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Solid Phase Spectrophotometric Determination of Silver Using Dithizone Immobilized in a Polymethacrylate Matrix
Abstract: 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.
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Potentials of thermal lens spectroscopy for polymethacrylate optical sensors
Abstract: 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.
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Solid Phase-Enhanced Photothermal Lensing with Mesoporous Polymethacrylate Matrices for Optical-Sensing Chemical Analysis
Abstract: 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 sensitivities. 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 mercury(II), Fe(II), Ag(I), Cu(II), and ascorbic acid, with subnanomolar to nanomolar limits of detection.
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Determination of chromium(VI) using 1.5-diphenylcarbazide immobilized in a polymethacrylate matrix
Abstract: The interaction of chromium(VI) with 1.5-diphenylcarbazide immobilized in transparent polymethacrylate matrix was studied. The optimal conditions were found for interaction metal with reagent in solid phase. The solid-phase spectrophotometric procedure was proposed for determination of chromium(VI) with the range of determinated concentrations 0.05...1.0 mg/L and the detection limit 0.014 mg/L. The possibility of using thermal lens spectrometry as a more sensitive method of molecular absorption spectroscopy for lowering the limit of detection of chromium(VI) was studied. The thermal lens spectrometer with the modulated excitation beam at 514.5 nm was used for measurement thermal lens signal. Changes in the preparation of transparent polymethacrylate matrix and analytical procedures for photothermal measurements compared with spectrophotometry not required. The using of thermal lens spectrometry allowed decreasing of the detection limit to the value 0.002 mg /L. The range of determinated concentrations was 0.005...0.05 mg/L.
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Solid phase spectrophotometric determination of selenium(IV) dithisone immobilized in a polymethacrylate matrix
This paper presents a solid-phase spectrophotometric method for the selenium(IV) determination.The proposed method is based on the reaction between selenium(IV) and immobilized into transparent polymethacrylate matrix dithizone in strongly acidic solution. It was shown that the interaction of selenium(IV) with dithizone in solid phase was accompanied by the formation of the complex with a 420 nm absorption maximum. As an analytical signal, the change of absorption at 610 nm wavelength corresponding to the absorption of excess dithizone remaining after the reaction in polymethacrylate matrix was chosen. The investigation of an effect of dithizone content in polymethacrylate matrix on the analytical characteristics of the proposed method showed that the sensitivity of the selenium(IV) determination increases with its contents. Range of values for the determined concentrations are 0.1...0.5 mg/L with the limit of detection 0.09 mg/L where the time of the contact of the sample solution with the polymethacrylate matrix is 60 min. The proposed method was successfully applied to the determination of selenium(IV) in pharmaceutical multivitamin and mineral formulations. Statistical analysis of the results confirms the precision and accuracy of the proposed method. The relative error of determination does not exceed ±8%. The developed method is ecological, cost-effective and involves easily accessible instrumentation technique which can be used by ordinary research laboratories.
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