Di- and tricarboxylic acids play an important biological role in the citric acid cycle, and provide an interesting analytical challenge, because of their similar structures and lack of spectroscopic features. We approached this problem using multivariate analysis and pattern recognition methods. We constructed receptors for these anions non-covalently, using positively charged poly(amidoamine) (PAMAM) dendrimers as binding partners in water at neutral pH. These macromolecules were combined with an organic dye, pyranine, to provide a reporter for the interaction between the polymers and the small anions. In this system, the analyte anions partially displace the dye from its complex with the dendrimer upon binding; this process causes a marked change in the dye’s optical properties, and provides a macroscopic signal reporting on the binding event. The analysis was carried out on 384-well microplates. Absorption and fluorescence spectroscopy methods were used to monitor the dye binding and displacement processes with the aid of a plate reader. The analytical data obtained was then interpreted using pattern recognition algorithms (principal component analysis and linear discriminant analysis). After appropriate data reduction, we were able to separate these anions into qualitative super-clusters at concentrations in the millimolar range, thanks to subtle differences in their binding behavior. The internal grouping and position of these super-clusters provided significant insight into the chemical features of the carboxylates that are responsible for their differentiation.

Chemical features influencing the fingerprinting of polycarboxylates

255th National Meeting (2018)

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