Assessment of Analytical Information

The principle of chemical measurements, as realized in the analytical process (Fig. 2.1), corresponds in its significant steps to the general principle of information processing (Fig. 3.1). 

According to classical information theory, founded by Shannon [1948] (see also Shannon and Weaver [1949]), information is eliminated uncertainty about an occurrence or an object, obtained by a message or an experiment. Information is always bound up with signals. They are the carriers of information in the form of definite states or processes of material systems (Eckschlager and Danzer [1994] Danzer [2004]) see Sect. 3.1. 

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Again we see a significant community effect resulting from a failure to properly manage the assessment of risk. Information was released based on an inappropriate analytical base without adequate epidemiological information or independent review. 

Complementary Information by Additional Detectors or Mass Spectrometry WIN Not Save the World It is a well-known saying that mass spectrometry is one of the most powerful analytical tools the world has ever seen. Without a shadow of a doubt, the sheer amount, the detail degree, and the accuracy of analytical information provided by mass spectrometers is very impressive however, they cannot solve the impossible, and performing miracles beyond common sense is also not their business. Here is a small collection of the most widespread hypes and (partially) wrong assessments on mass spectrometers ... 

Analytical information taken from a chromatogram has almost exclusively involved either retention data (retention times, capacity factors, etc.) for peak identification or peak heights and peak areas for quantitative assessment. The width of the peak has been rarely used for analytical purposes, except occasionally to obtain approximate values for peak areas. Nevertheless, as seen from the Rate Theory, the peak width is inversely proportional to the solute diffusivity which, in turn, is a function of the solute molecular weight. It follows that for high molecular weight materials, particularly those that cannot be volatalized in the ionization source of a mass spectrometer, peak width measurement offers an approximate source of molecular weight data for very intractable solutes. 

Commission Directive 96/46/EC of 16 July 1996, amending Annex II to the Directive 91/414/EEC, is the basis for the assessment of residue analytical methods for crops, food, feed, and environmental samples." Provisions of this Directive cover methods required for post-registration control and monitoring purposes but not data generation methods. Because it is necessary to provide applicants as precisely as possible with details on the required information, the guidance document S ANCO/825/00 rev. 6 dated 20 June 2000 (formerly 8064/VI/97 rev. 4, dated 5 December 1998)" was elaborated by the Commission Services in cooperation with the Member States. 

Additionally, the integration of geographic information system (GIS) with analytical data is an effective procedure in addressing the problem of spatial and temporal variability of the different parameters involved in the environmental fate of chemicals. Based on accurate local estimations, GIS-based models would then also allow deriving realistic and representative spatially averaged regional PECs. Table 4 shows some studies that have used GIS-based methodologies to perform a site-specific risk assessment of PECs in different exposed ecosystems. 

The situation becomes more complex when aspects of the trueness of analytical results are included in the assessment. Trueness of information cannot be considered neither by the classical Shannon model nor by Kullback s divergence measure if information. Instead, a model that takes account of three distributions, viz the uniform expectation range, po(x), the distribution of the measured values, p(x), and that of the true value, r(x), as shown in Fig. 9.5, must be applied. 

The Kerridge-Bongard model of information is of great importance in quality assurance, in particular for the assessment of interlaboratory studies. Examples of the information-theoretical evaluation of analytical results within the context of interlaboratory comparisons have been given by Danzer et al. [1987, 2001], Wienke et al. [1991] and Danzer [1993]. 

On the other hand, not only the enormous number of signals in multicomponent methods but also the large number of species that can be detected in highly resolved spectra and chromatograms, respectively, influence the information amount. Therefore, Matherny and Eckschlager [1996] proposed the introduction of so-called relevancy coefficients, k, into the system of information-theoretical assessment. In analytical practice, the coefficients k can be considered as being weight factors of the information contents of the respective species with which Eq. (9.21) becomes... 

Based on the information flow, a number of information-theoretical performance quantities can be derived, and some important ones are compiled in Table 9.2. The information performance of analytical methods can be related to the information requirement of an given analytical problem. The resulting measures, information efficiency and information profitability, may be used to assess economical aspects of analytical chemistry. 

Each of these considerations is addressed in detail below. Potential contractors are asked to provide the information requested in Part A of this document when submitting ROAME forms in order to aid the assessment of the relative merits of each project from the analytical/data quality point of view. This information is best supplied in tabular form, for example that outlined in Part A, but may be provided in another format if thought appropriate. The tables should be expanded as necessary. Parts B and C should not be completed when submitting completed ROAME forms. 

Part A describes the information that is to be provided by potential contractors at the time that the ROAME Bs are completed for submission to the Group. Provision of this information will permit any FSA Analytical Group and customers to make an informed assessment and comparison of the analytical quality of the results that will be obtained from the potential contractors bidding for the project. Previously potential contractors have not been given defined guidance on the analytical quality assurance information required of them and this has made comparison between potential contractors difficult. Part A is supplied to potential contractors at the same time as further information about the project is supplied. 

A natural extension of analytical automation is some means of data processing all the results that are generated. This usually takes the form of a central computer which accepts information from different analysers for presentation in a useful manner. The identification of a sample and the tests performed are typed in using a keyboard and the computer collates all the data on each sample. As well as collecting information, computing and statistically assessing results, an important facility of the computer lies in its ability to store information for future recall via a visual display unit. 

The assessment of health effects due to exposure to the total petroleum hydrocarbons requires much more detailed information than what is provided by a single total petroleum hydrocarbon value. More detailed physical and chemical properties and analytical information on the total petroleum hydrocarbons fraction and its components are required. Indeed, a critical aspect of assessing the toxic effects of the total petroleum hydrocarbons is the measurement of the compounds, and the first task is to appreciate the origin of the various fractions (compounds) of the total petroleum hydrocarbons. Transport fractions are determined by several chemical and physical properties (i.e., solubility, vapor pressure, and propensity to bind with soil and organic particles). These properties are the basis of measures of teachability and volatility of individual hydrocarbons and transport fractions (Chapters 8, 9, and 10). 

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