Definitions chemical analysis terms

A definition of Chemometrics is a little trickier of come by. The term was originally coined by Kowalski, but nowadays many Chemometricians use the definition by Massart [4], On the other hand, one compilation presents nine different definitions for Chemometrics [5, 6] (including What Chemometricians do , a definition that apparently was suggested only HALF humorously ). But our goal here is not to get into the argument over the definition of the term, so for our current purposes, it is convenient to consider a perhaps somewhat simplified definition of Chemometrics as meaning multivariate methods of data analysis applied to data of chemical interest . 

Another definition of the term chemical analysis is also worth mentioning. The dictionary definition as found in Vogel s Textbook of Quantitative Inorganic Analysis says that chemical analysis is The resolution of a chemical compound into its proximate or ultimate parts the determination of its elements or of the foreign substances it may contain . 

The literature gives a wide range of practical guidelines for the evaluation of method performance characteristics [58]. Besides the diversity of approaches, also the terminology and way of reporting results vary widely. Differences may occur depending on the purpose and the application field of the method, and validation studies may become more difficult as the complexity of the analysis increases [86]. In what follows, terms and formulas are taken from the accepted IUPAC nomenclature for the presentation of results of chemical analysis [66]. For each validation parameter, definitions, ways of expression, determination guidehnes, and acceptance criteria are reported in Table 5. 

Unusual are measurements for which a direct link to the mole is useful. We should probably not talk about traceability in that connection, because that term is defined as a relation between measured values. An acceptable chain of measurements for compound X of established purity, containing element E that has isotope E and that would establish a link to the mole, then would take one of the following general routes the amount of substance (X)->n(E)->n( E)-> (12C) or n(X)->n(E)-> (C)-> (12C). The ratio of atomic masses m( E)lm( 12C) is also involved in the definition, but that ratio is known with a negligible uncertainty compared with the other links in the chain. Clearly, only in a few instances will laboratories attempt to execute such a chain of measurements for a link to the SI unit. Is it fear that such a difficult process is involved in every chemical analysis that has kept so many chemists from using the mole as the way to express chemical measurement values Or is it just habit and the convenience of a balance that subconsciously links amount of substance to amount of mass ... 

Previously the authors have brought into discussion principles for traceability in chemical analysis [1], In this Journal is also the first part of this contribution [2] on protocols for traceability of analytical-chemical measurements. This first part is intended mainly for specialists who develop such protocols. It deals with terminology and definitions used when describing protocols for traceability1. These terms are mostly taken from recognized literature sources [3-7], Analysts, who want to judge the applicability of an established protocol and to use it, will be familiar with most of these terms and find others self explanatory. They may, nev-... 

Even a cursory perusal of any analytical journal must lead one to the conclusion that trace and ultratrace analyses is a domain of chemical analysis that is gaining in importance. This conclusion is corroborated not only by the feelings and opinions of analysts. According to the current IUPAC definition of the term trace component, the limit from which we can talk about trace analysis is the concentration of 100 ppm (100 pg g ) Naturally, this limit is purely conventional and is not constant. As recently as 30 years ago, trace analysis was understood to denote activities aiming to determine components at a concentration level one order of magnitude higher, that is, below 1000 ppm, or 0.1%. 

This correspondence between facts, ideas, and words would allow Lavoisier to formulate a chemical algebra or embryonic chemical equations. Insofar as each chemical substance was designated by a unique idea and a unique word, chemists could trace their operations as an algebra of these words. The definition of elements as the limit of chemical analysis provided the first step in this chemical algebra. Each substance that was stabilized in analytic practice would be given a unique identity and a unique name. Their combination would be reflected in the name of the compound in the same way that the name of a neutral salt was given in terms of its acid and alkali. Ideally, chemical nomenclature should be designed so that the addition or subtraction of chemical substances would be reflected exactly in the name. 

The nomenclature reform of the French chemists was of fundamental importance, replacing the old body-spirit terminology with new terms, based on oxygen. The calx was now termed the oxide, and the spirit of vitriol became sulfuric acid. The assumption that oxygen was the acid generator, as its name implied, was flawed, but the systematic nomenclature based on the increase of acidity with increase of oxygen content lived on, e.g. the acidic component of the sulfides, sulfites, and sulfates. The definition of a chemical element as the latest term whereat chemical analysis has arrived ... 

The results of most investigations performed in clinical chemistry laboratories are expressed in quantitative terms, and the characteristics of the methods adopted by different laboratories can therefore be assessed according to the standard criteria of quantitative chemical analysis. In such an assessment, definitions of terminology are important, and this section defines and discusses the following terms used frequently in this review ... 

The definitions given below are not always the official statistical or metrological definition. They are given in the context of chemical analysis, and are the authors best attempt at understandable descriptions of the terms. 

In discussing the manufacture of activated carbon it is important to keep in mind that the term activated carbon comprises a family of substances. None of the mpmtw nf the.family is characterized by a definite structural formula nor can any be separately identified by chemical analysis. Our only basis for differentiating is by adsorptive and catalytic properties. As is well known, carbons from such... 

The comprehensive definition for a chemical sensor is a device that transforms chemical information, ranging from the concentration of a specific sample component to total composition analysis, into an analytically useful signal [3]. However, the chemical sensors are the far better system than the standard analysis of chemical in terms of (1) produce a qualitative output, (2) can often be easier to automate, and (3) can be used in real-time analysis. For various chemical sensors different operating... 

Qualitative headspace analysis is used in many applications to determine differences between selected samples and to assess the importance of specific compoimds in defining the aroma character of certain substances. This approach is often termed fingerprinting as in many instances the composition remains chemically unknown. For additional qualitative data, headspace may be used in conjunction with knowledge of GC retention data or with GC-MS techniques for a more definitive chemical identification. 

In this statement, Lavoisier cut the bond between the old search for ultimate elements or principles and the chemical analysis that had been developing alongside that search for many decades. As we have seen above, that bond had been further elaborated and refined, especially by G. E. Stahl and P. J. Macquer. By contrast, Lavoiser proclaimed that it was metaphysical ballast, which caused endless problems. One of his main achievements, which may justify to some extent the claim that his chemistry was revolutionary, was the rigid destruction of the many sophisticated links his predecessors had created between experimental analysis and its perceptible analytical products, on the one hand, and theories of matter such as the philosophy of principles and atomism, on the other. Lavoisier s definition of elements or principles as substances which cannot be further decomposed by chemical analysis came as a postulate we must not take elements to be more than substances that can actually be isolated from more compound substances in the laboratory and we must not speculate about the possibility of further decomposing substances as long as we cannot achieve that decomposition in practice. This definition of element was relative, that is, it depended on the available tools and techniques of chemical analysis. Lavoisier did not argue theoretically for his notion of element, and he did not exclude the idea that simpler elements existed than the ones hitherto isolated by chemical art. Therefore he substituted the term simple substance for the ancient term element. In so doing he left open some space for theoretical speculation about the proper ultimate... 

This is a particularly important subcommittee, since the work in this area affects the activities of all the other subcommittees. The scope of the subcommittee is to standardize the definitions of the terms used in surface chemical analysis (31. At present eight countries are participating actively in the work of the subcommittee under the guidance of Dr. M. P. Seah from the United Kingdom. 

The lUPAC (International Union for Pure and Applied Chemistry) recommends the following definitions for the terms chemical species , speciation analysis and speciation ... 

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