Specifity of method

The precision, accuracy, reliability, and specificity of methods to determine 2-hexanone in water and air are not well documented, and additional work is needed in this area. 

Interlaboratory trials with the organiser making detailed assessments of the laboratories is clearly particularly suited to helping individual laboratories and will at least qualitatively indicate the parameters requiring attention. This approach is, however, very expensive in total effort. The Intercal approach does not identify the causes of variability immediately but certainly alleviates the effect and, because trials are on-going, allows improvement to be monitored. Systematic quantification of the effect of individual parameters is probably the most cost effective approach and is the most useful for aiding standards committees to improve the specification of methods, but is of less direct help to individual laboratories. 

Pacheco, C.P. (2002) Sensibility and specificity of methods for Alicyclohacillus detection and quantification a collaborative study. Fruit Processing 12(11), 478-82. 

This review will be more concerned with the determination and maintenance of standards of precision, particularly of reproducibility, than with the assessment of accuracy and specificity of methods in clinical chemistry. This is because accuracy and specificity can be determined in a laboratory in advance of introducing a method, and the limitations of each method in these respects defined and allowed for, whereas the precision obtained for the same method may differ markedly from time to time in one laboratory and from one laboratory to another. The trials of interlaboratory accuracy (Section 1.2) have not so far been able to distinguish fully between inaccuracy and imprecision in the performance of individual laboratories for the chemical determinations under evaluation. Imprecision, however, has probably been the main factor underlying the disturbing findings revealed by these trials, and the emphasis placed in this review upon the search for improved precision and its subsequent maintenance is justified by the fact that most of the work in clinical... 

The above recipe is not directly indicated in [1292], which reports six different recipes for magnetites. Electron micrographs of three powders and specific surface areas of two powders are reported. IEP (data points not reported) was given without specification of method. 

Specifications of methods for determining melting points are given in the British Pharmacopoeia (2000). See also section 4.5.1. 

Our interest in the analysis of nonvolatiles, thus, may involve taste substances or substances that indirectly influence taste or aroma. As mentioned earlier, in the first case, we are interested in the analysis of substances that impart sweetness, tartness, bitterness, saltiness, or unmami sensations. The analysis of these substances is reasonably well defined. In the latter case, the analyses employed are less well defined and are unique to the components one wishes to analyze. For example, we may wish to measure substances (e.g., melanoidins) that interact with sulfur aroma compounds (in coffee). There are no standardized methods for the analysis of melanoidins in foods and thus, the protocols have to be developed. In this chapter, we will only briefly discuss the established methods for the analysis of taste substances. Due to the specificity of methods for the analysis of nonvolatiles that may indirectly influence flavor perception, we will only refer the reader to the literature [93-100]. 

It is a measure of the degree of concern about mycotoxins that a great deal of effort has been expended in increasing the sensitivity and specificity of methods of analysis. Knowledge about the ecology of mycotoxin production and the extent of mycotoxin contamination of food and feeds is usually related to the availability of analytical methods suitable for repetitive wide-ranging screens. Although such methods are available for aflatoxin, zearalenone and ochratoxin, they... 

Specifications and test methods for jet fuel. The specifications of jet fuels are set at the international level and are written into the Aviation Fuel Quality Requirements for Jointly Operated Systems". 

A number of methods have been described in earlier sections whereby the surface free energy or total energy could be estimated. Generally, it was necessary to assume that the surface area was known by some other means conversely, if some estimate of the specific thermodynamic quantity is available, the application may be reversed to give a surface area determination. This is true if the heat of solution of a powder (Section VII-5B), its heat of immersion (Section X-3A), or its solubility increase (Section X-2) are known. 

Experimental investigations of the model system of dye molecules adsorbed onto surfaces of polystyrene spheres have finuly established the sensitivity and surface specificity of the SHG method even for particles of micrometre size [117]. The surface sensitivity of die SHG process has been exploited for probing molecular transport across the bilayer in liposomes [118], for measurement of electrostatic potentials at the surface of small particles [119] and for imaging... 

The principal idea behind the CSP approach is to use input from Classical Molecular Dynamics simulations, carried out for the process of interest as a first preliminary step, in order to simplify a quantum mechanical calculation, implemented in a subsequent, second step. This takes advantage of the fact that classical dynamics offers a reasonable description of many properties of molecular systems, in particular of average quantities. More specifically, the method uses classical MD simulations in order to determine effective... 

An N-atom molecular system may he described by dX Cartesian coordinates. Six independent coordinates (five for linear molecules, three fora single atom) describe translation and rotation of the system as a whole. The remaining coordinates describe the nioleciiUir configuration and the internal structure. Whether you use molecular mechanics, quantum mechanics, or a specific computational method (AMBER, CXDO. etc.), yon can ask for the energy of the system at a specified configuration. This is called a single poin t calculation. ... 

In these methods, the specification of the parameters entering into Fja,v is carried out in the same fashion as in the CNDO/2 approach, except that ... 

HyperChem uses two types of methods in calculations molecular mechanics and quantum mechanics. The quantum mechanics methods implemented in HyperChem include semi-empirical quantum mechanics method and ab initio quantum mechanics method. The molecular mechanics and semi-empirical quantum mechanics methods have several advantages over ab initio methods. Most importantly, these methods are fast. While this may not be important for small molecules, it is certainly important for biomolecules. Another advantage is that for specific and well-parameterized molecular systems, these methods can calculate values that are closer to experiment than lower level ab initio techniques. 

The simplest approximation to the Schrodinger equation is an independent-electron approximation, such as the Hiickel method for Jt-electron systems, developed by E. Hiickel. Later, others, principally Roald Hoffmann of Cornell University, extended the Hiickel approximations to arbitrary systems having both n and a electrons—the Extended Hiickel Theory (EHT) approximation. This chapter describes some of the basics of molecular orbital theory with a view to later explaining the specifics of HyperChem EHT calculations. 

The probabilistic nature of a confidence interval provides an opportunity to ask and answer questions comparing a sample s mean or variance to either the accepted values for its population or similar values obtained for other samples. For example, confidence intervals can be used to answer questions such as Does a newly developed method for the analysis of cholesterol in blood give results that are significantly different from those obtained when using a standard method or Is there a significant variation in the chemical composition of rainwater collected at different sites downwind from a coalburning utility plant In this section we introduce a general approach to the statistical analysis of data. Specific statistical methods of analysis are covered in Section 4F. 

Before we look more closely at specific gravimetric methods and their applications, let s take a moment to develop a broad survey of gravimetry. Later, as you read through the sections of this chapter discussing different gravimetric methods, this survey will help you focus on their similarities. It is usually easier to understand a new method of analysis when you can see its relationship to other similar methods. 

The focus of this chapter is photon spectroscopy, using ultraviolet, visible, and infrared radiation. Because these techniques use a common set of optical devices for dispersing and focusing the radiation, they often are identified as optical spectroscopies. For convenience we will usually use the simpler term spectroscopy in place of photon spectroscopy or optical spectroscopy however, it should be understood that we are considering only a limited part of a much broader area of analytical methods. Before we examine specific spectroscopic methods, however, we first review the properties of electromagnetic radiation. 

An introduction to several of the more common methods of surface and interface analysis has been presented in this article. This treatment is certainly not comprehensive. An ever-expanding number of methods for the interrogation of surfaces and interfaces are available to the analyst. The ones chosen for discussion here were meant to be representative of methods that can answer the more general questions posed at the beginning of this article. The reader is encouraged to pursue further reading on other techniques for specific appHcations in the many excellent monographs on the subject of surface and interface analysis. 

Thermoformability is a property required by the many sheet materials used in the thermoforming industry. These properties are unique for the specific forming methods used, and are best determined by actual thermoforming tests on smaU-scale equipment. The softening or drape temperature of the material, residual stress in the sheet from its manufacture, and its melt strength and viscosity are important parameters relating to this use. 

The pubHcations detailing standards (5—8) generally include both specifications and methods of analysis for the substances. The estabHshment of standards of quaHty for chemicals of any kind presupposes the abiHty to set numerical limits on physical properties, allowable impurities, and strength, and to provide the test methods by which conformity to the requirements may be demonstrated. Tests are considered appHcable only to the specific requirements for which they were written. Modification of a requirement, especially if the change is toward a higher level of purity, often necessitates revision of the test to ensure the test s vaHdity. 

FDA Quality Standards. Although standards for many dmgs and biologicals are included in the USP—NF, and for many food additives in the FCC, the FDA also estabhshes some specifications of its own. In the dmg field, specifications and testing methods for antibiotics and biologicals are set by the FDA. Also, specifications and testing methods are prescribed for colorants. Many food-additive petitions are granted with the requirement that certain specifications are met. 

Immunoaffinity chromatography utilizes the high specificity of antigen—antibody interactions to achieve a separation. The procedure typically involves the binding, to a soHd phase, of a mouse monoclonal antibody which reacts either directly with the protein to be purified or with a closely associated protein which itself binds the product protein. The former approach has been appHed in the preparation of Factor VIII (43) and Factor IX (61) concentrates. The latter method has been used in the preparation of Factor VIII (42) by immobilization of a monoclonal antibody to von WiHebrand factor [109319-16-6] (62), a protein to which Factor VIII binds noncovalenfly. Further purification is necessary downstream of the immunoaffinity step to remove... 

The methods of analysis of the American Oil Chemists Society (AOCS) are the principal procedures followed in the United States and Canada and are official in commercial transactions. When the material is for human consumption or dmg use, it must meet the specifications of the USP (12). Commercial distilled grades of glycerol do not requite purification before analysis by the usual methods. The deterrnination of glycerol content by the periodate method (13), which replaced the acetin and dichromate methods previously used, is more accurate and more specific as well as simpler and more rapid. 

Large quantities of butane are shipped under contract standards rather than under national or worldwide specifications. Most of the petrochemical feedstock materials are sold at purity specifications of 95—99.5 mol %. Butane and butane—petroleum mixtures intended for fuel use are sold worldwide under specifications defined by the Gas Processors Association, and the specifications and test methods have been pubHshed (28). Butanes may be readily detected by gas chromatography. Butanes commonly are stored in caverns (29) or refrigerated tanks. 

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