Synthetic colorants quantitative analysis

Spectrophotometric determinations aim at evaluation of actual versus permitted concentrations of synthetic colorants. Quantitative analysis of colorants resulting from these procedures can be performed by various techniques. Spectrophotometry allows individual or simultaneous quantitative analyses of colorant mixtures having similar absorption spectra. " ... 

A systematic study was carried out using in parallel 50 standard solutions for each concentration of three natural colorants (curcumin, carminic acid, and caramel as yellow, red, and brown, respectively). No false positive results for synthetics were obtained up to concentrations of 15 and 20 ng/ml for natural red and yellow colorants, respectively, or 110 ng/ml for natural brown colorant. The concentrations have to be high enough to prove that the screening method is able to accurately discriminate natural and synthetic colorants. To make a clear interpretation of the quantitative UV-Vis spectrum, linear regression analysis was used. Quantitative UV-Vis analysis of a dye ° can be calculated according to the following formula ... 

Several hundred dyes are known, and this diversity has always posed a problem of identity for the analysis, for many dyes have similar characteristics and some occur as a mixture (158). Among the different techniques available for the analysis of food colors, HPLC can replace many of the traditional techniques, providing rapid results that are much more specific for the determination of colorants (131,142). The technique has been shown to have great potential for synthetic food color analysis in terms of simultaneous separation, qualitative identification, and quantitation (159). 

The majority of synthetic food colors are ideal candidates for separation by CE. This is because they commonly contain sulfonic acid or carboxylic acid functional groups that form negatively charged colored ions at alkaline pEI. CE has also been applied to the analysis of natural colors such as caramels, which occur as four distinct classes according to the reactants used during sugar caramelization. CE analysis can be used to identify and quantitate the class of caramel present in a sample. 

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