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Optical sensors based on cellulose triacetate films for heavy metals detection and processing spectrometric data by chemometric algorithms

Ekaterina V. Yurova, Tatyana Yu. Rusanova
Saratov State University, Saratov, Russia

Abstract

The increased content of heavy metals in water adversely affects all living organisms, therefore, a fast and accurate analysis is needed, which can be provided by optical sensors based on biopolymers, and the use of chemometrics can simplify the detection of components in a complex system.
Therefore, the purpose of this work was to develop a sensitive element of an optical sensor with spectrophotometric and colorimetric detection methods for determining Cu(II) in water, as well as to evaluate the possibility of chemometric methods for the separate determination of Cu(II) and Al(III) ions in the joint presence in model solutions.
Pyrocatechol violet (PV) was chosen as a photometric reagent, since it forms intensely colored complexes with a wide range of ions, in particular with copper. It is established that the interfering ion in the determination of copper in water is Al (III), since its complexes with PV are absorbed in the same long – wavelength region (λ=680 nm.). The complexation of copper and aluminum ions with PV (10^(-3) M) in the pH range 4.0-9.0 in an aqueous solution was previously studied. To enhance the analytical signal, a micellar medium of cetylpyridinium chloride (10^(-2) M) was used. The most intense response of the complex with Cu (II) was observed in a solution with pH = 6.5, and with Al(III) – in a solution with pH = 7.5, therefore, these conditions for complex formation were used in further work.
To solve the problem of spectrophotometric determination of metal ions in mixtures, it is proposed to use chemometric algorithms - projection on latent structures (PLS). The possibility of the PLS1 and PLS2 methods for the separate determination of ions in mixtures containing different amounts of Cu(II) and Al(III) ions in the range of 1-90 µmol/l was evaluated.
When developing the sensitive element of an optical sensor, a film made of cellulose triacetate was used as a matrix. The reagent was immobilized by physical sorption on the polymer film in the presence of cetylpyridinium chloride. The finished films were treated with an aqueous solution of copper sulfate of various concentrations, absorption spectra were recorded, and photographs of the films were processed, obtaining RGB characteristics.
It is established that the optical density and the chromaticity parameter B linearly depends on the concentration of copper (II) ion in the concentration range of 10^(-4) M – 10^(-1) M, which shows the prospects for further use of films based on cellulose triacetate with PV to create a sensitive element of an optical sensor.


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Ekaterina Yurova
Saratov State University
Russia

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