Accuracy round-robin

The molten salt standard program was initiated at Rensselaer Polytechnic Institute (RPI) in 1973 because of difficulties being encountered with accuracy estimates in the NBS-NSRDS molten salt series. The density, surface tension, electrical conductivity, and viscosity of KNO3 and NaCl were measured by seven laboratories over the world using samples distributed by RPI. The data from these round-robin measurements of raw properties were submitted to RPI for evaluation. Their recommendations are summarized in Table 2. 

Other classes of reference materials now in existence include secondary reference materials. These are materials produced commercially for reference purposes, but whose guarantee rests soley with the producer. "Analyzed" materials such as geological materials obtained from the United Staes Geological Survey, represent test samples that complement the variety available from the previously mentioned sources. However, the "accepted" analyses reported for these materials are based upon consensus values obtained from large scale interlaboratory collaborative tests (round robins). Analysis of these materials can provide a useful means of comparing performance with other laboratories, but it does not ensure accuracy. In addi-... 

A round robin study of accuracy and precision of the coulometric procedure identified sources of systematic error.33 In some labs, either the instruments were inaccurate or workers did not measure the quantity of standards accurately. In other cases, the solvent was not appropriate. Commercial reagents are designed for Karl Fischer analysis. Reagents recommended by the instrument manufacturer should be used with each instrument. 

As a measure of accuracy, we checked our method against NBS standards and mixtures of elements of known concentration and also participated in a round-robin analysis with NBS and EPA. We analyzed four NBS standards containing 60 elements in glass. Comparisons of results are given in Table VIII. With the exception of the cobalt result in the NBS 610 Standard, agreement is generally within 25% of the NBS value. 

Examine results of the recent EPA round robin study as they indicate the laboratory s ability to perform accurate analysis. A laboratory that does not participate in the EPA studies cannot be compared to other laboratories in terms of analytical accuracy. 

Merkus, H.G. Bischof, O. Drescher, S. Scarlett, B. Precision and accuracy in particle sizing. Round-Robin results from sedimentation, laser diffraction and electrical sensing zone using BCR 67 and 69, Proceedings 6th European Symposium on Particle Characterization, March, 21, 1995. 

This chapter focuses on the application of quantitative phase analysis (QPA) techniques for the extraction of phase abundance from diffraction data. Rather than repeat the extensive coverage of the QPA methodology covered in other texts, the focus will be on the basis and application of the most commonly used techniques. These were identified from participant responses to the recent round robin on QPA sponsored by the International Union of Crystallography (lUCr) Commission on Powder Diffraction (CPD). By far the greatest number of participants in that study used whole pattern (Rietveld based) methods but there are still several users of traditional single peak based methods and there are still many applications for which these methods suffice. Issues in the measurement of precision and accuracy will also be discussed. 

The materials used in the study (corundum - a-A Os, zincite - ZnO, and fluorite - CaF2) provided a relatively simple analytical system to determine the levels of accuracy and precision that could be expected under ideal conditions. Rather than being too prescriptive in the detail of the techniques to be used for analysis, the round robin organizers allowed the participants to select and report their own methodology. Thus, the RR also served as a survey of commonly used techniques for QPA. 

In an extensive IDFB round robin test made during spring 2002, the accuracy of the conventional tube-visibility test and the nephelometric measurement of turbidity units, or NTU, was compared. The findings were presented at the June 2002... 

We expect to get a better Idea of spreading resistance profile accuracy from a "round robin" test now In progress In the ASTM F-1 committee. This test Is being done In various laboratories throughout the world and will result In an experimental... 

Two interlaboratory studies were organised prior to the certification campaign. The first one dealt with the analysis of artificial seawater and the second exercise concerned the analyses of natural and spiked seawater. The results obtained for Cd, Cu, Pb and Zn are compared in Table 8.23. The CV between all the laboratories appeared to be quite high in the second round-robin exercise. However, the participation in such intercomparison combined with critical discussions of methods and results was found to be a most useful tool in obtaining a high level of accuracy (which is reflected in the... 

For x-ray spectrometry, K has been observed to have an approximate minimum value of 0.01 compared to a range of 0.008 to 0.05 for round-robin wet chemical analysis of metals. Currie [11] has discussed the limits of precision in analytical chemistry from a statistical basis, and Harvey [12] has described a method for identifying wild or potentially rejectable data points. Buchanan and Tsai [13] and Camp and Rhodes [14] have also recently investigated the precision and accuracy of the x-ray spectrometer method. 

Matter The laboratories and the data which we presented are all in the report. All of them are specialist laboratories with long experience in this field. We made the condition that the accuracy of the analyses be examined with the help of standard reference materials, and furthermore, that the laboratories also participated regularly in round robin experiments. It is clear that the most modern methods were used for these analyses. 

Even though this technique can correct the variation in sample size, one should still make the attempt to keep sample size the same. The same sample size then requires a uniform effort on the part of the chromatographic system regarding injection, vaporization, sample loading on the column, and response in the detector. For improved accuracy, component levels in the unknown are bracketed in the standards. Results obtained with the use of this technique on round-robin samples were reported by Emery (44). Emery s paper also provides some excellent data on various methods of peak measurement. 

H. G. Merkus, O. Bischof, S. Drescher, B. Scarlett, Precision and Accuracy in Particle Sizing - Round Robin Results from Sedimentation, Laser Diffraction, and Electrical Sensing Zone, PARTEC 95, 6 " European Symposium on Particle Characterization, 21-23 March 1995, Proceedings published by Nurnberg Messer GmbH, Niirnberg, Germany. 

The analysis of oxygen in titanium, zirconium and their alloys was the subject of several round robins within BCR, which led to the certification of five reference materials (133)(278)(239). These reference materials (Table VII-29) are essentially based on 14 MeV neutron activation analysis and reducing fusion which both allow precisions and accuracies of 3 to 5 % in the range 500 to 1750 /ig/g. Basically the most interesting method at these higher concentration levels has been up to now 14 MeV neutron activation analysis. This method has really been used as a reference method in the BCR programme, and has substantially contributed to the development of reducing fusion to its present level of accuracy. 

Merkus, H. G., Bischof, 0., Drescher, S., Scarlett, B., Precision and Accuracy in Particle Sizing, Round-robin Results from Sedimentation, Laser Diffraction and Electrical Sensing Zone Using BCR 67 and BCR 69, Prep. 6" European Symp. Part Charact, Nurberg, 1995,pp.427-436. 

To assure the accuracy and comparabihty of the results with other laboratories, an appropriate external quality assessment is necessary. For external quality control, participation in a round robin test is recommended. There are various quality control programs containing cadmium in blood and urine, e.g., the international program of the German External QuaUty Assessment Scheme (E-QUAS), where cadmium analysis can be tested for the concentration range found in occupational and environmental medicine [48], or the external quahty assessment schemes of the Centre of Toxicology in the National Institute of Public Health of Quebec [49]. 

The QPA of hydrated cements by XRD is not straightforward. It is important to stress that the XRD data of complex systems should not be analysed by black box approaches. Round-robins on QPA have revealed that the accuracy of the results, even for simple systems, is highly dependent on the adopted analysis strategy and the skill and experience of the analyst (Madsen et al. 2001 Scarlett et al. 2002). The experimenter should have... 

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