Measurement material quantities

In Chapter 2 we discuss briefly the thermodynamic functions whereby the abstract fugacities are related to the measurable, real quantities temperature, pressure, and composition. This formulation is then given more completely in Chapters 3 and 4, which present detailed material on vapor-phase and liquid-phase fugacities, respectively. 

Estimating Minimum Sample Quantity for Moisture Measurement Estimates of material quantity for testing moisture content depend on mechanisms of moisture distribution in the material. Moisture is physically retained on particle surfaces, chemically adsorbed on surfaces and within pores of particulate solids, and contained as an internal constituent of solids. Significant internal moisture is most often encountered in organic and agricultural source materials. 

Amplification methods. In determinations in which a very small amount of material is to be measured this may be beyond the limits of the apparatus available. In these circumstances if the small amount of material can be reacted in such a way that every molecule produces two or more molecules of some other measurable material, the resultant amplification may then bring the quantity to be determined within the scope of the apparatus or method available. 

Analytical laboratories need to check their performance with regard to the production of accurate results with satisfactory precision. The most desirable way to ensure the reliability of analytical results is the participation of laboratories into regular interlaboratory tests. An interlaboratory study has to be understood as a study in which several laboratories measure a quantity in one or more identical portions of homogeneous, stable materials under documented conditions, the result of which are compiled into a single document (IUPAC [1994] Prichard et al. [2001]). 

A study in which several laboratories measure a quantity in one or more identical portions of homogeneous, stable materials under documented conditions, the results of which are compiled into a single report . 

Dual-energy CT capability, providing measurement of a second, independent material quantity Zgfr of candidate threat objects, is expected to aid significantly in reducing false alarm rates and thereby to improve performance over single-energy CT systems. 

Precision describes the reproducibility of a result. If you measure a quantity several times and the values agree closely with one another, your measurement is precise. If the values vary widely, your measurement is not precise. Accuracy describes how close a measured value is to the true value. If a known standard is available (such as a Standard Reference Material described in Box 3-1), accuracy is how close your value is to the known value. 

With techniques of peak measurement in hand the next important step in quantitative analysis is to convert the size of the peak into some measure of quantity of the particular material of interest. In some fashion this involves chromatographing known amounts of the materials to be analyzed and measuring their peak sizes, then, depending on the technique to be used, relating the unknown peaks to the known amounts through peak size. 

Quiescent Solutions. Coulometry at constant current provides a simple method for measuring the quantity of electrogenerated species as long as the reaction proceeds with 100% current efficiency. However, this condition breaks down with depletion of the electroactive material in the diffusion layer (cf. chronopotentiometric transitions see Fig. 4.3). For low values of the applied current, the thermal and density gradients supplement diffusion sufficiently to sustain electrolysis without the potential shifting to a different reaction. This mode of radical generation has been employed successfully in the study of stable species. 

Another possibility is to heat the surface up slowly and to measure the quantity of desorbed material versus the temperature. This is called temperature programmed desorption (TPD) or thermal desorption spectroscopy (TDS). Usually distinct maximums are observed which correspond to the breaking of specific bonds. 

Measurement of quantities in samples of biological origins Presentation of reference measurement procedures Description of reference materials... 

ISO/TC 212/WG2 N65 prEN 17511 (2000) In vitro diagnostic medical devices Measurement of quantities in samples of biological origin Metro-logical traceability of values assigned to calibrators and control material. ISO/CEN, Geneva, Switzerland EU Lex Directive 98/79 EC (1998)... 

Potency and purity. Chromatographic methods are frequently used to measure the quantity of a single active species which is equated to the potency for most drugs. Related substances may be quantitated by similar procedures, usually incorporating gradient elution (for ion exchange or RP-HPLC methods) to insure that all species are observed. The related substance assay defines the purity of the material. The performance characteristics of these methods are crucial for the correct evaluation of potency and purity. 

Microscopy. A broad definition of microscopy is the observation and measurement of optical parameters with any instrument that uses energy sources such as photons, electrons or X-rays to provide an enlarged image of an object. Energetic material parameters that have been observed and measured include quantity, size, shape and color (Expls Refs 12-15, 19, 20, 25, 25a, 27, 28,... 

Viscoelastic Master Curves. In order to evaluate whether a given material is suitable for a particular damping application we need to know its viscoelastic properties over a broad range of temperature and frequency. However, in most instances we can measure these quantities only over a limited range of temperature or frequency. The data are then extended to other temperatures and frequencies by using the time-temperature-superposition procedure (5, 6) to form viscoelastic master curves that correlate the data and extend its utility. 

International Organization for Standardization (ISO). In vitro diagnostic medical devices— Measurement of quantities in biological samples—metrological trace-ability of values assigned to cafibrators and control materials (17511). Geneva ISO, 2003. 

In vitro diagnostic medical devicesr measurement of quantities in biological samples— metrological traceability of values for catalytic concentration of enzymes assigned calibrators and control materials... 

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