Analytical chemistry measurement assurance programs: More than just measurement control programs

Assurance of measurement accuracy and precision is required and/or recommended by regulations and guides for good laboratory practices for analytical chemistry laboratories. Measurement Control programs(MCPs) and or Measurement Assurance programs (MAPs) are means for determining and controlling the accuracy and precision of a laboratory`s measurements. Regulations and guides often allow for interpretation of what is necessary to assure measurement quality and how it is done. Consequently, a great diversity exists between laboratories` measurement quality control programs. This paper will describe various levels of measurement control(MC) and the differences between a comprehensive MAP and various levels of MCPs. It will explain the benefits of establishing a comprehensive MAP based on a set of basic principles. MCPs range from go/no-go testing of a check standard`s measurement against control limits to a comprehensive MAP. Features of the latter include: an independent verisimilitude (matrix matched) standard having known uncertainties; customer tolerance limits as well as control limits; statistical tests for bias and precision testing; and estimating the total measurement process uncertainty based upon the combination of both the measurement system and standard`s uncertainties. A commercial measurement assurance program (JTIPMAP TradeMark) was evaluated by the author`s laboratories and compared to locally developed as well as other commercial software packages. Results of the evaluation, comparisons, conclusions and recommendations are presented.