Measurements Laboratory in New York City (now DHS’s Environmental Measurements Laboratory). Many of the meetings were held at the National Institute of Standards and Technology in Gaithersburg, MD.

The manual went through an internal agency review, further revisions, and later a public review and a formal peer review by the Radiation Advisory Committee of EPA’s Science Advisory Board (SAB).

The manual was finalized in July 2004 and was officially approved by all the participating departments and agencies between August and December of 2004.

How to Obtain the Manual

To view or download the MARLAP manual, visit​radiation/​multi-agency-radiological-laboratory-analytical-protocols-manual-marlap. It is possible to download any or all chapters and appendices.


Listed below are some known errors in the MARLAP manual.

Acronyms and Abbreviations

  • In my (Keith’s) opinion the unit symbol for the tropical year (31 556 926 s) should be a, not y; however, there seems to be no final authority on the subject. The symbol a is recommended by ISO 31-1 (Quantities and units — Part 1: Space and time), but a search of the web finds that the same symbol is sometimes used for other types of years, such as the Gregorian year (365.2425 d). Note that no version of the year is currently accepted for use with the SI, although some version is obviously needed.

Chapter 5: Obtaining Laboratory Services

  • Page 5-16. Cited References. The most recent revision date for ANSI N42.23 was (and still is) 1996. According to a knowledgeable source, the document was reapproved without change in 2003; however, the ANSI web site shows the revision date as 1996.

Chapter 6: Selection and Application of an Analytical Method

  • Page 6-36. References. The most recent revision date for ANSI N42.23 is 1996. The document was reapproved without change in 2003.

Chapter 8: Radiochemical Data Verification and Validation

  • Pages 8-21 and 8-31. Some of the recommendations of Chapter 8 are inconsistent with those of Chapters 1, 16, 19, and 20. In particular, Chapters 1, 16, and 19 allow a lab to report either the combined standard uncertainty or an expanded uncertainty as long as the uncertainty is clearly explained. (This is consistent with the GUM.) Chapter 8 recommends an expanded uncertainty only. Furthermore, Chapter 8 explicitly recommends that the lab report a sample-specific MDC with each result. Chapter 20 conspicuously avoids such a recommendation, noting the likelihood that a sample-specific MDC will be misused. The principal author of Chapter 20 intended to ensure that no part of MARLAP explicitly recommended or forbade the reporting of sample-specific MDCs. The workgroup recognized that sample-specific MDCs would continue to be reported regardless of its recommendation, and chose to emphasize instead a correct understanding of the MDA/MDC concept.
  • Page 8-31. Bibliography. Every other chapter calls this section References, not Bibliography.

Chapter 19: Measurement Uncertainty

  • Page 19-1. Table of contents. The recommendations are in Section 19.3.9, as stated in the chapter overview. The references are listed in Section 19.6, and there is no Section 19.7.
  • Page 19-24. Equation 19.14 is written incorrectly. It is correct as written only when the sensitivity coefficients for each pair of correlated input estimates have the same sign. The problem is that the individual components of the standard uncertainty are always positive, regardless of the signs of the sensitivity coefficients. This equation was included only to illustrate concepts and obviously was not checked carefully enough before publication. It may be deleted from future editions of the document, since it is not actually necessary for calculating an uncertainty. Footnote 8 on page 25 also requires some changes in wording.
  • Page 19-30. Example 19.12. The second equation, which calculates uc(p), the combined standard uncertainty of p, uses an incorrect value for u(y). The standard uncertainty of y is actually 3, not 4. The rest of the equation, including the final result is correct; so, the error seems to be only a typo.
  • Page 19-58. Cited Sources. The most recent revision date for ANSI N42.23 is 1996. The document was reapproved without change in 2003.
  • Page 19-99. Apparently the author and the reviewers had never heard of conventional mass. According to OIML R 111-1, the values of mass standards are to be given as conventional mass, not true mass. (ASTM follows suit.) This subtlety can make a slight difference in how one corrects for buoyancy when the balance is calibrated in terms of conventional mass. Buoyancy effects in general are usually small, and the difference here is really tiny, because mass standards tend to be dense. In the buoyancy example, the density was 7.85 g/mL and the reference density for conventional mass is 8 g/mL. The corresponding relative error in the buoyancy correction factor would be only about −3 × 10−6. If the true mass of the standard is used for calibration, as the author of Chapter 19 apparently assumed, the buoyancy correction factor is OK as is. Nevertheless, the concept of conventional mass should be mentioned in the section.
  • A new definition is needed for a log-normally distributed quantity on page 19-68. Technically, one cannot take the logarithm of the value of a quantity unless that quantity has dimension 1. So, the new definition might say that a quantity X has a log-normal distribution if the logarithm of its numerical value is normally distributed. The numerical value of a quantity (with respect to an appropriate unit of measurement), unlike the value, always has dimension 1.

Chapter 20: Detection and Quantification Capabilities

  • Page 20-34. References. The standard number for the last reference on the page should be ISO 11929-3, not 11929-2. (Thanks to Manuel Martinez Moreno for pointing out this one.)


  • The reference for the definition of carrier should be IUPAC 1994, not IUPAC 1995.

Appendix G: Statistical Tables

  • There are no known errors in the downloadable PDF versions of Appendix G, but the printed copies have Arabic characters substituted for Greek letters. If you notice similar problems in your PDF version, please contact me using the link below.

If you find other errors in the manual, particularly in Chapters 19 and 20 and Appendices C, F, and G, please email me at I also have a particular interest in Chapters 1, 3, 6, 16, and 18; however, I will accept comments on all parts of the manual and pass them along.

Note: I seem to have difficulty putting all the words into Multi-Agency Radiological Laboratory Analytical Protocols. If you find examples of it on this website, please let me know about those errors too.

Other Recommended Improvements for Revision 1

Chapter 6: Selection and Application of an Analytical Method

  • Given the results of work performed in 2007 and discussed at the RRMC in Jackson, Wyoming, and additional work performed in 2022 and discussed at the RRMC in Atlanta, Georgia, the method validation acceptance criterion should be replaced with a more powerful statistical test based on mean squared error.

Chapter 19: Measurement Uncertainty

Chapter 20: Detection and Quantification Capabilities

  • A few of the equations for detection limits may be rewritten in different but equivalent forms.
  • Page 20-47. The Stapleton Approximation. The basis for this approximation is the Anscombe transform, which uses d = 3/8, or 0.375, instead of 0.4. Any mention of other constants should be omitted.


  • Many definitions could be improved.

Appendix F: Laboratory Subsampling

  • Page F-14. Footnote 10. I wrote this myself, and I apologize for offending the reader’s ears. It offends my ears too. It should have been corrected during one of the many reviews.