Multidetermination

Teyler, T. J. Cavus, I., Coussens, C. et al. Multideterminant role of calcium in hippocampal synaptic plasticity. Hippocampus, 4 623-634,1994. 

Depending on their sensing ability, flow-through sensors can be classified into single-parameter and multi-parameter according to whether they can sense one or more analytes on passage of each sample. Multideterminations usually rely on the use of an instrument e.g. a diode array spectrophotometer) for virtually simultaneous multidetection e.g. [20]). 

FLOW-THROUGH SENSORS FOR MULTIDETERMINATIONS BASED ON INTEGRATED RETENTION AND DETECTION... 

Sensors allowing two or more analytes to be determined by a simple procedure are technically more complex than single-parameter sensors, but also more advantageous, which justifies the R D endeavours devoted to them. Few multi-parameter sensors have so far been developed, however, and even fewer are actually operative, of which those commercially available are included. Progress in this area is therefore much needed and desired. Multideterminations based on sensors can be accomplished (a) by using a detector capable of distinguishing the signal produeed by each analyte, whether as... 

Multideterminations with ISEs entail using as many sensors as species are to be determined. Their placement in the hydrodynamic system used is dictated by both their selectivity and the way in which acquired data are to be subsequently processed. 

Figure 5.13 — Irreversible-reusable flow-through sensor for the kinetic multidetermination of phosphate and silicate based on integrated sorption of a reaction product, reaction (/ situ reduction) and photometric detection. (A) Microsensor block (1) and components (2). (B) Continuous-flow configuration coupled on-line to the sensor. P peristaltic pumps SV switching valve W waste. For details, see text. (Reproduced from [39] with permission of the American Chemical Society).

Cortina, M., Duran, A., Alegret, S., and Valle, M. A. (2006). Sequential injection electronic tongue employing the transient response from potentiometric sensors for anion multidetermination. Anal. Bioanal. Chem. 385(7), 1186-1194. 

The application of this concept to liquid samples is what we already refer to electronic tongue . It entails the use of multidimensional information coming from an array of chemical sensors, mimicking the animal sense of taste. As several possibilities exist on the side of which sensors form the array, the general response shown by the different sensors used is of paramount importance that is, cross-selectivity features are needed in order to profit from the multidimensional aspects of the information [7]. The performance of electronic tongues can be suited not only to qualitative purposes like identification of species and classification of sample varieties, but also to quantitative uses, normally the multidetermination of a set of chemical species, an interesting objective for process control. A more bioinspired trend is the artificial taste [8] in order to perform automated taste perception, especially in the industrial field. 

An ANN is a systematic procedure for data processing inspired by the nervous system function in animals. It tries to reproduce the brain logical operation using a collection of neuron-like entities to perform processing of input data. Furthermore, it is an example of a connectionist model, in which many small logical units are connected in a network [52]. Let us consider the proposed case, a multidetermination application employing an array of ISEs as input data. In a rather complex system,... 

Fig. 30.3. The electronic tongue concept applied for multidetermination employing a neural network model.

Some multidetermination cases employing electronic tongues with ISE arrays and ANNs developed in our laboratories... 

This chapter has presented the detailed application of electronic tongues as analytical systems for multidetermination of species, in batch conditions, and also integrated in FIA and SIA systems. The preferred chemo-metrics tool to model its response, ANNs, has been presented in detail. The different precautions for its use together with options and configurations have been described. The ways employed to check the goodness of fit of a developed response model have also been explained. In our applications, we usually employ a multiple output ANN, but nobody impedes the use of a different ANN with a single output for each species considered, except for the training effort which is multiplied. 

Configuration interaction treatments can also be easily extended to multideterminant problems but these require even more care and an exorbitant computational effort [15]. Multi-reference Cl approaches are ideally suited to determining, for example, electronic spectra, as they can deal with excited states in a straightforward fashion [16]. 

This sum is over the n occupied MOs ij/t for a closed-shell molecule, for a total of 2n electrons. Equation 7.1 applies strictly only to a single-determinant wave-function T, but for multideterminant wavefunctions arising from configuration interaction treatments (Section 5.4) there are similar equations [10]. A shorthand for p(x, y, z) dxdydz is p(r)dr, where r is the position vector of the point with coordinates (x, y, z). 

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