Nataliya A. Gavrilenko

Solid Phase-Enhanced Photothermal Lensing with Mesoporous Polymethacrylate Matrices for Optical-Sensing Chemical Analysis

Procedures for the photothermal lens determination of metals and organic compounds, on the basis of solid-phase mesoporous optical-sensing materials (polymethacrylate [PMA]) matrices with immobilized reagents, were developed. These procedures combine (i) selective and efficient preconcentration of trace substances to be analyzed in specially designed and synthesized transparent mesoporous PMA plates; (ii) sensitive determination with the reliable and traceable photometric reactions previously developed for classical spectrophotometry; and (iii) the sensitivity enhancement of photothermal lens detection in polymers, which provides at least a ten-fold increase in sensitivity compared with solutions due to polymer thermo-optical properties (solid phase–enhanced thermal lensing). It is shown that the overall sensitivity of photothermal lens measurements in PMA matrices is two orders higher than photometric absorbance measurements for the same excitation source power, which is in good agreement with the expected theoretical sensitivity. Changes in the preparation of transparent PMA plates and analytical procedures for photothermal measurements compared with spectrophotometry are discussed. PMA matrices modified with various analytical reagents were applied to trace determination of Hg(II), Fe(II), Ag(I), Cu(II), and ascorbic acid, with subnanomolar to nanomolar limits of detection.

Sorption-spectrophotometric determination of iron(II, III) with the use of organic reagents immobilized in a polymethacrylate matrix

The interaction of iron(II) with 2,2′-dipyridyl and 1,10-phenanthroline immobilized in a polymethacrylate matrix was studied. The optimum conditions of the complexation of iron(II) with the immobilized reagents and the chemical analytical properties of the complexes in the polymethacrylate matrix were determined. A sorption-spectrophotometric procedure was developed for the determination of iron(II) and the total of iron(II, III) after the reduction of iron(III) by ascorbic acid. The procedure with 2,2′-dipyridyl was used for the analysis of samples of tap, well, and mineral water and a solution of glucose.

An optical sensor for the determination of ascorbic acid

It is shown that an optically transparent polymethacrylate matrix modified with 2,2′-dipyridyl and iron(III) can be used as a sensor for ascorbic acid. A procedure for the solid-phase spectrophotometric and visual determination of ascorbic acid in model solutions and juices using this sensor has been developed and validated.

Analytical properties of 1-(2-pyridylazo)-2-naphthol immobilized on a polymethacrylate matrix

The adsorption of 1-(2-pyridylazo)-2-naphthol (PAN) with a polymethacrylate matrix from a water-ethanol solution is studied. It is shown that PAN immobilized on a polymethacrylate matrix retains its analytical properties.

Solid phase spectrophotometric determination of silver using dithizone immobilized in a polymethacrylate matrix

Interaction of silver with Dithizone immobilized in a polymethacrylate matrix was studied. A simple procedure was proposed for the solid phase spectrophotometric determination of silver; the detection limit is 0.01 mg/L. The procedure was used for the analysis of mineral waters and the Protargol medication.

A sensitive optical element for mercury(II)

A transparent polymethacrylate matrix modified with copper dithizonate was used to determine mercury(II). Optimum conditions for modifying the polymethacrylate matrix with copper dithizonate were found, and its reaction with mercury(II) in model solutions was studied.

Preconcentration of phenols on a polymethacrylate sorbent for their gas-chromatographic determination in water

The preconcentration of phenol and its homologues by sorption on a polymethacrylate sorbent followed by capillary gas-chromatographic determination is studied. The optimal sorption conditions are the following: the sorbent mass, 400 mg; the volume of aqueous solution with pH 3, 150 mL; the flow rate of solution, 3–4 mL/min; and the volume of ethylacetate for elution, 3 mL. The detection limit is 0.7–1.0 μg/mL.

Potentials of thermal lens spectroscopy for polymethacrylate optical sensors

The sensitivity of the earlier proposed procedures for the determination of iron(II, III) with 1,10-phenanthroline, silver(I) with dithizone, mercury with copper(II) dithizonate, copper(II) with lead diethyldithiocarbamate, and ascorbic acid with 2,6-dichlorophenolindophenol using polymethacrylate optical sensitive elements for solid phase spectrophotometry is enhanced through the use of thermal lens spectrometry as the most sensitive method of molecular absorption spectroscopy. The limits of detection for all photometric reactions in the polymethacrylate matrix are reduced by an order of magnitude (to 10 nM) without substantial changes in the experimental conditions.

A colorimetric sensor based on a polymethacrylate matrix with immobilized 1-(2-pyridylazo)-2-naphthol for the determination of cobalt

A colorimetric sensor is proposed for the determination of cobalt. It is prepared by immobilizing 1-(2-pyridylazo)-2-naphthol (PAN) in an optically transparent polymethacrylate matrix. The conditions for determining cobalt by the proposed colorimetric sensor are found in the study of the complexation of cobalt with a PAN-modified polymethacrylate matrix. The determination is based on the interaction of the sensor with a cobalt solution at pH 4 for 5 min, followed by the measurement of absorbance at 620 nm. The sensor ensures the determination of 0.05–0.50 mg/L of cobalt with the detection limit 0.03 mg/L. It is demonstrated that the sensor can be used for the determination of cobalt in the Cyanocobalamin medical preparation and potable water.

Redox and acid-base properties of 2,6-dichlorophenolindophenol immobilized on a polymethacrylate matrix

The effect of the immobilization of 2,6-dichlorophenolindophenol (DCIP) on a polymethacrylate matrix on its redox and acid-base properties was studied. The ionization constant and formal redox potentials of the immobilized DCIP were determined by solid-phase spectrophotometry. It was shown that the acidity constant and the formal potentials of DCIP decreased upon the immobilization in the polymethacrylate matrix. The results of studying the interaction of ascorbic acid with immobilized DCIP are presented.