Discrimination procedures quantitative

However, the availability of (a) chemometric evaluation procedures for qualitative discrimination and quantitative determination [25-28] and (b) the perception that the low band intensities can be advantageously exploited in terms of larger sample thicknesses and therefore much easier sample handling has eventually led to the breakthrough of the NIR technique. 

Discriminant Sensory Analysis. Discriminant sensory analysis, ie, difference testing, is used to determine if a difference can be detected in the flavor of two or more samples by a panel of subjects. These differences may be quantitative, ie, a magnitude can be assigned to the differences but the nature of the difference is not revealed. These procedures yield much less information about the flavor of a food than descriptive analyses, yet are extremely useful eg, a manufacturer might want to substitute one component of a food product with another safer or less expensive one without changing the flavor in any way. Several formulations can be attempted until one is found with flavor characteristics that caimot be discriminated from the original or standard sample. 

A general method has been developed for the estimation of model parameters from experimental observations when the model relating the parameters and input variables to the output responses is a Monte Carlo simulation. The method provides point estimates as well as joint probability regions of the parameters. In comparison to methods based on analytical models, this approach can prove to be more flexible and gives the investigator a more quantitative insight into the effects of parameter values on the model. The parameter estimation technique has been applied to three examples in polymer science, all of which concern sequence distributions in polymer chains. The first is the estimation of binary reactivity ratios for the terminal or Mayo-Lewis copolymerization model from both composition and sequence distribution data. Next a procedure for discriminating between the penultimate and the terminal copolymerization models on the basis of sequence distribution data is described. Finally, the estimation of a parameter required to model the epimerization of isotactic polystyrene is discussed. 

In combination with mass-selective detection (MIM mode), this technique may be ideal for quantitation of trace compounds from complex mixtures. But one should note that labelled internal standards may be discriminated by chemical and/or physical procedures (extraction, distillation, chromatography, derivati-sation). 

In formulating hypotheses for the mechanism of a given complex reaction, and in using different procedures for the selection of one out of many hypotheses (discrimination of hypotheses), the question arises as to the hierarchy of the hypotheses. The intuitive principle of simplicity cannot play the role of a tool for the selection of hypotheses in the case of multiroute reactions because the number of vertices and cycles and the ways of linking cycles in the kinetic graph are already variables. Proceeding from linear mechanisms, we examine here possible approaches to the construction of a quantitative scale for mechanistic complexity or to the selection of a complexity index". 

Submicroliter samples are needed for the capillary on-column injection technique. To counter a general scepticism following the development of this injection technique, excellent quantitative results have been reported [42). The major advantages of this injection procedure seem to be in minimizing thermal decomposition of labile compounds as well as the lack of sample discrimination toward the later eluting components. This latter problem, observed frequently with the vaporizing injector... 

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