Composite proportional sample procedure

The composite proportional sample (COMP) procedure is a method that actually aims to collect samples of each draw of water used for dietetic purposes at the monitored tap. This is, therefore, the only procedure that takes into account all variations within one week. Thus, the composite proportional sample should be considered to be the only really representative sample, i.e. representative for the average weekly intake of the consumers sharing the tested tap during the test week. 

By definition, the proportional sampling procedure scores 100 % for the criteria of representativeness and reproducibility. However, this applies only when consumers operate the proportional device correctly. To test whether the consiuner has used the device correctly, the volume of the composite proportional sample can be checked. In some test areas the volmne of the composite proportional sample was noted and used to calculate the average daily water consumption per person. Figure 3.7 shows the water consumption distribution for these test areas, and Figure 3.8 shows the... 

In summary, all tested sampling procedures show a linear relationship with the composite proportional sample, albeit that the correlation is poor. RDT and the 30-minute stagnation samples, 30MS1, 30MS2 and 30MSA show the best correlation R = 0.5-0.6). RDT however, generally seems to overestimate COMP (slope > 1), whereas 30MS somewhat rmderestimates COMP (slope > 1). FF clearly shows the poorest relationship to COMP = 0.29 and the slope is 0.57. 

The copolymer composition equation relates the r s to either the ratio [Eq. (7.15)] or the mole fraction [Eq. (7.18)] of the monomers in the feedstock and repeat units in the copolymer. To use this equation to evaluate rj and V2, the composition of a copolymer resulting from a feedstock of known composition must be measured. The composition of the feedstock itself must be known also, but we assume this poses no problems. The copolymer specimen must be obtained by proper sampling procedures, and purified of extraneous materials. Remember that monomers, initiators, and possibly solvents are involved in these reactions also, even though we have been focusing attention on the copolymer alone. The proportions of the two kinds of repeat unit in the copolymer is then determined by either chemical or physical methods. Elemental analysis has been the chemical method most widely used, although analysis for functional groups is also employed. 

Because much of Wollaston s platinum was produced by this second process, we decided to purify a crude platinum sample by this method to see if the purity of the product was adversely affected. The analytical results are given in Table IV and indicate that the platinum purified by the second process did not differ in any important respects from that obtained by the first process. The slight decrease in platinum content (98.57% to 97.35%) is balanced by small increases in the levels of the metallic impurities. Given the inherent uncertainties in the sampling procedure, the compositional differences between the platinum produced by the two methods are insignificant. The relative proportions of... 

Spectra of s.o. samples differed markedly from those of a.p. samples and were unaffected by a subsequent evacuation up to 673 K (Fig. 4, a). Spectra consisted of a composite envelope of heavily overlapping bands at 980-1070 cm-, with two weak bands at 874 and 894 cm-. Irrespective of the preparation method, the integrated area (cm- ) of the composite band at 980-1070 cm- was proportional to the V-content up to 3 atoms nm-2. An analysis of spectra by the curve-fitting procedure showed the presence of several V=0 modes. The relative intensity of the various peaks contributing to the composite band depended only on the V-content and did not depend on the method used for preparing the catalysts. Samples with V > 3 atoms nm-2 R-spectra features similar to those of pure V2O5 (spectrum 8 in Fig. 4, a). 

Thus for an ideal two-phase system the total calibrated intensity that is scattered into the reciprocal space is the product of the square of the contrast between the phases and the product of the volume fractions of the phases, Vi (1 — Vi) = V1V2. V1V2 is the composition parameter66 of a two-phase system which is accessible in SAXS experiments. The total intensity of the photons scattered into space is thus independent from the arrangement and the shapes of the particles in the material (i.e., the topology). Moreover, Eq. (8.54) shows that in the raw data the intensity is as well proportional to the irradiated volume. From this fact a technical procedure to adjust the intensity that falls on the detector is readily established. If, for example, we do not receive a number of counts that is sufficient for good counting statistics, we may open the slits or increase the thickness of a thin sample. 

A further advancement comes from inter-laboratory comparison of two standards having different isotopic composition that can be used for a normalization procedure correcting for all proportional errors due to mass spechomehy and to sample preparation. Ideally, the two standard samples should have isotope raUos as different as possible, but still within the range of natural variations. There are, however, some problems connected with data normalization, which are still under debate. For example, the CO2 equilibration of waters and the acid extraction of CO2 from carbonates are indirect analytical procedures, involving temperature-dependent fractionation factors (whose values are not beyond experimental uncertainties) with respect to the original samples and which might be re-evaluated on the normalized scale. 

Vacancy chromatography has a number of applications areas in practice, none of which appear to have been extensively exploited. One particularly interesting application is that of quality control. If a particular product has a number of components present, and their relative composition must be kept constant as in, for example, a pharmaceutical product, Vacancy Chromatography can provide a particularly simple analytical procedure for quality control. The mobile phase is made up containing the components of the product in the specified proportions, but at a low concentration suitable for LC analysis. A sample of the product is dissolved in some pure mobile phase at the same total mass concentration as the standards in the mobile phase. A sample is then injected on the column. If the product contains the components in the specified proportion, no peaks will appear on the chromatogram as the sample and mobile phase will have the same composition. If any component is in excess, it will show a positive peak. If any component is present below specifications, it will show a negative peak. The size of the peak will provide an accurate measure of the difference between the sample and that of the required standard. 

For chemical analysis, we used a mild acid-extraction procedure, based on recent experimental work (13, 26, 36, 37). We chose the extraction procedure over total digestion of the sample (35) because we are interested specifically in anthropogenic inputs by way of inorganic P and other elements, and not the total compositional chemistry (i.e., anthropogenic and diagenetic inputs). The extractant we used, composed of 20 ml of dilute 0.60 molar hydrochloric acid and 0.16 molar nitric acid, has been experimentally determined to remove soluble and readily labile P and other elements. While the extraction is not always proportional to the total P (or other elements) in soil, for activity area research we are concerned with the spatial patterns of elemental concentrations rather than absolute concentrations, as many variables affect elemental levels in soils (39, 40). 

The raw juice in the diffusors is not of uniform composition, so that the whole, mass should be well mixed before sampling or, if this is not possible, amounts proportional to the bulks in the different parts should be taken and mixed. A similar procedure is followed with the defecated juice, the sample in either case being stored in a tightly stoppered bottle. 

The state of tin in Pt/Sn/alumina catalysts was investigated bv Li and Shia (25) via Mossbauer spectroscopy (i/9Sn enriched isotopes) and XPS. The former technique indicated the presence of Sn+, Sn+2 and Sn, in proportions that depended on the method of preparation, but in all cases the Sn+4 component dominated. These conclusions were confirmed by the XPS experiments. Additional TPR tests on the reduced catalyst and on samples exposed to air showed that reoxidation of Pt/Sn/alumina reduced preparations was rather slow, confirming our EXAFS observations. The presence of zero valent tin in similar preparations, using the acetone complexation procedure, was recently confirmed by Li, Stencel and Davis (12) in an extended XPS investigation. For reduced samples, with a Pt Sn ratio 1 5, these authors estimated that approximately 68% of the tin was in the metallic state. However, they observed that exposure of the sample to air for 10 minutes entirely eliminated the XPS detectable Sn°. Their data also indicated that upon reduction, chlorine migrated from the surface to the alumina. Thus, XPS which measures surface composition indicates a higher sensitivity to oxidation than was demonstrated by our EXAFS experiments, which is a bulk diagnostic. 

The Formation of Cubic Ice in Pure Water Droplets as a Function of Droplet Size. We have investigated the formation of cubic ice in pure water droplets as a function of droplet size. These droplets were cooled at a rate of 10 K min to 173 K where a diffraction pattern was measured between 26 = 20 to 50°. The diffraction patterns are presented elsewhere. We have used the least squared fitting procedure to determine the amount of cubic ice in each frozen emulsion sample and the results are reported in Figure 4. The proportions of cubic ice reported by us previously are a little different to those reported here, because our fitting routine has improved (we now allow the normalisation parameter associated with the composite pattern to vary during the least squared fitting routine, which improves the quality of the fits). 

The method of manufacture must ensure reproducibility between batches and the conditions should be chosen to preclude the possibility of contamination with other plastic materials or their constituents. Containers made should be similar in every respect to the type sample. For the testing on the type sample to remain valid, there must be no change in the composition of the material or in the manufacturing process, particularly with regard to temperature to which the plastic material is exposed during conversion or subsequent procedures such as sterilisation. Scrap materials should not be used. Recycling excess material of a well-defined nature and proportion may be permitted if the appropriate validation is carried out. 

The VI of a base stock depends on its chemical composition the value for a sample reflects the components present and proportions and boiling range, but there is no published procedure for calculating VI based on composition. The converse, calculating composition from VI, will someday materialize, but will have to solve the issue that there generally are multiple compositions that will give the same VI. 

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