Primary measurement method

The fundamentals and several applications of isotope dilution mass spectrometry requiring accurate isotope ratio measurements are reviewed by Heumann.50,51 Today isotope dilution mass spectrometry (IDMS) is recognized as a primary measurement method, by means of which accurate results with sufficiently small uncertainties can be achieved and therefore it has been used in certifying the composition of reference materials. A requirement of isotope dilution analysis in mass spectrometry is to achieve equilibration of spike and sample so that very careful sample preparation steps, especially in solid mass spectrometry, are necessary when a homogeneous sample spike mixture is to be prepared. 

Small particles deposited on a surface can be observed by optical or electron miemscopy, depending on their size. This is the primary measurement method upon which most aerosol sizing methods arc tiki male ly based. 

It has been proved lately that the NAA method of Mo determination meets the requirements of primary ratio methods of measurements. 

The primary reference method used for measuring carbon monoxide in the United States is based on nondispersive infrared (NDIR) photometry (1, 2). The principle involved is the preferential absorption of infrared radiation by carbon monoxide. Figure 14-1 is a schematic representation of an NDIR analyzer. The analyzer has a hot filament source of infrared radiation, a chopper, a sample cell, reference cell, and a detector. The reference cell is filled with a non-infrared-absorbing gas, and the sample cell is continuously flushed with ambient air containing an unknown amount of CO. The detector cell is divided into two compartments by a flexible membrane, with each compartment filled with CO. Movement of the membrane causes a change in electrical capacitance in a control circuit whose signal is processed and fed to a recorder. 

The primary classical method of study of Langmuir monolayers is clearly that of recording H-A isotherms. Another classical method applied to the study of Langmuir monolayers is the measurement of surface potential [8,9], which is sensitive to changes in the orientation and density of the molecular dipoles of the monolayer. In addition, surface potential fluctuations were clearly observed in the coexistence region of palmitic acid [35]. 

The measurement method used for the homogeneity study should have a very good repeatability. For a stability study, where often samples are measured at different days, the reproducibility of the measurement method is of primary importance. 

The amount of total lead in the blood can be measured to determine if exposure to lead has occurred. This test can tell if you have been recently exposed to lead. Lead can be measured lead in teeth or bones by X-ray techniques, but these methods are not widely available. These tests tell about long-term exposures to lead. Exposure to lead can be evaluated by measuring erythrocyte protoporphyrin (EP) in blood samples. EP is a part of red blood cells known to increase when the amount of lead in the blood is high. However, the EP level is not sensitive enough to identify children with elevated blood lead levels below about 25 micrograms per deciliter ( ig/dL). For this reason, the primary screening method is measurement of blood lead. For more information on tests to measure lead in the body, see Chapters 2 and 6. 

The primary measure of the amount of free radical must depend on those properties unambiguously due to the unpaired electron. In the past the most common method has been the measurement of the paramagnetic susceptibility, now subject to difficulties of quantitative interpretation. The method of paramagnetic resonance absorption is... 

Gravimetric analysis is a wet chemical method of analysis in which the measurement of weight is the primary measurement, and most of the time the only measurement, that is made on the analyte and its matrices. 

The experimental system consists of a PBC system and a measurement system. The PBC system consists of a conversion system and a combustion system, according to the three-step model, and primary and secondary air lines. A boiler system is not required to realise the measurement method. The measurement system consists of twelve measuring devices (sensors) and a data acquisition system. 

The hardware of the method is a newly constructed experimental PBC system. It is designed according to the three-step model. The object (variable) of the measurement method is the conversion system, which can be varied that is, different conversion systems in small-scale range (<300 kW) can be studied by this method. The method works well on both continuous and batch conversion systems. However, the primary and secondary air flow need to be constant during the test. 

The control of NO from stationary sources includes techniques of modification of the combustion stage (primary measures) and treatment of the effluent gases (secondary measures). The use oflow-temperature NO,.burners, over fire air (OFA), fiue gas recirculation, fuel reburning, staged combustion and water or steam injection are examples of primary measures they are preliminarily attempted, extensively applied and guarantee NO reduction levels of the order of 50% and more. However, they typically do not fit the most stringent emission standards so that secondary measures or flue gas treatment methods must also be applied. 

Any dosimeter used to determine absorbed dose in an irradiated product has to be calibrated. The adiabatic character of electron beam deposition is used in calorimetry, which is the primary absolute method of measuring the absorbed dose (energy per unit mass). An example of the instrument for this purpose is the water calorimeter developed in Ris0 National Laboratory in Denmark. " This calorimeter is reported to be suitable for electrons from a linear accelerator with energies higher than 5 MeV and... 

A primary measurement standard is expected to have a known quantity value with minimum uncertainty, although this is not specified as such in the definitions. Because the measurement uncertainty is propagated down the calibration hierarchy, you should start with as small an uncertainty as possible and choose methods to establish purity of primary reference materials with this in mind. 

Measurements of the wave-lengths of lines in the high frequency spectra of iodine and tellurium by the primary ray method have given... 

The ideal humidity instrument would he n linear, wide-range pressure gage, specific to water vapor and employing a primary or fundamental measuring method. Such an instrument, although physically possible, would be cumbersome. Most humidity measurements arc made hy some secondary instrument which is responsive io humidity-related phenomena. 

A primary method [2] is one that is capable of operation at the highest metrological level, which can be completely described and for which a complete uncertainty statement can be produced in SI units. The amount of substance can be measured either directly, without reference to any other chemical standard, or indirectly, by use of a ratio method which relates the amount of unknown entity X to a chemical standard. Primary direct methods, such as gravimetry and certain electrochemical and thermal methods are the exceptions in chemistry, as the majority of measurements are made indirectly by comparison with other pure substance RMs as discussed above and below. These ratio methods include isotope dilution mass spectrometry and chromatographic and classical methods. Hence the importance of pure substance RMs. 

This example is of a traceability [1] protocol [2] for the chemical measurement of an element by a primary method of measurement [3]. It can be used for the certification of a single-element reference material by a national reference laboratory. This protocol relates to a very pure strontium nitrate solution, stabilized by 10% (by volume) nitric acid1. This solution is to be certified for the amount of strontium substance n(Sr) per unit mass of aqueous solution m (sol). The general measurement method described is based in part on the experience of certifying a currently available certified reference material (CRM) [4], Standard Reference Material (SRM) 3153a [5],... 

In 1999, a Working Group on Instrumentation in Electrochemical Analysis (WG 5) was created by the Technical Committee - Laboratory Equipment of the European Committee for Standardisation (CEN/TC 332). The standard relates to requirements for how to establish traceability between pH measurements performed by the user and the primary reference method using hydrogen electrodes. The revised IUPAC draft for pH is intended to serve as a basis for the new European standard on pH. It has been clearly stated that this standardisation work will not duplicate the work already completed by IUPAC or by the International Electrotechnical Commission (IEC). 

Most of the primary measurement standards are the realization of the SI units, and are under custody of each country s National Metrology Institute (NMI). The link between the realization of the SI units and primary standards is established through primary methods of measurement. These are methods which do not require any reference of the same quantity. Additionally, through a series of comparisons between NMIs, comparability of measurements among traceable measurement systems at international level are recognized by each country. 

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