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Identification & Differentiation of Multiple Sugars

Sugar identification - Keit IRmadillo

There are many types of sugar molecules, many of which have very similar structures making them difficult to differentiate with standard analytical methods. Industry is looking for a better way to monitor the presence of sugars with precise, real-time results. The IRmadillo FTIR spectrometer was used to analyse aqueous mixtures of up to seven different sugars simultaneously. The spectrometer is capable of qualitatively and quantitatively differentiating between monosaccharides, even when the structural differences between them are minimal.

IRmadillo & Analysis of Seven Sugar Varieties

The IRmadillo generated spectrum from analysing a solution containing seven different sugars.  With the data, a PLS (partial least squares) model was used to provide the quantification of the sugar.  The analysis showed not only how much sugar was present, but the instrument could also differentiate which sugars were present in the solution in real time.

Example spectra acquired during the experiment for the single component solutions are shown in Figure 2. The large feature at 1660 cm-1 present in all spectra arises from water, but the strong features between 1000 and 1200 cm-1 arise from the 5 and 6 membered rings (furanose and pyranose respectively) present in the sugar molecules. The exact structure of the molecule dictates the pattern and intensity of the peaks as they correspond to complicated vibrations of C-C and C-O bonds.

It should be noted that it is fairly easy using FTIR spectroscopy to differentiate between similar structures. For example, xylose and arabinose are isomers of each other, but in the MIR spectrum they show clearly different features. Other spectroscopic techniques, such as NIR, would struggle to differentiate between them. A PLS model was made of all the mixtures and a graph showing the predicted value vs reference values is shown in Figure 1. In all cases the predictions match up very well with the reference values, showing that the model is able to predict the concentrations using the spectral features.

Figure 1 predicted vs cross validation sugars IRmadillo
Figure 1: Collated data for predictions vs reference value for sugar quantification using a PLS model. It should be noted that the predicted values and cross validated predicted values are so close that in most cases they overlap.
IRmadillo Sugar spectra with structures
Figure 2: Spectra of seven sugar solutions acquired simultaneously on an IRmadillo with a 120 s sampling time between 900 and 2000 cm-1. The structures of the sugars are shown to the right.


The results demonstrate that the IRmadillo FTIR spectrometer operates as a sugar sensor to monitor the concentrations of up to seven different sugars in an aqueous mix simultaneously. This means that real-time online analysis of complicated mixtures is now possible, without the need for extractive sampling techniques or HPLC.

Industrial Applications

Many manufacturing processes make use of sugars. Bioethanol & Biofuels, Industrial Biotechnology and Pulp and Paper industries monitor the presence and concentration of sugars as some of their processes involve fermentation and sugar production as intermediaries and by-products.  Keit has developed the solid-state IRmadillo FTIR spectrometer to provide rapid insight in monitoring industrial processes including sugars.

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