Reference measurements indirect

On the other hand, indirect reference measurements are based on empirical calibration functions obtained experimentally and frequently based on Unear models... 

On the other hand, indirect reference measurements which result in an empirical calibration function, frequently based on a linear model, y = a + b - x + ey see Sect. 2.4, Eq. (2.22), where the intercept a corresponds to... 

In analytical practice, some methods using definitive measurements, in principle, are also calibrated by indirect reference measurements using least squares estimating to provide reliable estimates of b (spectrophotometry, potentiometry, ISE, polarography). 

In the second category of assays, the coupled assay method, activity is measured indirectly. In this method two reactions are involved. The first is the reaction of interest, such as A - B, second, the reaction that converts B to C, might be referred to an indicator reaction, not only because it uses the product of the first reaction (i.e., B) as a substrate, but also because the... 

Community on In-Vitro Diagnostics) is a European legislative regulation directed at in vitro manufacturers. The directive demands that the manufacturer have a quality management system and that products are validated by competent laboratories. It is required that the traceability of values assigned to calibrators or control materials or both must be ensured through available reference measurement procedures and/or available materials of higher order. Explicit statement of the uncertainty of calibrator values is not required, but indirectly the manufacturers have to... 

Unlike direct reference assays, indirect index methods use two separate tests to estimate the free hormone concentration a total serum T4 (or T3) measurement and an assessment of either the serum TBG concentration or the fraction of T4 (or T3) that is free m serum the latter is traditionally derived using equilibrium tracer dialysis or T uptake methods. Results of these tests are then combined mathematically to give estimates of the free hormone concentration. Indirect index-based methods have essentially fallen out of favor in deference to the direct immunoassay methods. 

Figure 9.15 (a) laboratory-scale apparatus for the measurement of the ratio between attracted and injected water [3II, (b) upwelling flow results for three different up-tube lengths and two measurement methodologies [30], Note In the right figure, label "d" refers to the results obtained by direct flow meter measurements while "c" refers to indirect (concentration)... 

The Measuring methods of adsorption amount of flotation reagent on mineral surface are divided into direct method and indirect method. Direct method refers to that the adsorption amount of flotation reagent is direcdy measured. Indirect method refers to that the adsorption amount of flotation reagent is indirectly measured by computing the difference between initial concentration and residual concentration of reagent solution. 

Capacity. Pumps deHver a certain capacity, Q, sometimes referred to as flow, which can be measured directly by venturi, orifice plate (11), or magnetic meters (12) (see Flow measurement). The indirect way to determine capacity is often used. Whereas this method is less accurate than applying a flow meter, it often is the only method available in the field. The total head is measured and the capacity found from the pump head—capacity (H— curve (Fig. 2). More recently, sonic flow meters (13) have been used, which can be installed on the piping without the need for pipe disassembly. These meters are simple to use, but require relatively clean single-phase Hquid for reHable measurements. 

In the USA, there is the ASTM standards and the well-known General Electric requirements. The total useful life of turbine oil is its most important characteristic. ASTM method D943 (IP 157) measures the life indirectly by assessing the useful life of the oxidation inhibitor contained in the formulation and are often referred to as the TOST life of the oil. Rust prevention is generally assessed by the ASTM D665 (IP 135) method. 

Direct or indirect methods may be used to determine moisture in dehydrated foods. Indirect methods must be calibrated in terms of direct methods—the most common of which are the oven, distillation, and Fischer methods. Accuracy of the direct methods is difficult to evaluate except by comparison with a chosen reference method. Several reference methods are reviewed, but none can be given an unqualified recommendation as most practical and suitable for all foods. An indirect measure of moisture is the equilibrium vapor pressure of water, which can be measured easily and accurately. Arguments are presented to show that vapor pressure may be a better index of the stability of dehydrated foods than the moisture content, which has been frequently used for this purpose. 

Measurements of tropospheric HO and H02 concentrations have been accomplished by both direct and indirect means. Direct techniques are based on the measurement of the hydroxyl or hydroperoxyl radical using some physical property of the radicals themselves e.g. optical absorption. Indirect techniques refer to methods based on the measurement of compounds that are uniquely and/or quantitatively formed from or destroyed by HO or HO2. Examples of these techniques for both [HO ] and [HO2 ] will be given. 

The electrolytes Na", and Cl are second only to glucose in being the most frequently run hospital tests. Many clinical chemistry analyzers now contain an ISE module for electrolyte analysis. Most commonly the module will consist of a Na -glass electrode, a valinomycin/PVC electrode, a Ag/AgCl pellet or a quaternary ammonium ion/PVC electrode and a reference electrode. A selective electrode for the bicarbonate ion continues to elude workers in the field. An indirect measurement of HCOf must be made. The sample is usually reacted with acid to evolve carbon dioxide gas which is measured with a traditional Severinghaus type CO2 electrode. Alternatively, the sample is treated with base to convert HCO to CO3 and a carbonate ion-selective electrode is used In this manner, the complete primary electrolyte profile is obtained electrochemically. 

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