N. V. Saranchina

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.

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.

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.

Solid-phase spectrophotometric iodometric determination of nitrite and selenium(IV) using a polymethacrylate matrix

Procedures for the iodometric solid-phase spectrophotometric determination of nitrite and selenium( IV) using a polymethacrylate matrix are proposed. The procedures are based on the reaction of nitrite and selenium(IV) with iodine in an acidic medium with the release of free iodine in amounts equivalent to those of the substances to be determined, extraction of the iodine formed with a polymethacrylate matrix, and measurement of absorbance of the matrix at 370 nm. The developed procedures ensure the determination of 0.01–0.12 mg/L of nitrite and 0.05–0.40 mg/L of selenium(IV) with limits of detection of 0.005 and 0.03 mg/L, respectively. It was shown that the proposed procedures can be applied to the determination of selenium(IV) in mineral water and nitrites in vegetables and soil.

Solid-phase spectrophotometric iodometric determination of iodate in food salt using а polymethacrylate matrix

Предложена иодометрическая твердофазно-спектрофотометрическая методика количественного определения иодата с использованием полиметакрилатной матрицы. Методика основана на реакции иодата с избытком иодида в кислой среде (рН = 1-2) с выделением свободного иода в эквивалентных определяемому веществу количествах, экстракции образовавшегося иода полиметакрилатной матрицей и измерении светопоглощения матрицы при 365 нм. Разработанная методика позволяет проводить определение иодата в диапазоне концентраций 0.10-3.60 мг/л с пределом обнаружения, рассчитанным по 3s-критерию, 0.03 мг/л, при этом время контакта полиметакрилатной матрицы с анализируемым раствором составляет 5 минут. Описано влияние мешающих ионов на определение иодата. Методика использована для определения иодата в образцах поваренной соли. Проведено сравнение результатов, полученных предлагаемой методикой, с результатами определения иода методом титриметрии в соответствии с ГОСТ 51575. Преимуществом разработанной твердофазно-спектрофотометрической методики иодата по сравнению с титриметрическим методом является повышение чувствительности, простота, экспрессность определения и отсутствие потерь иода при анализе образцов поваренной соли. Показана возможность использования полиметакрилатной матрицы в качестве готовой аналитической формы для экспрессного визуально-тестового определения иодата в поваренной соли. Ключевые слова: иодат, иодометрия, полиметакрилатная матрица, твердофазная спектрофотометрия, визуально-тестовое определение.