McMillan, Norman D., O'Rourke, Brian, Riedel, Sven, O'Neill, Martina, O'Neill, A. E., Bertho, A. C., Doyle, Greg, Beverley, Katharine J., Hammond, J, Augousti, Andy, Mason, Julian, Skelly, Donal, O'Neill, A. T., Boller, D. and Cave, S. J. (2004) A new democratic phase coherent data-scatter technique for calibration, measurement, fingerprinting and rapid archival identification of ultraviolet-visible multi-component food spectra. Analytica Chimica Acta, 511 (1). pp. 119-135. ISSN 0003-2670

The new theory of democratic phase coherent data-scatter (DPCD-S) is introduced. Basics of UV-visible spectrometry theory and error propagation have been presented. The qualitative spectral analysis provided is point-by-point over the complete data set and not just limited to Lambda-maxima. Equal weightings of the ‘voting’ data scattering algorithm are employed in the analysis of both the calibration and food colour data and this is consequently the democratic algorithm. The paper shows how the technique can be used with UV-visible standards to analyse the wavelength and photometric calibration of a spectrophotometer. The main results relate to the analysis of a series of spectra taken on complex mixtures of three important food dyes and their quantitative analysis using the phase coherent data-scatter technique. This method is shown to offer new possibilities for identifying and archiving UV-visible spectra from a single point in a transform space. Complex spectra can therefore be represented by a single point in this transform space, which is weighted by the ‘votes’ of all the data points in the complex data set. The software allows the user to interrogate the scatter results and locate the scatter point to the specific spectral positions. A new mathematical operator has been introduced to resolve any possible coincidence of two spectral projection points. Analysis of two close spectra from very-different admixtures of food colours shows powerfully the utility of this operator. Error propagation severely limits the accuracy of the usual UV-method of simultaneous equation secondary mixtures analysis.

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