Round robins

As a first step in the direction outlined here some manufacturers and BAM last year discussed the problems and the possible procedures of such a system of quality assurance. As a result of this meeting round robin tests for the harmonization of the measurements of film system parameters and a possible procedure of surveillance of the quality of film systems were proposed. Closely related to these the BAM offers to perform the classification of film systems. But as during the production of films variations of the properties of the different batches cannot be avoided, the results of measurements of films of a single batch will be restricted to this charge, while only the measurements and mean of several batches of a film type will give representative values of its properties. This fact is taken into account already in section 4 of the standard EN 584-1 which can be interpreted as a kind of continuous surveillance. In accordance with this standard a film system caimot be certified on the base of measurements of a single emulsion only. 

A first comprehensive round robin test described in 4.1 which is open to all interested parties will be followed periodically by round robin tests in a reduced extent to ensure the further harmonisation of measurement procedures. The check of measurering equipments and procedures is an inalienable requirement for the further steps for providing the users with constant film quality. Together with sample tests performed by BAM as indicated in section 4.2 and and the production control by the manufacturer it will be possible to survey the film systems whether they meet the requirements of one of the film classes of EN 584-1. 

In case of mixed systems the procedure must be varied and it would be restricted to the special film systems of interest, of course. Mixed systems would be used by inspection companies and industrial users who normally do not dispose of the equipment for measurements as mentioned above. In these cases instead of a round robin test only periodical measurements of the properties of these mixed film systems by an independent third party institution can be used for film classification and continuous surveillance. 

Round robin tests for the harmonization of the measurements of film system parameters according to EN 584-1... 

At the beginning of the supervision of films systems first of all the influences of the exposure-and processing installations of the project partners on the determination of the film system parameters shall be found out and subsequently the equipments for measurement shjdl be compared one with another. This round robin test comprises in detail ... 

The detection sensitivity of radiography is related among others to the properties and quality of industrial x-ray film systems. Changes of the products, variations due to different emulsions and combinations of products of different manufacturers can influence the decisive properties of film systems as classified in EN 584-1.To ensure the quality of industrial x-ray film systems a system for quality assurance open to all interested parties is proposed which is based on periodical round robin tests and quality controls of the manufacturer or an independent third party institution. 

When the adsorption capacity of a carbon unit is exceeded, there is breakthrough of the contaminant in the treated stream. Eixed beds may be operated in series to allow continuous treatment while spent or exhausted units are replaced with fresh carbon. In series operation, there are two or more units. The majority of the contaminant is removed by the first unit in the series with the downstream units acting as polishing units. When breakthrough occurs in the first or primary unit, it is replaced with fresh carbon and becomes a polishing unit while the next unit in the series takes over and becomes the primary treatment unit. An example of this round-robin operation of a three-carbon bed is shown in Eigure 2. 

Fig. 2. Round robin operation of a tiiree-bed carbon adsorption unit.

J. Homer, Microhardness Testing of Plating Coatings Recent Round-Robin Experiences, ia Ref. 47. 

If the technical staff from the client company recognizes that a toller may be asked to perform new analyses and make operating decisions based upon the results, the client may help the toller develop the needed procedures and skills required to make these decisions. Typically a round robin laboratory qualification exercise will be performed. Samples of known standards and unknown concentrations of the materials to be analyzed for the toll will be prepared and sent to both laboratories. This can help ensure that equipment calibration is synchronized and that the toller is capable of performing accurate measurements. In some cases, the toller may be the party with the chemical, process, or synthesis specific expertise. 

Round robin A process involving an exchange of samples intended to transfer analytical capabilities from the client to the toller to support the toll project. 

Fig. 3.36. Experimental, Fe-related HF- calculated according to [3.74] from plasma SNMS sensitivity factors S(pe)x Ref [3.71] (salts) [3.72] alloys, [3.73] with elements X ordered according to round robins (r.r.). their post-ionization probabilities...

Fig. 2. Results of interfacial shear strength measurements of the same fiber/matrix systems using four different micro-mechanical tests during a round-robin program involving 12 different laboratories, (a) Results for untreated, unsized carbon fibers, (b) Results for carbon fibers with the standard level of surface treatment. Redrawn from ref. [13].

Leung, J. C., Creed, M. J. and Fisher, H. G., Round-Robin Vent Sizing Package Results, Proceedings of the International Symposium on Runaway Reactions, CCPS, Cambridge, MA, March 1989. 

Round Robin No 30 of the ICRPG Working Group on Analytical Chemistry Particle Size Analysis of Nominal 20- to 30-Micron Ammonium Perchlorate with the Mine Safety Appliances Analyzer", RK-TR-69-13 (1969) 40) R.A. Dobbins L.D. Strand, AIAA Joum 8, 1544 (1970) 41) R.W. Hutchinson, Use of... 

M. Roth, Evaluation of Assay Methods for Ammonium Perchlorate , ICRPG Round Robin No 28, PATR 3498 (1966) 16, AD 645935... 

The corrected excitation and emission spectra for quinine sulfate from previous work (17) and from a round-robin exercise (11) are given In Figure 1. The coefficients of variation are also given at each point to Indicate the amount of agreement In measured values from the ten laboratories participating In the round-robin exercise. 

Figure 1. Average corrected emission spectrum (- -) and excitation spectrum (- -) for quinine sulfate In 0.1 mol/L HC10 obtained during round-robin test with ten laboratories coefficient of variation at each wavelength (-t).

Analysis of variance (ANOVA) tests whether one group of subjects (e.g., batch, method, laboratory, etc.) differs from the population of subjects investigated (several batches of one product different methods for the same parameter several laboratories participating in a round-robin test to validate a method, for examples see Refs. 5, 9, 21, 30. Multiple measurements are necessary to establish a benchmark variability ( within-group ) typical for the type of subject. Whenever a difference significantly exceeds this benchmark, at least two populations of subjects are involved. A graphical analogue is the Youden plot (see Fig. 2.1). An additive model is assumed for ANOVA. 

The same parameter is tested on at least two samples by each of several laboratories using the same method (round-robin test 3 2 ), or... 

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. 

An interesting discussion about reliability of size/strain analysis methods can be found in Ref. [29] where the results on peak shape analysis of a round-robin sample are reported and commented. 

In paired comparison tests two different samples are presented and one asks which of the two samples has most of the sensory property of interest, e.g. which of two products has the sweetest taste (Fig. 38.3). The pairs are presented in random order to each assessor and preferably tested twice, reversing the presentation order on the second tasting session. Fairly large numbers (>30) of test subjects are required. If there are more than two samples to be tested, one may compare all possible pairs ( round robin ). Since the number of possible pairs grows rapidly with the number of different products this is only practical for sets of three to six products. By combining the information of all paired comparisons for all panellists one may determine a rank order of the products and determine significant differences. For example, in a paired comparison one compares three food products (A) the usual freeze-dried form, (B) a new freeze-dried product, (C) the new product, not freeze-dried. Each of the three pairs are tested twice by 13 panellists in two different presentation orders, A-B, B-A, A-C, C-A, B-C, C-B. The results are given in Table 38.3. 

One of the first attempts to use a biological RM was for the analysis of the fat content of milk. This was carried out in London in the late i88o s by a number of analytical chemists who were trying to identify adulterated milk. At that time milk was sold impackaged and at least 20 % of the miUc sold in London was adulterated by dilution with water. This work appears to be the first empirical round-robin approach for characterization of a RM. 

It must be remarked that terminology is not consistent and there are many widely used synon)ms. Quality control in this Chapter refers to practices best described as internal quality control. Quahty assessment is often referred to as external quality control, proficiency testing, interlaboratory comparisons, round robins or other terms. Internal Quality Control and External Quality Assessment are preferred because they best describe the objectives for which the RMs are being used, i.e. the immediate and active control of the results being reported from an analytical run or event, and an objective, retrospective assessment of the quality of those results. 

Standardisation of EPDM characterisation tests (molecular composition, stabiliser and oil content) for QC and specification purposes was reported [64,65]. Infrared spectroscopy (rather than HPLC or photometry) is recommended for the determination of the stabiliser content (hindered phenol type) of EP(D)M [65]. Determination of the oil content of oil-extended EPDM is best carried out by Soxhlet extraction using MEK as a solvent [66], A round robin test was reported that evaluated the various techniques currently used in the investigation of unknown rubber compounds (passenger tyre tread stock formulations) [67]. 

As to Irgafos 168 the reader is advised to notice the results of a round-robin involving PP/(Irganox 1076, Irgafos 168) [209a], Ultrasonication at room temperature with anhydrous n-hexane or acetone is a suitable soft extraction mode for the determination of aromatic phosphites and phosphonites, such as Ultranox 626 and Sandostab P-EPQ, which easily degrade in heating extraction procedures [210]. 

Table 3.30 shows the excellent performance of OSM for the extraction of the medium polar additive Irganox 1010. The reader may compare the results with a round-robin comprising the analysis of PP/(Irganox 1010, Irgafos 168) [209a]. 

Applications Dissolution/reprecipitation is claimed to be the most widespread approach to polymer/additive analysis [603], but recent round-robins cast some doubt on this statement. Dissolution appears to be practised much less than LSEs. However, in cases where exhaustive extraction is difficult, e.g. for polyolefins containing high-MW (polymeric) additives, a dissolution/precipitation method is preferred. 

Quantitative analysis of multicomponent additive packages in polymers is difficult subject matter, as evidenced by results of round-robins [110,118,119]. Sample inhomogeneity is often greater than the error in analysis. In procedures entailing extraction/chromatography, the main uncertainty lies in the extraction stage. Chromatographic methods have become a ubiquitous part of quantitative chemical analysis. Dissolution procedures (without precipitation) lead to the most reliable quantitative results, provided that total dissolution can be achieved follow-up SEC-GC is molecular mass-limited by the requirements of GC. Of the various solid-state procedures (Table 10.27), only TG, SHS, and eventually Py, lead to easily obtainable accurate quantitation. 

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