Intralaboratory quality control

Intralaboratory Quality Control. In its efforts to establish minimum intralaboratory quality control, the USEPA has incorporated certain mandatory quality control practices into each of the 600-series organic methods promulgated as part of final rule making on October 26, 1984 (10). These quality control practices are found in Section 8 of each EMSL method. 

The intralaboratory quality control program consists of a number of appropriately defined procedmes. For every batch of analyses for water quality samples, the... 

Clesceri, L.S., A.E. Greenberg, and R.R. Trussell (Eds.). 1989. Intralaboratory quality control guidelines. In Standard Methods for the Examination of Water and Wastewater. 17th edition, Part 9020B, pp. 9-5 to 9-23. American Public Health Association. Washington, DC. 

The repeatability (sr) can be used to check duplicate repeats during normal operation of a method (see chapter 1). On its own, repeatability is not a complete basis for estimation of measurement uncertainty because it omits many effects that contribute to the bias of measurements made within a single laboratory. However, combined with a good estimate of the run bias, the intralaboratory precision, obtained from quality control data, can be used to give an estimate of measurement uncertainty. See section 6.6.3.2 for details on correction for bias and recovery. 

Since we are aware now that the species of an element is often, on the basis of its essentiality or toxicity, much more important than the total mass of the element this aspect is also extensively treated. Quality control and the means to achieve reliable data are discussed in chapters that deal with inter- and intralaboratory surveys, and reference methods. The reference materials presently available for the treated elements and the philosophy of their production and certification are reviewed in a separate chapter. Last... 

Several standards arc available for intralaboratory and intcr-laboralyry quality control studies, which also include day-to-day control of the precision and accuracy of within-run and between-run imprecision of activity measurements. Commercially available standard.s also provide information on the activity of the standards for a given substrate at specified experimental conditions. 

Since important decisions affecting the health and welfare of humanity must be made on the basis of analytical results, considerable effort must be directed toward assuring greater confidence in the reliability of the output of analytical laboratories. The Commission of the European Communities, after performing a study to determine the comparability of chemical analyses for drinking water quality, concluded that analytical quality control must be required as a routine component of analytical work. They state ( ), "Only the combination of intralaboratory controls of precision and accuracy complemented by interlaboratory intercomparison tests can lead to a significant evaluation and improvement of analytical results."... 

There are other routinely practiced procedures in terms of intralaboratory and interlaboratory quality control, such as the control chart, round-robin interlaboratory testing, and various proficiency tests offered by different agencies, such as the PATs (Proficiency Analytical Testing) by AHA in the US and WASPs (Workplace Analysis Scheme for Proficiency) by the Health and Safety Laboratory in Great Britain. In normal circumstances, a combination of these quality control measures should be used in performing workplace air analysis. 

QCPs are the means by which a quality assurance program (QAP) is implemented. A QAP is usually divided into two classifications, namely the intralaboratory (in-house) and interlaboratory (between laboratory) quality control programs. The former program is a continuing and systematic regime carried out by each individual laboratory. Unless several appropriate standard reference materials are available for the specific parameter, substrate, sample matrix, and concentration levels imder study, an in-house QAP can only reflect the performance of each laboratory in isolation. In order to assess and/or ensure the reliability and compatibility of sets of data generated by different laboratories, an interlaboratory QAP is necessary in addition to the intralaboratory QAP. 

Se levels <0.4 (imol/liter. Laboratories using quality control schemes had lower interlaboratory CVs, but the advantage began to diminish at blood Se levels <0.4 xmol/liter. Thus, in the diagnosis of Se deficiency in livestock, where the levels of interest are in the range 0.15-0.5 xmol/liter, the high interlaboratory CVs, the low intralaboratory CVs, and the ineffectiveness of quality control schemes at blood Se concentrations <0.4 jimol/liter are matters of concern. 

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